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ODESSA NATIONAL MEDICAL UNIVERSITY
FAMILY MEDICINE AND GENERAL PRACTICE DEPARTMENT
Subject Title: “General Practice - Family Medicine”
Students’ Study Guidelines for practical sessions for 6th year Medical Faculty students
MODULE 1: «ORGANIZATIONAL ASPECTS OF PRIMARY HEALTHCARE IN
UKRAINE, ITS PRIORITY ROLE IN THE DEVELOPMENT AND REFORM OF
HEALTHCARE. FEATURES OF OUTPATIENT CARE»
CONTEXT MODULE 5: “Emergency Medical Aid in an Outpatient Setting”
Lesson 10: «EMERGENCY CARE IN FAMILY PRACTICE. SUDDEN DEATH IN
OUTPATIENTS. FIRST AID PRINCIPLES»
Year: 6 th
Faculty: Medical
Approved
By the department methodical board
“____”_____________20__
Protocol № ______
Department Head
___________Velichko V.I., M.D., PhD.
Odessa
Session Topic: «EMERGENCY CARE IN FAMILY PRACTICE. SUDDEN DEATH IN
OUTPATIENTS. FIRST AID PRINCIPLES» - 6 hours.
І. Сurrent Applications :
Sudden cardiac death (SCD) is an unexpected death due to cardiac causes occurring in a short time period
(generally within 1 h of symptom onset) in a person with known or unknown cardiac disease. Most cases of SCD
are related to cardiac arrhythmias. Approximately half of all cardiac deaths can be classified as SCDs. SCD
represents the first expression of cardiac disease in many individuals presenting with out-of-hospital cardiac arrest.
This article explores the epidemiology, pathophysiology, diagnostic approach, and treatment of patients who
experience SCD.
ІІ. Goals and Objectives:
- understand the work principles of first aid organizations,
- diagnose diseases and conditions that demand emergency care,
- know the causes of sudden cardiac death and circulation arrest algorithms,
- promptly assess patient condition and administer emergency aid in common conditions in Family Practice,
- be able to perform cardio-pulmonary resuscitation, maintain patent airway, arrhythmia treatment, defibrillation,
- know the dosage, indications and contraindications for basic medications,
- consider cases demanding FP to provide emergency care (consciousness disorders, seizures, pain, shortness of
breath, hemorrhage, agitation, animal bites, electrocution, drowning, trauma, heat or cold exposure).
Topic Contents:
The most common electrophysiological mechanisms leading to SCD are tachyarrhythmias such as ventricular
fibrillation (VF) or ventricular tachycardia (VT). Interruption of tachyarrhythmias, using either an automatic
external defibrillator (AED) or an implantable cardioverter defibrillator (ICD), has been shown to be an effective
treatment for VF and VT. The implantable defibrillator has become the central therapeutic factor in the prevention
and treatment of sudden cardiac death. Patients with tachyarrhythmias, especially VT, carry the best overall
prognosis
among
patients
with
sudden
cardiac
arrest
(SCA).
There are multiple factors at the organ (eg imbalance of autonomic tone), tissue (eg reentry, wave break, and
action potential duration alternans), cellular (eg triggered activity, and automaticity) and subcellular (abnormal
activation or deactivation of ion channels) level involved in generation of VT or VF in different conditions. An
anatomical or a functional block in the course of impulse propagation may create a circuit with the wave front
circling around it and resulting in VT. Other mechanisms such as wave break and collisions are involved in
generating VF from VT. While at the tissue level the above-mentioned reentry and wave break mechanisms are
the most important known mechanisms of VT and VF, at the cellular level increased excitation or decreased
repolarization reserve of cardiomyocytes may result in ectopic activity (eg automaticity, triggered activity),
contributing to VT and VF initiation.
At the subcellular level, altered intracellular Ca2+ currents, altered intracellular K+ currents (especially in
ischemia), or mutations resulting in dysfunction of a sodium channel (Na+ channelopathy) can increase the
likelihood of VT and VF.
Approximately 20-30% of patients with documented sudden death events have bradyarrhythmia or asystole at the
time of initial contact. Oftentimes, it is difficult to determine with certainty the initiating event in a patient
presenting with a bradyarrhythmia because asystole and pulseless electrical activity (PEA) may result from a
sustained VT. Less commonly, an initial bradyarrhythmia producing myocardial ischemia may then provoke VT
or VF.
Most cases of SCD occur in patients with structural abnormalities of the heart. Myocardial infarction (MI) and
post-MI remodeling of the heart is the most common structural abnormality in patients with SCD. In patients who
survive a myocardial infarction, the presence of premature ventricular contractions (PVCs), particularly complex
forms such as multiform PVCs, short coupling intervals (R-on-T phenomenon), or VT (salvos of 3 or more
ectopic beats), reflect an increased risk of sudden death. However suppression of the PVCs with antiarrhythmic
drugs increases mortality, owing to the proarrhythmic risk of currently available medications.
Hypertrophic cardiomyopathy and dilated cardiomyopathy are associated with an increased risk of SCD. Various
valvular diseases such as aortic stenosis are associated with increased risk of SCD. Acute illnesses, such as
myocarditis, may provide both an initial and sustained risk of SCD due to inflammation and fibrosis of the
myocardium.
Less commonly, SCD happens in patients who may not have apparent structural heart disease. These conditions
are usually inherited arrhythmia syndromes.
Even though many patients have anatomic and functional cardiac substrates that predispose them to develop
ventricular arrhythmias, only a small percentage develop SCD. Identifying the patients at risk for SCD remains a
challenge. The strongest known predictor of SCD is significant left ventricular dysfunction of any cause.
The interplay between the regional ischemia, LV dysfunction, and transient inciting events (eg, worsened
ischemia, acidosis, hypoxemia, wall tension, drugs, metabolic disturbances) has been proposed as being the
precipitator of sudden death.
Interplay of various risk factors that can lead to sudden cardiac death.
Interplay of various risk factors that can lead to sudden cardiac death.
Frequency
United States
SCD accounts for approximately 325,000 deaths per year in the United States; more deaths are attributable to
SCD than to lung cancer, breast cancer, or AIDS. This represents an incidence of 0.1-0.2% per year in the adult
population. SCD is often the first expression of CAD and is responsible for approximately 50% of deaths from
CAD.
In several population-based studies, the incidence of out-of-hospital cardiac arrest has been noted as declining in
the past 2 decades, but the proportion of sudden CAD deaths in the United States has not changed. A high
incidence of SCD occurs among certain subgroups of high-risk patients (congestive heart failure with ejection
fraction <30%, convalescent phase after myocardial infarction, patients who survived cardiac arrest). However,
these populations are much smaller than patients with minimal or even inapparent coronary artery disease.
Consequently, in the overall population, most SCD occurs in lower risk patients. The time dependence of risk for
SCD has been noted in several studies, with an increased number of events in the first 6-24 months after surviving
a major cardiovascular event.
International
The frequency of SCD in Western industrialized nations is similar to that in the United States. The incidence of
SCD in other countries varies as a reflection of the prevalence of coronary artery disease or other high-frequency
cardiomyopathies in those populations. The trend toward increasing SCD events in developing nations of the
world is thought to reflect a change in dietary and lifestyle habits in these nations. It has been estimated that SCD
claims more than 7,000,000 lives per year worldwide.
Mortality/Morbidity
Of more than 300,000 deaths attributed to SCD in the United States each year, a large portion (as many as 40%)
are unwitnessed. For most people who experience SCD, their survival depends on the presence of individuals who
are competent in performing basic life support, the rapid arrival of personnel and apparatus for defibrillation and
advanced life support, and transfer to a hospital. Even under ideal circumstances, only an estimated 20% of
patients who have out-of-hospital cardiac arrest survive to hospital discharge. In a study of out-of-hospital cardiac
arrest survival in New York City, only 1.4% of patients survived to hospital discharge. Other studies in suburban
and rural areas have indicated higher rates of survival (as high as 35%). Placement of automatic external
defibrillators throughout communities and training people to use them has the potential to markedly improve
outcomes from SCD.
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Upon emergency department (ED) presentation, the most important determinants of survival include (1)
an unsupported systolic blood pressure (SBP) greater than 90 mm Hg, (2) a time from loss of consciousness to
return of spontaneous circulation (ROSC) of less than 25 minutes, and (3) some degree of neurological
responsiveness.
A major adverse outcome from a SCD event is anoxic encephalopathy, which occurs in 30-80% of
cases.
Race
Most studies demonstrate inconclusive data with regard to racial differences as they relate to the incidence of
sudden death. Some studies suggest that a greater proportion of coronary deaths were "sudden" in blacks
compared to whites. In a report by Gillum et al on SCD from 1980-1985, the percentage of coronary artery
disease deaths occurring out of the hospital and in EDs was found to be higher in blacks than in whites.
Cardiac death, sudden. Plots of mortality rates (deaths per 1000 persons) for ischemic heart disease
occurring out of the hospital or in the emergency department (top) and occurring in the hospital (bottom)
by age, sex, and race in 40 states during 1985.
Sex
Men have a higher incidence of SCD than women, with a ratio of 3:1. This ratio generally reflects the higher
incidence of obstructive coronary artery disease in men. Recent evidence suggests that a major sex difference may
exist in the mechanism of myocardial infarction. Basic and observational data point to the fact that men tend to
have coronary plaque rupture, while women tend to have plaque erosion. Whether this biologic difference
accounts for the male predominance of SCD is unclear.
Age
The incidence of SCD parallels the incidence of coronary artery disease, with the peak of SCD occurring in
people aged 45-75 years. The incidence of SCD increases with age in men, women, whites, and nonwhites as the
prevalence of coronary artery disease increases with age. However, the proportion of deaths that are sudden from
coronary artery disease decreases with age. In the Framingham study, the proportion of coronary artery disease
deaths that were sudden was 62% in men aged 45-54 years, but this percentage fell to 58% in men aged 55-64
years and to 42% in men aged 65-74 years. According to Kuller et al, 31% of deaths are sudden in people aged
20-29 years.
Clinical
History
Obtaining a thorough history from the patient, family members, or other witnesses is necessary to obtain insight
into the events surrounding the sudden death. Patients at risk for SCD may have prodromes of chest pain, fatigue,
palpitations, and other nonspecific complaints. History and associated symptoms, to some degree depend on the
underlying etiology of SCD. For example, SCD in an elderly patient with significant coronary artery disease may
be associated with preceding chest pain due to a myocardial infarction, while SCD in a young patient may be
associated with history of prior syncopal episodes and/or a family history of syncope and SCD and due to
inherited arrhythmia syndromes. As many as 45% of persons who have SCD were seen by a physician within 4
weeks before death, although as many as 75% of these complaints were not related to the cardiovascular system.
A prior history of LV impairment (ejection fraction <30-35%) is the most potent common risk factor for sudden
death.
Risk factors that relate to coronary artery disease and subsequent myocardial infarction and ischemic
cardiomyopathy also are important and include a family history of premature coronary artery disease, smoking,
dyslipidemia, hypertension, diabetes, obesity, and a sedentary lifestyle. Specific considerations include the
following:
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Coronary artery disease
Previous cardiac arrest
Syncope
Prior myocardial infarction, especially within 6 months
Ejection fraction less than 30-35%
History of frequent ventricular ectopy (more than 10 PVCs per h or nonsustained VT)
Dilated cardiomyopathy
Previous cardiac arrest
Syncope
Ejection fraction less than 30-35%
Use of inotropic medications
Hypertrophic cardiomyopathy
Previous cardiac arrest
Syncope
Family history of SCD
Symptoms of heart failure
Drop in SBP or ventricular ectopy upon stress testing
Palpitations
Most are asymptomatic
Valvular disease
Valve replacement within 6 months
Syncope
History of frequent ventricular ectopy
Symptoms associated with severe uncorrected aortic stenosis or mitral stenosis
Long QT syndrome
Family history of long QT and SCD
Medications that prolong the QT interval
Bilateral deafness
Wolff-Parkinson-White (WPW) syndrome (with atrial fibrillation or atrial flutter with extremely rapid
ventricular rates): With extremely rapid conduction over an accessory pathway, degeneration to VF can occur.
Brugada syndrome, arrhythmogenic right ventricular (RV) cardiomyopathy/dysplasia, and others
Physical
The physical examination may reveal evidence of underlying myocardial disease or may be entirely normal,
depending on the underlying cause. Initial evaluation studies show that patients who survive to ED presentation
can be stratified by a cardiac arrest score, which has excellent diagnostic value. The cardiac arrest score,
developed by Thompson and McCullough, can be used for patients with witnessed out-of-hospital cardiac arrest
and is defined by the following criteria:
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Clinical characteristic points
ED SBP greater than 90 mm Hg = 1 point
ED SBP less than 90 mm Hg = 0 points
Time to ROSC less than 25 minutes = 1 point
Time to ROSC more than 25 minutes = 0 points
Neurologically responsive = 1 point
Comatose = 0 point
Maximum score = 3 points
Patients with a score of 3 points can be expected to have an 89% chance of neurologic recovery and an
82% chance of survival to discharge.
Cardiac death, sudden. Figure a shows neurologic outcome stratified by initial cardiac arrest score.
Neurologic recovery is defined as discharged home and able to care for self. Figure b shows overall survival
stratified by initial cardiac arrest score.
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McCullough indicates that even in the setting of ST elevation and early invasive management with
primary angioplasty and intraaortic balloon pump insertion, patients with low cardiac scores are unlikely to
survive.
Severe anoxic encephalopathy in patients with scores of 0, 1, or 2 mitigates conservative management
with empiric supportive and medical therapy. Given the very poor actuarial survival rates for these patients,
invasive management with catheterization and electrophysiology studies (EPS) is rarely justified.
Causes
Ischemic heart disease
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Cardiac arrest due to ventricular arrhythmias may be due to post-MI remodeling of the heart with scar
formation and interstitial fibrosis (intramyocardial collagen deposition) or to acute MI/ischemia. A chronic infarct
scar can serve as the focus for reentrant ventricular tachyarrhythmias. This can occur shortly after the infarct or
years later. Interestingly, post-MI remodeling and ischemic cardiomyopathy may be associated with increased
interstitial fibrosis even in noninfarcted areas of the heart. Interstitial fibrosis can provide anatomical block similar
to a scar. Fibroblasts and myocytes shown to be coupled through gap junctions and fibroblasts can reduce
repolarization reserve of myocytes. In addition to post-MI remodeling, many other structural heart diseases
associated with SCD (eg, dilated cardiomyopathy, hypertrophic cardiomyopathy, and aortic stenosis) are also
associated with increased myocardial fibrosis.
Many studies support the relationship of symptomatic and asymptomatic ischemia as a factor for risk of
SCD. Patients resuscitated from out-of-hospital cardiac arrest represent a group of patients with increased
recurrence of cardiac arrest and have been shown to express an increased incidence of silent ST-segment
depression. Experiments inducing myocardial ischemia in animal models have a strong relationship with the
development of VF. However, in patients with prior myocardial infarction and scarring, ventricular arrhythmias,
especially VT, do not require an acute ischemic trigger.
In postmortem studies of people who have died from SCD, extensive atherosclerosis is a common
pathologic finding. In survivors of cardiac arrest, coronary heart disease with vessels showing greater than 75%
stenosis is observed in 40-86% of patients, depending on the age and sex of the population studied. Autopsy
studies show similar results; in one study of 169 hearts, approximately 61% of patients died of SCD, and more
than 75% stenosis in 3 or 4 vessels and similar severe lesions were present in at least 2 vessels in another 15% of
cases. No single coronary artery lesion is associated with an increased risk for SCD. Despite these findings, only
approximately 20% of SCD-related autopsies have shown evidence of a recent MI. A greater proportion of
autopsies (40-70%) show evidence of a healed MI. Many of these hearts also reveal evidence of plaque fissuring,
hemorrhage, and thrombosis.
The Cardiac Surgery Study (CASS) showed that improving or restoring blood flow to an ischemic
myocardium decreased the risk of SCD, especially in patients with 3-vessel disease and heart failure, when
compared with medical treatment over a 5-year period.
The efficacy of beta-blocking agents, such as propranolol, in decreasing sudden death mortality, especially
when administered to patients who had MI with VF, VT, and high-frequency PVCs, may be due in part to the
ability of beta-blockers to decrease ischemia, but they are also effective in patients with nonischemic
cardiomyopathy for reduction of SCD. Beta-blockers also increase the VF threshold in ischemic animals and
decrease the rate of ventricular ectopy in patients who had MI.
Reperfusion of ischemic myocardium with thrombolysis or direct percutaneous coronary intervention can
induce transient electrical instability by several different mechanisms.
Coronary artery spasm is a condition that exposes the myocardium to both ischemia and reperfusion insults.
It is occasionally associated with VT, VF, and SCD. Since some of the episodes of coronary vasospasm may be
silent, this disease should be considered in a patient with unexplained SCA. The exact mechanism of ventricular
arrhythmia in coronary vasospasm is not known, but factors associated with both ischemia and reperfusion may
contribute in induction of arrhythmia.
Nonatherosclerotic coronary artery abnormalities, including congenital lesions, coronary artery embolism,
coronary arteritis, and mechanical abnormalities of the coronary artery, have been associated with an increased
incidence of sudden death.
Nonischemic cardiomyopathies
Patients with nonischemic cardiomyopathies represent the second largest group of patients who experience SCD
in the United States. Nonischemic myopathies, for the purpose of this article, can be divided into the categories
dilated and hypertrophic.
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Dilated cardiomyopathy
Dilated cardiomyopathy can result from prior ischemia and myocardial infarction or from nonischemic
causes. Nonischemic dilated cardiomyopathy (DCM) is becoming increasingly more common, with an incidence
of approximately 7.5 cases per 100,000 persons each year. Of cases of SCD, 10% are estimated to be attributable
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to DCM. The prognosis is very poor for these patients, with a 1-year mortality rate of 10-50%, depending on the
New York Heart Association functional class; approximately 30-50% of these deaths are SCD.
The causes of DCM are uncertain; viral, autoimmune, genetic, and environmental (alcohol) origins are
implicated. The predominant mechanism of death appears to be ventricular tachyarrhythmia, although
bradyarrhythmia and electromechanical dissociation also have been observed, especially in patients with
advanced LV dysfunction. Extensive fibrosis of the subendocardium, leading to dilated ventricles and subsequent
generation of reentrant tachyarrhythmias, is a proposed factor in mechanism of sudden death. Multiple factors
have been shown to contribute to increased risk for SCD in this population. The most important hemodynamic
predictor is an increase in end-diastolic pressure and subsequent wall tension. Other important factors are
increased sympathetic tone, neurohumoral activation, and electrolyte abnormalities.
Many drugs used in the treatment of heart failure, such as antiarrhythmics, inotropic agents, and
diuretics, have direct or indirect (eg, through electrolyte abnormalities) proarrhythmic properties, which may
provoke arrhythmias in some cases. Potassium-sparing diuretics may be helpful in decreasing SCD.
Nonsustained ventricular tachycardia (NSVT) is common in patients with dilated cardiomyopathy and
approximately 80% of persons with DCM have abnormalities on Holter monitoring. Although NSVT may be a
marker, it has not been shown to be a reliable predictor of SCD in these patients. Recent studies have shown
possibility of increased mortality following suppression of NSVT by antiarrhythmic medications due to
proarrhythmic properties of these medications and involvement of several other factors in generation of VT and
VF. Given the possibility of sustained VT being the underlying cause, a history of syncope should be aggressively
pursued. Unexplained syncope, especially in patients with class 3 or 4 heart failure, has been shown to be a
predictor of SCD in most patients with cardiomyopathy
Hypertrophic cardiomyopathy
Hypertrophic cardiomyopathy (HCM) is an autosomal-dominant, incompletely penetrant genetic
disorder resulting from a mutation in one of the many (>45) genes encoding proteins of the cardiac muscle
sarcomere. Among the genetic abnormalities described, mutations in the genes coding for the beta-myosin heavy
chains, and cardiac troponin T make up most cases. Other mutations may include alpha-myosin heavy chain
MYH6), cardiac troponin C (TNNC1), alpha-tropomyosin (TPM1), myosin binding protein-C (MYBPC3), cardiac
troponin (TNNI3), essential and regulatory light-chain genes (MYL 3 and MYL 2, respectively), cardiac alphaactin gene (ACTC), and titin (TTN). The incidence of SCD in this population is 2-4% per year in adults and 4-6%
per year in children and adolescents. HCM is the most common cause of SCD in people younger than 30 years.
The vast majority of young people who die of HCM are previously asymptomatic. The patients may
experience SCD while at rest or with mild exertional activity; however, in a significant portion of these patients,
the SCD event occurs after vigorous exertion. HCM is the single greatest cause of SCD in young athletes and,
hence, is the major entity for which to screen during the physical examination of an athlete.
The mechanism of SCD in HCM is not entirely understood. Initially, it was thought to be due to
obstruction of the outflow tract because of catecholamine stimulation. However, later studies suggested that
individuals with nonobstructive HCM are at high risk for SCD as well, primarily related to VT or VF. The
mechanism of arrhythmia in this setting is not clear, and hypertrophy may be a part of cardiac remodeling in these
patients that provides the substrate for lethal arrhythmia.
Rapid or polymorphic symptomatic NSVT may have better predictive value compared with
asymptomatic and monomorphic NSVT. Other clinical markers that may have predictive value for SCD in
patients with HCM are young age at onset, thickness of the septum, and family history of SCD.
Arrhythmogenic right ventricular cardiomyopathy
Arrhythmogenic RV cardiomyopathy is characterized by replacement of the RV wall with fibrofatty
tissue. Involvement of the interventricular septum and left ventricle is associated with poorer outcomes.
About 30-50% of cases occur as a phenotypically apparent familial disorder. Several genetic defects,
including mutations in the desmoplakin domain locus on chromosome 6 and the ryanodine receptor locus on
chromosome 1 (although this has been debated), have been correlated with SCD. Again, interstitial fibrosis plays
an important role in ventricular arrhythmia in this condition. Autosomal dominant inheritance is common, but
autosomal recessive transmission has been reported for select mutations. The autosomal recessive form, Naxos
disease (named after the Greek Island), has been reported in a geographically isolated area mainly in
Mediterranean countries and is usually associated with wooly hair and palmoplantar keratoderma or similar skin
disorder. This disorder is associated with mutation in the gene for plakoglobin, a protein involved in cellular
adhesion, found on chromosome 17p.
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Arrhythmogenic RV dysplasia affects men more often than women. The annual incidence rate of SCD in
this population is approximately 2%. Patients may present with signs and symptoms of RV hypertrophy and
dilation, often with sustained monomorphic or polymorphic VT of a left bundle-branch block morphology with an
axis usually between negative 90-100°
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Atrial arrhythmias may be present in as many as 25% of patients. Syncope and sudden death often are
associated with exercise. In many patients, sudden death is the first manifestation of the disease. Clinicians should
be alerted to the epsilon wave finding on ECG studies. The epsilon wave can be present in as many as 23% of
patients after the first VT event. The percentage of patients with the epsilon wave finding on ECG increases to
27% and 34% at 5 and 10 years, respectively, after the first VT event.
Cardiac death, sudden. Epsilon wave in a patient with arrhythmogenic right ventricular dysplasia.
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Uhl anomaly is a condition in which the RV wall is extremely thin secondary to apposition of
endocardial and epicardial layers.
Valvular disease
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Prior to the advent of surgical therapy for valvular heart disease, SCD was fairly common in patients with
progressive aortic stenosis.
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Most aortic stenosis deaths were sudden. In a study by Chizner et al of 42 patients who had isolated aortic
stenosis and did not undergo valve replacement, as many as 56% of deaths were sudden at 5 years of follow-up.
Of these 42 patients, 32 were symptomatic and 10 were asymptomatic.
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The mechanism of sudden death is unclear, and both malignant ventricular arrhythmia and
bradyarrhythmia have been documented.
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The incidence of SCD has decreased significantly with advent of aortic valve replacement. However, it
still accounts for the second most common cause of death postoperatively in this population and especially in
those with prosthetic and heterograft aortic valve replacement. The incidence of SCD after aortic valve surgery is
highest in the first 3 weeks after the procedure and then plateaus at 6 months of follow-up.
Other valvular lesions
The risk of SCD is much lower in other valvular diseases compared with aortic stenosis.
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Aortic insufficiency usually presents with signs of heart failure and progressive LV dilatation. As part of
this process, reentrant or automatic ventricular foci may develop and ultimately lead to a symptomatic ventricular
arrhythmia. After valve replacement, LV wall tension can be expected to reduce and the risk of arrhythmia can be
expected to decrease.
Mitral stenosis is becoming increasingly uncommon in the United States because of widespread use of
antibiotics in primary streptococcal infections. SCD due to mitral stenosis is very rare.
The incidence of SCD is low in patients with mitral valve prolapse (MVP). MVP has a 5-7% incidence
in the general population. In clinically significant MVP, the risk of SCD seems to rise along with total mortality.
Kligfield et al estimated that the incidence of sudden death varies with the presence of symptoms and the severity
of mitral regurgitation. Ventricular tachyarrhythmias are the most frequent arrhythmia in patients with SCD. Risk
factors for SCD to consider in these patients include a family history of SCD, echocardiographic evidence of a
redundant mitral valve, repolarization abnormalities, and lengthening of the corrected QT interval (>420 ms in
women and >450 ms in men).
Congenital heart disease
In the pediatric and adolescent age groups, SCD occurs with an incidence of 1.3-8.5 cases per 100,000 patients
annually, accounting for approximately 5% of all deaths in this group. The causes of SCD are much more diverse
in children than adults. In reviewing 13 studies involving 61 children and adolescents with SCD, Driscoll found
50% of cases were due to HCM; 25% were due to anomalous origin of the left coronary artery; and the remaining
patients had aortic stenosis, cystic medial necrosis, and sinus node artery obstruction. The following is a
classification of SCD in the pediatric population.
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In patients with known, previously recognized (including repaired) congenital heart disease,
abnormalities associated with SCD include the following:
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Tetralogy of Fallot
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Transposition of the great arteries
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Fontan operation
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Aortic stenosis
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Marfan syndrome
Mitral valve prolapse
Hypoplastic left heart syndrome
Eisenmenger syndrome
Congenital heart block
Ebstein anomaly
In patients with known, previously recognized (including repaired) heart disease, acquired causes of
SCD include the following:
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Kawasaki syndrome
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DCM or myocarditis
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In patients with previously unrecognized heart disease who have structural heart disease, causes of
SCD include the following:
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HCM
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Congenital coronary artery abnormalities
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Arrhythmogenic RV cardiomyopathy
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In patients with previously unrecognized heart disease who do not have structural heart disease,
causes of SCD include the following:
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Long QT syndrome
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WPW syndrome
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Primary ventricular tachycardia and ventricular fibrillation
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Primary pulmonary hypertension
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Commotio cordis - Traumatic blow to the chest wall (eg, from a hockey puck or baseball) causing
VT/VF and SCD in the absence of significant identifiable trauma
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The predominant mechanism is ventricular arrhythmias. In tetralogy of Fallot after postoperative
correction of the anomaly, as many as 10% of these patients have VT and the incidence of sudden death is 2-3%.
In the Fontan procedure, ie, to correct a physiologic single ventricle, even atrial arrhythmias can cause severe
hemodynamic compromise and arrhythmic death. Patients who develop secondary pulmonary hypertension
(Eisenmenger syndrome), despite attempted correction of the anatomic defects, have a very poor prognosis. The
terminal event may be bradycardia or VT progressing to VF.
Primary electrophysiologic abnormalities
This generally represents a group of abnormalities in which patients have no apparent structural heart disease but
have a primary electrophysiological abnormality that predisposes them to VT or VF. Some imaging techniques
have detected abnormal sympathetic neural function in these patients. An ECG study can provide clues to the
diagnosis; consider a familial component to these conditions. Normal early repolarization may be associated with
increased SCD, though this often represents a benign finding.
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Long QT syndrome
Idiopathic long QT syndrome, in which patients have a prolonged QT with a propensity to
develop malignant ventricular arrhythmias, is a rare familial disorder.
Two inheritance patterns of congenital long QT syndrome have been described. The JervellLange-Nielsen syndrome, associated with congenital deafness, has an autosomal-recessive pattern of inheritance.
The Romano-Ward syndrome is not associated with deafness and has an autosomal dominant pattern of
inheritance with variable penetration. This syndrome accounts for 90% of long QT syndrome cases. More than
200 mutations in the 10 or more genes related to long QT syndrome have been found. Among the most common
are mutations of SCN5A on chromosome 3, the HERG gene on chromosome 7, and the KVLTQT1 gene on
chromosome 11.
Alteration in the function of a myocellular channel protein that regulates the potassium flux
during electrical repolarization is thought to be causative, though in some subsets of long QT syndrome, such as
those with mutations in SCN5A (long QT3), Na channels are primarily impaired. A relationship with sympathetic
nervous system imbalance also appears to exist. The prolongation that occurs makes these patients susceptible to
develop a specific form of VT called torsade de pointes.
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The clinical course of patients with long QT syndrome is quite variable, with some patients
remaining asymptomatic while others develop torsade de pointes with syncope and sudden death. Symptoms and
SCD are more common among homozygous individuals (those with two copies of the mutant allele), compared
with heterozygous individuals (who have a single mutant allele). The risk of SCD is impacted by environmental
factors such as hypokalemia, medications and the presence of sinus pauses. SCD in these patients also has been
associated with emotional extremes, auditory auras or stimulation, and vigorous physical activity. Symptoms
usually begin in childhood or adolescence.
The probability that a specific patient has congenital long QT syndrome is divided to low,
intermediate, and high probability based on the following criteria: (1) ECG criteria including long QT, torsade de
pointes, notched T wave, T wave alternans, bradycardia for age; (2) clinical criteria including syncope with or
without stress, deafness; and (3) family history of long QT syndrome or SCD.
When measuring QTc, selecting rhythm strips that have minimal variability of RR intervals and
a stable heart rate is important.
Treatment for long QT syndrome includes beta-blockers and often pacemaker or ICD
implantation. Beta-blockers decrease the overall mortality in patients with long QT syndrome. However, they do
not eliminate the risk of syncope, cardiac arrest, and SCD completely. They are not effective in patients with
mutation in Na channel genes (long QT3). Torsade de pointes in patients with long QT syndrome is associated
with bradycardia and pauses. Therefore, a pacemaker can prevent torsade de pointes in these patients by
preventing bradycardia. ICD therapy may be indicated in patients with recurrent symptoms despite treatment with
beta-blockers.
Acquired long QT syndrome
A number of antiarrhythmics (especially class Ia and class III) and other medications, electrolyte
abnormalities, cerebrovascular diseases, and altered nutritional states are known to cause QT prolongation and put
patients at risk for torsade de pointes. This usually occurs when QT prolongation is associated with a slow heart
rate and hypokalemia.
The QT interval is prolonged in as many as 32% of patients with intracranial hemorrhage
(especially in subarachnoid hemorrhages). Lesions in the hypothalamus are thought to lead to this phenomenon.
Reports of sudden death due to ventricular arrhythmia in patients with hypocalcemia,
hypothyroidism, nutritional deficiencies associated with modified starvation diets, and in patients who are obese
and on severe weight-loss programs have been reported.
Class Ia antiarrhythmic drugs that cause acquired long QT syndrome include quinidine,
disopyramide, and procainamide. Class III antiarrhythmic drugs that cause acquired long QT syndrome include
sotalol, N -acetyl procainamide, bretylium, amiodarone, and ibutilide.
Other drugs that cause acquired long QT syndrome include bepridil, probucol, tricyclic and
tetracyclic antidepressants, phenothiazines, Haldol, antihistamines (eg, terfenadine, astemizole), antibiotics (eg,
erythromycin, sulfamethoxazole/trimethoprim), chemotherapeutics (eg, pentamidine, anthracycline), serotonin
antagonists (eg, ketanserin, zimeldine), and organophosphorus insecticides.
Electrolyte abnormalities that cause acquired long QT syndrome include hypokalemia,
hypomagnesemia, and hypocalcemia.
Altered nutritional states and cerebrovascular disease that cause acquired long QT syndrome
include intracranial and subarachnoid hemorrhages, stroke, and intracranial trauma.
Hypothyroidism and altered autonomic status (eg, diabetic neuropathy) can cause acquired long
QT syndrome.
Hypothermia can cause acquired QT prolongation. The ECG will typically also demonstrate an
Osborn wave, a distinct bulging of the J point at the beginning of the ST segment. This ECG finding resolves
upon warming.
Short QT syndrome
The short QT syndrome is a newly recognized syndrome, first time described in 2000, which can
lead to lethal arrhythmias and SCD. Three mutations in potassium channels have been described that lead to gain
of function in potassium channels and shortening of action potential and decreased QT interval.
To diagnose short QT syndrome, the QTc should be less than 330 msec and tall and peaked T
waves should be present. Clinical manifestations are variable from no symptoms, to palpitations due to atrial
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fibrillation, syncope due to VT, and SCD. VF is easily inducible at electrophysiology study in these patients, and
SCD can happen at any age.
Although antiarrhythmic medications, such as sotalol, ibutilide, and procainamide, have been
proposed as a therapy (to prolong the QT), data to support this approach are insufficient at present. ICD
placement may be considered to prevent VT and SCD, although T-wave oversensing, resulting in inappropriate
ICD discharges, has been problematic.
Wolff-Parkinson-White syndrome
WPW syndrome is a recognized but rare cause of sudden death. The existence of an
atrioventricular accessory pathway in this syndrome results in ventricular preexcitation, which appears with short
PR interval, wide QRS complex, and delta wave on ECG. The refractory period in the anterograde direction of
accessory pathway determines the ventricular rate in the setting of atrial fibrillation and WPW. Most patients with
WPW syndrome and SCD develop atrial fibrillation with a rapid ventricular response over the accessory pathway,
which induces VF (see Media file 5). In a study by Klein et al of 31 patients with VF and WPW syndrome, a
history of atrial fibrillation or reciprocating tachycardia was an important predisposing factor. The presence of
multiple accessory pathways, posteroseptal accessory pathways, and a preexcited R-R interval of less than 220 ms
during atrial fibrillation are associated with higher risk for SCD.
Cardiac death, sudden. Ventricular fibrillation appeared during rapid atrial fibrillation in a patient with
Wolff-Parkinson-White syndrome.
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Symptomatic patients should be treated by antiarrhythmic medications (eg, procainamide),
catheter ablation of the accessory pathway, or electrical cardioversion depending on the severity and frequency of
symptoms. Asymptomatic patients may be observed without treatment.
Medications such as digoxin, adenosine, and verapamil that block the AV node are
contraindicated in patients with WPW and atrial fibrillation because they may accelerate conduction through the
accessory pathway, potentially causing VF and SCD.
Brugada syndrome
In 1992, Brugada and Brugada described a syndrome of a specific ECG pattern of right bundlebranch block and ST-segment elevation in leads V1 through V3 without any structural abnormality of the heart,
that was associated with sudden death.
In 25-30% of these patients, a mutation in SCN5A on chromosome 3 is detected. This mutation
results in a sodium channelopathy. The most common clinical presentation is syncope, and this mutation is most
common in young males and in Asians. It is associated with VT, VF, and SCD.
Three ECG types of Brugada pattern are described. Only type 1,- which consists of a coving ST
elevation in V1 to V3 with downsloping ST segment and inverted T waves, pseudo RBBB pattern with no
reciprocal ST changes and normal QTc, is specific enough to be diagnostic for Brugada syndrome when it is
associated with symptoms. The other two ECG patterns of Brugada are not diagnostic, but they merit further
evaluation.
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The Brugada ECG pattern can be dynamic and not found on an index ECG. When clinical
suspicion is high, a challenge test with procainamide or some other Na channel blocker may be diagnostic by
reproducing the type 1 ECG pattern.
Although antiarrhythmic medications, catheter ablation and pacemaker therapies all have potential, in
young and symptomatic patients, an ICD should be implanted to prevent VF and SCD. ICD therapy is the only
proven treatment to date. Whether ICD placement is indicated in older or asymptomatic patients is controversial
at present.
Catecholaminergic polymorphic ventricular tachycardia
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a syndrome that
presents with polymorphic VT, syncope, or SCD, and in about half of these patients, a mutation in one of two
different genes have been detected.
The polymorphic VT is characteristically induced by emotional or physical stress (eg,
exercise stress test). The medical therapy of choice is administration of beta-blockers, and ICD may be indicated.
New data may support the use of flecainide in the treatment of this disease.
Primary ventricular fibrillation occurs in a structurally normal heart due to idiopathic etiology.
An estimated 3-9% of cases of VT and VF occur in the absence of myocardial ischemia. As
many as 1% of patients with out-of-hospital cardiac arrest have idiopathic VF with no structural heart disease. As
many as 15% of patients younger than 40 years who experience VF have no underlying structural heart disease.
Viskin and Behassan noted that of 54 patients with idiopathic VF, 11 patients had histologic abnormalities on
endomyocardial biopsy.
SCD is often the first presentation of VF in patients at risk but who have had no preceding
symptoms. In those patients who survive, VF may recur in as many as one third of patients.
The options for medical therapy include beta-blockers and class 1A antiarrhythmic drugs, but
limited data are available regarding their efficacy. The mainstay of treatment is preventing VF by ICD placement.
Mapping and radiofrequency ablation of the triggering foci is an option for those patients who experience
frequent episodes of VF following ICD placement.
Right ventricular outflow tract ventricular tachycardia
Right ventricular outflow tract (RVOT) tachycardia is the most common form of idiopathic VT,
comprising 70-80% of all idiopathic VTs. RVOT tachycardia is a very rare cause of SCD. It also has been
referred to as exercise-induced VT, adenosine-sensitive VT, and repetitive monomorphic VT.
RVOT tachycardia occurs in patients without structural heart disease and arises from the RV
outflow region. Current data suggest that triggered activity is the underlying mechanism of RVOT tachycardia.
RVOT tachycardia is believed to be receptor-mediated because exogenous and endogenous adenosine can
terminate this process. Maneuvers that increase endogenous acetylcholine also have been demonstrated to
antagonize this process.
Symptoms typical of RVOT tachycardia include palpitations and presyncope or syncope, often
occurring during or after exercise or emotional stress. VT also can occur at rest. The ECG during VT displays a
left bundle-branch block/inferior axis morphology.
Treatment is based on frequency and severity of symptoms. The first line of therapy is a betablocker or calcium channel blocker. Patients with symptoms not relieved by medical therapy are best treated with
radiofrequency catheter ablation. Successful ablation is reported in 83-100% of cases.
Other causes of sudden death
Two major causes of sudden cardiopulmonary death deserve mention.
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Pulmonary embolism is a frequent cause of sudden death in people at risk. Risk factors include previous
personal or family history of deep venous thromboembolism, malignancy, hypercoagulable states, and recent
mechanical trauma such as hip or knee surgery.
Aortic dissection or aneurysmal rupture is the other major cause of out-of-hospital nonarrhythmic
cardiovascular death. Predisposing factors for aortic dissection include genetic deficiencies of collagen such as
Marfan syndrome, Ehlers-Danlos syndrome, and aortic cystic medial necrosis.
Laboratory Studies
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Cardiac enzymes (creatine kinase, myoglobin, troponin): Elevations in these enzyme levels may indicate
ischemia and MI. The extent of myocardial damage usually can be correlated to the extent of elevation in the
enzyme levels. Patients are at increased risk for arrhythmia in the peri-infarct period.
Electrolytes, calcium, and magnesium: Severe metabolic acidosis, hypokalemia, hyperkalemia,
hypocalcemia, and hypomagnesemia are some of the conditions that can increase the risk for arrhythmia and
sudden death.
Quantitative drug levels (quinidine, procainamide, tricyclic antidepressants, digoxin): Drug levels higher
than the levels indicated in the therapeutic index may have a proarrhythmic effect. Subtherapeutic levels of these
drugs in patients being treated for specific cardiac conditions also can lead to an increased risk for arrhythmia.
Most of the antiarrhythmic medications also have a proarrhythmic effect.
Toxicology screen: Looking for drugs, such as cocaine, that can lead to vasospasm-induced ischemia is
warranted if suspicion exists. Obtaining levels of drugs (antiarrhythmics) also may be warranted.
Thyroid-stimulating hormone: Hyperthyroidism can lead to tachycardia and tachyarrhythmias. Over a
period of time, it also can lead to heart failure. Hypothyroidism can lead to QT prolongation.
Brain natriuretic peptide (BNP): BNP has predictive value especially in post MI patients and in patients
with heart failure. Although preliminary and not conclusive, emerging data support the notion that an elevated
BNP level may provide prognostic information on the risk of SCD, independent of clinical information and
LVEF.
Imaging Studies
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Chest radiography: This may reveal whether someone is in congestive heart failure. It also can show
signs suggesting LV enlargement or RV enlargement. Signs of pulmonary hypertension also may be evident on
the chest radiograph.
Echocardiography: Two-dimensional echocardiography with Doppler is essential in the evaluation of
SCD. A number of studies have demonstrated that the use of 2-dimensional echocardiogram to evaluate left wall
motion abnormalities after an acute MI (using the LV wall-motion score index) is useful in predicting the risk for
major cardiac events, including sudden death. A decrease in the ejection fraction and worsening wall motion
abnormalities upon exercise echocardiography in patients who have had an MI has been suggested to confer
increased risk of cardiac death.
Nuclear imaging techniques: Resting thallium or technetium-99m scintigraphy is helpful in assessing
myocardial damage after MI. A larger defect has been associated with greater risk for future cardiac events.
Exercise nuclear scintigraphy is very sensitive for detecting the presence, extent, and location of myocardial
ischemia. Gibson et al found that pharmacologic-stress nuclear (dipyridamole or adenosine) scintigraphy was
better than submaximal exercise ECG and coronary angiography in predicting cardiac death and other cardiac
events. These tests can be very helpful in patients with low functional capacity such as chronic obstructive
pulmonary disease, peripheral vascular disease, or orthopedic problems. The Multi-Center Post-Infarction
Research Group provided evidence that resting ejection fraction was the most important noninvasive predictor of
SCD and other cardiac events in patients with MI.
Other Tests
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Electrocardiogram: This study is indicated in all patients. Evidence of MI, prolonged QT interval, short
QT interval, epsilon wave, Brugada sign, short PR, a WPW pattern, or other conditions should be sought.
Signal-averaged ECG (SAECG) has been variably reported to be useful in analysis of patients with
SCD. What may be more useful is analysis of T wave alternans in patients with VT, VF, and/or SCD. Small
changes in T amplitude are not detected in 12-lead ECG. Microvolt T wave alternans (MTWA) amplifies the
alternans and may be used in the workup to predict the risk of SCD. However, to date, the use of T wave alternans
to predict which patients with ischemic or nonischemic cardiomyopathy would benefit from ICD placement has
not been conclusive.
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Genetic testing: The value of genetic testing in conditions such as congenital long QT and HCM is still
being evaluated. Some studies have recommended the testing of siblings and close relatives of people with SCD
due to these conditions.
Procedures
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Coronary angiography: Perform cardiac catheterization in patients who survive SCD to assess
the state of ventricular function and the severity and extent of CAD.
The number of vessels with severe obstruction and the degree of LV dysfunction are
important variables in predicting cardiac events. Ejection fraction is the best predictor of significant cardiac
events and survival.
Coronary angiography also can help identify coronary anomalies and other forms of
congenital heart disease.
Angiography is performed with the aim of identifying patients who may benefit from
revascularization. Revascularization is indicated when ischemic myocardium is present as the underlying
substrate of VT/VF.
Electrophysiology studies: In targeted patients, EPS play diagnostic, prognostic, and
therapeutic roles. EPS usually are performed after ischemic and structural heart disease has been diagnosed and
addressed. These studies have been used to identify patients who have inducible versus noninducible sustained
monomorphic VT. The presence of inducible sustained VT, at baseline or when the patient is on antiarrhythmic
medications, confers a higher risk for sudden death. Significantly lower ventricular function also has been
observed in patients with inducible sustained VT. Inducible bundle-branch reentrant VT can be seen in patients
with DCM and in the postoperative period after valvular replacement. As many as 20% of patients with HCM
have inducible sustained monomorphic VT. The identification of accessory pathways also is possible with these
studies. EPS are performed with an eye toward the following:
Ablation of VT foci, eg, bundle branch VT, RVOT VT, and some cases of idiopathic
LV tachycardia
ICD implantation, which is generally the case in survivors of SCD
III. Out-of-class preparation questions.
1.
Study the anatomic build of cardiopulmonary system. Estimate the location of major blood vessels and
the heart.
2.
Study the histostructure for every element in the human circulatory system.
3.
Study the physiological characteristics of the human circulatory system. Innervation of the circulatory
system.
4.
Study the Pathology characteristics of rhythm disturbances, pathology basics of cardiac arrest.
5.
Study the pharmacokinetics, pharmacodynamics and dosage principles for medications used in
resuscitation.
6.
Study the characteristics of the circulatory system examination methods (clinical, lab and instrumental).
Perform a clinical and instrumental examination of the patients’ circulatory system.
IV. Theoretical questions.
1. What are the current viewpoints on the problem of sudden cardiac death?
2. What pathological condition is considered to be cardiac death?
3. What etiological factors cause sudden death?
4. What are the main mechanisms of circulation arrest?
5. What are the clinical signs of circulation arrest?
6. What is the overall influence of patient sex and age on the duration of clinical death?
7. What diagnostic criteria are required to diagnose sudden cardiac death?
8. Differential diagnosis for terminal arrhythmias.
9. Medical aid sequence for patients in a state of clinical death.
10. Pharmacology specifics for medications used during CPR.
11. Treatment tactics for postresuscitation disease following sudden death.
12. Name diseases and conditions that lead to sudden death development.
V. In-class individual study.
Practical skills to be perfected during practical sessions.
1. Students should be able to take complete history (stressing the existing cardiologic, pulmonologic conditions,
list of concurrent medication, family history), perform patient examination: inspection, palpation, percussion,
auscultation.
2. Register and interpret an ECG: apply electrodes, take an ECG, analyze the rhythm source, regularity, hear rate,
conduction disturbances.
3. Interpret lab and instrumental examination results (according to the case history): CBC, biochemistry, lipids,
coagulation, transaminase, elecrolytes.
3. Evaluate the state of respiratory and circulatory systems.
4. Learn CPR: study the CPR with one rescuer and two rescuers.
Study the method of airway passage restoration with triple Safar maneuver.
Study the mouth to mouth lung ventilation method.
Study the nose to mouth ventilation method.
Study the artificial ventilation method using airway adjuncts.
Study the artificial ventilation method using the Ambu bag.
Study the artificial ventilation method using the respiratory apparatus.
Study the chest compressions method (stress the correct hands position, pumps strength, rate of compressions);
5. Study the defibrillation method;
6. Study the intensive drug therapy algorithms in sudden death (according to the clinical death treatment
algorithm, consider the order and necessity for drug administration, post resuscitation patient support).
VI. Literature.
Main literature.
1. Chevalier P., Kirkorian G., Touboul P. Arrhythmic sudden cardiac death due to coronary artery spasm// Card
Electrophysiol Rev. – 2002. – Vol. 6 (1-2). – P. 104–106.
2. Cohen M., Stinett S. S., Weatherley B. D. еt al. Predictors of recurrent ischiemic events and death in unstable
coronary artery disease after treatment with combination antithrombotic therapy// Am Heart J. – 2000. – Vol.
139. – P. 962–970.
3. Elliott P. M., Poloniecki J., Dickie S. et al. Sudden death in hypertrophic cardiomyopathy: identification of
high risk patients// J Am Coll Cardiol. – 2000. – Vol. 36. – P. 2212–2218.
Additional literature.
1.
Florenciano-Sanchez R., Castillo-Moreno J. A., Molina-Laborda E. et al. The exercise test that indicates
a low risk of events. Differences in prognostic significance between patients with chronic stable angina and
patients with unstable angina// J Am Coll Cardiol. – 2001. – Vol. 38 (7). – P. 1974–1979
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