DOCTOR'S VIEW ARCHIVE

Heart Disease & Stroke - Progress Through Research

Gene therapy designed to grow new blood vessels in the heart muscle led the list of the top 10 research advances in heart disease and stroke compiled by the American Heart Association. The list, first created in 1996, recognizes achievements in basic and clinical research that may have the most impact on the prevention and treatment of cardiovascular disease.

The most recent edition of the list is as follows:

1. Gene therapy to create a "natural" bypass around blockage
2. New drugs to prevent clots causing heart attacks and strokes
3. Relationship between inflammation and heart attacks
4. Detection of unstable plaques in vessels by imaging technology
5. Heart cells recover thanks to left ventricular assist device
6. Tobacco's effects from fewer than 10 cigarettes a day
7. Impact of diet and exercise on blood cholesterol levels
8. Education of people with heart symptoms to go to the emergency room
9. Epidemic of cardiovascular disease and stroke
10. Nobel Prize for discovery of nitric oxide (which relaxes blood vessels).

This list was issued at the end of 1999 by the American Heart Association and is based upon developments reported during 1998. We will comment upon each of these ten advances:

1. Gene therapy to create a "natural" bypass to circumvent plaques obstructing the heart's blood vessels.

People with heart disease may be routinely treated in the future by a genetically engineered technique that induces the growth of new blood vessels. The new vessels would help restore blood flow to the hearts of people whose arteries are obstructed by plaques. By impeding blood flow, these obstructions can cause severe chest pain (angina) and heart attacks.

Scientists reported that they had used a human growth factor called FGF-1 (fibroblast growth factor-1), obtained through genetic engineering, to induce the growth of new blood vessels in 20 patients with heart disease. In their three-year follow-up study of the patients, the scientists reported that the treatment resulted in a two to three times more blood flow to the heart.

Another growth factor called VEGF (vascular endothelial growth factor) also appears capable of inducing new blood vessel growth for the heart. Gene therapy may thus become an important part of the treatment of heart disease.

2. New drugs to prevent clots causing heart attacks and strokes.

Drugs called platelet blockers (or, more formally, IIb/IIIa receptor blockers) were found to keep blood platelets from clumping and forming blood clots that can trigger a heart attack or stroke. In this regard they are like aspirin. However, the platelet blockers -- eptifibatide (brand name: Integrilin), tirofiban (Aggrastatin) and abciximab (ReoPro) -- are more potent than aspirin. And they are administered intravenously (IV).

To test the usefulness of the platelet inhibitor drugs, a total of about 32,000 heart patients received a platelet blocker as part of their treatment for a heart attack or severe chest pain. Some individuals received only the platelet blockers while others were treated with a platelet blocker plus angioplasty -- a procedure that uses a balloon-tipped catheter to restore blood flow in the blood vessel. Those who received the platelet blockers had a 30 percent reduced risk of all-cause death than those who did not receive the drugs. The individuals who particularly benefited from the drugs were those who also were treated with angioplasty. In these individuals the drug was administered just as the coronary arteries were being opened by inflation of the balloon-tipped catheters used for the procedure.

3. Relationship between inflammation and heart attacks.

It is recommended that people at elevated risk for heart attack and stroke take aspirin because it helps prevent the blood clots that can cause heart attacks and strokes. Aspirin, however, may have another benefit for people at high risk for heart attacks and stroke. Aspirin is an anti-inflammatory drug, and research suggests that the body's inflammatory response may play a role in cardiovascular disease.

The area of the blood vessel where an obstructive plaque develops can become inflamed. The inflammatory response may not be localized to the blood vessel wall in that area. It also can occur throughout the bloodstream. This systemic inflammation may explain the development of blood clots on top of relatively stable plaques.

4. Detection of unstable plaques in vessels by imaging technology.

Most heart attacks and strokes are caused by blood clots unleashed by plaques in the blood vessels. The clots, which are formed when the plaques rupture, block blood flow to the heart and brain, thereby causing a heart attack or stroke. It was found that magnetic resonance imaging (MRI) can detect plaque obstructions that are prone to rupture in the carotid artery (a blood vessel in the neck that carries blood to the brain), and the thoracic aorta (the large blood vessel that carries blood from the heart to the body). MRI can be adapted to freeze-frame the beating heart so that "unstable" plaque in the coronary arteries can be detected.