Blood flow dynamics in heart failure.
BACKGROUND
Exercise intolerance in heart failure (HF) may be due to inadequate vasodilation, augmented vasoconstriction, and/or altered muscle metabolic responses that lead to fatigue.


RESULTS
Vascular and metabolic responses to rhythmic forearm exercise were tested in 9 HF patients and 9 control subjects (CTL) during 2 protocols designed to examine the effect of HF on the time course of oxygen delivery versus uptake (protocol 1) and on vasoconstriction during exercise with 50 mm Hg pressure about the forearm to evoke a metaboreflex (protocol 2). In protocol 1, venous lactate and H+ were greater at 4 minutes of exercise in HF versus CTL (P<0.05) despite similar blood flow and oxygen uptake responses. In protocol 2, mean arterial pressure increased similarly in each group during ischemic exercise. In CTL, forearm blood flow and vascular conductance were similar at the end of ischemic and ambient exercise. In HF, forearm blood flow and vascular conductance were reduced during ischemic exercise compared with the ambient trial.


CONCLUSIONS
Intrinsic differences in skeletal muscle metabolism, not vasodilatory dynamics, must account for the augmented glycolytic metabolic responses to moderate-intensity exercise in class II and III HF. The inability to increase forearm vascular conductance during ischemic handgrip exercise, despite a normal pressor response, suggests that enhanced vasoconstriction of strenuously exercising skeletal muscle contributes to exertional fatigue in HF.
Shoemaker
J K
JK
Department of Medicine, Section of Cardiology, Pennsylvania State University College of Medicine, Hershey, PA, USA. kshoemak@gcrc.hmc.psghs.edu
Naylor
H L
HL
Hogeman
C S
CS
Sinoway
L I
LI
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001794:Blood Pressure; D005080:Exercise Test; D005542:Forearm / Q000098:blood supply*; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000097:blood; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D005082:Physical Exertion; D012016:Reference Values; D012039:Regional Blood Flow; D013997:Time Factors; D014655:Vascular Resistance
D007773:Lactates; D010100:Oxygen