Effect of cardioplegic arrest and reperfusion on coronary reserve and autoregulation

Cardioplegia Dose Effect on Immediate Postoperative Alterations in Coronary Artery Flow Velocities After Congenital Cardiac Surgery

Abnormalities in coronary artery (CA) flow detected by echocardiography are increasingly used to guide clinical decisions in patient management. Increased CA flow has been seen postoperatively in congenital cardiac surgery. This study sought to determine immediate postoperative changes in left anterior descending (LAD) CA flow velocities, and to investigate possible factors associated with these changes. CA flow in the proximal LAD was sampled with pulsed-wave Doppler during trans-esophageal echocardiography imaging in the immediate preoperative and postoperative studies in 46 subjects. The peak velocity, velocity time integral (VTI), VTI corrected for heart rate (VTIc), and VTI rate pressure product (VTIrpp) were determined. The percent change in each measure between the preoperative and postoperative study was calculated and compared to age, body surface area (BSA), cardiopulmonary bypass time, cross-clamp time, and number of cardioplegia (CP) doses. The pH, oxygen saturation, temperature, and hemoglobin concentration (Hb) were compared for those with and without increased flow characteristics. There was an overall increase in LAD flow parameters in subjects who underwent congenital cardiac surgery. There was a significant and positive correlation of percent change in VTI, VTIc, and VTIrrp with number of CP doses and lower Hb. We propose that this phenomenon is likely of multifactorial origin, involving autoregulatory mechanism disturbance. The imaging and measurement of LAD flow velocities are feasible, reliable, and is positively correlated with number of CP doses. Interpretation of postoperative LAD flow velocities should be made in the context of intraoperative events since heart rate, blood pressure, and Hb concentration also influence CA flow parameters.