Tag Archives: sudden cardiac death

Primary prevention ICD in Nonischemic cardiomyopathy

There is a recent online first article in NEJM  ( Defibrillator Implantation in Patients with Nonischemic Systolic Heart Failure – DANISH Study). The study is summarized below:


The benefit of an implantable cardioverter–defibrillator (ICD) in patients with symptomatic systolic heart failure caused by coronary artery disease has been well documented. However, the evidence for a benefit of prophylactic ICDs in patients with systolic heart failure that is not due to coronary artery disease has been based primarily on subgroup analyses. The management of heart failure has improved since the landmark ICD trials, and many patients now receive cardiac resynchronization therapy (CRT).


In a randomized, controlled trial, 556 patients with symptomatic systolic heart failure (left ventricular ejection fraction, ≤35%) not caused by coronary artery disease were assigned to receive an ICD, and 560 patients were assigned to receive usual clinical care (control group). In both groups, 58% of the patients received CRT. The primary outcome of the trial was death from any cause. The secondary outcomes were sudden cardiac death and cardiovascular death.


After a median follow-up period of 67.6 months, the primary outcome had occurred in 120 patients (21.6%) in the ICD group and in 131 patients (23.4%) in the control group (hazard ratio, 0.87; 95% confidence interval [CI], 0.68 to 1.12; P=0.28). Sudden cardiac death occurred in 24 patients (4.3%) in the ICD group and in 46 patients (8.2%) in the control group (hazard ratio, 0.50; 95% CI, 0.31 to 0.82; P=0.005). Device infection occurred in 27 patients (4.9%) in the ICD group and in 20 patients (3.6%) in the control group (P=0.29).


In this trial, prophylactic ICD implantation in patients with symptomatic systolic heart failure not caused by coronary artery disease was not associated with a significantly lower long-term rate of death from any cause than was usual clinical care.

This is the summary of the study. This study proves the point that primary prevention ICD doesn’t reduce the all cause mortality. But there are few points to consider in this very well designed study:

  1. SCD was the cause of death in 24 out of 120 (20%) total deaths in the ICD group. SCD was the cause of death in 46 out of 131 (35%) total deaths in the non-ICD (usual care group). So that means majority of mortality even in the non-ICD usual care group are due to non arrhythmic causes.
  2. The number of non-arrhythmic mortality in the ICD group is 96 out of total of 120 (80%) and in the non-ICD group is 65%.
  3. The question still remains that – How is a device (i.e. ICD) which prevents arrhythmic deaths, is expected to reduce the All Cause Mortality (the primary end point of this study) when the majority of deaths are due to non-arrhythmic causes.
  4. When considering the sudden cardiac deaths, ICD definitely reduced the mortality [Sudden cardiac death occurred in 24 patients (4.3%) in the ICD group and in 46 patients (8.2%) in the control group (hazard ratio, 0.50; 95% CI, 0.31 to 0.82; P=0.005)].

This study is a landmark study. It shows that the present indications for primary prevention ICD in non-ischemic cardiomyopathy are likely  include patients who may not after all benefit from a primary prevention ICD. It further shows that ICD is effective in preventing SCD in non-ischemic cardiomyopathy.

So to conclude this important study shows that we need to find markers of SCD in non-ischemic cardiomyopathy so that ICD implantation can be more effectively done in patients who are at high risk of SCD.

(Disclaimer: The views expressed are entirely personal of the author of this blog and are aimed towards an educational discussion on the study. These opinions are not meant for application in medical practice and are for the purpose of discussion only)

Keywords: Electrophysiology, Cardiomyopathy, Implantable cardioverter defibrillator, Sudden cardiac death

Sudden cardiac death

What is sudden cardiac death (SCD) ?

Sudden cardiac death is 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. Related terms are sudden cardiac arrest and cardiovascular collapse. Sudden cardiac arrest means abrupt cessation of cardiac
mechanical function, which may be reversed by prompt intervention but will lead to death in its absence. Cardiovascular collapse means sudden loss of effective
blood flow due to cardiac and/or peripheral vascular such as cardiac arrest or syncope.

What is the relation to heart disease?

preexisting heart disease may or maynot have been known to be present. The mode of death is natural rapid and unexpected.

What are the symptoms?

Prodromes occuring weeks or months before an event are not very accurate to predict SCD. Sudden onset of chest pain, dyspnea, palpitation, lightheadedness
often precede the onset of cardiac arrest and eventual death.

How big is the problem?

For an adult population 35 years of age and older, the overall incidence of sudden cardiac death is 0.1% to 0.2% per year (that means in a country like India
12,00,000 to 24,00,000 people die suddenly from natural cardiac causes each year). Among people who have disease of coronary arteries of heart around 50% die
suddenly and unexpectedly. Even in developed countries where there is a decrease in total number of deaths due to coronary artery disease, the proportion of
deaths that are sudden and unexpected has remained same. These examples highlight the extent of the problem.

Who are at increased risk?

The conditions increasing the risk of sudden cardiac death are

  1. Coronary artery disease- Myocardial infarction, Angina etc
  2. Myocardial diseases and heart failure- e.g. dilated cardiomyopathy, ischemic cardiomyopathy etc
  3. Hypertrophy of ventricular myocardium – hypertrophic cardiomyopathy, left ventricular hypertrophy due to hypertension, etc
  4. Inflammatory diseases of heart- viral myocarditis, sarcoidosis, amyloidosis,
  5. Arrhythmogenic right ventricular dysplasia
  6. Diseases of cardiac valves- Aortic stenosis/insufficiency, mitral valve prolapse
  7. Electrical diseases of heart – long QT syndrome, Brugada syndrome, idiopathic ventricular fibrillation etc.
Mechanism of Sudden death

In 80% of cases sudden cardiac death is caused by ventricular tachycardia (VT) or ventricular fibrillation (VF) and in 20% of cases
SCD is caused by bradycardia. Patients having tachycardia have a relatively better outcome and chances of survival than those having bradycardia.


The acute management of cardiac arrest is cardiopulmonary resusitation. More information about latest guidelines of CPR can be found


Prevention of SCD is divided into two parts: Secondary prevention and Primary prevention. Secondary prevention means preventing further cardiac arrest
in people who have survived one cardiac arrest. Primary prevention means preventing cardiac arrest in people who have rish factors for cardiac arrest
but so far haven’t suffered a cardiac arrest.
Implantable cardioverter-defibrillator(ICD) is a device shown to be effective in secodary and primary prevention of SCD. This device is implanted like
a pacemaker and it gives an electrical shock from inside of the heart to abort an episode of VT or VF. It also has pacing function to support when the
heart rate falls.
Clinical trials like AVID, CASH, CIDS have shown effectiveness of ICD in secondary prevention of SCD. Clinical trials like MADIT, CABG-Patch, MUSTT, DEFINITE and
SCD-HeFT have shown benefit odf ICD in SCD.
Many modifications of the device has come like- subcutaneous ICD and wearable ICD.

Electrophysiological study
EPS and radiofrequency ablation can be done in selected patients to prevent further episodes of cardiac arrest.

Summary: sudden cardiac death is a devastating event resulting in rapid, unexpected and natural death due to cardiac causes. It can occur in persons
with known or unknown heart disease. Effective therapies are available. Increasing awareness about the condition and early therapy can result in
reduction of risk of sudden cardiac death
Keyword: Sudden cardiac death, sudden cardiac arrest, implantable cardioverter defibrillator (ICD), coronary artery disease, heart failure, heart disease, cardiology.