1. Atrial Fibrillation: A very fast and irregular beating or quivering of the upper two chambers of the heart. This condition happens just before a cardiac arrest or just as the heart stops altogether.

2. Cardioversion: Delivery of a shock to the heart to interrupt arrhythmias. Paddles on the chest or electrodes placed directly on the heart are used.

3. Hypertrophic Cardiomyopathy: Is a disease of the myocardium (the muscle of the heart) in which a portion of the myocardium is thickened without any obvious cause. It is most well known as a leading cause of sudden cardiac death in young athletes.

4. Myocardial infarct: Occurs when one or more regions of the heart muscle experience a severe or prolonged decrease in oxygen supply caused by a blocked blood flow to the heart muscle, which causes the heart to stop. Also known as a heart attack.

5. Premature Arterial Contraction: An early heartbeat started by the atria.