Many of these gaseous compounds alter as the temperature of the burning cigarette rises and falls with inhalation. Evidence also indicates that such damage diminishes when one quits smoking. The two most commonly cited culprits in cigarette smoke are nicotine and carbon monoxide. Nicotine, best known as the addictive agent in cigarettes, is readily absorbed through tiny air sacs in the lungs and is metabolized primarily in the liver. Atherosclerosis, or the build-up of fatty substances or plaque in the inner lining of the artery, is promoted and accelerated by nicotine through several mechanisms.
Nicotine damages the endothelium, or cells lining the blood vessels.
Nicotine in the bloodstream also lowers one's threshold for ventricular fibrillation, the most serious cardiac rhythm disturbance. Smokers are 20 times more likely to experience a vasospasm, also known as a coronary artery spasm, due to nicotine. Simultaneously, nicotine and other components of cigarette smoke acutely increase blood pressure and heart rate. When heated, materials in a cigarette convert to numerous gaseous agents, among them, carbon monoxide. Carbon monoxide reduces the amount of oxygen carried by the red blood cells, which consequently reduces oxygen in the tissues.