Biology – 8.2 Transport in humans | e-Consult

Coronary heart disease (CHD) occurs when the coronary arteries, which supply blood and oxygen to the heart muscle, become narrowed or blocked. This blockage is most often caused by the buildup of a fatty substance called plaque, a process known as atherosclerosis. Plaque is composed of cholesterol, fats, calcium, and other cellular debris.

As the plaque accumulates, the arteries become progressively narrower, reducing blood flow to the heart muscle. This reduced blood flow leads to a condition called ischemia, meaning insufficient oxygen supply. The heart muscle requires a constant and adequate supply of oxygen to function properly. Ischemia can manifest in several ways:

• Angina: This is chest pain or discomfort caused by temporary ischemia. It occurs when the heart muscle is working harder than usual and doesn't receive enough oxygen.
• Myocardial Infarction (Heart Attack): This occurs when a coronary artery is completely blocked, completely cutting off blood supply to a portion of the heart muscle. Without oxygen, the heart muscle cells begin to die. The extent of damage depends on the duration of the blockage.

The consequences of the blockage are significant and can lead to heart failure, arrhythmias (irregular heartbeats), and even sudden cardiac death.