Postischemic functional recovery in immature hearts is influenced by performance index and assessment technique

In the in vivo immature heart, conflicting results are reported for postisc hemic functional recovery. This study determines whether interpretations of functional recovery are influenced by the contractile performance index (s ystolic pressure, developed pressure, and maximum rate of systolic pressure increase per unit time) reported or the assessment technique (isovolumetri c and variable-volume) utilized. In neonatal pigs (n=6) on cardiopulmonary bypass, each performance index was examined using both assessment technique s before myocardial ischemia and at 15, 30, and 60 min of reperfusion. With the use of the isovolumetric technique, all performance indexes had signif icantly different recovery. With the use of the variable-volume assessment technique, recovery of systolic pressure was significantly better than the other indexes. When recovery was compared between the two assessment techni ques, systolic pressure recovered significantly better when assessed using the variable-volume technique. For each performance index, the correlation between isovolumetric and variable-volume techniques was positive before is chemia but negative during reperfusion, suggesting that the assessment tech niques identified conflicting postischemic contractile performances. Thus b oth the contractile performance index reported and the assessment technique employed are ultimately important in interpreting postischemic functional recovery in the immature heart.