Impact of exercise training on the clinical course of left ventricular systolic dysfunction in post-CABG patients

Abstract

Background: Patients with ischemic cardiomyopathy (LVEF <40%) undergoing CABG surgery represent a high-risk clinical subset, with greater overall morbidity and mortality than patients without LV dysfunction (LVD). Frequently, they show symptoms of CHF and signs of persistent LVD, despite effective mechanical revascularization. Recent studies suggest that exercise training modifies LV geometry and may have beneficial effects on contractile dysfunction, caused by ischemia as well as reperfusion. We evaluated the effects of a 12-week physical training program in patients with impaired global LV systolic performance (LVEF <40%), initiated 10-14 days after CABG. From 1/2000 to 12/2002, 138 patients (mean age 67.25 years; 13% female) with ischemic cardiomyopathy (CMP) underwent successful revascularization by CABG, and were enrolled in a supervised exercise program. Of these, 10.9% had prior MI and 88.3% had multivessel CAD. The exercise prescription used a preset protocol and consisted of ECG-monitored, symptom-limited cycle ergometry and treadmill walking up to 60 minutes per session, 3 days a week for 12 weeks, at 60-70% of heart rate reserve (calculated by Karvonen's formula based on resting HR, maximum predicted HR, and “conditioning intensity”). Multiple indices of exercise tolerance, echo-based LVEF and metabolic parameters were recorded at the time of entry into and at completion of (Phase II) cardiac rehabilitation. Conclusions: (1) In selected patients with persistent moderate-to-severe LVD following mechanical revascularization by CABG, a supervised exercise training program significantly improves multiple indices of functional capacity, and major metabolic parameters that are known to add to comorbidity. (2) This is paralleled by significant improvement in global LV systolic and diastolic performance. (3) Our data demonstrates that exercise training may be an important factor in the course and progression of ischemic CMP following CABG. These promising results should stimulate a wider and more aggressive use of exercise training in patients with LVD. ∗ResultsVariablePre-RehabPost-Rehab‘P’ ValueWeight (lb)177.4172.36<0.0001∗: P value significant at <0.0001NYHA Class3.41.120.003: P value significant at <0.05; FBS: fasting blood sugarResting HR (bpm)84.9374.38<0.0001∗: P value significant at <0.0001Exercise HR (bpm)98.2490.93<0.0001∗: P value significant at <0.0001Treadmill Time (min)12.2221.00<0.0001∗: P value significant at <0.0001TM Workload (METS)2.514.56<0.0001∗: P value significant at <0.0001Cycle Ergometry Time (min)9.7820.85<0.0001∗: P value significant at <0.0001GXT Workload (METS)3.528.29<0.0001∗: P value significant at <0.0001GXT Double Product15,47623,555<0.0001∗: P value significant at <0.0001LVEF (%)32.4839.380.002: P value significant at <0.05; FBS: fasting blood sugarDiastolic dysfunction39.1%12.4%0.001: P value significant at <0.05; FBS: fasting blood sugarTotal Cholesterol (mg/dL)180.7167.7<0.0001∗: P value significant at <0.0001HDL (mg/dL)37.6539.66<0.0001∗: P value significant at <0.0001LDL (mg/dL)106.35100.63<0.0001∗: P value significant at <0.0001FBS (mg/dL)122.48101.600.001: P value significant at <0.05; FBS: fasting blood sugar∗ : P value significant at <0.0001∗∗ : P value significant at <0.05; FBS: fasting blood sugar Open table in a new tab