Delayed contrast agent kinetics in ischemic skeletal muscle

Area of Science:

• Radiology and Imaging
• Vascular Medicine
• Exercise Physiology

Background:

• Skeletal muscle ischemia, often caused by peripheral artery disease, leads to intermittent claudication.
• Accurate detection of exercise-induced ischemia is crucial for diagnosis and management.
• First-pass contrast-enhanced MRI offers a potential non-invasive method for assessing muscle perfusion.

Purpose of the Study:

• To evaluate the utility of first-pass gadolinium (Gd) kinetics using signal intensity (SI) time-curve analysis for detecting exercise-induced skeletal muscle ischemia.
• To correlate MRI findings with physiological measurements of ischemia.

Main Methods:

• Eleven subjects with intermittent claudication underwent symptom-limited plantar flexion exercise during MRI.
• Regional ROIs were placed in gastrocnemius and soleus muscles to analyze SI time-curves.
• Ischemia was validated using the ankle-arm blood pressure index (AAI) after treadmill exercise.

Main Results:

• Exercise induced ischemic pain in 16 of 22 legs, confirmed by a significantly reduced AAI.
• Time to contrast arrival (TCA) was delayed in symptomatic ischemic legs compared to asymptomatic legs (16.3 vs. 11.1 seconds).
• Symptomatic regions showed a less steep SI upslope, indicating reduced perfusion, although some ischemic regions exhibited pseudonormalization.

Conclusions:

• SI time-curve analysis can detect exercise-induced skeletal muscle ischemia.
• Potential misinterpretation of ischemic regions may occur if arterial input function and distribution volume are disregarded.