Download CARDIOMYOPATHY DEFINITION Cardiomyopathy is a chronic

CARDIOMYOPATHY
S. Kache, MD
DEFINITION
Cardiomyopathy is a chronic, often progressive, decrease in cardiac output due either to
systolic and/or diastolic dysfunction of the myocardium.
ETIOLOGIES
Although pediatric cardiomyopathy is one of the leading causes of cardiac death in
children, majority of cases are idiopathic. Etiologies of CM include genetic, acquired, and
secondary to other diseases.
• Etiologies of acquired cardiomyopathy include:
1) Viral myocarditis – most common cause
2) Cardiovascular conditions - i.e. Kawasaki disease, congenital heart defects,
hypertension, cardiac transplantation or surgery, persistent arrhythmias
problems, abnormal coronaries
3) Infectious or inflammatory diseases
4) Immunologic diseases (i.e. HIV)
5) Obesity or dietary deficiencies
6) Toxin reactions - i.e. drug, alcohol, radiation exposure
7) Connective tissue and autoimmune diseases
8) Endocrine diseases
9) Pregnancy related complications
10)Genetic Mutations
•
Certain genetic mutations can be the primary cause for pediatric cardiomyopathy.
Many children with hypertrophic cardiomyopathy (50-60%) and to a lesser degree with
dilated cardiomyopathy (20-30%) have a family history of the disease. Recent
advancements in genetic research show that hypertrophic cardiomyopathy involves
defects in the sarcomere genes and can be inherited in an autosomal dominant
manner. Dilated cardiomyopathy involves defects in the cytoskeleton genes and can be
inherited in an autosomal dominant, autosomal recessive or X-linked fashion.
•
Cardiomyopathy can be related to another inherited metabolic or congenital muscle
disorder such as Noonan syndrome, Pompe disease, fatty acid oxidation defect or Barth
syndrome. Most often, symptoms of these disorders present early in life.
PATHOPHYSIOLOGY
The three types of cardiomyopathy include:
• Dilated
• Hypertrophic
• Restrictive
Although the presenting signs / symptoms, diagnosis, and outpatient management maybe
quite varied with these forms of cardiomyopathy, the inpatient management converges.
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As cardiac output decreases the body develops compensatory mechanisms so supply
can equal demand. This may include both decreasing demand, e.g. lessening exercise,
and increasing supply, e.g. releasing intrinsic catecholamines to increase stroke volume
and heart rate. When these mechanisms allow supply to equal demand, the patient is
in a compensated state. Ideally, a patient is maintained in this state on an outpatient
regiment as long as tolerated.
If the cardiac function worsens, the patient will eventually develop decompensated
shock (demand > supply) and will require admission to the ICU. In cardiogenic shock,
the cardiac output is low and systemic vascular resistance (SVR) is high. Myocardial
ischemia may also develop secondary to decreased coronary perfusion pressure,
increased myocardial demand, or a hypertrophic myocardium.
INPATIENT MANAGEMENT (See Chapter 16 – Shock)
Patients presenting in decompensated shock need immediate admission to the ICU and
treatment to provide end organ perfusion. Patients presenting with cardiogenic shock can
present with the following:
Signs & Symptoms
Depressed mental status
Tachycardia
Hypotension (Hypertension – due to
increased systemic vascular resistance, but
poor perfusion)
Arrhythmias
Abdominal discomfort / emesis
Poor urine output
Prolonged capillary refill time
Laboratory Studies
Elevated cardiac enzymes
Increased BUN / Cr
Increased LFTs
Decreased mixed venous saturation*
Elevated lactate
*Changes in mixed venous saturation and lactate can predict patient decompensation prior
to an arrest situation, and therefore should be monitored closely.
Upon admission to the ICU, treatment measurements are implemented to increase cardiac
output and decrease total body demand.
Increasing Cardiac Output
Initiation of inotropic support: (See Chapter 15 – Inotropes) milrinone, dopamine,
dobutamine, and if required epinephrine. Dopamine improves systolic function, but
increases SVR. Dobutamine improves systolic function and decreases SVR. Milrinone
improves diastolic dysfunction and also decrease SVR. Should the patient continue
hypotensive, epinephrine is started. It is a very effective inotrope, but increases SVR
and myocardial oxygen demand.
Anti-arrhythmia treatment should be initiated if required.
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Mechanical Support: If all other medical treatments are optimized and cannot provide
adequate cardiac output, patients should be considered either for extracorporeal
membranous oxygenation (ECMO) or a ventricular assist device (VAD) placement.
• ECMO provides both pulmonary and cardiac support, can be initiated in acute
situations, and can act as a bridge to heart transplant. Given the tenuous positions
of the cannulas, patients often need to remain deeply sedated and perhaps even
paralyzed. They also require systemic anti-coagulation and are therefore at risk of
developing intra-cranial hemorrhages.
• VADs can be used for either right or left ventricular support, but do not provide
pulmonary support. It should therefore not be considered in patients whose lungs
cannot provide adequate oxygenation or ventilation. Cardiomyopathy patients
rarely have pulmonary disease that cannot be reversed upon improvement of
cardiac output. VADs are placed in the operating room since a thorocotomy is
required for cannula insertion, and also act as a bridge to heart transplant. Since
the cannulas are in firmer position, patients are extubated and can often have
many activities of daily living. Patients also require systemic anticoagulation for a
VAD and are therefore also at risk of developing intra-cranial hemorrhages.
Patients have remained on VADs for several years awaiting a transplant as
compared to only 1 - 2 months on ECMO. The Berlin Heart is a small VAD device
that can be used in infants and children.
Decreasing Demand
Intubation should be considered in any patient that remains in cardiogenic shock
despite initiation of inotropic support. The work of breathing consumes a tremendous
amount of total cardiac output and in infants can account for up to 40%. Intubation
medications should be carefully selected since patients are often at risk of arresting
upon initiation of positive pressure ventilation. The drugs of choice usually are
Etomidate or Ketamine for sedation and a fast acting paralytic.
Diuretics should be started or continued. Intravascular volume status, e.g. CVP
(central venous pressure), should be monitored closely as urine output improves.
Patients with dilated cardiomyopathy in particular should not be preload diminished.
Enteral feeds should only be started slowly as cardiac output improves with inotropes.
The mixed venous saturations and lactate should be monitored closely as feeds are
begun.
Fevers should be aggressively controlled due to the tremendous increase in demand.
Active infections / sepsis should be treated with appropriate antibiotics / antifungals.
Sedation and paralysis is often considered in patients with severe cardiogenic shock to
decrease the overall demand created by movement.
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