Evaluation of ischemia tolerance in the rabbit heart isolated before maturation

ABSTRACT

Several studies have shown that cardiac tolerance of ischemia, before maturation is greater in the newborn than adults and it decreases gradually in the rest of life. Most studies on cardiac tolerance before maturation have shown this tolerance gradually decreases before maturation. But a few studies have not confirmed such results. In regard to its clinical importance this study was designed to determine the change in the pattern of tolerance of ischemia before maturation. Hearts of 2, 3, 6 and 8 week-old rabbits were isolated and perfused under constant pressure according to langendorff method. Coronary flow [CF] and functional parameters including heart rate [HR] and fluctuations in the left ventricular developed pressure [LVDP] were measured and the product of [HR x LVDP] [RPP] was calculated. Steps of the experiment included baseline period [20 min], ischemia [35 min] at temperature of 37°C and reperfusion for 45 minutes. Cardiac parameters including RPP were evaluated 45 minute after reperfusion and at the baseline period. ANOVA test was used for data analysis. Recovery of the heart function in 3 week old rabbits [85.81 +/- 4.36] [mean +/- SE] was significantly greater than those of 2, 6 and 8 week old rabbits [67.57 +/- 3.27], [61.19 +/- 2.83] and [52.03 +/- 5.09] respectively [P<0.05]. It can be concluded that tolerance of ischemia in rabbit before maturation doesn't decrease and reaches its maximum between birth and maturation