CARDIOVASCULAR ENGINEERING Journal for Extracorporeal Circulation, Assist Devices,Transplantation and Artificial Organs
	Volume 2, 1997, No 3

Myocardial Capillaries after Crystalloid Cardioplegic Arrest and Reperfusion

P. R. Belcher, V. L. Pathi, D. J. Wheatley

Abstract:
Background: The effects of cardiopulmonary bypass, crystalloid cardioplegia and reperfusion on the myocardial capillaries, were tested in a pig model of cardiac surgery and compared to the effects of cardiopulmonary bypass alone on the kidney. Methods: Cardiac: Three groups were studied: Group A (n=6) underwent 30 minutes of hypothermic (28oC) cardiopulmonary bypass. Groups B (n=6) and C (n=6) also had 90 minutes of cardioplegic arrest. Group C hearts were then reperfused for 30 minutes. Renal: The kidneys from Group B and C pigs were compared to a control Group O (n=6) which solely underwent anaesthesia and heparinisation. Microvascular methylmethacrylate corrosion casts defined coronary and renal capillary anatomy. Capillary abundance was assessed by electron microscopy and cast weight. Ischaemic damage was graded by microscopy. Renal cortical blood flow was measured using radio-labelled microspheres. Results: Cardiac: In Group A, mean (+/-SD) myocardial density was 125+/-9 mg.mm-3. After cardioplegic arrest (Group B) it fell to 74+/-7 mg.mm-3 (p <0.0001) due to absence of capillaries. on reperfusion (group c), capillary numbers partially recovered but luminal diameter was reduced; cast density was 94+/-5 mg.mm-3 (p < 0.0001 vs. groups a and b). renal: in group o, renal vascular resistance was 61+/-5 mmhg/ml/min, but fell to 25+/-4 in b (p < 0.05). it rose in group c to 40+/-4 (p < 0.05 vs. o and b). cortical thickness in groups o and b, was 33 and 31 mm, with equal perfusion of all cortical layers, but was lower in group c, to 22mm (p < 0.05 vs. o and b), with loss of the superficial cortex. mean glomerular capillary diameters were 4.7 +/-0.3 mm in group o, 3.6 +/-0.2 mm in b and 3.7 +/-0.3 mm in c (p < 0.05, o vs. b and c). conclusions: following cardiopulmonary bypass microvascular changes were marked. myocardial changes were partially reversed by 30 minutes reperfusion, but may be a source of postoperative organ dysfunction. in the kidney, changes worsened with prolonged perfusion.

Keywords:
Myocardium, kidney, ischaemia, reperfusion, cardioplegia, coronary artery, capillary

Address for Correspondence:

Reference:
(CVE. 1997; 2 (3): 191-197)

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