Exaggerated increase in cardiac output during exercise in patients with peripheral high-flow arteriovenous malformations.
OBJECTIVE
To test the hypothesis that cardiac output (Q) in patients with arteriovenous malformations (AVMs) is normal at rest and increases disproportionately during exercise.


METHODS
Q was measured in eight patients with large peripheral AVMs and in nine healthy subjects using a noninvasive carbon dioxide (CO₂)-based differential Fick method. Subjects were tested while seated at rest and during mild exercise (repeated leg straightening while sitting). Oxygen consumption (VO₂) was monitored as an index of the degree of exercise.


RESULTS
Average resting Q was similar between AVM patients and healthy subjects (7.40 L/min ± 3.29 vs 6.13 L/min ± 0.94, respectively, P = .29). During exercise, AVM patients showed a smaller increment in VO₂ (0.50 L/min ± 0.11 vs 0.78 L/min ± 0.26, P = .012) but with more apparent effort and shortness of breath compared with healthy subjects. The change in Q per unit change in VO₂ (ΔQ/ΔVO₂) was greater in AVM patients than in healthy subjects (16.00 L/min ± 6.50 vs 9.79 L/min ± 5.33, P < .045).


CONCLUSIONS
Exercise intolerance in AVM patients may be due to an imbalance in ΔQ/ΔVO₂ resulting from increased shunting through the AVM. Exercise provocation may increase the sensitivity of Q in the clinical evaluation of AVM patients.
Department of Anesthesia, University Health Network, University of Toronto, Toronto, Ontario, Canada.
Alexandra
A
Mardimae
Jay S
JS
Han
David
D
Preiss
Lisa
L
Rodrigues
S Murthy
SM
Chennapragada
Marat
M
Slessarev
Martin E
ME
Simons
Joseph A
JA
Fisher
D000222:Adaptation, Physiological; D000328:Adult; D000368:Aged; D001165:Arteriovenous Malformations / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy; D002302:Cardiac Output; D016022:Case-Control Studies; D004621:Embolization, Therapeutic; D015444:Exercise; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D010101:Oxygen Consumption; D012039:Regional Blood Flow; D016896:Treatment Outcome