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Exaggerated renal vasoconstriction during exercise in heart failure patients
H R Middlekauff1, E U Nitzsche, C K Hoh
1Division of Cardiology, Department of Medicine, UCLA School of Medicine, Los Angeles, CA 90095, USA.
Circulation
|February 23, 2000
Summary
Heart failure patients show exaggerated renal vasoconstriction during exercise, lasting longer than in healthy individuals. Muscle metaboreceptor contribution to this response is reduced in heart failure.
Area of Science:
- Cardiovascular Physiology
- Renal Physiology
- Exercise Physiology
Background:
- Healthy humans exhibit reflex renal cortical vasoconstriction during static exercise.
- Muscle metaboreceptors significantly contribute to this exercise-induced renal vasoconstriction.
- The response of renal vascular tone to exercise in heart failure patients remains unclear.
Purpose of the Study:
- To investigate reflex renal vasoconstriction during exercise in patients with heart failure.
- To compare renal vascular responses between heart failure patients and healthy controls during exercise.
- To elucidate the role of muscle metaboreceptors in renal vasoconstriction in heart failure.
Main Methods:
- Thirty-nine heart failure patients (NYHA class III-IV) and 38 controls underwent dynamic positron emission tomography for renal blood flow measurement.
- Graded handgrip exercise and post-handgrip ischemic arrest were employed to assess reflex mechanisms.
- Renal vasoconstriction was quantified during sustained handgrip and during circulatory arrest to isolate muscle metaboreceptor influence.
Main Results:
- Heart failure patients demonstrated significantly greater peak renal vasoconstriction during sustained handgrip compared to controls (70+/-13 vs. 42+/-1 U, P=0.02).
- Renal vasoconstriction persisted longer in heart failure patients (increased at 2-5 min) compared to controls (returned to baseline).
- During post-handgrip circulatory arrest, renal vasoconstriction was blunted in heart failure patients (20+/-5 vs. 30+/-2 U, P=0.05), indicating reduced muscle metaboreceptor contribution.
Conclusions:
- The magnitude and duration of reflex renal vasoconstriction are exaggerated during sustained exercise in heart failure patients.
- Muscle metaboreceptors play a blunted role in mediating reflex renal vasoconstriction in heart failure patients compared to healthy individuals.
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