Download Which Patients with Coronary Artery Disease are at Greater Risk for

Which Patients with Coronary
Artery Disease are at Greater
Risk for Sudden Cardiac Death,
and What Can We Do To Lower
the Risk?
Dr Stanley Chia MB ChB, MD, MRCP, FAMS
Consultant Cardiologist
National Heart Centre Singapore
Sudden Cardiac Death (SCD)
•
•
•
Catastrophic and unpredictable event resulting
from an abrupt loss of cardiac function
Occurs within minutes after symptoms appear
•
To reduce the incidence of SCD, accurate and
timely prediction of risk is of paramount
importance.
Most common underlying reason for SCD is
coronary artery disease and is frequently the
consequence of an acute ischaemic event
•
However, no tests have been proven to predict
SCD accurately
Who is at Risk?
•
Although SCD often occurs in active, outwardly
healthy people with no known heart disease, but the
truth is that SCD is not random and most victims do
have underlying heart diseases or other health
problems, albeit unknown
•
There are numerous contributors to cardiac arrest,
but two of the most important ones are:
•
Previous myocardial infarction: 75% of
people who die of SCD show signs of a previous MI.
•
Coronary artery disease: 80% of SCD’s victims
have signs of coronary artery disease.
Atherosclerosis: an Inflammatory Disease
Fig 1
Fig 2
Fig 3
Fig 4
Ross R. NEJM 1999
Decades
Years-Months
Healthy
Subclinical
Months-Days
Symptomatic
Intima
Lumen
Media
Lumen
narrowing
Plaque
Progression
Compensatory expansion
preserves lumen
diameter
Normal
Vessel
Minimal
CAD
Moderate
CAD
Expansion overcome:
lumen narrows
Severe
S
CAD
Identifying Patients with
Silent Coronary Artery
Disease
Smoking
Diabetes Mellitus
Hypertension
Obesity
Sedentary lifestyle
Depression
Diet
Emotional stress
Investigations to Detect Significant Coronary
Artery Disease, Myocardial Ischaemia and LVEF
ECG & Stress ECG test
Calcium Score and CT
Coronary Angiography
Echo & Stress Echocardiography
Myocardial Perfusion Study
Coronary
Angiography
Risk Stratification for SCD
•
Studied primarily in patients with
•
•
History of acute myocardial infarction
Congestive heart failure
Both recognized to be at increased risk for SCD
•
Most randomized trials with Implantable Cardioverter
Defibrillator (ICD) therapy have shown reduction in
SCD and mortality, but most patients (2/3) enrolled in
these trials did not receive therapy (ICD shock or antitachycardia pacing)
•
Hence, in addition to left ventricular ejection fraction
(LVEF), how can we determine who will benefit from
ICD??
Assessment of SCD Risk
• Left Ventricular Ejection
Fraction (LVEF)
• Symptoms of Heart Failure: NYHA class
• Other Tests to predict SCD vulnerability?
• Non-sustained Ventricular tachycardia, Microvolt Twave alternans, measures of cardiac autonomic
modulation, QT interval, Signal-averaged ECG,
Electrophysiology study and Imaging studies, Genetic
studies
Normal Left ventricular
systolic function
Echocardiogram
Impaired Left
ventricular systolic
function
Left
Ventriculogram
Left
Ventriculogram
Left Ventricular Ejection Fraction
•
LVEF is well recognized as a predictor of allcause mortality in patients with CAD
•
In the VALIANT trial (I=14 609), LVEF was a strong
predictor of SCD or cardiac arrest
•
Risk of SCD or cardiac arrest increased by 21% for
every 5% decrease in LVEF
•
Low LVEF (35%) was the main entry criterion in large
randomized trials of primary prevention ICD therapy
(MADIT-II and SCD-HeFT ICT studies).
•
However, 2/3 of patients randomized to ICD therapy in
did not use their ICD during 3-5 year follow-up
Sudden Death in Patients with Myocardial
Infarction and Left Ventricular Dysfunction
Kaplan Meier Estimates and Rate of Sudden Death or Cardiac Arrest with Resuscitation over
the Course of the Trial in the Three Categories of Left Ventricular Ejection Fraction (LVEF).
Solomon S. NEJM 2005
Heart Failure Symptoms:
NYHA Class
•
Functional class provide a potent risk
stratification tool
•
Patients with NYHA class II and III symptoms are at
higher risk for SCD than death from progressive pump
failure, and are more likely to benefit from ICD.
(Improvement in survival for class III: HR=0.66)
•
In contrast, patients with NYHA class IV symptoms are
more likely to die of pump failure.
•
No clinical trials done exclusively for patients with class
1 symptoms, although they are well represented in
primary prevention trials
Other Specific tests that may
potentially predict SCD
•
Presence of nonsustained ventricular tachycardia (NSVT)
post myocardial infarction
•
•
In a large study of post-AMI patients, NSVT predicted SCD, but
could not discriminate between risk of SCD and non-SCD.
Furthermore, it was not a predictor for patients with LVEF35%
Microvolt T-wave Alternans
•
•
•
Change in T-wave amplitude, width or shape in alternate beats
High negative predictive value, but low positive predictive value
Major limitations: High percentage of indeterminate tests and
absence of prospective data on treatment guided by MTWA.
Other Specific tests
•
•
•
•
Measures of cardiac autonomic modulation
•
Heart rate variability, Baroreflex sensitivity, QT interval, QT
dispersion and QT variability
•
May be predictive of all-cause or cardiac mortality, but do not
predict SCD, and have not been proven to be clinically useful
Signal-averaged ECG
•
To detect low amplitude, high-frequency electrical signals at the
end of QRS complex, known as late potentials
•
Associated with higher rate of arrhythmia in patients with CAD
and poor LVEF, but poor predictive value on its own.
Invasive Electrophysiology study: not predictive of SCD
Imaging studies, Genetic testing , Serum markers
•
Exploratory
Although many tests of SCD vulnerability
have been examined in patients with IHD,
current data do not support the consistent
use of any test, other than LVEF, to risk
stratify these patients.
How to lower the risk of SCD?
•
Optimal Management of Coronary Artery Disease
•
Lifestyle Modification: Healthy Diet, Exercise,
Smoking cessation, Reduce Stress
•
Pharmacotherapy: Anti-platelet agents (Aspirin/
ticlopidine/clopidogrel), Anti-anginal agents (blockers, calcium channel blockers, nitrates), ACE
inhibitors, Lipid lowering therapy
•
Revascularization to Relieve Ischaemia and
Improve LVEF: Percutanenous Coronary Intervention
or Coronary Artery Bypass Grafting Surgery
Severe Coronary Artery Stenosis
Definitive Therapy:
Implantable Cardioverter-Defibrillator
ICD Therapy
DC
Cardioversion
Antitachycardiac
Pacing
MADIT II: All-cause mortality
Endpoint
ICD
group
Conventional
therapy
group
Hazard
ratio
(95% CI)
p value
All-cause
105
97 (19.8%)
0.65 (0.51
– 0.93)
0.016
mortality (14.2%)
MADIT II: Mortality events
Cause of death
ICD group
Conventional therapy
group
Noncardiac
26
20
Cardiac
74
67
27 (3.6%)
46 (9.4%)
41
18
Arrhythmic
Nonarrhythmic
Patients with LVEF30%, 1 mth after AMI
Randomized to ICD or medical therapy
Moss et al. N Engl J Med 2002;346(12):877-83.
Probability of Survival with Defibrillator
Post AMI
Efficacy of ICD For Primary Prevention of
Death, in Patients with Coronary Artery
Disease and Impaired LV Systolic Function
Summary
• Sudden cardiac death occurs most frequently in
•
•
•
patients with prior MI, Heart Failure and underlying
CAD
Current available tests are unable to predict SCD
accurately
LVEF remains the best predictor of SCD
Management is targeted at treating the underlying
CAD and heart failure
• Consider ICD for patients with LVEF 30-35%
• Most patients with ICD, however, do not receive any
therapy from the ICD over the initial 3-5 years
Thank you