STENTS and Prevention of Heart Attacks

By Paul E. Lemanski, MD, MS, FACP

Editor’s Note: This is the 92nd in a series on optimal diet and lifestyle to help prevent and treat disease. Any planned change in diet, exercise or treatment should be discussed with and approved by your personal physician before implementation. The help of a registered dietitian in the implementation of dietary changes is strongly recommended.

Medicines are a mainstay of American life and the healthcare system, not only because they are perceived to work by the individuals taking them, but also because their benefit may be shown by the objective assessment of scientific study. Clinical research trials have shown that some of the medicines of Western science may reduce the risk of heart attacks, strokes and cardiovascular death.

In the first 91 installments of the Non-Medicated Life, certain dietary practices and a healthy lifestyle have been shown to accomplish naturally for the majority of individuals most of the benefits of medications in the prevention and treatment of chronic medical conditions such as hypertension, high cholesterol, pre-diabetes, diabetes and heart disease. For those at highest risk, including those with documented established coronary artery disease, maximal lifestyle improvement as well as medication has been the general recommendation of this column. 

Recently, the results of a new study of stable heart patients comparing optimal medical therapy (OMT) of coronary artery disease with the invasive approach of STENT placement corroborates this general recommendation. OMT includes optimal medications to reduce cholesterol and blood pressure, aspirin, and diet and lifestyle improvement including daily exercise, weight loss when obese and tobacco cessation. 

Indeed, the study, called the ISCHEMIA trial, suggests that with respect to cardiovascular outcomes including heart attack, and heart attack death, OMT alone is no different than OMT and STENT placement. Thus, contrary to popular belief, the invasive approach of STENT placement in the coronary arteries of stable heart patients does not help prevent a heart attack or heart attack death beyond what can be accomplished with diet, exercise and medication alone.

While a significant majority of coronary artery disease patients fall into this stable category, it is important at the onset of the discussion to describe what a coronary artery STENT is, and emphasize that STENT placement in an unstable patient (someone having increasing symptoms or presenting with a heart attack) can be life-saving and even in a stable patient can have a major impact on quality of life, due to a reduction or elimination of exercise-induced chest pain. Only the assessment of one’s cardiologist and primary care physician can reliably determine who may or may not be an appropriate candidate for a STENT.

A coronary artery STENT is an expandable metal lattice resembling a short, thin tube which is introduced into a narrowed heart artery to re-establish normal blood flow past a cholesterol plaque. Cholesterol plaques grow within the walls of diseased heart arteries and may narrow the lumen or central space of the artery where blood flows. 

Prior to placement, the STENT surrounds a collapsed balloon at the end of a long thin tube known as a catheter. A cardiologist threads the catheter through the arteries of the leg or arm back toward the heart and finally down the arteries of the heart itself to the area of narrowing. Once in position, the balloon is inflated thereby expanding the metal lattice to flatten the cholesterol plaque. (Alternatively, the flattening may first be done by a balloon without STENT, and repeated by a balloon with STENT.) The balloon is then deflated, the catheter removed, and the expanded STENT remains to continue flattening the plaque, thereby reducing the narrowing and re-establishing normal blood flow.

The ISCHEMIA trial failed to show that a STENT reduced cardiovascular death, heart attack, unstable chest pain, or heart failure among patients with stable coronary artery disease. More specifically, stable disease meant the frequency of exertion-induced chest pain and the degree of activity required to induce the pain was similar week to week. Stable disease was also defined as moderate to severe ischemia (the heart muscle downstream from a plaque not getting enough blood) on stress testing.

The ISCHEMIA trial corroborated the findings of the COURAGE trial from 2007 that also found no survival benefit to STENT placement over OMT. COURAGE, however, had flaws in study design that called some of its conclusions into question. Those design flaws were addressed by the ISCHEMIA trial.

From a pathophysiological perspective, however, the ISCHEMIA trial makes some sense. It has been known for years that the majority of heart attacks occur from blood clots that form on smaller rather than larger cholesterol plaques. For example, a cholesterol plaque that narrows the artery lumen (where the blood flows) by 30% is much more likely to be the cause of a heart attack than one that narrows the artery 90%. This is because the smaller plaque is compositionally different than the larger plaque, the former containing more oxidized extracellular lipid, the latter containing more smooth muscle cells and calcium. Oxidized lipid may make plaque more likely to crack and tear the inner most cell layer of the artery wall allowing platelets to form a clot on top the tear. 

While more heart attacks occur with smaller plaques, it is the larger plaques that significantly narrows the artery that causes symptoms of exertion induced chest pain or angina. STENTS are only approved for use with larger plaques, thus they do not treat the actual cause of heart attack in stable patients.

What then does successfully treat the smaller plaques that are the actual cause of heart attacks? Preventing heart attacks requires maximally reducing the LDL or bad cholesterol, reducing the blood pressure, stopping tobacco, and improving metabolic parameters. All part of optimal medical therapy (OMT) with medication and aggressive lifestyle improvement, including improvement of body weight when elevated, a heart healthy diet and daily exercise. Indeed, the Lyon Diet Heart Study using a high omega-3 Mediterranean diet, as compared to a prudent Western diet, reduced cardiac death and non-fatal heart attack by 70%.

In summary, the prevention of heart attacks requires maximally aggressive lifestyle improvement, and in those with established coronary artery disease maximal lifestyle improvement and medication. STENTS do not prolong life or prevent heart attacks in those with stable disease, but may be life-saving in those with unstable disease or those presenting with a heart attack. STENTS will, however, reduce exertion-induced chest pain frequency and severity, and thereby improve the quality of life. 

Lifestyle improvement, medication, and STENTS are part of the armamentarium for the treatment of coronary artery disease, but invasive treatment should be reserved for those for whom it is most appropriate.

Paul E. Lemanski, MD, MS, FACP (plemanski3@gmail.com) is a board-certified internist practicing internal medicine and lifestyle medicine in Albany. Paul has a master’s degree in human nutrition, he’s an assistant clinical professor of medicine at Albany Medical College, and a fellow of the American College of Physicians.