Key result
Aortopulmonary shunts do not increase myocardial VO2 more than controls during strenuous exercise in lambs.
Why the study?
The extent to which myocardial oxygen consumption increases during additional cardiac load in lambs with an aortopulmonary shunt compared to controls was unclear.
Does an aortopulmonary left-to-right shunt increase myocardial O2 consumption to a greater extent than in controls during strenuous exercise in lambs?
Does an aortopulmonary left-to-right shunt increase myocardial O2 consumption to a greater extent than in controls during strenuous exercise in lambs?
Absolute Event Rate: 1692% vs 1579%
In a lamb model, despite the volume load of an aortopulmonary shunt, myocardial oxygen consumption does not increase to a greater extent than in controls during strenuous exercise.
Shunt volume load does not disproportionately raise myocardial O2 use during exercise in lambs; leaves open translation to human congenital shunts.
To determine how much myocardial O2 consumption (VO2) 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, mean +/- SE) and 11 control lambs during exercise at 80% of their predetermined peak VO2 (VO2peak), 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.min-1 x 100 g-1) and myocardial VO2 (847 +/- 101 to 1,692 +/- 136 vs. 528 +/- 58 to 1,579 +/- 178 mumol O2 x min-1 x 100 g-1). We conclude that, despite the volume load, myocardial VO2 of shunt lambs does not increase to a greater extent than in control lambs during a considerable additional load on the heart.
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Gratama et al. (1993) studied Aortopulmonary left-to-right shunt (n=23). Aortopulmonary left-to-right shunt vs. Control lambs was evaluated on Myocardial O2 consumption (VO2) during exercise (mumol O2 x min-1 x 100 g-1). Despite a volume load, myocardial oxygen consumption in lambs with an aortopulmonary shunt did not increase to a greater extent than in control lambs during strenuous exercise.
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