What do we know about heart attacks?
The heart is an important organ that helps to provide blood flow in order to transfer adequate nutrient and oxygen to different organs in our body. Despite the current medical advances in the past few decades, that is, the development of medications to control blood pressure, cholesterol, and diabetes, cardiovascular diseases remain the number 1 killer in the developed world. Within the United States, cardiovascular diseases constitute about 20% of our healthcare dollars, costing us about 444 billion USD per year. These includes the treatment of heart conditions such as heart failure, stroke, peripheral artery disease, and hypertension.
Heart disease begins with the development of atherosclerotic plaque within the intima of our blood vessels. There are multiple contributor to this chronic issue, these includes chronic inflammation in the blood vessel itself through various cytokine pathways including TNF-alpha, IL6, and IL1b. These inflammatory cytokine leads to increase vascular permeability, or leakiness in the blood vessels, that ultimately cause monocyte and macrophages infiltration into the endothelium. These macrophages then ingest LDL cholesterol, transforming in a foam cell that adheres to the blood vessel. Through time, these foam cells accumulate and lead to thickening of the blood vessel wall, as shown in figure 2 below. There are multiple pharmacological intervention such as preventing the formation of cholesterol, or cytokine signaling inhibitors that leads to the aberration of atherosclerotic plaque in the medical literature. Specifically, statin medication inhibits HMG-CoA reductase, one of the key enzyme in the synthesis of LDL cholesterol, has consistently been proven to reduce the mortality secondary to cardiovascular diseases.
Figure 1. Schematic showing the development of acute coronary syndrome, or heart attack (Top). The development of atherosclerosis (Bottom).
When the size of the atherosclerotic plaque reaches a certain threshold, it may break off from the vessel wall and lead to the obstruction of the coronary artery, causing ischemic injury and changes within the myocardium. This short term obstruction in blood flow leads to pressure overload, ischemic injury, apoptosis, and cardiac arrest.
How do we treat heart attacks in the hospital?
Heart attack is a general term that can be describing multiple cardiac conditions. We refer heart attacks as myocardial infarction, or acute coronary syndrome as clinicans. Within the realm of MI, we further characterized them base on EKG findings, that is, the measurement of electrical activity within the heart. The most common type of heart attack is an ST segment elevation myocardial infarction. In the hospital setting, the door to ballon and stent time appears to be the single most important factor in determining the mortality of patients suffering from an MI. However, prior to sending the patient to the cath lab for stent placement, one should be started on nitroglycern to reduce ischemic pain, oxygen supplementation for those who is in respiratory failure, initiation of beta blocker if no evidence of congestive heart failure, and heparin infusion for anticoagulation. The patient should then be transferred immediately to the cath lab to receive a stent placement for revascularization. These procedures are typical done via insertion of a catheter guidewire either from the groin through the femoral artery or through the radial artery of the arm. Patient may experience minor chest pain or chest discomfort as the ischemic injury is relieved immediately. Most academic centers in the US use drug-eluting stents, which are stents that were coated with immunomodulating medication to prevent acute rejection and clotting of the stent. Patient receive stents will also require a 1 year worth of dual ant-platelet therapy to prevent blood clot development. Although there are new trials and studies that suggest shorter duration of anti-coagulation may be non-inferior to the standard length of treatment, the consensus continues to put those people on DAPT for at least 1 year. The figure below shows a stent that is commonly used in cardiac catherization for restoration of blood flow. Interestingly, these stents can be placed throughout the entire coronary artery to form a “full-metal jacket” in severe cases.
Figure 2. Stent placement in the coronary artery. Photo adapted from heathline.
Does the vegan diet reduces the risk of coronary artery disease?
Interestingly, recent studies from multiple dietary gurus from the United States have suggested a vegan diet that may be beneficial in reversing coronary artery disease. Multiple physicians from the vegan society such as Dr. Neal Bernard, Dr. Caldwell Esselstyn, and Dr. John McDougall have consistently demonstrated the benefits of vegan diet in terms of preventing cardiovascular diseases in both mouse models and humans. As shown by the angiogram below, where contrast dye is inserted into the coronary artery to visualize the patency of the artery. You can clearly see that for those adhere to a vegan diet have reversed disease artery within 1 year of initiation of a vegan diet. This is a small study performed in 2014 by Dr. Caldwell Esselystyn from the Cleveland Clinic in Ohio to examine the role of dietary modification in coronary artery disease. They enrolled 198 individuals and placed them on a vegan diet and to be followed within 3 years. 89% of those individuals were adherent to the diet. 0.6% of the the vegans have further episodes of chest pain but 62% of those who did not adhere to the diet suffered from additional non-fatal heart attacks. That is a 100 fold decrease in heart attack risk! However, the studies did not clearly elucidate the precise mechanism of a plant base diet and it has been criticized by the scientific community due to many confounding variables. These questions include: Are those patient population more active? Are they more health conscious when compared to the general population? How does the health of the vegan population differ when compared to omnivorous healthy individuals? It is therefore a very controversial topic in the field of cardiology that will require further investigation. Please note that the current guidelines of the American College of Cardiology and the American Heart Association do not recommend a vegan diet as a mean to reverse heart disease at this point. They feel that there is insufficient data to suggest that vegan diet may be beneficial at this time. There are also other risks involving dietary and mineral deficiency associated with an imbalanced vegan diet.
Figure2. Heart disease reversal proposed by Dr. Caldwell Esselstyn from the Cleveland Clinic.
Can sexual activity precipitate a heart attack? what are some contraindication to Viagra?
One of the common question that I found during my cardiology clerkship at the VA hospital is regarding the use of PDE inhibitor for erectile dysfunction on patient with known risk factor for coronary artery disease. Unfortunately, the process of atherosclerosis occurs in most blood vessels within our body, that includes the blood vessels in the genital area and the lower extremities. The impeding blood flow causes flaccid penis and foot pain with significant physical activity. The use of sildenafil, or Viagra, has been shown to precipitate heart attack when used in conjunction with nitroglycerin, or other vasodilator medications. However, there is no sufficient evidence to support the use of these medication in patient who has stable coronary artery disease, including those who had stent placed previously. One also need to be mindful with their blood pressure as it may potentiate hypotension and increases the likelihood for dizziness and syncope. Thus, one should consult their cardiologist or primary care doctors to assess their risk before initiating on these agents.
Is it better to have a bypass surgery or placing a drug eluting stent?
- High cholesterol, type 2 diabetes, hypertension are risk factors for the development of coronary artery disease.
- Diet and exercise remains the best method to reduce the development of atherosclerosis in at risk population.
- The vegan diet appears to be beneficial in reducing the incidence and the progression of coronary artery disease. However, the mechanism remains poorly understood.
- The use of viagra can be detrimental in patients with unstable coronary artery disease and patient who is on certain medications.
- Both the coronary artery bypass graft surgery and the drug eluting stent are life-saving and there are a lot of ongoing research regarding the refinement of these procedures in the field of cardiology.
Jeffrey Lei, MSIV
University of Utah School of Medicine