RESUMO
PURPOSE: To evaluate the influence of atrial fibrillation in the natural history of hypertrophic cardiomyopathy. METHODS: Eighty-eight patients under ambulatory treatment were studied. Most of them presented the asymmetric type of hypertrophic cardiomyopathy (87.5%). Group I (77 cases) was formed by patients who had never had atrial fibrillation and group II (11 cases) by those who had this arrhythmia paroxysmal or established. RESULTS: In group I, with ages 48.02 +/- 14.82 years, left atrial dimensions 4.21 +/- 0.66 cm, there was one sudden death; 69 were treated by clinical means and 7 by surgery; no patient developed thromboembolism neither cardiac failure. In group II, with ages 58.02 +/- 11.04 years and left atrial dimension 5.32 +/- 0.45 cm, there were 4 deaths, 4 thromboembolisms and 3 with cardiac failure; all received only clinical treatment, having improved in clinical status in 71.42% after amiodarone therapy. CONCLUSION: Atrial fibrillation was present in 12.5%, mostly in the asymmetric type, and in patients after 5th decade, all of them with enlarged left atrium (> 4.7 cm), with highest morbidity (thromboembolism and cardiac failure) and mortality. Among the survivors, amiodarone therapy improved functional class in 71.42%.