Give yourself a natural bypass before you need a surgeon to perform a more painful and hazardous one?

When cholesterol-clogged plaque narrows an artery that feeds the heart, the body responds by trying to bulk up tiny blood vessels in the heart.

As these so-called collateral vessels grow more muscular and interconnected, they begin to reroute some of the blood flow around the blockage. Scientists have been trying for years to nudge collateral blood vessels to develop and prosper, but without great success. However, you can do it at home without anything more high-tech than a comfortable pair of shoes, reports the Harvard Heart Letter in its January 2008 issue.

Growing new collateral blood vessels can ease chest pain (angina), limit heart attack damage, improve survival, and perhaps even offer extra time for emergency therapy in the case of a heart attack. And exercise can boost these blood vessels.

Exercise dramatically increases blood flow through the coronary arteries. The inner lining of the arteries responds to this "stress" much as it does to the stress of atherosclerosis, by stimulating collateral blood vessels to elongate, widen, and form new connections.

The Heart Letter notes that a little bit of exercise won't do the trick. You need to push your heart. If you aren't used to exercising, that may mean brisk walking. Any activity that gets your heart beating faster will do as long as you keep it up for 20 to 30 minutes at a time and do it several times a week.

Exercise is a great way to prevent heart disease, and a host of studies show that it can help some people with narrowed coronary arteries safely avoid bypass surgery or angioplasty. The Harvard Heart Letter asks: Why not give yourself a natural bypass before you need a surgeon to perform a more painful and hazardous one?

Also in this issue:

• Genetic testing to predict heart risk
• New technology in implanted left ventricular assist devices
• Stem cells to regenerate heart muscle
• Ask the doctor: Diuretics for people with electrolyte imbalances? Can a massage cause a stroke?