Sudden Cardiac Death: Are you at risk?

Sudden Cardiac Death: Are you at risk?

Equip yourself with the knowledge about the problem as your first line of defence

What is sudden cardiac death? 

Sudden cardiac death (SCD) describes the unexpected natural death from a cardiac cause within a short time period, generally ÉI hour from the onset of symptoms, in a person without any prior condition that would appear fatal, l SCD represents the most dramatic presentation of cardiac disease often engulfing its victims ‘out of blue’ at unexpected places and in unforeseen times, leaving a little opportunity to the patients or physicians to seek or provide necessary treatment to avoid fatality. Another interchangeable term used to describe this condition is sudden cardiac arrest (SCA). This term must not be confused with Heart Attack or Myocardial Infarction (MI), a condition resulting from acute blockage of a major blood vessel of the heart, leading to injury or death of a portion of heart muscle. Although Heart attack can lead to sudden cardiac death, the two terms are not synonymous. 

What is the magnitude of this problem? 

Cardiovascular disease is the leading cause of death worldwide accounting for approximately 17 million deaths annually. 2 The fact that SCD can occur as a first event in apparently healthy individuals without known cardiac disease and approximately 40% of SCD events are unwitnessed, makes it difficult to estimate the true prevalence of this condition.3 Population based studies suggest that 25-50% of all cardiac deaths are sudden, depending upon the definitions used and populations studied, with an annual incidence of around 0.1-0.2% in the general population. 3 4 

What are the warning symptoms of Sudden Cardiac Death? 

The typical symptoms of SCD are immediate and drastic and include sudden collapse, loss of consciousness, pulselessness, and loss of breathing effort. These symptoms often give little or no time to the patient to seek help and unless a bystander witnesses/recognizes the event, calls for emergency medical help, and performs resuscitative manoeuvres like cardiac massage and mouth to mouth breathing, the outcome is almost always fatal. Some patients may experience warning symptoms like chest discomfort, shortness of breath, palpitations, fatigue, blackouts or dizziness for a few minutes before the terminal event and therefore get a chance to seek medical attention. However, these symptoms are nonspecific and can occur due to variety of other non-serious conditions and hence cannot be totally relied upon. 

What are the risk factors for Sudden Cardiac Death? 

The basic mechanism of SCD is arrhythmia, a term used to describe abnormal heart rhythm and characterised by either very fast or very slow heart rates, which leads to inadequate blood supply to various vital organs of the body to the extent that is incompatible with sustenance of life. Arrhythmias usually occur in a diseased heart and the disease may be overt or concealed It is in the concealed disease states where SCD occurs as a first manifestation of the disorder, making it difficult to predict who, when, and where will become the victim of this fatal event. 

The cardiac diseases that predispose a patient to SCD are broadly divided into two groups i.e. genetic and acquired heart diseases. The genetic predisposition of SCD is evident from the fact that family history of SCD in a first degree relative increases the risk of its occurrence by an astounding 50 0/0. 5 An individual With single parental history of SCD has approximately 2 fold increased risk of dying suddenly and this risk increases to almost 10 fold in those with two parental histories of sudden death. 6 The genetic disorders that can cause SCD include those which cause abnormalities in cardiac muscle (cardiomyopathies) or those causing electrical disturbances in the heart without grossly affecting cardiac structure (channelopathies), These disorders are the most common causes of sudden death among young individuals including apparently healthy competitive athletes. Another group of genetic disorders are associated with abnormal formation or maturation of heart during embryonic period inside the mother’s womb, leading to variety of structural defects in the heart (congenital heart defects), which may manifest anytime from birth to early adulthood. Other major risk factors of SCD in young people include myocarditis (infection of heart, usually viral) and illicit use of drugs (prescription or recreational), a problem highly prevalent in Kashmir in present days. Among recreational drugs, cocaine, heroin/ omphetamines (ecstasy) and heavy alcohol consumption have been associated with high risk of SCD. Various prescription or over the counter medicines including some pain killers, antibiotics, antidepressants and antipsychotic drugs have also been linked to SCD. 

Among acquired heart diseases, coronary artery disease (CAD) that results from excessive fat deposition within the walls of vessels supplying blood to the heart is the most common cause of SCD. CAD is responsible for nearly 80% of all sudden cardiac deaths. This disease is 3 times more common in males as compared to females and its prevalence increases with age. The trends of SCD run parallel to those of CAD with peak incidence of SCD occurring in the age group of 45 to 75 years with male predominance. Among patients with CAD, those who have experienced a heart attack are at highest risk of SCD. Nearly 75% of all SCDs occur in a patient with previous heart attack with large area of damaged or dead cardiac muscle. The highest risk of SCD is within first 6 months to I year after a heart attack. Risk factors for CAD including smoking, hypertension, high cholesterol levels, diabetes, obesity, and sedentary life style are therefore risk factors for SCD too. Smoking in particular is a strong risk factor for SCD and people who smoke more than 20 cigarettes a day have almost 2.5 fold increased risk of SCD as compared to non-smokers.7 Other acquired heart diseases associated With SCD include hypertensive heart disease, diseases of heart valves, and congestive heart failure. Patients with heart failure face the highest risk of death with almost 50% dying within 5 years of diagnosis. These patients are at 5 to 9 fold increased risk of SCD as compared to general population and nearly half of all heart failure related deaths are sudden.8-10 

Another important group of risk factors are referred to as ‘transient risk factors’. These risk factors come into play in patients with established heart disease and trigger electrical instability in the heart leading to arrhythmias and sudden death. These include electrolyte disturbances like low or high potassium levels, acute emotional stress, systemic infections, exposure to certain drugs, low oxygen levels, acute blood loss, and some neurological events. Time of day is also important, with more sudden cardiac deaths occurring in the morning on 

arising from bed, perhaps related to increased sympathetic discharge from the central nervous system. 

KEY POINTS 

Sudden Cardiac Death (SCD) accounts for 25-50% of all cardiovascular deaths occurring worldwide annually. 

SCD may occur as a first manifestation of heart disease in a previously healthy individual. 

Majority of SCD events occur without any warning symptoms. Even if patients experience symptoms, they are nonspecific and unreliable. 

SCD results from electrical instability of the heart leading to dangerously fast or slow 

heart rates. 

Most important risk factors for SCD include: Previous episode of aborted SCD. Family history of sudden cardiac death. Previous episodes of unexplained fainting (syncope). 

Previous Heart Attack or Myocardial Infarction. 

Heart failure due to reduced pumping capacity of heart. Smoking, heavy alcohol intake and illicit drug abuse. 

Dr. Nisar Tramboo is HoD Cardiology SKIMS