The natural history of left ventricular hypertrophy in hypertrophic cardiomyopathy: an electrocardiographic study.

The natural history of electrocardiographic left ventricular hypertrophy was assessed in relation to clinical features, treatment with propranolol and prognosis in 100 patients with hypertrophic cardiomyopathy who were followed 5--20 years (mean 8 years). Seventy-one patients received propranolol, 120--800 mg/day (mean 240 mg). At diagnosis, the voltage measurement from SV1 + RV5 was 37 +/- 20 mm, the R wave in aVL was 12 +/- 6 mm and the mean frontal plane voltage was 15 +/- 10 mm. After 5 years, these values were increased to 43 +/- 22 mm (p less than 0.0002), 14 +/- 6 mm (p less than 0.003) and 17 +/- 10 mm (p less than 0.01), respectively. Neither a left ventricular outflow tract gradient nor propranolol treatment influenced these voltage changes. Twenty patients had an increase of more than 10 mm in SV1 + RV5, which was associated with exertional chest pain (p less than 0.006) and death (p less than 0.02). Four patients had a decrease of more than 10 mm in SV1 + RV5. Two of these received high-dose propranolol, one 720 mg/day for 12 years and another 800 mg/day for 12 years. No other patient received more than 480 mg of propranolol daily. In hypertrophic cardiomyopathy there is electrocardiographic evidence of progressive hypertrophy, which is associated with poor prognosis and is not influenced by treatment with propranolol in moderate dosage. Regression of hypertrophy is rare and may be related to long-term treatment with high-dose propranolol.