Impact of All-Day Physical Activity on Ventilatory Perfusion Coupling in Patients Undergoing Cardiac Resynchronization Therapy

OBJECTIVES: There is still little information about the cardiorespiratory effects of cardiac resynchronization therapy (CRT) in patients undergoing all-day physical activity. This study aimed to assess the effects of CRT on ventilatory perfusion coupling during submaximal exercise. METHODS: Metabolic and hemodynamic parameters were obtained during treadmill exercise testing as well as during rest for each single-right (RV), -left (LV) and biventricular (BiV) pacing mode as well as during intrinsic conduction (VVI 30) in 37 patients. Only responders to CRT (>10% increase in cardiac output (CO) during BiV pacing; n = 27) were included into the evaluation. RESULTS: LV and BiV pacing increased systolic (144 +/- 25 and 142 +/- 28 vs. 118 +/- 29 mm Hg, p < 0.05) and mean blood pressure (108 +/- 19 and 109 +/- 19 vs. 94 +/- 25 mm Hg, p < 0.05) as well as CO (7.0 +/- 0.6 and 7.2 +/- 0.8 vs. 6.0 +/- 0.6 l/min, p < 0.05 and p < 0.01) during exercise as compared to VVI 30. Simultaneously, LV and BiV pacing decreased dead space ventilation (18 +/- 3 and 17 +/- 3 vs. 20 +/- 4, p < 0.01) and the ventilatory equivalent for oxygen (31 +/- 4 and 31 +/- 5 vs. 36 +/- 6; p < 0.05) compared to intrinsic conduction. CONCLUSION: The improvement in ventilatory efficacy during CRT, which is demonstrated by the decrease in the ventilatory equivalent for oxygen, results from an increase in CO and thus from a reduction in the ventilatory perfusion mismatch.