Myocardial blood flow and VO2 in lambs with an aortopulmonary shunt during strenuous exercise
Gratama, J.W.; Meuzelaar, J.J.; Dalinghaus, M.; Koers, J.H.; Gerding, A.M.; Monchen, M.T.; te Nijenhuis, F.C.; Zijlstra, W.G.; Kuipers, J.R.
American Journal of Physiology 264(3 Pt 2): H938-H945
1993
ISSN/ISBN: 0002-9513 PMID: 8456994 Document Number: 414610
To determine how much myocardial O-2 consumption ( ovrhdot VO-2) would increase during an additional load on the heart in shunt as compared with control lambs, we studied 12 7-wk-old lambs with an aortopulmonary left-to-right shunt (59 +- 3% of left ventricular output, means +- SE) and 11 control lambs during exercise at 80% of their predetermined peak ovrhdot VO-2 ( ovrhdot VO-2 peak), at 12 +- 1 days after surgery. During exercise, systolic aortic pressure increased by 25% in the two groups. Left atrial pressure and left ventricular stroke volume did not change significantly and remained considerably higher in shunt than in control lambs. Heart rate, however, increased less in shunt than in control lambs (163 +- 8 to 235 +- 8 vs. 107 +- 7 to 230 +- 8 beats/min). The same was true for left ventricular myocardial blood flow (245 +- 19 to 391 +- 27 vs. 128 +- 10 to 320 +- 45 ml cntdot min-1 cntdot 100 g-1) and myocardial ovrhdot VO-2 (847 +- 101 to 1,692 +- 136 vs. 528 +- 58 to 1,579 +- 178 mu-mol O-2 cntdot min-1 cntdot 100 g-1). We conclude that, despite the volume load, myocardial ovrhdot VO-2 of shunt lambs does not increase to a greater extent than in control lambs during a considerable additional load on the heart.