OBJECTIVES: We sought to determine the relationship of contractile function to the transmural extent of infarction (TEI) in patients with chronic coronary artery disease. BACKGROUND: In the setting of reperfused, chronic myocardial infarction (MI), the relationship of contractile function to the TEI has not been established. METHODS: We studied function by cine magnetic resonance imaging (MRI) and the TEI by contrast-enhanced MRI in 31 patients with single-vessel disease 162 +/- 62 days after reperfused first MI. RESULTS: Of all 516 segments with MI, blinded observers were unable to detect abnormal thickening in 193 (37%), and wall thickening measured quantitatively in these segments was 66 +/- 28%. Of the 193 segments, 163 (84%) were infarcts limited to the subendocardium. The average TEI reached 53% before half of the patients had abnormal contractile function. When patients with small MI (< or =5% of total left ventricular [LV] mass) were excluded, the average TEI reached 43% before half the patients had abnormal function. In subjects with small MI (< or =5% of total LV mass [n = 13]), even segments with TEI >75% had normal function (14 of 14) because they were surrounded by normally moving neighbor segments. CONCLUSIONS: In the setting of reperfused chronic MI, the TEI approaches 50% before contractile dysfunction can be systematically identified. Contractile function cannot be used to rule out chronic MI.