Pathophysiology of Heart Failure/Cardiomyopathy

'Chronic Heart Failure' or 'Congestive Heart Failure'?

The word “congestive” means different things to different people and leads to a great deal of confusion. Overall, it is better to discuss “heart failure” with your patients. Different kinds of heart failure include:

• Acute heart failure
• Chronic heart failure
• Systolic heart failure
• Diastolic heart failure
• Left ventricular heart failure
• Cardiomyopathy

How the Normal Heart Functions

The heart is a hollow muscle about the size of a fist. A normally functioning heart is one of the strongest muscles in the human body. It pumps blood through the lungs to deliver oxygen to the remainder of the body.

The heart is divided into four cavities: two atria and two ventricles. The left atrium receives oxygenated blood from the lungs. From there, the blood passes to the left ventricle, which pumps it via the aorta through the arteries to supply the tissues of the body. The right atrium receives the blood after it has passed through the tissues and given up much of its oxygen. The blood then passes to the right ventricle, and then to the lungs, to be oxygenated. The heart tissue itself is nourished by the blood in the coronary arteries.

Definition of Heart Failure

Heart failure (HF) is a state in which the heart is unable to pump blood at a rate that meets the requirements of metabolizing tissues or can do so only from an elevated filling pressure.¹

The incidence of heart failure rises with increasing age, and is three times more likely to occur in men than women. Analysis of numerous published studies indicates that the incidence of heart failure is between 2.3 to 3.7 per thousand per year.²

Usually, HF manifests initially during exertion, however, as the disease progresses the contractile performance of the heart deteriorates and shortness of breath and fatigue result, even when the body is at rest.

Etiology of Heart Failure/Cardiomyopathy

The two main causes of HF are:

1. Myocardial infarction, with loss of heart muscle secondary to coronary artery disease
2. Chronic hypertension

Heart failure can also result from:

• Viral infection of the heart
• Valvular disease
• Alcoholism or other toxins
• Congenital conditions
• Acquired immunodeficiency syndrome

Heart failure can be aggravated by:

• Diabetes
• Anemia
• Thyroid disease³

These symptoms may be accompanied by:

• Angina
• Cool extremities
• Tachypnea
• Tachycardia
• Elevated jugular venous pressure
• Positive hepato-jugular reflux
• Rales, wheezes
• Added heart sounds
• Pleural effusion
• Detection of enlarged heart on x-ray⁴

References

1. Colucci W, Braunwald E. Pathophysiology of heart failure. In: Braunwald E, ed. Heart disease. 5th Edition. Philadelphia: WB Saunders, 1997;394-420.
2. Cardiology Preeminence Roundtable. CHF in Brief. In: Beyond four walls: research summary for clinical and administrators for CHF management. Washington D.C.: The Advisory Board Company, 1994.
3. Adams KF, Zannad F. Clinical definition and epidemiology of advanced heart failure. Am Heart J 1998;135(Suppl 2, Part 6):S204-S215.
4. Canadian Cardiovascular Society. Report on the 1993 Consensus Conference on the Diagnosis and Treatment of Heart Failure. Guidelines for the management of heart failure. Toronto: Publications Ontario, 1996.