Maintained exercise pressor response in heart failure.
Shoemaker, J. Kevin, Allen R. Kunselman, David H. Silber, Lawrence I.
Sinoway,.
Section of Cardiology1 and Section of Biostatistics2, The
Pennsylvania State University College of Medicine, The Milton S.
Hershey Medical Center, Hershey, PA 17033, and Lebanon VA Medical
Center3, Lebanon, PA 17042
APStracts 5:0302A, 1998.
The impact of forearm blood flow limitation on muscle reflex
(metaboreflex) activation during exercise was examined in 10 heart
failure (HF) (NYHA Class III and IV) and 9 control (CTL) subjects.
Rhythmic handgrip contractions (25% maximal voluntary contraction, 30
contractions/min) were performed over 5 min under conditions of
ambient pressure or with +50 mmHg positive pressure about the
exercising forearm. Mean arterial blood pressure (MAP) and venous
effluent hemoglobin (Hb) oxygen saturation, lactate and hydrogen ion
concentration ([H+]) were measured at baseline and during exercise.
For ambient contractions the increase in MAP by end exercise ((MAP)
(i.e., the exercise pressor response) was the same in both groups
(10.1 +/- 1.2 vs. 7.33 +/- 1.3 mmHg, HF vs. CTL, respectively)
despite larger (lactate and ([H+] for the HF group (P < 0.05). With
ischemic exercise, the (MAP for HF (21.7 +/- 2.7 mmHg) exceeded that
of CTL (12.2 +/- 2.8 mmHg) (P < 0.0001). Also, for HF, (lactate
(2.94 +/- 0.4 mmol) and ([H+] (24.8 +/- 2.7 nmol) in the ischemic
trial were greater than CTL (1.63 +/- 0.4 mmol and 15.3 +/- 2.8 nmol;
lactate and [H+], respectively) (P < 0.02). Hb oxygen saturation
was reduced in CTL from 43% in the ambient trial to 27% with ischemia
(P < 0.0001). Oxygen extraction was maximized under ambient
exercise conditions for HF but not for CTL. Despite progressive
increases in blood perfusion pressure over the course of ischemic
exercise, no improvement in Hb oxygen saturation or muscle metabolism
was observed in either group. These data suggest that muscle reflex
activation of the pressor response is intact in heart failure but the
resulting improvement in perfusion pressure does not appear to
enhance muscle oxidative metabolism or muscle blood flow in these
subjects possibly due to associated increases in sympathetic
vasoconstriction of active skeletal muscle.
Received 27 January 1998; accepted in final form 9 July 1998.
APS Manuscript Number A83-8.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 30 July 1998