Tachycardia:  Excessive rapidity in the action of the heart, usually above 100 beats per minute in an adult.

Thrombus:  A clot in the cardiovascular system.

Torsade de Pointes (Twisting of the points):  A unique form of ventricular tachycardia that can be congenital in origin or can result from antiarrhythmic or psychotropic drug therapy, hypocalcemia, or acute myocardial infarction.