Broadly defined, the cardiomyopathies are a heterogeneous group of disorders that primarily or secondarily affect the myocardium leading to impairment of systolic and/or diastolic performance. Several schemes have been proposed to classify the cardiomyopathies. While differences in classification exist between the various schemes, the basic approach to the patient with heart muscle disease remains unchanged: a comprehensive history and physical examination and appropriately targeted imaging are required in all patients for appropriate diagnosis and treatment. Echocardiography is usually employed in the initial patient evaluation and is often sufficient to provide an adequate assessment of the heart based on morphology and physiology. Selected patients may qualify for more advanced imaging techniques, invasive biopsy, or genetic testing depending upon individual circumstances. Using a case-based approach, this chapter will review the clinical and imaging features, pathophysiology, and management of the cardiomyopathies.
SECTION I: ISCHEMIC CARDIOMYOPATHY
CLINICAL CASE PRESENTATION
An actively smoking 85-year-old man with a history of previous myocardial infarction, permanent atrial fibrillation, peripheral arterial disease, coronary artery bypass surgery 12 years prior, and an LV ejection fraction of 20% presented to an outside hospital with severe respiratory distress that required endotracheal intubation and mechanical ventilation. He denied having experienced chest discomfort. He was transferred to our institution for further care. On arrival, a 12-lead electrocardiogram (ECG) showed atrial fibrillation with right bundle branch block and lateral ST-segment depressions. Chest radiography revealed cardiomegaly and the presence of bilateral pleural effusions and interstitial edema. A brain natriuretic peptide (BNP) level was >4000 pg/mL; cardiac troponin I levels were within normal limits. Echocardiography demonstrated LV dilatation and evidence of regional wall motion abnormalities with akinesis and thinning in the distributions of the circumflex and right coronary arteries and severe hypokinesis in the distribution of the anterior descending artery. The left atrium was markedly dilated, and LV filling pressures were elevated. Moderate to severe mitral regurgitation (MR) was demonstrated and the pulmonary artery systolic pressure (PASP) was estimated to be about 50 to 55 mm Hg. With aggressive diuresis, the patient was able to be separated from the ventilator within 24 hours. Appropriate guideline-recommended medical therapy was initiated and titrated to tolerance; smoking cessation was stressed. A subsequent SPECT-thallium viability study confirmed the depressed LVEF and documented infarct (scar) involving the entirety of the distributions of the circumflex and right coronary arteries; no evident ischemia was demonstrated in the LAD distribution. After discussion with his primary cardiologist, and taking into consideration his clinical status, a decision not to pursue coronary angiography and prophylactic ICD implantation was made.
As demonstrated by this case vignette, a history of prior coronary heart disease (CHD) is evident in most patients, although some may offer no such history.