Introduction to Heart Failure. Cardiovascular disease is the leading cause of death in the United States. In heart failure, the cardiac muscle is unable to contract adequately to pump blood throughout the body. In the United States there are approximately 2,000,000 people with heart failure and there are about 400,000 new cases every year. Heart failure has become the most frequent reason for hospitalization due to heart disease. This happened because in recent decades we have learned to save patients who used to die during a heart attack, we can by-pass blocked arteries, we can operate small infants with malformed hearts, we can repair or replace damaged valves. All these advances have diminished dramatically the mortality of patients with heart disease, but still, despite being able to save many lives we are facing a new threat in heart disease; Heart Failure.
The mechanisms of heart failure are many, however, a growing number of patients develop heart failure. Heart failure can be the result of dysfunction of one or more subsystems in the heart. The three main subsystems are: 1. The heart muscle itself. 2. The valves that control the flow through the four heart chambers during specific phases of the cardiac cycle (beat to beat). 3. The coronary arteries which provide the blood flow to the heart itself.
The greatest progress in the last three decades occurred in the areas of valvular and coronary artery disease. However, the causes of primary heart muscle dysfunction are not well understood and in many cases cannot be treated effectively. This subgroup of patients is the fastest growing in recent times.
Heart failure? Cardiomyopathy? Are they the same?
Many patients with heart failure are told that they have a cardiomyopathy. However, although doctors sometimes interchange these two terms, their meaning is not exactly the same. The term Cardiomyopathy is used to indicate a diminished performance capacity of the heart due a dysfunction of the cardiac muscle itself. There are several subtypes of cardiomyopathy recognized by an expert task force and published by the American Heart Association (Richardson P, et al: Report of the 1995 World Health Organization / International Society and Federation of Cardiology Task Force on the Definition and Classification of cardiomyopathies. Circulation. 1996. 93:841-842). Regardless of the type, the common denominator is a dysfunction of the cardiac muscle (myocardium) that cannot be attributed to valvular disease or myocardial infarction. Therefore, all cases of cardiomyopathy lead to heart failure, but not all cases of heart failure are due to cardiomyopathy.
How do we distinguish between heart failure and cardiomyopathy?
Technological advances allow cardiologists to evaluate a patient’s heart better than ever before. Using these methods, they can evaluate the heart’s ability to pump blood throughout the body and to itself, they can measure volumes of circulating blood, pressures within diverse compartments of the heart and the body, electrical activity of the heart, oxygen consumption and many more parameters. The status of the coronary arteries (the arteries that feed the heart) can also be assessed very accurately. In this manner accurate diagnoses can promptly give the cardiologist the answers to choose the best treatment for a given patient. However in a number of cases the correct diagnosis can only be achieved by analyzing a sample of the heart muscle. To this end, the cardiologist obtains small samples of the heart muscle (endomyocardial biopsy) by using a catheter and a special small device called a bioptome. Analysis of the samples obtained is performed by very physicians in the Pathology department. This type of tissue analysis is not common and therefore is usually performed only in highly specialized centers by physicians specifically trained in Cardiovascular Pathology.