Which cardiovascular condition is known as the "silent killer" because it usually presents no overt symptoms?

The cardiovascular condition with no overt symptoms and known as the "silent killer" is the hypertension.

Blood pressure is recorded in two numbers. The upper limit is the systolic pressure and the lower limit is diastolic pressure. Systolic pressure is the maximum pressure at which the heart pumps the blood to the different parts of the body and it is 120 mm/Hg. Diastolic pressure is the minimum pressure in the arteries during the relaxation of the heart and it is 80 mm/Hg. The normal blood pressure is given by 120/80 mmHg.

Hypertension, also known as the high blood pressure is a condition in which the blood pressure in the arteries is constantly high or elevated. Blood pressure with a value higher than 140/90 mm/Hg is considered to be hypertension. It is a silent killer because it normally does not exhibit any distinctive symptoms. The most common symptoms of hypertension are head ache, problems with vision, fatigue which are often ignored and remain untreated. This untreated, long-term hypertension is one of the important causes of cardiac diseases, renal failure, stroke and other fatal conditions.

Thus, no overt symptoms and the impact of hypertension associated with many life-threatening diseases makes it a "silent killer".