Sudden Cardiac Death (SCD)

Sudden Cardiac Death (SCD)

Sudden Cardiac Death (SCD) can be defined as natural death from cardiac causes heralded by abrupt loss of consciousness within 1 hour of the onset of an acute change in cardiovascular status. Annual incidence of SCD is about 3 lakhs in the US and 24 million worldwide.

Causes

1. Coronary artery disease: 80%
2. CAD is by and large, the most important cause of SCD
3. Cardiomyopathy: 15%
4. Left ventricular hypertrophy is a strong independent risk factor for SCD
5. ARVD is being recognized as an important cause of exercise induced SCD
6. Aortic stenosis
7. Channelopathies – Long QT syndrome, Brugada syndrome, Short QT syndrome
8. Coronary anomalies – Anomalous origin of left coronary artery from pulmonary artery (ALCAPA)
9. Aortic valve endocarditis
10. Myocarditis
11. Sarcoidosis
12. Operated Tetralogy of Fallot

Predictors of Sudden Cardiac Death (SCD)

1. 1. LV ejection fraction: LV ejection fraction < 30% is the single most powerful independent predictor of SCD. The incidence of SCD increases as the ejection fraction decreases, but the proportion of SCD to all deaths due increase in deaths due to pump failure.
2. NYHA class is similar to LV ejection fraction, but patients may shift from one class to another frequently.
3. Non sustained ventricular tachycardia (NSVT) is a predictor in a small group of patients.
4. Signal averaged ECG – Late potential predict SCD. It has a high negative predictive value. It is not useful in patients with bundle branch block.
5. QRS duration – higher QRS duration is an indicator.
6. T wave alternans – very good marker of SCD in ischemic and non-ischemic cardiomyopathy.
7. QT dispersion is the variability in QT interval between the leads – does not give any meaningful prognostic information.
8. QT interval variability is the variability in QT interval during the period of ECG recording – predictive of SCD, but more studies are needed.
9. Baroreceptor sensitivity – sensitivity of change in heart rate with change in blood pressure.
10. Heart rate variability in short term and long term – short term heart rate variability is a predictor of SCD while long term heart rate variability is a predictor of total mortality.
11. Heart rate turbulence – transient slowing of heart rate after the post ventricular ectopic beat followed by an acceleration. Heart rate turbulence is an important predictor of SCD.
12. Heart rate recovery following a treadmill exercise test is a predictor of SCD.
13. Inducible ventricular tachycardia on EP study