Why sudden cardiac arrest happens is not clearly understood. It is most often caused by a dangerous heart rhythm called ventricular fibrillation.
SCA can happen to anyone at any age. But the risk is greater among certain people. For example, it is more likely if you’ve had an SCA. And it’s more likely if a parent, child or sibling has had one. Men and African Americans also are at greater risk.
Still, certain diseases or conditions can cause the heart’s electrical system to misfire and lead to SCA. These include:
• Coronary heart disease
• Structural changes in the heart, for example, a thickened heart muscle/enlarged heart
• Heart failure with reduced pumping function, often referred to as a low ejection fraction (ejection fraction less than 35%)
• Heart attack – 75% of people who suffer sudden cardiac arrest were found to have had a heart attack, many of which went undiagnosed; survivors of heart attack are 4 to 6 times more likely to have SCA than the general population
• Physical stress such as trauma, blood loss, dehydration/electrolyte imbalance or (in rare cases) very intense physical activity
• Heart problems you are born with make you more prone to heart rhythm problems.
Some studies have linked SCA to low levels of potassium or magnesium in the body.