Cardiac abnormalities can affect the structure and/or the function of the heart. Some of the abnormalities affect the cardiac muscle layer and interfere with its ability to function. An abnormal structure in the cardiac valves, tumors and abnormal rhythms can all interfere with the flow of blood and possibly damage the heart itself.
Cardiomyopathies
A cardiomyopathy is a disease of the myocardium, or the muscle layer of the heart. There are three types of cardiomyopathies: restrictive, hypertrophic and dilated, as explained by Malcolm Arnold, M.D., cardiologist at University Hospital in “The Merck Manual for Healthcare Professionals.” When disease, scarring or too much fibrous tissue infiltrates the muscle, this leads to restrictive cardiomyopathy. The heart can no longer expand like it should and fill up with blood. In hypertrophic cardiomyopathy, some of the walls of the heart are too thick for the heart to fill up with enough blood. People with dilated cardiomyopathy have an abnormal heart because their heart is dilated, or enlarged. The heart can fill with blood but cannot pump the blood like it should.
Abnormal Valves
The heart has four chambers. The atria are the two upper chambers, and the ventricles are the two lower chambers. Blood goes from the atria to the ventricles by passing through valves. When blood leaves the right ventricle to go to the lungs, it passes through a pulmonary valve. Blood leaving the left ventricle to circulate throughout the body has to pass through an aortic valve.
An abnormal valve can be stenotic, which means it is too narrow and interferes with normal blood flow. When a valve does not properly close, it is called regurgitation; instead of all the blood passing from one chamber to another, some goes backwards. All four valves can be stenotic or regurgitate.
The valve between the left atrium and left ventricle can prolapse. It can move backwards into the left atrium when the heart pumps blood. Approximately 1 to 3 percent of the U.S. population has this abnormality, writes Paul Tanser, M.D., Professor Emeritus of Medicine at McMaster University in “The Merck Manual for Healthcare Professionals.”
Tumors
Primary cardiac tumors are tumors that develop within the heart. These are rare, according to Thomas Bashore, M.D., professor of medicine at Duke University Medical Center in “Current Medical Diagnosis & Treatment.” The most common primary cardiac tumor is the atrial myxoma. It attaches to the wall of the atrium, usually the left atrium. Metastatic tumors spread to the heart from other areas of the body, usually from the skin, lungs and breast.
Abnormal Rhythms and Conduction
A normal heart rate is 60 to100 beats per minute. A heart rate slower than 60 beats per minute is called bradycardia. Tachycardia is a heart rate faster than 100 beats per minute.
Electrical signals to the ventricles can be delayed or even blocked. This leads to abnormal conduction and irregular rhythms. Atrial fibrillation is one of the most common abnormal rhythms. Over 10 percent of Americans older than 75 years old have this cardiac abnormality, writes Jane Chen, M.D., of the Department of Medicine at Washington University School of Medicine in “The Washington Manual of Medical Therapeutics.”
References
- “Current Medical Diagnosis & Treatment 2010”; Stephen McPhee, M.D., Maxine Papadakis, M.D.; 2010
- The Merck Manual for Healthcare Professionals: Cardiomyopathies
- The Merck Manual for Healthcare Professionals: Mitral Valve Prolapse (MVP)
- “The Washington Manual of Medical Therapeutics”; Gopa Green, M.D., Ian Harris, M.D., Grace Lin, M.D., Kyle Moylan, M.D.; 2004
