Echocardiographic Assessment
A protocol for evaluating performance during diastole by intraoperative TEE was introduced at JHH in January 2017 and intended for all patients undergoing CAB surgery. Examinations were performed after induction of anesthesia and prior to coronary artery revascularization, i.e. prior to CPB, though timing in relation to sternotomy or phase of respiratory cycle were not standardized. All TEEs were performed by physicians NBE-certified in advanced perioperative TEE or by cardiac anesthesia fellows under the direct supervision of a certified physician. Metrics of performance during diastole were interpreted by a single physician (JMD) blinded to each subject’s preoperative comorbidities and postoperative course. The TEE evaluation of performance during diastole was modified from that of Swaminathan et al [14] and included: 1) spectral pulsed wave Doppler velocity of transmitral early (E) inflow; 2) spectral tissue Doppler imaging of diastolic myocardial velocity at the lateral mitral annulus (e’). Unless atrial fibrillation was present, the most representative waves were chosen. In the case of atrial fibrillation, values were averaged over 6-7 beats. Abnormal performance during diastole, hereafter referred to as diastolic dysfunction, was defined dichotomously as e’ < 10 cm/s. If LV dysfunction during diastole existed unlike during systole when it was normal, severity was defined as: 1) Grade 1 if E/e’ < 8.5; 2) Grade 2 if E/e’ 8.6-12.5; 3) Grade 3 if E/e’ > 12.6. These compromise E/e’ cutoffs were chosen to accommodate noninteger values not specifically categorized in the reference manuscript [14]. Abnormal E was defined dichotomously as E > 50 cm/sec [15].