August 2014

Atherosclerotic Heart Disease

Atherosclerotic Heart Disease

 

The Problem

Atherosclerotic heart disease is the leading cause of death in the U.S., causing more than 490,000 deaths in 1993. The American Heart Association estimated that more than 1.5 million Americans will suffer a myocardial infarction (MI) in 1996, and one third of these people will die suddenly from their Heart Attack. Atherosclerotic Coronary Artery Disease, sometimes abbreviated as CAD, is the underlying cause for most heart attacks. It is also one of the most common causes for congestive heart failure (CHF), cardiac arrhythmias (irregular heart beat), and sudden death due to heart attack (often referred to as a myocardial infarct -blockage of a coronary vessel - an MI).

Heart attack is generally unusual in men and women under 40. However, it does occur. During the teens, twenties and thirties cholesterol plaque builds up in the arteries of the heart and brain gradually increasing the risk of heart attack and stroke. As people age the risk steadily increases until it becomes a major problem in men over 50 and in women the leading cause of death in the post menopausal era. The risk of atherosclerotic heart disease increases substantially with smoking, hypertension, diabetes, high cholesterol, and family history of heart disease. Although the total numbers of deaths from heart disease have decreased steadily over the past thirty years in the U.S., it has been estimated that it is about to begin rising again over the next 30 years because the total number of people over 60 years of age is increasing. Estimates suggest that the cost of medical care and lost economic productivity due to heart disease in the U.S. will exceed $ 60 billion in 1995-1996.

Often the only symptom of CAD is chest pain. However, this may be preceded by many years by a host of predisposing symptoms such as high blood pressure, elevated cholesterol especially elevated LDL-Cholesterol. Elevated triglyceride has in recent years also been associated with an increase risk of CAD.

For many Angina (also referred to as Symptomatic or Ischemic Heart Disease) occurs when there is insufficient blood flow to the heart muscles and they actually are starving for oxygen and needed nutrients) is the first presenting symptom of advanced CAD, however for many people the first real evidence of CAD may be a heart attack or sudden death. It has been estimated that somewhere in the range of 1-2 million middle-aged men have asymptomatic but meaningful coronary disease. This condition is commonly referred to as "silent myocardial ischemia."

In Diagram 1 we see a normal heart and its main structures are identified. In Diagram 2 we see a heart which is compromised and where the individual suffers from symptomatic, ischemic heart disease or angina pectoris.

 

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Diagram 1.

 

 

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Diagram 2.

 

Evaluation and Screening for CAD

There are generally two primary screening strategies used in medical practice today. Their overall goal should be directed at reducing morbidity and mortality from CAD. The first involves evaluation for controllable cardiac risk factors, such as hypertension, elevated serum cholesterol, smoking, physical inactivity, and diet.

The second strategy is based on early detection of asymptomatic CAD. The principal tests for detecting asymptomatic CAD include resting and exercise ECGs, which can provide evidence of previous silent myocardial infarctions and silent or inducible myocardial ischemia. Thallium-201 scintigraphy, exercise echocardiography, and ambulatory ECG (Holter monitoring) are less commonly used for screening purposes. The value of each of these tests must be judged on its ability to detect atherosclerotic plaque, and its ability to predict the occurrence of a serious of potential acute heart attack or sudden cardiac death.

Unfortunately there is little evidence that routine screening is the most effective means of reducing the incidence of acute coronary ischemia in otherwise asymptomatic persons. This fact underscores the great importance of prevention and reversal of early atherosclerotic disease.

A second important problem with screening for asymptomatic CAD is the lack of evidence that earlier detection leads to better outcomes. The only interventions proven to reduce heart attack in asymptomatic persons are modifications of risk factors such as smoking, high cholesterol, and elevated blood pressure. These strategies should be encouraged for all patients with modifiable risk factors, not only those with screening tests suggestive of CAD. The benefits of more aggressive treatments for coronary artery (e.g., cardiac bypass surgery, angioplasty) are unproven in asymptomatic persons.

What is the role of Cholesterol in atherosclerosis.

Triglycerides and their roles in CAD,