Intraoperative techniques to assess cardiac function-feasiblity of strain rate imaging in the perioperative period in children

The noninvasive assessment of cardiac function during mechanical circulatory support is challenging because conventional markers (like ejection fraction) are significantly load-dependent. Yet loading conditions are abnormal and change during support and weaning process. Tissue Doppler and strain rate imaging are echocardiographic techniques that permit quantitation of regional wall motion. Peak systolic strain rate (SR) is a fairly load-independent marker of ventricular systolic function in experimental validation studies. We hypothesized that SR changes would improve assessment of right and left ventricular function during mechanical circulatory support. Color tissue Doppler images were acquired before surgery, 8 and 24 hours postoperatively in 18 children undergoing open heart surgery. Clinically, all patients were hemodynamically stable and on low doses of inotropics without death or resuscitation events. Wall motion analysis revealed a significant drop of peak systolic velocities and SR postoperatively in both ventricles. On the next day, all parameters improved with regional differences. SR appeared to be more sensitive to changes than velocities. In conclusion, tissue Doppler imaging appears to be a sensitive marker of ventricular mechanics in children and may improve perioperative monitoring. It offers a method to quantitatively assess left and right ventricular performance and may help to compare different cardio-protective strategies.