The Annals of Thoracic Surgery, Vol 32, 475-485, Copyright © 1981 by The Society of Thoracic Surgeons
Reduction of myocardial infarct size in swine: a comparative study of intraaortic balloon pumping and transapical left ventricular bypass
Y Takanashi, CD Campbell, J Laas, RL Pick, P Meus and RL Replogle
This study compared intraaortic balloon pumping (IABP) and transapical left
ventricular (LV) bypass for their effectiveness in reducing infarct size in
swine. In 28 pigs (25.4 +/- 4.7 kg) the left anterior descending coronary
artery was ligated distal to the first diagonal branch. Nine animals served
as controls. Nine animals were treated with IABP and the remaining 10, with
transapical bypass. Ten animals-3 control, 3 IABP, and 4 transapical
bypass--died prior to completion of the study, thereby resulting in 6
animals in each group. Both assist devices were begun 45 minutes after
coronary ligation, this being as rapid as mechanical intervention could be
accomplished in the patient after infarction. With transapical LV bypass,
70 to 100% bypass was accomplished and the LV systolic pressure remained in
the range between mean aortic pressure and 30 mm Hg less than that. All
animals were killed after 24 hours. The hearts were excised and stained
with nitroblue tetrazolium, and infarct size was quantitated in grams of
infarct per 100 gm of LV and septal mass. After 24 hours the mean aortic
pressure was 73 +/- 12 mm Hg in controls, 105 +/- 20 mm Hg in animals with
IABP (p less than 0.01), and 91 +/- 13 mm Hg in those with transapical LV
bypass (p less than 0.05). The infarct size was 22.7 +/- 4.9 gm per 100 gm
of LV and septal mass in control animals. With IABP, the infarct size was
nonsignificantly changed to 19.4 +/-5.9 gm per 100 gm (p greater than 0.3).
With transapical LV bypass, the infarct size was significantly reduced to
15.9 +/- 3.5 gm per 100 gm (p less than 0.025). This represented a 30%
reduction of infarct size from controls. These results demonstrate that
despite hemodynamic improvement with IABP, transapical LV bypass is
necessary to markedly decrease myocardial work and significantly reduce
infarct size.