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Cardiovascular Research 2002 56(3):479-486; doi:10.1016/S0008-6363(02)00545-X
© 2002 by European Society of Cardiology
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Copyright © 2002, European Society of Cardiology

Dynamics of microvascular oxygen partial pressure in contracting skeletal muscle of rats with chronic heart failure

E.R. Diederich, B.J. Behnke, P. McDonough, C.A. Kindig, T.J. Barstow, D.C. Poole and T.I. Musch*

Departments of Kinesiology, Anatomy and Physiology, Kansas State University, Manhattan, KS 66506, USA

* Corresponding author. Tel.: +1-785-532-4523; fax: +1-785-532-4557 musch{at}vet.ksu.edu

Objective: This investigation tested the hypothesis that the dynamics of muscle microvascular O2 pressure (PO2m, which reflects the ratio of O2 utilization [Formula O2] to O2 delivery [Formula O2]) following the onset of contractions would be altered in chronic heart failure (CHF). Methods: Female Sprague–Dawley rats were subjected to a myocardial infarction (MI) or a sham operation (Sham). Six to 10 weeks post Sham (n = 6) or MI (n = 17), phosphorescence quenching techniques were utilized to determine PO2m dynamics at the onset of spinotrapezius muscle contractions (1 Hz). Results: MI rats were separated into groups with Moderate (n = 10) and Severe (n = 7) CHF based upon the degree of left ventricular (LV) dysfunction as indicated by structural abnormalities (increased right ventricle weight and lung weight normalized to body weight). LV end-diastolic pressure was elevated significantly in both CHF groups compared with Sham (Sham, 3±1; Moderate CHF, 9±2; Severe CHF, 27±4 mmHg, P<0.05). The PO2m response was modeled using time delay and exponential components to fit the PO2m response to the steady-state. Compared with Shams, the time constant ({tau}) of the primary PO2m response was significantly speeded in Moderate CHF ({tau}, Sham, 19.0±1.5; Moderate CHF, 13.2±1.9 s, P<0.05) and slowed in Severe CHF ({tau}, 28.2±3.4 s, P<0.05). Within the Severe CHF group, {tau} increased linearly with the product of right ventricular and lung weight (r = 0.83, P<0.05). Conclusions: These results suggest that CHF alters the dynamic matching of muscle Formula O2-to-Formula O2 across the transition from rest to contractions and that the nature of that perturbation is dependent upon the severity of cardiac dysfunction.

KEYWORDS Heart failure; Infarction; Oxygen consumption


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