Diagnosing Cardiomyopathy

In some cases, cardiomyopathy is the end result of another underlying health condition. In arriving at a medical diagnosis, the physician must rule out any treatable diseases by determining the etiology or primary cause of the cardiomyopathy.

Some types of cardiomyopathy are reversible. These include cardiomyopathy that results from pregnancy or a hormonal imbalance, alcohol or cocaine abuse, and certain vitamin deficiencies.

 

Inherited forms of cardiomyopathy involve mutations in the gene coding for beta myosin, alpha tropomyosin and troponin T. Defects in these genes, which lead to problems with heart muscle contraction, are currently impossible to treat.

To diagnose cardiomyopathy, the doctor asks about symptoms of breathlessness, fatigue, chest pain, dizziness and fainting. The doctor then looks for signs of heart failure including edema, cyanosis and unusual sounds in the lungs. When listening to the heart, the doctor listens for an unusual heartbeat or a murmur. If the doctor suspects cardiomyopathy, other tests can be administered to confirm the medical diagnosis.

Patients are typically screened to rule out underlying causes such as infection or metabolic disorder. Kidney and liver function status is checked to ensure that adequate blood circulation is reaching these vital organs.

The electrocardiogram, or EKG, is a non-invasive diagnostic tool that doctors use to see how the heart is functioning. An EKG measures the electrical firing of the heart and can detect previous heart attacks, areas of decreased blood flow to the heart and arrhythmias or abnormal heartbeats.

The diagnosing physician may also order one or more imaging tests to help with the diagnosis:

Chest x-ray: A plain x-ray of the heart and lungs can provide information about the size of the heart and the status of the lungs. In cardiomyopathy, the silhouette of the heart is often slightly enlarged. In the dilated form of cardiomyopathy, the enlargement may be more dramatic.

Echocardiography: This technique uses ultrasound imaging to visualize the heart while it is beating. The procedure is safe and non-invasive and allows assessment of heart function, valve integrity, filling of the heart and the amount of blood that is pumped out with every heartbeat—the "ejection fraction." In suspected cardiomyopathy, the thickness of the heart walls is measured and the general symmetry of the chambers is noted.

In some cases the doctor may also take a biopsy of tissue from the heart to determine the exact nature of the disease and rule out other conditions that affect the heart.

Resources

Beers, M.H. & Berkow, R. (ed). Cardiomyopathy. The Merck Manual of Diagnosis and Therapy, 17th Edition. Merck Research Laboratories, NJ, 1999.

Fauci, A., Braunwald, E., Isselbacher, K., Wilson, J., Martin, J., Kasper, D., Hauser, S. & Longo, D. (ed). Harrison's Principles of Internal Medicine, 14th Edition. McGraw-Hill, New York, 1998.

National Library of Medicine. (updated 2004). Cardiomyopathy.MedlinePlus Medical Encyclopedia.