How Is Cardiomyopathy Diagnosed?
Cardiomyopathy is heart failure, the failure of the heart as an efficient pump due to structural abnormalities that create functional abnormalities. The structural abnormalities involve enlargement of the left or both ventricles which affects systolic pumping and diastolic filling sequences. In patients who present clinically with signs of heart failure, the structural changes can be diagnosed with echocardiography (B mode ultrasound) and the functional changes with Doppler (flow) echocardiography.
Two types of heart failure are:
- Heart failure with preserved ejection fraction
- Heart failure with reduced ejection fraction
Clinical Presentations Suspicious for a Diagnosis
The clinical presentations (signs and symptoms of heart failure) for both of these are similar and warrant investigation:
- Dyspnea (dyspnea on exertion, paroxysmal nocturnal dyspnea, orthopnea)
- Higher than normal pressure in the jugular veins of the neck
- Pulmonary rales heard on auscultation of the chest
- Edema in the dependent portions of the body (legs)
Atrial fibrillation, associated with right-sided (preserved ejection fraction) heart failure, will subsequently reduce left ventricular filling and cardiac output. This results in hypotension and pulmonary congestion (pulmonary edema). Increased stress on the left ventricular wall, from hypertension, can delay relaxation of the myocardium.
Diastolic dysfunction raises the pulmonary venous pressure due to increased left atrial pressure. This can present clinically with wheezing and shortness of breath.
The degree of hemodynamic compromise can be severe enough to become life-threatening.
The approach to diagnosis includes ruling out other causes of heart failure: valvular heart disease, pulmonary hypertension, ventricular infarction, pericarditis, cardiac tamponade, amyloidosis, metastatic cancer, and drug toxicity.
- Chest X-ray: demonstrates cardiac enlargement or pulmonary edema (fluid back-up from dysfunctional systole and/or diastole).
- Electrocardiogram: ECG findings are usually nonspecific, but if there has been a prior infarction or current ischemia, this can be detected.
- Echocardiography: identifies let ventricular hypertrophy, left atrial enlargement, and elevations in pulmonary artery systolic pressure. A cardiac echogram is especially useful in proving that the ejection fraction is preserved, and the left ventricle remains normal. Alternately, it can determine left ventricular hypertrophy, left atrial enlargement, and reduced ejection fraction; alternately, it can steer the diagnosis away from cardiomyopathy by documenting valve disease.
The Doppler component can examine the flow dynamics that can determine diastolic filling pressures and left atrial volume. The remodeling of the left ventricle and diastolic dysfunction, when identified, portend morbidity and possible mortality.
- Blood tests: plasma natriuretic peptide levels are elevated in heart failure.
- Exercise testing: this can help separate heart failure from lung disease.
- Cardiac catheterization: generally used only when other diagnostic tests are inconclusive.