Detection of skeletal muscle hypoperfusion during exercise using phosphorus-31 nuclear magnetic resonance spectroscopy

Abstract

Blood flow to working skeletal muscle is frequently reduced in patients with heart failure or peripheral vascular disease. To determine if phosphorus nuclear magnetic resonance (NMR) can noninvasively detect such muscle underperfusion, gated phosphorus-31 NMR spectroscopy was used to compare muscle inorganic phosphate, phosphocreatine and pH during mild wrist flexion exercise at 0.2, 0.4 and 0.6 W in eight normal men, before and after reduction of forearm blood flow. Forearm flow was reduced by cuff inflation to a pressure determined by Doppler ultrasound to bring flow to 40 to 60% of control. Attention was focused on the inorganic phosphate to phosphocreatine (Pi/PCr) ratio and pH, two variables potentially sensitive to muscle oxygen delivery. At rest with normal flow, Pi/PCr averaged 0.12 +/- 0.03 and pH averaged 7.02 +/- 0.04. Exercise produced a progressive increase in Pi/PCr (0.2 W = 0.43 +/- 0.12; 0.4 W = 0.75 +/- 0.31; 0.6 W = 1.04 +/- 0.47) and a modest decrease in pH (0.2 W = 6.94 +/- 0.04; 0.4 W = 6.86 +/- 0.18; 0.6 W = 6.85 +/- 0.06). Flow reduction had no effect on Pi/PCr or pH at rest. In contrast, flow reduction during exercise was associated with higher Pi/PCr at all three work loads (0.2 W = 0.60 +/- 0.27; 0.4 W = 0.99 +/- 0.50; 0.6 W = 2.00 +/- 1.26 [all p less than 0.05 versus normal flow]) and lower pH (0.2 W = 6.78 +/- 0.12; 0.4 W = 6.69 +/- 0.23; 0.6 W = 6.65 +/- 0.30 [p less than 0.01 versus normal flow at 0.2 and 0.4 W; p = 0.05 at 0.6 W]).(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed Calf Muscle Phosphocreatine Recovery After Exercise Identifies Peripheral Arterial Disease

“…These findings are in accordance with other studies that have demonstrated delayed regeneration of PCr as a reliable marker of arterial obstruction (12,17,24,25). When compared with normal subjects in our study, there was an approximate three-fold increase in the recovery time constant among patients.…”

Peripheral Arterial Disease Assessment

“…These findings are in accordance with other studies that have demonstrated delayed regeneration of PCr as a reliable marker of arterial obstruction. 13,58,65,66 When compared with normal subjects in our study, there was an approximate 3-fold increase in the recovery time constant among patients. The area under the fitted curve of the ROC analysis is 0.925, demonstrating that PCr recovery kinetics can be used to discriminate mild to moderate symptomatic PAD patients from normals.…”

Skeletal muscle response to exercise training in congestive heart failure.

“…During submaximal exercise, a reduction of oxygen delivery to exercising skeletal muscle results in a higher Pi/PCr and greater lactate production (22). Since the peripheral blood flow response to exercise in CHF is inappropriately low (18,23), an increase in blood flow could be expected to improve exercise metabolism.…”