The occurrence of unanticipated and seemingly unexplicable major complications of hepatic, pulmonary, and cardiac dysfunction after palliative operation for obstructive hypertrophic cardiomyopathy prompted a review of 71 sequential patients. Fifty-five patients had been treated preoperatively with beta-blockers, calcium-channel inhibitors, or both, and 16 had received amiodarone for six to 566 days (mean time, 210 days) at total doses ranging from 8 to 175 g (mean dose, 82 g) and had drug-free intervals prior to operation of zero to 457 days (mean time, 91 days). Comparisons were made between the two treatment groups and between those with and without major complications within the amiodarone-treated group. Preoperative cardiac studies, sex, age, functional class, and type of operation were not related to outcome for the entire patient cohort. In amiodarone-treated patients, the major findings were as follows: a 50% incidence of hepatic dysfunction with a tenfold increase in concentrations of serum glutamic-oxaloacetic transaminase and serum glutamic-pyruvic transaminase; a 25% incidence of pulmonary dysfunction necessitating a fourfold increase in the number of days of ventilator support; and a 19% incidence of low cardiac output syndrome with two deaths. Only 44% of the amiodarone-treated group had no serious complications. The incidence of major complications of the liver, lungs, and heart was 2%, 0%, and 2%, respectively, in patients not treated with amiodarone. Abnormal preoperative pulmonary function studies were predictive of prolonged postoperative ventilatory support. Discontinuation of amiodarone for several months prior to operation appeared to reduce the incidence of major complications. The necessary drug-free interval required preoperatively could not be determined from this retrospective experience.(ABSTRACT TRUNCATED AT 250 WORDS)