Arrhythmias are categorised into two types, being tachycardia and bradycardia.
Tachycardia Tachycardia is when your heart beats too fast, generally more than 100 beats per minute. Some forms of tachycardia are easily treated and not serious, but others can be life threatening. Tachycardia can be a normal response to physical activity, but can also be a sign of a medical problem.
The two main types of tachycardia are supraventricular tachycardia and ventricular tachycardia. Supraventricular tachycardia is a rapid heartbeat that starts in the atria or AV node, and is not usually life threatening. Common types of supraventricular tachycardia are atrial flutter and atrial fibrillation.
Ventricular tachycardia is when the ventricles beat too fast and is very dangerous. If ventricular tachycardia becomes so severe that the ventricles can’t pump effectively, it can lead to ventricular fibrillation. This life-threatening condition occurs when the electrical signal that should trigger your heartbeat splits away in uncontrolled ‘waves’ around the ventricles. It must be corrected immediately.
Ventricular fibrillation isn’t something that happens from stress. In most every case, a person is at risk for this if he or she has had a heart attack, has cardiomyopathy, has a congenital heart defect, has suffered an electrical shock, or abuses certain drugs. Her brother said she had no heart problems. Of course, only her physician knows for sure; but one would think the coroner would get her medical records in order to determine a cause of death. Prior cardiograms will tell the tale, if she had any heart problems or was on any medication for a heart condition. This is a diagnosis of “exclusion”, since they cannot do a cardiogram on a non-beating heart. They found no other cause, so settled on this as the explanation, imo. Examination of her body would have shown any preexisting condition that may have put her at risk factor for ventricular fibrillation. VP Cheney has an internal defibrillator for just this kind of situation—to shock his heart should it go into V-fib or V-tach. Of course, his prior heart attacks are what put him at risk.