Long-term observations in mild forms of cardiomyopathy

24 patients suffering from a mild cardiomyopathy with normal or nearly normal ejection fraction and histologic evidence of cardiac fiber hypertrophy were followed-up over 5.5 +/- 1.9 years. Patients presented predominantly with dyspnea, angina and palpitations. During the observation period, the severity of symptoms increased only slightly. The ECG showed atrial arrhythmias in 34% and premature ventricular beats or conduction disturbances in the majority. During the 5.5 year follow-up period four patients had developed an intermittent III AV-block and two patients a bundle branch block. The heart volume determined by X-ray increased insignificantly (893 +/- 224 to 933 +/- 245 ml/1.73 m2; n.s.), while left ventricle end-diastolic (5.5 +/- 1.1 to 5.6 +/- 0.6 cm) and end-systolic (3.9 +/- 1.2 to 3.7 +/- 0.7 cm) diameter remained nearly constant. Pulmonary artery pressure at rest (18 +/- 5.9 to 17.8 +/- 4 mm Hg) and during exercise (40.5 +/- 9.5 to 37.4 +/- 7.8 mm Hg) showed no significant change. However, cardiac output decreased significantly at rest from 5.6 +/- 1.6 l/min/1.73 m2 to 4.5 +/- 0.7 l/min/1.73 m2 (p less than 0.01) and during exercise from 13 +/- 4.1 l/min/1.73 m2 to 10.4 +/- 2.3 l/min/1.73 m2 (p less than 0.05). It is concluded that patients with this mild cardiomyopathy show only minor changes over a period of 5.5 years. The prognosis seems to be promising in most cases.