The objective of this study was to examine for any relationship between the sites of papillary muscle insertion in left ventricular free wall (LVFW) and the site of LVFW rupture postinfarct. Twenty-five consecutive patients with LVFW rupture (12 men and 13 women, mean age 72.3 yr, range = 48 to 93) at the University of Ottawa Heart Institute during the period of July 1, 1988 to 1992 were studied. Clinical charts were reviewed, and the Formalin-fixed hearts were re-examined grossly and microscopically. Each patient died of tamponade or after surgery for tamponade. Eight (32%) of the 25 infarcts were anteroseptal or anterior, 11 of 25 (44%) were lateral, and 6 of 25 (24%) were inferior or inferoseptal. Four (16%) of the 25 infarcts were less than 2 days old, 9 of 25 (36%) were 2 to 5 days old, and 12 of 25 (48%) were 5 to 10 days old. A separate pre-existent and healed infarct was noted in 36% of patients; however, rupture adjacent to these areas of old infarct occurred in only 8% of cases. In 15 of 25 (60%) cases, free wall rupture occurred in the lateral wall between and at the level of the two papillary muscles. In a further 5 of 25 (20%) cases, the rupture was beside one of the papillary muscles but in anterior or posterior walls. In 20 of 25 (80%) cases, the endocardial tear associated with the LVFW rupture was within 1 cm of the base of one of the papillary muscles as they inserted in LVFW.(ABSTRACT TRUNCATED AT 250 WORDS)