Heart attacks and strokes are mostly caused by build up of fatty plaque, which leads to blockage of blood supply to the heart muscle or brain. As far as heart attacks are concerned, much research has been done to identify their cause and occurrence. It is learned that with time, the fatty plaque either would grow in size with progressively blocking the artery or may rupture leading to formation of blood clot and thus instantly closing the artery. This latter property of ripping apart is thought to be the most common form of heart attack and is responsible for 7 out of 10 heart attacks. Such plaques are known as vulnerable plaques and are the subject of much scientific deliberations and contemplations.

VULNERABLE PLAQUE:Heart attack occurs when blood and oxygen supply to the heart muscle is blocked due to atherosclerotic plaque. These plaques, when occupy 70% of the lumen of the artery become clinically significant. Such stable plaques may cause chest pain and may lead to total blockage of the artery leading to heart attack. These plaques are easily diagnosed by coronary angiography and are treated by balloon angioplasty or bypass surgery. But increasingly it has become more apparent, that majority of the heart attacks are actually caused by smaller vulnerable plaques than these. These smaller unstable plaques are actually blocking only 40 to 50 % of the coronary artery lumen and can be easily missed at times on angiography. They have a high chance of ripping apart and causing abrupt heart attack. Thus, determining the degree of stenosis by angiogram, currently the routine method for clinical decision-making will be quite unreliable in predicting most of the future heart attacks. Such vulnerable plaques have large amount of cholesterol, are softer and have a thin wall, which ruptures easily, causing instant blockage of the artery by formation of blood clot. The medical term for this is atherothrombosis. The thrombosis halts the blood flow in the vessel, which causes damage of the heart or brain, resulting in heart attack or stroke. The artery may also squeeze during the event because of inflammation and thrombus formation.

SIGNIFICANCE OF VULNERABLE PLAQUE:Sadly, all revascularization treatments are directed at the larger non-vulnerable plaques, which are less likely to cause heart attacks. Thus, those who are without symptoms presently and would get heart attack in the future, are being missed. These dangerous plaques are ubiquitously common and most of us who have them do not feel any symptoms. There are innovative imaging modalities such as intravascular ultrasound, thermography and near-infrared spectroscopy available now, which can image such “hot plaques.” But such modalities are largely investigational and are currently used largely for research purposes only. The best approach is again in lifestyle modification and taking care of risk factors. Drugs such as aspirin and statins are helpful, but should only be taken under physician supervision. Heart-healthy habits still play the most important role in reducing the risk of vulnerable plaque formation and thus saving us from their catastrophic consequences.