How can smoking increase my risk for heart disease?

You already know that smoking damages your lungs and increases your chance of developing dangerous lung diseases. You might also have heard that smoking is bad for your skin and eyes. But did you know that smoking can also hurt your heart? Here's what it can do:

• Speed up atherosclerosis. Smoking damages the tissues of the artery walls, constricts blood vessels, and raises blood cholesterol. All of these can speed the buildup of fatty plaque in your arteries -- and increase your risk for heart problems.
• Increase strain on your heart. When atherosclerosis narrows blood vessels, your heart has to work harder to pump blood throughout the body. Nicotine also causes your heart rate to increase and the blood vessels to constrict -- both of which add to the strain on your heart.
• Lower the amount of oxygen in your blood. Because a smoker's heart muscle is working harder, it requires more oxygen. Yet smoking actually decreases the oxygen level in the blood. The carbon monoxide in cigarette smoke replaces as much as 15% to 20% of the oxygen normally carried by the red blood cells.
• Increase your risk of spasms and blood clots in your coronary arteries. Spasms and blood clots can cause heart attacks.