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Effects of off-pump versus on-pump coronary artery bypass grafting on early and late right ventricular function.
BACKGROUND: Off-pump CABG (OPCABG) results in better preservation of left ventricular function in the perioperative period than conventional on-pump CABG (ONCABG); however, evidence is conflicting as to the effect of OPCABG and ONCABG on right ventricular (RV) function, possibly because of the complexity involved in measuring this. METHODS AND RESULTS: In a single-center randomized pilot study, 60 patients with normal left ventricular function undergoing CABG were randomly assigned to OPCABG or ONCABG. Patients underwent cardiac magnetic resonance imagine for assessment of RV function preoperatively, early postoperatively, and at 6 months after surgery. Fifty-one patients completed the first 2 scans, and 47 completed all 3 scans. Preoperative characteristics and RV function did not differ significantly between the 2 groups (mean+/-SD): RV stroke volume index was 49+/-10 mL/m(2) for OPCABG and 49+/-16 mL/m(2) for ONCABG. After surgery, RV stroke volume index fell to 36+/-7 mL/m(2) in the OPCABG group and 39+/-11 mL/m(2) in the ONCABG group, but this did not differ significantly between the 2 groups (P=0.41). All markers of RV function recovered to preoperative levels by 6 months, with no long-term difference between the surgical techniques. CONCLUSIONS: RV function is impaired early after surgery but recovers by 6 months. The changes were similar in both the OPCABG and ONCABG groups.
Effects of off-pump versus on-pump coronary surgery on reversible and irreversible myocardial injury: a randomized trial using cardiovascular magnetic resonance imaging and biochemical markers.
BACKGROUND: There is biochemical evidence that off-pump coronary artery bypass grafting (OPCABG) reduces myocardial injury compared with the use of cardiopulmonary bypass (ONCABG), but the functional significance of this is uncertain. We hypothesized that OPCABG surgery would result in reduced postoperative reversible (stunning) and irreversible myocardial injury, as assessed by cardiovascular MRI (CMRI). METHODS AND RESULTS: In a single-center randomized trial, 60 patients undergoing multivessel total arterial revascularization were randomly assigned: 30 to OPCABG and 30 to ONCABG. Patients underwent preoperative and early postoperative cine MRI for assessment of global left ventricular function, and contrast-enhanced CMRI for assessment of irreversible myocardial injury. Serial troponin I measurements were obtained perioperatively and correlated with the CMRI findings. The mean preoperative cardiac index was similar in the 2 surgical groups (2.9+/-0.7 ONCABG; 2.9+/-0.8 OPCABG; P=0.9). After surgery, the cardiac index was significantly higher in the OPCABG group (2.7+/-0.6 ONCABG; 3.2+/-0.8 OPCABG; P=0.04). New irreversible myocardial injury was similar in incidence (36% ONCABG; 44% OPCABG; P=0.8) and magnitude (6.3+/-3.6 g ONCABG; 6.8+/-4.0 g OPCABG; P=0.9) across the 2 groups. The median area-under-the-curve (AUC) troponin I values were significantly larger in the ONCABG group (182 versus 135 microg/L; P=0.02). There was a moderate correlation between the troponin I AUC values and mean mass of new myocardial hyperenhancement (r(2)=0.4; P=0.008). CONCLUSIONS: OPCABG results in significantly better left ventricular function early after surgery but does not reduce the incidence or extent of irreversible myocardial injury.
Abnormal cardiac and skeletal muscle energy metabolism in patients with type 2 diabetes.
BACKGROUND: It is well known that patients with type 2 diabetes have increased risk of cardiovascular disease, but it is not known whether they have underlying abnormalities in cardiac or skeletal muscle high-energy phosphate metabolism. METHODS AND RESULTS: We studied 21 patients with type 2 diabetes with no evidence of coronary artery disease or impaired cardiac function, as determined by echocardiography, and 15 age-, sex-, and body mass index-matched control subjects. Cardiac high-energy phosphate metabolites were measured at rest using 31P nuclear magnetic resonance spectroscopy (MRS). Skeletal muscle high-energy phosphate metabolites, intracellular pH, and oxygenation were measured using 31P MRS and near infrared spectrophotometry, respectively, before, during, and after exercise. Although their cardiac morphology, mass, and function appeared to be normal, the patients with diabetes had significantly lower phosphocreatine (PCr)/ATP ratios, at 1.50+/-0.11, than the healthy volunteers, at 2.30+/-0.12. The cardiac PCr/ATP ratios correlated negatively with the fasting plasma free fatty acid concentrations. Although skeletal muscle energetics and pH were normal at rest, PCr loss and pH decrease were significantly faster during exercise in the patients with diabetes, who had lower exercise tolerance. After exercise, PCr recovery was slower in the patients with diabetes and correlated with tissue reoxygenation times. The exercise times correlated negatively with the deoxygenation rates and the hemoglobin (Hb)A1c levels and the reoxygenation times correlated positively with the HbA1c levels. CONCLUSIONS: Type 2 diabetic patients with apparently normal cardiac function have impaired myocardial and skeletal muscle energy metabolism related to changes in circulating metabolic substrates.