Silent ischemia and Sudden cardiac death

What it is?

We all have heard stories about how some individuals with no previous ailments suddenly fall ill and expire within a span of minutes to hours. It understandably comes as a shock to the near ones who find it difficult to comprehend how a previously hale and hearty person can suddenly collapse in so dramatic a way as to be unable to be brought back to life. It also brings a sense of foreboding that such a spectre can happen anytime and to anybody. Such events, viz. the sudden cessation of cardiac function preceding death are called sudden cardiac death(SCD). These have been the subject of intense scrutiny and rigorous research over the years. Unfortunately, there are many facets of this entity which are not entirely clear. More worrying is the fact that even in this age of technological advancement, there are no foolproof means to predict such events and consequently, prevent such disastrous outcomes.

Causes

However, we have been able to determine the majority of causes of SCD. Some of these diseases are inherited. They are genetically acquired defects in cardiac electrical or muscular function which make the heart susceptible to experience sudden pathological increase in heart rates( called ventricular tachycardia). If these episodes persist even for brief periods, they can result in sudden cessation of heart pumping and, consequently, death.

One such entity is called hypertrophic cardiomyopathy, where the heart becomes abnormally thick to the extent that heart pumping as well as heart beating can suddenly stop. It is the most common cause of sudden cardiac death in young populations.

In older populations, the problem of coronary artery disease(CAD) predominates. The arteries of the heart get clogged up because of lipid deposition leading to impaired oxygen supply to the heart.
Over the years, we as cardiologists have come to appreciate that many people have no symptoms of CAD like chest pain but have ongoing underlying ischemia . It either produces no symptoms or very vague symptoms like,

  • Fatigue
  • Uneasiness
  • Sweating
  • Palpitations

Which can very well be ascribed to other more common disorders( like acidity). More ominously, they may present for the very first time with cardiac arrest from which the person may or may not be revived successfully.

How to recognise people at risk?

The only way to recognise people with genetic disorders is to identify families where members have died suddenly and then submit them to clinical examination and investigation. Such people usually require common investigations like echocardiography, ECG and TMT but may require special investigations like,

  • 24- hour Holter monitoring
  • Cardiac MRI
  • Genetic analysis

It is essential for family members of victims, especially if victims are Childers or youngadults, to seek advice of cardiologists and undertake investigations which are necessary. People with depressed heart function and enlarged hearts(dilated cardiomyopathy) are a group of patients at high risk of SCD. If such people develop symptoms such as Loss of consciousness,Dizziness, Transient blackout they should immediately report to qualified cardiologists who can advise the relevant investigations for them.

Thankfully, we have come a long way into diagnosing coronary artery disease. It includes investigations like,

  • Treadmill test
  • Special nuclear scans
  • Coronary angiography( confirmatory)

It only requires for us to be aware of the possibility of silent ischemia. People who are diabetics, smokers, hypertensive, obese or have multiple family members with heart attacks, should be especially careful.

Treatment

For certain patients with genetic or inherited disorders who have survived cardiac arrest or have been found to have ventricular tachycardia, cardiologists may prescribe special pacemakers called implantable cardioverter defibrillator(ICD). These devices detect ventricular tachycardia whenever it occurs and give an electrical shock to terminate it and avoid cardiac arrest. This device has proven to be a boon in saving lives of many patients with poor heart function and no other means of treatment.

Certain patients benefit from very specialised procedures called radio frequency ablation which target abnormal electrical currents in the heart and ablate/ burn them. People with obstruction in the blood supply actually have good outcomes because of the tremendous development in operations like coronary angioplasty and bypass surgery. Vast numbers of patients who have heart attack and undergo primary angioplasty(angioplasty within hours of heart attack) are saved from the heart attack as well as the future risk of sudden death.

In short, early diagnosis and treatment by qualified physicians goes a long way in preventing dismal outcomes.

Published By:- Dr. Saujatya Chakraborty
MBBS(Hons), MD(PGI), DM Cardiology(PGI-Chandigarh)
Consultant Interventional Cardiologist
Medica Institute of Cardiac Sciences
Medica Superspecialty Hospital, Kolkata, India

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