Since 1984, 122 orthotopic heart transplants have been performed at the University of Ottawa Heart Institute. Of the 114 adult patients, 100 (87.8%) were males and 14 (12.2%) females, with mean ages of 45.8 and 47.9 yr, respectively. The hearts of these adults were pathologically diagnosed as chronic ischemic heart disease (CIHD) in 55 (48.2%), acute ischemic heart disease (AIHD) in 17 (14.9%), dilated cardiomyopathy (DC) in 30 (26.3%), valvular heart disease in five (4.4%), congenital heart disease in three (2.6%), myocarditis in three (2.6%), and other in one (0.9%) of the cases. The adult hearts (94) among the first 100 transplants were studied morphologically, to look for differences among the three major groups with clinical "end-stage" heart failure. The mean heart weights were 435, 356, and 463 gm in the CIHD, AIHD, and DC groups, respectively, with AIHD less than CIHD or DC (p less than 0.01). The ventricular wall thicknesses were similar in CIHD and DC, but the left ventricular (LV) wall thicknesses in AIHD were more than in CIHD or DC (p less than 0.01). The ventricular diameters were greater in DC than in CIHD or AIHD (p less than 0.01) and greater in CIHD than in AIHD (p less than 0.01). The mean LV cavity volumes were 158, 94, and 200 ml in CIHD, AIHD, and DC, respectively, with DC greater than in CIHD or AIHD (p less than 0.01) and CIHD greater than in AIHD (p less than 0.01). The relative differences in AIHD compared to CIHD and DC are referrable to the shorter duration of disease in the acute ischemic group.2+ off