How Did That Happen? The Cause of Sudden Coronary Death in “Healthy” People
My friend Edward is cautious when it comes to his health. This past spring he wasn’t feeling like his normal self and went to the hospital for testing. Two-and-a-half days and $40,000 later (insurance covered 70%), Edward was released to go home, feeling relieved and happy. When I asked him why he made such a fuss about feeling a little unwell he told me the following story.
Edward had a friend who was a very successful real estate businessman. He was 50 years old and in great physical shape. He watched his diet, took supplements and was very serious about his fitness training. He often exercised with a group of marines and had no problems keeping up. One day, after he had finished a run on the treadmill, he began to experience some pain. At first he ignored it, but it just got worse. When his 16-year-old son suggested calling an ambulance, he insisted he was fine and that they should just drive to the hospital. In the car he began to lose his breath and then collapsed. He died while his son was behind the wheel. What a tragedy! The autopsy revealed that he had suffered from severe atherosclerosis, with large amounts of arterial plaque, and this is what led to his sudden death.
Vulnerable Plaque: A Ticking Time Bomb
Sudden cardiac death can have different causes. But generally they can be ischemic or nonischemic in nature (“ischemic” means a restriction of blood supply to the tissues). Atherosclerosis is a disease in which plaque builds up in the arteries. It can be found in adolescence and even earlier. The amount of plaque build-up, which varies widely from individual to individual, determines the severity and threat of the atherosclerosis. Some people suffer from heart disease for many years and show signs of angina. Others — specifically middle-aged men — suffer from acute myocardial infarction (heart attack) and sudden coronary death without ever having any symptoms. Why? Gender aside, it’s important to understand what causes arterial plaque to clog arteries.
Plaque on the arterial wall can be divided into two main types, stable plaque and vulnerable (unstable) plaque. Characteristics of vulnerable plaque include:
1. A high percentage of lipid cholesterol in the core—about 3-4 times more than stable plaque. In essence you might compare vulnerable plaque to a fragile oil bubble.
2. Severe local inflammation. The body’s reaction to foreign invaders is to stimulate an immune response. The purpose is to remove any damaging threat, clean up dead cells and start tissue repair. The problem is that the amount of inflammation can often cause more harm than good—too much or too little can cause an adverse impact on health. In fact, chronic inflammation is implicated in many degenerative diseases.
3. The relatively thin fibrous cap covering the surface of the vulnerable plaque causes instability.
Plaque rupture happens much more often with vulnerable plaque. Vulnerable plaque is one of the leading risks when it comes to heart attacks or sudden cardiac death.
Blockage is Caused by Plaque Rupture, Not Vascular Plaque
Sudden heart attacks are generally not caused by the clogging of blood vessels due to the plaque itself. Rather, they mostly result from vulnerable plaque rupture, followed by induced local coagulation and cardiovascular blockage. Sometimes broken pieces of plaque and small clots flow through the bloodstream into smaller vessels, causing blockages. This can induce an acute ischemic stroke or other diseases.
Vulnerableplaque is relatively small, and the degree of vascular obstruction usually does not exceed 30-40%. In fact, in the early formation of plaque growth, the elastic vessel walls extend outwardly and plaque does not invade the blood vessel lumen (the space inside the tube), so there is little change in vessel diameter. Only when plaque covers about 40% of the peripheral vascular diameter does it begin to invade the lumen.
Vulnerable plaque does not usually cause significant blood vessel blockage, so it’s difficult to detect with routine medical testing. Because it is often so small, it can be present without affecting people in their normal activities, and may not show any clinical symptoms. The problem is, vulnerable plaque can suddenly rupture, causing the lipids to overflow, followed by clotting and blood vessel blockage. This is why seemingly healthy people can suffer from a sudden heart attack.
Vulnerable Plaque Control in Reduction of Cardiovascular Disease
It is possible for vulnerable plaque to turn into stable plaque and even calcification may occur. Stable plaque may continue to grow and cause blood vessel blockage, although risk of sudden death is lower than with its vulnerable counterpart. Extensive blood vessel blockage will usually produce clinical symptoms, which gives the opportunity to initiate timely treatment and control the disease. This decreases the probability of plaque rupture. Even when the artery is severely blocked, collateral vessels may form to bypass the blockage. This can improve the local blood supply and reduce symptoms of infarction (obstruction of the blood supply).
Contrary to the popular belief, plaque can be reduced and reversed. In fact, stabilization and even complete regression of vulnerable plaque is now possible with interventions such as medical treatment, proper diet, and other lifestyle changes. So there is hope that we will prevent most acute heart attacks and sudden coronary death at every age, but especially for older people.
- Douglas P. Ziper, Hein J.J. Wellens (2006) Sudden Cardiac Death. Circulation Research 99:567-569