Getting to the heart of sudden cardiac death
Sudden Cardiac Death is the largest cause of death, causing about 325,000 adult deaths in the US each year.
It is responsible for more than 50 per cent of all heart disease-related deaths. Sudden cardiac arrest is NOT a heart attack (myocardial infarction), though it can occur during one. A heart attack occurs when there is a blockage in one of the arteries to the heart; with that, the blood cannot reach the heart muscle, and the latter becomes partially damaged. In contrast, sudden cardiac arrest occurs when the electrical system to the heart suddenly malfunctions, becoming very irregular and dangerously fast. The heart may quiver (ventricular fibrillation) and blood is not delivered to the body, particularly the brain. Death follows within minutes, unless emergency treatment is begun immediately.
What are the symptoms of sudden cardiac arrest?
Some people may experience a racing heartbeat or feel dizzy, alerting them that a potentially dangerous heart problem has started. In over half of the cases, however, SCD occurs without prior symptoms.
What are the risk factors of sudden cardiac arrest?
• Previous heart attack, particularly if there is a large area of residual damage, weakening the performance of the heart muscle below 40 per cent.
• Coronary artery disease: 80 per cent of SCD cases are linked with this disease.
• Some forms of cardiomyopathy (or heart muscle disease).
• History of congenital heart defects.
• Significant changes in blood levels of potassium and magnesium.
• Illicit drug use, or rarely, some prescription drugs that may increase the risk for life-threatening arrhythmias.
• Personal or family history of fainting, abnormal heart rhythms or cardiac arrests.
Can sudden cardiac death be prevented?
Yes … to a good extent! Your doctor will ask you a detailed personal and family history, and may want to pursue tests that could shed more light on your cardiac situation, like an electrocardiogram, blood/urine work, ambulatory rhythm monitoring, echocardiogram, stress evaluation, cardiac catheterisation, cardiac MRI, and even an electrophysiology study (a special invasive test to analyse cardiac electrical system).
Medications: There are no drugs that would directly prevent sudden death. However, to help reduce its risk, doctors may prescribe medications to people who have had heart attacks, coronary disease and coronary risk factors — diabetes, hypertension, high cholesterol — or arrhythmias, as all these conditions may lead to SCD.
Implantable cardioverter-defibrillator (ICD): For people whose cardiac profile puts them at sudden-death risk, an ICD may be inserted as a preventive treatment. It is a small machine similar to a pacemaker that is designed to detect, then stop, the dangerously fast heart rhythm. In fact, a defibrillator constantly monitors the heart rhythm; when it detects a very fast one, it delivers a special pacing intervention or a small electrical shock to bring it back to normal.
Interventions or surgery: For patients with coronary disease, an interventional procedure such as angioplasty (blood vessel repair) or bypass surgery may be needed to improve blood flow to the heart muscle and reduce SCD risk. For patients with other conditions, such as a cardiomyopathy or a congenital heart defect, an interventional procedure or surgery may be needed to correct the problem. Catheter ablations may also be used to treat abnormal heart rhythms.
Can sudden cardiac arrest be treated?
Sudden cardiac arrest can be treated and reversed, but emergency action must take place immediately. Survival can be as high as 90 per cent if treatment is initiated within the first minutes after cardiac arrest. It decreases by ten per cent each minute longer it takes to initiate therapy. If you witness sudden cardiac arrest, dial 911 and initiate CPR. It uses repetitive chest compressions and periodic breathing into the person's airways that keep enough blood and oxygen flowing to the brain until a normal heart rhythm is restored with an electric shock to the chest (or defibrillation). Emergency squads use portable defibrillators for that purpose, though commonly, AEDs (ambulatory external defibrillators) are easily accessed in public locations and are intended to be used by citizens who observe cardiac arrest. If done properly, CPR can save a person's life.
* In memory of Niall Aitken, MD, who died suddenly on November 20.
Joe Yammine is a cardiologist at Bermuda Hospitals Board. He trained at the State University of New York, Brown University and Brigham and Women's Hospital. He holds five American Board certifications. He was in academic practice between 2007 and 2014, when he joined BHB. During his career in the US, he was awarded multiple teaching and patients' care recognition awards. The information herein is not intended as medical advice nor as a substitute for professional medical opinion. Always seek the advice of your physician. You should never delay seeking medical advice, disregard medical advice or discontinue treatment because of any information in this article