Common causes of Sudden Cardiac Death

The sudden death of Bollywood star Sridevi has shocked millions. Slim, looking fit and fine, it was the last thing to expect her to die to heart attack. Dr KK Aggarwal, Padma Shri awardee, President Heart Care Foundation of India and Immediate Past National President IMA explains the reasons for sudden cardiac death

Over 70% of all sudden cardiac deaths are due to underlying heart blockages

The frequency of heart blockages is much lower in sudden deaths occurring under the age of 30 (24%)

10% of sudden deaths are due to underlying  structural heart disease (congenital coronary artery anomalies, myocarditis, hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy). The frequency is much higher in subjects under the age of 30 (35%)

5-10% of sudden cardiac deaths are arrhythmias occurring in the absence of underlying structural heart disease (long QT syndrome, Brugada syndrome, Wolff-Parkinson-White syndrome, catecholaminergic polymorphic VT, all abnormalities seen on ECG).

15-25% of cardiac arrests are noncardiac in origin. The causes include trauma, bleeding, drug intoxication, intracranial hemorrhage, pulmonary embolism, near-drowning, and central airway obstruction.

Sudden cardiac deaths accounts for 30 to 50 percent of deaths in patients with heart failure

Women are less vulnerable to sudden death than men and a higher fraction of sudden deaths in women occur in the absence of prior overt blockages

60% of deaths associated with acute heart attack occur within the first hour and were attributable to a ventricular arrhythmia, in particular ventricular fibrillation

Sudden cardiac arrest (SCA) and sudden cardiac death (SCD) refer to the sudden cessation of cardiac activity with hemodynamic collapse, often due to sustained ventricular tachycardia/ventricular fibrillation. Other causes of SCA and SCD are asystole and pulseless electrical activity. These events most commonly occur in patients with structural heart disease (that may not have been previously diagnosed), particularly coronary heart disease.

Silent angina:   is defined as the presence of objective evidence of myocardial ischemia in the absence of chest discomfort or another anginal equivalent symptom (eg, breathlessness, nausea, sweating etc). 

Between 25 and 45 percent of patients with coronary heart disease have myocardial ischemia during daily life, and most (>75%) of these ischemic episodes are not associated with chest pain.

Most "silent" ischemic episodes occur during minimal or no physical exertion

Patients with diabetes, older adults, and those with prior heart attack or prior bypass surgery are particularly susceptible to silent myocardial ischemia

In a review of over 430,000 patients with confirmed acute heart attack from the National Registry of Myocardial Infarction 2, one-third had no chest pain on presentation to the hospital. These patients may present with breathlessness alone, nausea and/or vomiting, palpitations, syncope or transient loss of consciousness, or cardiac arrest. They are more likely to be older, diabetic, and women. [JAMA 2000; 283:3223.]

65% of out of hospital cardiac arrests occur at home. If not resuscitated fewer than 2% will be alive after one month. Having an arrest at home is a strong independent predictor of adverse outcome.

Bystander CPR is the only answer in out of hospital cardiac arrest.

Survival to hospital discharge with favorable neurologic status improve approximately twofold with bystander CPR

Bystander CPR with chest compressions alone results in improved survival to hospital discharge

First aid in cardiac arrest

Heart Care Foundation of India guidelines encourage the performance of CPR using excellent chest compression alone.

Lay rescuers should not interrupt excellent chest compression to palpate for pulses or check for the return of spontaneous circulation, and should continue CPR until an electric shock machine is ready to give a shock, doctor assume care, or the patient wakes up. No mouth-to-mouth ventilation is required.