Sudden Cardiac Death (SCD) - Who, Where, Why ?

Dateline: 10/18/98

Have you read my first article on SCD syndrome - Sudden Cardiac Death - What is it ?

What exactly is SCD ?

The syndrome of SCD progresses through four stages:

• The Prodrome - In this phase, new or worsening cardiovascular symptoms like breathlessness, chest pain, palpitations, fatigability and weakness are noticed. The prodrome may last for weeks to months before the acute event.
• The Onset - This is an abrupt change in the clinical status that leads within an hour to a cardiac arrest. Arrhythmias, low blood pressure, angina, breathlessness or light headedness may be present in this stage.
• Cardiac Arrest - The words are dramatic in themselves - CARDIAC ARREST. The heart stops, and there is a sudden collapse caused by the loss of an effective circulation of blood as the heart stops beating. The brain no longer receives blood supply, so there is a loss of consciousness.
• Biological Death - This is the irreversible final stage, reached after resuscitation attempts have failed to restore heart and brain function.

Epidemiology - The magnitude of the problem

Sudden Cardiac Death (SCD) receives global attention when famous athletes die of it. While the world was shocked by Florence Joyner's sudden demise, what remains generally unknown is that nearly 300,000 Americans die from SCD every year - a figure that represents 50 % or more of all cardiovascular deaths in the United States !

What is more worrying is that, despite the recent decline in coronary heart disease mortality in the US, the fraction of coronary deaths that are sudden and unexpected has NOT CHANGED.

If these numbers are hard to digest, here is something simpler and more scary - 1 or 2 out of every 1000 Americans will die of SCD each year !

Demographics - Who is likely to die of SCD ?

Extensive studies of victims of SCD have provided some demographic data.

1. SCD is common in two age groups - from birth upto age 6 months (when it is called Sudden Infant Death Syndrome or SIDS), and between 45 and 75 years of age when it is primarily a consequence of coronary artery disease.
2. SCD has a hereditary basis in some families, for instance in those with the Long QT syndrome, hypertrophic cardiomyopathy (HOCM) or familial SCD.
3. SCD is commoner in males
4. As many as 75% of SCD victims had had an earlier heart attack (myocardial infarction)
5. Marked left ventricle failure, with an ejection fraction below 30%, is a very strong predictor of SCD
6. Frequent Ventricular ectopy, a form of heart rhythm disturbance, can be a predictor of SCD

Recommended Reading:

Sudden Cardiac Death : Past, Present, and Future
(American Heart Association Monograph Series)
by Sandra B. Dunbar(Editor), et al / Hardcover / Published 1997
Buy it from Amazon.com. Visit the Heart Bookstore for more titles on SCD.

To learn more about Sudden Cardiac Death syndrome, read the next article in this series.