Sudden Cardiac Death
According to the American Heart Association, Sudden Cardiac Death (SCD) affects approximately 450,000 people each year in the United States and an estimated 95% die before reaching the hospital. SCD kills more Americans than lung cancer, breast cancer and AIDS combined. SCD or Cardiac Arrest is reversible in most victims if it’s treated within first 3 minutes by the delivery of an electrical shock.
With the development of hospital coronary care units in the 1960s, it was found that electrical devices that shocked the heart could turn an abnormally rapid rhythm into a normal one.
Later, it also became clear that cardiac arrest could be reversed outside the hospital if specially trained emergency rescue teams reached the person quickly. The chances of survival are reduced by 7-10% with every passing minute. However, even after survival, the prognosis continued to be dismal. The first-year recurrence rate in survivors of SCD was 20-40%.
SCD victims range from young children to the elderly.
SCD is caused by the rapid and/or chaotic activity of the heart known as ventricular tachycardia (VT) or ventricular fibrillation (VF). This is the problem of electrical conduction system of heart and should not be confused with a heart attack (myocardial infarction), which is caused by a blocked blood vessel leading to loss of blood supply to a portion of the heart muscle. However, some people may experience SCD during a heart attack. However it has been observed that people are scared of heart attack but do not understand the concept of SCD.
Both ventricular tachycardia (VT) and ventricular fibrillation (VF) are life-threatening heart rhythms. In hospital these arrhythmias can be treated with external defibrillators by the paramedics or medical personnel. However, for long-term out of hospital treatment option an electronic device (ICD) is implanted in the patient’s body to treat these arrhythmia.
An Implantable Cardioverter Defibrillator (ICD) monitors the heart’s electrical conduction system and delivers electrical energy (shock) to the heart to convert VT/VF to a normal rhythm.
In the mid-1980s, the ICD was designed and was called “an emergency room in the chest”. Today, ICD’s do much more and have been proven to be 99% effective in treating these ventricular arrhythmias and preventing SCD. As of today, ICD is about the size of a small stopwatch and is implanted in the upper chest, below the clavicle bone. It continuously monitors the electrical conduction system of the heart, watching for dangerous patterns and delivering electrical impulses when needed that may range from a tiny pulse like a cardiac pacemaker or a life-saving shock that can return the heart to normal rhythm.
Risk of SCD is high in patients with:
*At least one experience of VT/VF
(malignant rhythm arising from lower chamber of heart)
*Previous cardiac arrest or abnormal heart rhythm that caused patient to pass out
*A fast heart rhythm that keeps returning and could cause death
*A fast heart rhythm that cannot be controlled with drugs
*Severe side effects from drug therapy used to control these fast rhythms
*Previous heart attack and a low ejection fraction (poor heart function)