Middle cerebral artery blood velocity during exercise in patients with atrial fibrillation

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Abstract
Atrial fibrillation limits the ability to increase cardiac output during exercise and may, in turn, affect the exercise-associated elevation in cerebral perfusion. In nine patients with atrial fibrillation (AF) and in five age-matched healthy subjects, middle cerebral artery blood velocity (MCA Vmean) was measured during incremental exercise using the transcranial Doppler. The AF patient group exhibited a lower aerobic capacity than the control group [peak work rate: 106 W (71–153 W; median and range) vs. 129 W (118–159 W) and maximal oxygen uptake: 1·4 l min–1 (1·0–1·9 l min–1) vs. 1·7 l min–1 (1·4–2·2 l min–1); P =  0·05]. At rest, MCA Vmean was not significantly different between the two groups [43 cm s–1 (39–56 cm s–1) vs. 52 cm s–1 (40–68 cm s–1)]. During intense cycling, the increase in MCA Vmean was to 51 cm s–1 (40–78 cm s–1) (9%) in the AF group and lower than in the healthy subjects [to 62 cm s–1 (50–81 cm s–1) 23%; PVmean and the ability to increase cardiac output (r2 = 0·55, P<0·01). We suggest that, during exercise with a large muscle mass, atrial fibrillation affects the ability to elevate cerebral perfusion, and this results from an impaired ability to increase cardiac output.