Changes in pericardial surface pressure during pulmonary hypertensive crises after cardiac surgery

Reactive pulmonary hypertension in children after surgical repair of large left-to-right shunts is an important cause of postoperative low cardiac output. Low output may be caused by impaired left ventricular filling from right ventricular dilatation. We studied 12 children during the first 72 hr after surgery by measuring right ventricular pericardial surface pressure with a flat balloon and compared the results with acute changes in pulmonary arterial pressure (PAP). All 12 children (ages 4 to 14 months) had preexisting large left-to-right shunts with systemic PAPs. We found a highly significant linear correlation between acute rises in PAP and rises in the pericardial pressure (PP). The regression equation was PAP = 1.48(PP) + 5.7, R2 = .61, p less than .001. There was an average of 15.6 pulmonary hypertensive episodes per patient during the 72 hr study period, but only 9% of these episodes were associated with either no change or a fall in systemic pressure. We conclude that changes in right ventricular pericardial pressure reflect acute changes in PAP.