Author(s): FARICIER, R., GULUZADE, N., KELTZ, R., HARTLEY, T., HUITEMA, A., MCKELVIE, R., SUSKIN, N., KEIR, D., Institution: UNIVERSITY OF WESTERN ONTARIO , Country: CANADA, Abstract-ID: 1776

INTRODUCTION:
Patients with coronary artery disease (CAD) typically exhibit reduced peak oxygen uptake (V̇O2peak) which is associated with adverse clinical outcomes. Hemoglobin mass (Hbmass) and intravascular blood volumes are key determinants of V̇O2peak but have not yet been well characterized in this population. Therefore, we compared carbon monoxide rebreathing-derived Hbmass and intravascular blood volumes and V̇O2peak between patients with CAD and healthy controls (CON).
METHODS:
Forty-nine patients with CAD (12 females) and 27 healthy adults (13 females) completed a cardiopulmonary exercise test using a step-ramp-step protocol to determine V̇O2 and power output (PO) at the gas exchange threshold (GET), respiratory compensation point (RCP), and peak exercise (V̇O2peak and POpeak). On a separate day, Hbmass and intravascular volumes (total blood volume [BV], plasma volume [PV], and red blood cell volume [RBCV]) were assessed using a 5-min carbon monoxide rebreathing method. Group differences were analyzed using two-tailed independent samples t-tests with alpha set to 0.05.
RESULTS:
Height (172±10 vs 172±8 cm, p=0.960) and body mass (82±18 vs 78±12 kg, p=0.379) did not differ between CAD and CON groups, respectively. CAD were older than CON (64±11 vs 56±13 years; p=0.010, respectively). Compared to CON, CAD had lower V̇O2peak when expressed relative to body mass (23.7±6.3 vs 31.7±9.1 mL·kg-1·min-1; p<0.001) and as percentage of age-predicted maximum (102±23 vs 128±20 %; p<0.001), lower POpeak (146±53 vs 212±75 W; p<0.001), lower V̇O2 at RCP (19.8±4.7 vs 26.7±7.8 mL·kg-1·min-1; p<0.001) and at GET (15.4±4.0 vs 18.8±4.6 mL·kg-1·min-1; p=0.001) and lower PO at RCP (87±33 vs 133±47 W; p<0.001) and GET (64±26 vs 100±34 W; p<0.001). In contrast, no CAD vs CON differences were observed for Hbmass (9.9±1.9 vs 10.7±2.0 g·kg-1; p=0.077), BV (5.4±1.3 vs 5.8±1.1 L; p=0.285), PV (3.0±0.7 vs 3.2±0.6 L; p=0.291), nor RBCV (2.4±0.7 vs 2.6±0.6 L; p=0.346). In the CAD group, Hbmass (g·kg-1) was positively correlated with relative V̇O2peak (r=0.44, p=0.003). In CON, relative V̇O2peak correlated positively with Hbmass (g·kg-1; r=0.68, p<0.001), BV (L; r=0.61, p=0.001), PV (L; r=0.50, p=0.013), and RBCV (L; r=0.67, p<0.001).
CONCLUSION:
Despite reduced submaximal and maximal aerobic capacity in patients with CAD, Hbmass and intravascular volumes were comparable to healthy controls. These findings suggest that oxygen-carrying capacity does not contribute to the reduced V̇O2peak observed in CAD which may instead reflect limitations in peripheral or cardiovascular oxygen utilization.