Abstract 16770: Effect of Locomotor Muscle Afferent Feedback Inhibition on Cardiac Power During Submaximal Exercise in Heart Failure
Introduction: Heart failure (HF) patients demonstrate increased locomotor muscle afferent neural feedback during exercise which is known to influence the exercise pressor response. The influence of this feedback on central hemodynamics during exercise in HF remains less clear.
Hypothesis: We investigated whether inhibition of locomotor muscle afferent feedback during submaximal constant-load exercise influences cardiac power in HF.
Methods: Nine HF (age 60±2 yrs; EF, 27±2%; NYHA class, 2±1) and 9 matched control (CTL; age 63±2 yrs) completed 5 min of submaximal constant-work cycling (65% peak power) with intrathecal fentanyl (FEN; impairing cephalad projection of opioid receptor sensitive afferents) or sham, on separate days in random order. Mean arterial pressure (MAP), heart rate (HR), and oxygen consumption (VO2) were measured at rest and during exercise. Cardiac power (VO2 x MAP) was calculated. Assessment for cephalad migration of fentanyl was conducted by hypercapnic ventilatory response with no differences within or between groups. At rest, there were no differences in cardiac power within or between groups.
Results: During exercise with FEN, cardiac power was attenuated in HF compared to CTL (133±15 vs 199±23 mL/kg/min/mmHg, p=0.03) and sham (139±11 vs. 218±21 mL/kg/min/mmHg, p<0.01). Similarly, the increase in cardiac power from rest to end-exercise was attenuated in HF compared to CTL with FEN (89±19 vs 169±21 mL/kg/min/mmHg, p=0.01) and sham (110±10 vs. 185±21, p<0.01). The percent change in cardiac power from rest to end-exercise was also smaller in HF compared to CTL with FEN (360±40% vs 558±50%, p<0.01) and sham (378±32% vs 578±65%, p=0.01). The absolute difference and percent change and in cardiac power from rest to end-exercise did not differ between fentanyl and sham for HF or CTL.
Conclusion: These data suggest HF patients have significantly attenuated cardiac power during submaximal constant-load exercise compared to CTL. Further, cardiac power appears to be less influenced by locomotor muscle afferent feedback inhibition in HF compared to CTL suggesting a transition in the physiologic mechanisms of cardiovascular control during exercise associated with HF pathophysiology.
Author Disclosures: E.H. VanIterson: None. E.M. Snyder: None. M.J. Joyner: None. B.D. Johnson: None. T.P. Olson: Research Grant; Significant; AHA - 12GRNT11630027.
This research has received full or partial funding support from the American Heart Association.
- © 2014 by American Heart Association, Inc.