Efficacy of coronary artery bypass grafting in patients with a dilated left ventricle due to myocardial infarction

Abstract

This study was designed to clarify the efficacy of coronary artery bypass grafting (CABG) on left ventricular (LV) function in 16 patients with a dilated LV due to myocardial infarction (LV end-systolic volume index: LVESVI >60 ml/m2). All had attained complete revascularization. To estimate the LV wall motion quantitatively using echocardiography, a wall motion score (WMS) was used (LV was divided into 17 segments with a four-point scale: akinesis=3, severe hypokinesis=2, hypokinesis=1, normal=0 and then summed). Exercise stress tests were performed after surgery, revealing that anginal symptoms had vanished in all the patients. In 5 patients with a preoperative end-systolic volume index (ESVI)>100 ml/m2, the ejection fraction (EF) did not change, and both were under 30% (before to after: 26±4 to 26±4%). Neither the ESVI (148±50 to 133±39 ml/m2) nor the end-diastolic volume index (end-diastolic volume index (EDVI): 198±62 to 180±37 ml/m2) changed; the WMS did not change (33±2 to 33±3). During exercise, in spite of the increase in heart rate (HR) (at rest, 81±20; HR during exercise, 111±21 beats/min, p<0.005) and LV end-diastolic pressure (EDP) (22±9; 35±13 mmHg, p<0.02), both cardiac index (CI) (2.4±0.3; 2.6±0.4 L/min.m2) and minute work (MW: 4.0±1.1; 4.1±0.4kg. M/min) did not increase. In 11 patients with a preoperative ESVI < 100 ml/m2, EF was extremely increased in 5 patients (more than 10%, 35±4 to 60±6%, p<0.005= improved subgroup) in whom the EDVI (130±16 to 120±13 ml/m2) did not change whereas the ESVI (82±14 to 48±7 ml/m} was reduced. However, in the 6 remaining patients (ie nonimproved subgroup), neither ESVI (78±8 to 74±12ml/m2), EDVI (115±10 to 115±20ml/m2) nor EF (31±7 to 35±3%) changed. During exercise, HR (at rest, 88±13; during exercise, 108±11 beats/min, p<0.005), LVEDP (20±6; 29±7 mmHg, p<0.01), CI (2.5±0.6; 3.3±0.5 L/min.m2, p<0.05), MW (4.6±1.0; 6.5±1.5 kg·M/min, p<0.05) increased. The WMS in the nonimproved subgroup did not change (29±6 to 27±2), but in the improved subgroup it reduced after surgery (27±3 to 19±4, p<0.01). These data suggested that CABG in patients with a dilated LV was effective against anginal symptoms, but was restricted to left ventricular function. It may be possible to estimate postoperative LV function, including exercise tolerance, from the preoperative LVESVI.