Impact of all-day physical activity on ventilatory perfusion coupling in patients undergoing cardiac resynchronization therapy.
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. 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. 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. 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.