What is Sudden Cardiac Death (SCD)? How to minimize associated risks?

A multi-regional awareness outreach to spread key messages and educate people on CPR must be undertaken on high priority to save lives and reduce incidences of sudden deaths in our country, says Dr T S Kler, Chairman, Fortis Heart and Vascular Institute, Fortis Memorial Research Institute, Gurugram.
Sudden Death, also called Sudden Cardiac Death (SCD), is an unexpected, natural death within an hour, caused by an abrupt stoppage of the heart, preceded by fainting at the onset of acute cardiac malfunction. It can affect any individual with or without pre-existing heart disease but those with higher risk factors are more at risk. Many victims also die in their sleep. In recent times, many well-known public figures have succumbed to it, so there are a number of questions and even fear in people’s minds on the causes, symptoms if any, and ways to prevent it if possible.
Sudden Death almost always has cardiovascular causes with more than 95 per cent of the fatalities due to sudden cardiac arrest. Less than five per cent of these are due to rupture of some relatively big vessel (artery or aorta) leading to massive bleeding into the stomach, chest or brain. One of the important reasons for rupture of the aorta is excessive dilatation defined as an aortic aneurysm, which is a balloon-like bulge in the aorta, the large artery that carries blood from the heart through the chest and torso.

What tests are required for prevention?

The only way to diagnose these aneurysms is a routine ultrasound of the torso, particularly for those above 55 years of age. Aneurysm of the aorta in the chest can be picked up by X-ray or echocardiography. Hoarseness of voice can be a symptom of an aneurysm of the ascending aorta in our chest. The most common cause of bleeding in the brain in the elderly is hypertension, but among the young, it is mostly due to some congenital anomalies of vessels (arteriovenous anomalies or abnormal tangle of blood vessels in the brain, or even, connecting arteries and veins disrupting normal blood flow and oxygen circulation) in the brain. It is usually difficult to diagnose before at least one instance of bleeding.

Despite the rising number of SCDs in India, the levels of coverage of vital registration and the reliability of the cause of death as stated on the death certificate is often low, particularly in the rural areas, which has significantly impacted the estimation of SCD incidence. The first study on SCD in India in 2012 put the overall mortality due to SCD at 10.3 per cent, which translates to 7 lakh cases annually. Among the victims, 21 per cent were people below the age of 50 years.

What are risk factors?

A family history of coronary artery disease, smoking, high blood pressure, high blood cholesterol, obesity, diabetes and a sedentary lifestyle are some of the factors that increase the risk of Sudden Death. Men are at a greater risk than women. Other risk factors include a previous heart attack, using illegal drugs such as cocaine or amphetamines, nutritional imbalance such as low potassium/magnesium levels, obstructive sleep apnea, and chronic kidney disease.

Causes of Sudden Death

Cardiac arrest, which leads to sudden death, occurs due to three dangerous rhythm abnormalities— Ventricular Tachycardia or VT, Ventricular Fibrillation or VF and Asystole. VT is a very high heart rate coming from the lower chambers of the heart. Normal heartbeat originates from the right upper chamber of the heart called the sinus node. If VT is not treated within a few minutes, it degenerates into Ventricular Fibrillation, a type of abnormal heart rhythm. VF is practically cardiac arrest because a person has only chaotic electric activity but there is no mechanical pumping of the heart. Blood pressure immediately drops to zero and if not treated with electric shock or cardiopulmonary resuscitation (CPR), a patient dies within five to eight minutes. In Asystole, there is no heartbeat or any electric or mechanical activity in the heart. Immediate CPR is the only hope of survival and the outcome of Asystole is much worse compared to VT/VF even if the best treatment is given immediately.

While sudden death almost invariably involves the heart, we must understand that there are differences between cardiac arrest and heart attack. Every cardiac arrest is not due to a heart attack and every heart attack does not cause cardiac arrest.

How is SCD different from a heart attack?

A heart attack occurs due to sudden, total (100 per cent) blockage of the two coronary arteries. If a heart attack occurs due to blockage in a major or big coronary artery, it can certainly lead to cardiac arrest. Only 15 per cent of sudden cardiac arrests occur due to heart attacks while 85 per cent are due to an already damaged heart. If we assess people susceptible to cardiac arrest, about 85 per cent of cardiac arrest cases occur if the heart’s pumping capacity falls (LVEF less than 35 per cent) either due to a previous heart attack (coronary artery disease) or due to disease of the heart muscle (cardiomyopathy). LVEF, which stands for Left Ventricular Ejection Fraction, is a medical term to describe the pumping capacity of the heart. The normal level of LVEF is 55-65 per cent.

The most common cause of sudden death in adults above 35 years of age is coronary artery disease which causes blockages in these vessels, leading to heart attacks. It is a different story for people under the age of 35 years for whom the most common cause is a disease called hypertrophic cardiomyopathy in which the muscle of the left ventricle thickens and becomes hypercontractile. It is largely hereditary and can be detected by echocardiography.

Other reasons for sudden death in young people are rare gene problems. A few of these disorders are QT prolongation in which the heart’s electrical system takes longer than usual to recharge between beats and Brugada syndrome, a rare but potentially life-threatening heart rhythm condition (arrhythmia) that is sometimes inherited. While an ECHO procedure may show a normal heart for these people, an ECG can detect abnormalities.

Reducing risks to SCD

The risk of sudden death can be reduced with regular checkups, screening for heart disease (particularly for those with a family history), adopting a heart-healthy lifestyle and reducing obesity. Individuals with diabetes must keep it under control with a combination of lifestyle modification, exercise and medicines. The ideal control is to keep HbA1c which detects average blood sugar level in the last three months between 6 and 7 per cent. Those with blood pressure must keep it under control through lifestyle modification, exercise and drugs if required. The ideal BP control is to keep it below 130/80. Regular exercise, including yoga and meditation for 45 minutes at least five days a week, learning to overcome stress and adopting a positive attitude in life will also help cut the risk of SCD. For young people who want to play competitive sports or want to do high-intensity exercise, cardiac check-ups, ECG and ECHO are recommended.

Way forward

By 2030, India is likely to reach the highest number of cardiac deaths in the world. It is a formidable challenge to neutralise but it is certainly not a lost cause. While there is no magic solution yet for cardiac problems that could eliminate SCD, adopting a lifestyle change is the first and most obvious step to counter it. Families with a history of someone young dying suddenly should screen themselves regularly/undergo echocardiography. Along with lifestyle changes, we must raise awareness levels about Sudden Death through public education and make health and wellness promotion a priority. Most importantly, each of us must learn CPR and administer it within the first six minutes if someone needs it. This can greatly improve the chances of survival as it immediately restarts heart functions, provides blood supply to the brain and gives the victim a chance to stay alive until he/she is taken to a hospital. A multi-regional awareness outreach to spread key messages and educate people on CPR must be undertaken on high priority to save lives and reduce incidences of sudden deaths in our country.