Background: Exercise training reduces mortality in patients with coronary artery disease (CAD); however, the impact of habitual physical activity level (PAL) on vascular endothelial function and circulating endothelial progenitor cells (EPCs) remain unknown.
Methods: We assessed habitual PAL using a validated International Physical Activity Questionnaire in 116 patients (67.8+/-9.5 years; 81% male) with stable CAD and preserved left ventricular ejection fraction > or =45%. The number of circulating CD34/KDR+ and CD133/KDR+ EPCs was determined by flow cytometry, and brachial artery flow-mediated dilation (FMD) was measured.
Results: The mean PAL of CAD patients with 1644 MET min/week (where MET is metabolic equivalents). With higher habitual PAL tertiles, there were significant linear trends of increased FMD (P = 0.001) and CD133/KDR+ EPCs (P = 0.03), but not of CD34/KDR+ EPCs. Patients with the highest tertile of PAL were associated with an absolute increase of 1.89% in FMD (relative increase 68%, P = 0.003) and 0.12% in CD133/KDR+ EPCs (relative increase 44%, P = 0.01) compared with those in the lowest tertile of PAL, after adjusting for age, sex, presence of hypertension, diabetes mellitus, hypercholesterolemia, smoking, and the use of medications including statins. However, neither CD34/KDR+ nor CD133/KDR+ EPCs significantly correlated with FMD.
Conclusion: This study showed that higher habitual PAL in patients with CAD was associated with higher FMD and EPC count. Nonetheless, FMD only significantly correlated with increased PAL, but not EPC, suggesting that increased physical activity improves endothelial function through mechanisms other than increasing EPC count.