LEFT-VENTRICULAR DYSFUNCTION AFTER OPEN REPAIR OF SIMPLE CONGENITAL HEART-DEFECTS IN INFANTS AND CHILDREN - QUANTITATION WITH THE USE OF A CONDUCTANCE CATHETER IMMEDIATELY AFTER BYPASS

Objective: Quantification of myocardial injury after the simplest pedi atric operations by load-independent indices of left ventricular funct ion, using conductance and Mikro-Tip pressure catheters (Millar Instru ments, Inc., Houston, Tex,) inserted through the left ventricular apex , Methods: Sixteen infants and children with intact ventricular septum undergoing cardiac operations had left ventricular function measured, immediately before and after bypass, Real-time pressure-volume loops were generated by conductance and Mikro-Tip pressure catheters placed in the long-axis via the left ventricular apex, and preload was varied by transient snaring of the inferior vena cava, Results: Good quality pressure-volume loops were generated in 13 patients (atrial septal de fects, n = 11; double-chambered right ventricle, n = 1; supravalvular aortic stenosis, n = 1; age 0.25 to 14.4 years, weight 3.1 to 46.4 kg) , Their mean bypass time was 41 +/- 14 minutes and mean aortic crosscl amp time 27 +/- 11 minutes, End-systolic elastance decreased by 40.7% from 0.34 +/- 0.17 to 0.21 +/- 0.15 mm Hg-1 . ml(-1) . kg(-1) (p < 0.0 01), There were no significant changes in the slope of the stroke work -end-diastolic volume relationship, end-diastolic elastance, time cons tant of isovolumic relaxation, and normalized values of the maxima and minima of the first derivative of developed left ventricular pressure , Conclusion: Load-independent indices of left ventricular function ca n be derived from left ventricular pressure-volume loops generated by conductance and Mikro-Tip pressure catheters during the perioperative period in infants and children undergoing cardiac operations, Incomple te myocardial protection was demonstrated by a deterioration in systol ic function after even short bypass and crossclamp times.