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

Atrial fibrillation limits the ability to increase cardiac output during ex ercise and may, in turn, affect the exercise-associated elevation in cerebr al perfusion. In nine patients with atrial fibrillation (AF) and in five ag e-matched healthy subjects, middle cerebral artery blood velocity (MCA V-me an) 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 (118-15 9 W) and maximal oxygen uptake: 1.41 min(-1) (1.0-1.91 min(-1)) vs. 1.71 mi n(-1) (1.4-2.21 min(-1)); P = 0.05]. At rest, MCA V-mean was not significan tly different between the two groups [43 cm s(-1) (39-56 cm s(-1)) vs. 52 c m s(-1) (40-68 cm s(-1))]. During intense cycling, the increase in MCA V-me an 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%; P<0.05], whic h corresponded with the smaller than expected increase in cardiac output [1 56% (130-169%) vs. 180%]. Thus, there was a correlation between the increas e in MCA V-mean and the ability to increase cardiac output (r(2) = 0.55, P< 0.01). We suggest that, during exercise with a large muscle mass, atrial fi brillation affects the ability to elevate cerebral perfusion, and this resu lts from an impaired ability to increase cardiac output.