Data pertaining to factors associated with cardiac failure were collected as part of a study on sow mortality in which cardiac failure was the major cause of death. A total of 116 sows from 24 herds was used and divided into two groups: group 1 comprised sows dead of cardiac failure (n = 43), and group 2, sows dead of other causes (n = 73). Individual sow records, clinical history, backfat thickness, body weight, heart weight, selenium content in liver, and urea concentration in aqueous humor were obtained for each sow. Results from the groups were compared using Student's t-test. Maximum and minimum outside daily temperatures were obtained for the study period. A stressful or demanding event for the cardiovascular system of sows was identified in 84% of the cases of cardiac failure: nearly two-thirds of the cases occurred during the peripartum period, and other stressful events included heat, fighting, mating, and transport. More than 40% of the cardiac failures occurred during the months of July and August. Sows dead of cardiac failure were heavier and fatter than sows dead of other causes. The former group also had a significantly smaller heart weight to body weight ratio; this difference was attributed to a greater body weight since the heart weights were similar in the two groups. The hepatic selenium contents and urea concentrations in aqueous humor were not significantly different between the two groups.