Human Heart
The heart is a muscular organ in all vertebrates responsible for pumping blood through the blood vessels by repeated, rhythmic contractions.

Heart Attack
A heart attack occurs when blood flow to a section of heart muscle becomes blocked.

Heart Block
Heart block is a problem that occurs with the heart's electrical system. This system controls the rate and rhythm of heartbeats.

Heart Failure
Heart failure is a condition in which a problem with the structure or function of the heart impairs its ability to supply sufficient blood flow to meet the body's needs.

Bradycardia
Bradycardia is defined as a resting heart rate of under 60 beats per minute.

Sick Sinus Syndrome
Sick sinus syndrome is a group of abnormal heart rhythms presumably caused by a malfunction of the sinus node, the heart's primary pacemaker.

Sudden Cardiac Arrest
The abrupt cessation of normal circulation of the blood due to failure of the heart to contract effectively during systole.

Tachycardia
A heart rate that exceeds the normal range for a resting heartrate.

Ventricular Fibrillation
A condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them tremble rather than contract properly.