Delayed contrast agent kinetics in ischemic skeletal muscle

Abstract

To detect skeletal muscle ischemia with first-pass gadolinium (Gd) kinetics after exercise. Eleven subjects with intermittent claudication performed a symptom-limited bilateral plantar flexion exercise in the magnet. Regional ROIs were placed bilaterally in the gastrocnemius and soleus muscles, and a signal intensity (SI) time-curve analysis was performed. Induced ischemia was validated prior to the MRI with the systolic ankle-arm blood pressure index (AAI) measured after a symptom-limited treadmill exercise. Exercise induced ischemic pain in 16 of 22 legs with a significantly reduced AAI (0.31 +/- 0.15). The time to contrast arrival (TCA) was delayed in symptomatic ischemic legs vs. asymptomatic legs (16.3 +/- 6.9 seconds vs. 11.1 +/- 2.7 seconds, P < 0.05). The maximum SI during recovery was higher in the soleus muscle than in the gastrocnemius muscle in ischemic legs (1.55 +/- 0.1 vs. 1.44 +/- 0.1, P < 0.05). Symptomatic regions had a less steep upslope than asymptomatic regions (43 +/- 15 vs. 63 +/- 14, P < 0.001), with a graded upslope response to ischemia. However, a normal upslope was found in 10 of 29 ischemic regions, and some of the regions showed delayed contrast arrival, suggesting a pseudonormal upslope in ischemic regions. Exercise-induced ischemia was detected with the use of an SI time-curve analysis. However, disregarding the arterial input function and distribution volume of the tracer may lead to misinterpretation of some ischemic regions.