Improved tolerance of the pediatric myocardium to brain death

The occurrence of brain death has been shown to significantly diminish left ventricular function in the adult porcine model. This study examined whether the pediatric myocardium is as sensitive as the adult myocardium to the detrimental effects of brain death in the porcine model. Left ventricular intracavitary pressure and major and minor axis epicardial dimensions were measured in eleven 1-month old pigs (7.5 to 10 kg) during a vena caval occlusion. Brain death was induced in six pigs by acutely ligating the brachiocephalic and left subclavian arteries. The remaining five pigs served as controls. Data were then collected every hour for 6 hours. The plot of the stroke work versus the end diastolic volume, called the preload recruitable stroke work relationship, was determined from the measured pressure and calculated intracavitary volume data. The slope of this linear relationship is an index of contractility, and the x intercept (V(o)) is an index of diastolic mechanics. At each hour after instrumentation two vena caval occlusions were performed, and the mean slope of the preload recruitable stroke work line was calculated as a percentage of the baseline slope in both the brain-dead and control group. The mean values from the brain-dead pigs were 118%, 138%, 126%, 154%, 123%, and 87% of the baseline value for the 6 hours after brain death. The mean control values were 128%, 117%, 133%, 123%, 114%, and 111% of baseline for the 6 hours after instrumentation alone. There was no statistical difference between groups with the rank sum test. The shift in the x intercept was calculated for each group at each hour as well. The mean group shifts from the baseline V(o) in the brain-dead pigs were 0.97, 2.40, 2.63, 4.86, 5.00, and 5.00 ml. The mean control group shifts from the baseline V(o) were -0.63, 2.85, 3.29, 2.76, 2.96, and 2.69 ml. Only at the fourth and fifth hours were there any statistically significant differences between the groups with the rank sum test (p < 0.03). During acute brain death, the pediatric porcine myocardium is significantly more stable than the adult porcine myocardium, which rapidly declines to 8% of the baseline slope within 6 hours of brain death. If the mechanism for this tolerance is determined, perhaps it could be applied to the adult population of brain-dead donors to expand the organ supply. We conclude that in the porcine model of brain death, the pediatric myocardium demonstrates no decremental decline in left ventricular systolic function in contrast to the adult myocardium.

Duke Scholars

Author Thomas Anthony D'Amico Surgery, Cardiovascular and Thoracic Surgery