TABLE 513 Effect of Bedside Interventions on the Murmur of Hypertrophic Cardiomyopathy Compared to Mitral Valve Prolapse

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ECG findings of LV hypertrophy and left atrial enlargement are found in 30 percent and 25 to 50 percent, respectively, of HCM patients. Evidence of chamber enlargement is most common in patients with large gradients across the LV outflow tract. Q waves of considerable amplitude (more than 0.3 mV), termed septal Q waves, are seen in about 25 percent of patients and may be encountered in the anterior, lateral, or inferior leads. These Q waves may mimic those seen following myocardial infarction (pseudoinfarction pattern). The polarity of the T wave may serve as a diagnostic clue in the separation of HCM septal Q waves from Q waves due to myocardial infarction. Upright T waves in those leads with QS or QR complexes are usually found in HCM; T-wave inversion in such leads is highly suggestive of ischemic heart disease.

The chest x-ray is frequently normal, and identifiable abnormalities are largely nonspecific. Many patients do not show radiographic evidence of LV or left atrial enlargement. Evidence of pulmonary venous congestion is unusual but has been reported.

Echocardiography has played a substantial role in the diagnosis of HCM, in the correlation of the auscultatory and hemodynamic events with LV anatomic changes, and in defining inheritance patterns. The characteristic echocardiographic finding is disproportionate septal hypertrophy. Additional described echocardiographic abnormalities include normal or reduced LV end-diastolic dimensions, systolic anterior motion of the mitral valve, and midsystolic closure of the aortic valve.

TREATMENT AND DISPOSITION The majority of patients with HCM who seek medical care typically do so because of declining exercise tolerance, chest pain, or syncope.9 Symptoms may mimic those of ischemic heart disease, or in the young patient, symptoms may be ascribed to a noncardiac cause. The patient who presents complaining of exercise intolerance or chest pain in whom the typical murmur of HCM is heard should be referred for echocardiographic evaluation. Syncope in patients with HCM typically occurs during or immediately after exercise. If HCM is suspected in a patient with syncope, hospitalization is indicated. The workup in such cases is extensive and includes echocardiographic studies as well as extended ambulatory (Holter) monitoring, exercise stress testing to assess blood pressure response, and tilt testing. Syncope in patients with HCM may be due to one or more factors and may presage sudden cardiac death.9 Vigorous exercise is discouraged for such patients, and preparticipation screening guidelines have been developed for competitive athletes to minimize the risk of sudden death due to HCM.10 b blockers are the mainstay of therapy for patients with chest pain.

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