Cigarette smoking, high blood pressure and high cholesterol levels are the three most dangerous risk factors for coronary heart disease - with smoking being the most threatening. Fully 30 percent of all heart disease deaths are caused by smoking.
Inhaling tobacco smoke makes several things happen to the body almost immediately. Within one minute of starting to smoke, the heart rate begins to rise, blood pressure goes up and arteries become narrower. This makes the heart work harder to get the oxygen to other parts of the body. Carbon monoxide in the smoke reduces the ability of the blood to carry oxygen, which further strains the heart.
Smoking tends to raise cholesterol levels, which leads to clogged arteries. It also causes the walls of the arteries to become stiff and hardened and puts them at risk for rupture. Smokers risk blood clots that form and block the artery, which can result in a fatal heart attack, a stroke or other life-threatening conditions.