Prolonged asystole during intraoperative myocardial reperfusion: an experimental study

It has been observed in a proportion of patients, that clinically cardiac asystole persists for a prolonged period during intraoperative reperfusion. To evaluate this phenomenon, isovolumic functional indices (left ventricular [LV] balloon) and myocardial oxygen consumption (MV02) were compared in 22 canine preparations before and after two different interventions. After 45 minutes of normothermic global ischemia, (1) the control group (N = 11) was maintained on cardiopulmonary bypass with the hearts beating empty and (2) the experimental group (N = 11) was subjected to cardioplegia reperfusion at normothermia for one hour. In contradistinction to the initial hypothesis, functional recovery was better in the experimental group compared with the controls. Significant differences were observed in recovery of LV peak developed pressure (LVPDP) (controls, 66.8 +/- 7.3% [mean +/- standard error of the mean], and experimental group, 99.5 +/- 8.9%; p less than 0.05), maximum rate of rise of LV pressure (controls, 116.6 +/- 16.2%, and experimental group, 147.7 +/- 10.1; p less than 0.05), and maximum fall of LV pressure (controls, 100.3 +/- 15.8%, and experimental group, 143.1 +/- 11.5%; p less than 0.05). Correlation between LVPDP and MVO2 was also better preserved in the experimental group (controls: r = 0.15, N = 74, p = 0.18; experimental group: r = 0.47, N = 75, p less than 0.001). Values for myocardial water content and total creatine kinase in the two groups were similar. It was concluded that prolonged asystole during intraoperative reperfusion is not detrimental; on the contrary, there is enhanced functional recovery of the myocardium similar to that seen after secondary cardioplegia.