MRI Perfusion Index as a Measure of Peripheral Arterial Disease Severity Pubblico
Topel, Matthew Laurence (2013)
Published
Abstract
Background: Objective and quantitative evaluation of the functional impairment caused by peripheral arterial disease (PAD) is difficult and frequently assessed through proxy measurements such as the ankle-brachial index (ABI). While ABI is both sensitive and specific for the diagnosis of PAD, its value in assessing disease severity and monitoring disease improvement is poor. Recently, gadolinium-enhanced first-pass magnetic resonance imaging (MRI) of the lower extremities has emerged as a new method to assess perfusion in peripheral muscles immediately following peak exercise.
Objective: To demonstrate that calf muscle perfusion index (PI) measured with MRI is associated with PAD severity, as measured by peak treadmill walking time (PWT).
Methods: 82 subjects with PAD were included in the study. Subjects exercised until fatigue using an MR-compatible plantar-flexion ergometer. Images were acquired immediately following peak exercise using a dynamic, first-pass, dual-contrast sequence. PI was calculated as a ratio of muscle perfusion to arterial flow. Graded treadmill exercise testing was performed using the Gardner protocol. PWT, pre- and post-exercise ABI were recorded for each patient. Demographic and historical information were collected through screening questionnaires.
Results: 64 patients completed both the MRI and treadmill test. A 1 standard deviation increase in PI was associated with a 20.7% increase in PWT (95% CI, 3.42-40.9%; R2=0.087, P=0.018). PI was not correlated with pre- or post-exercise ABI. After adjusting for ABI, PI remained a significant predictor of PWT (F=8.91, P=0.004). Stratified analysis of potential interaction showed that the association between PI and PWT was significant only at "High" ABI levels (pre-exercise, R2=0.263, P=0.004; post-exercise R2=0.211, P=0.008) and in individuals without previous lower extremity vascular intervention (R2=0.105, P=0.042).
Conclusions : MR-based calf muscle PI is associated with PAD severity, as measured by PWT. Additionally, the association between PI and PWT appears stronger at "High" ABI levels and in subjects without a history of previous lower extremity vascular intervention. PI may be a valuable tool to objectively and quantitatively assess muscle perfusion in a PAD population with borderline normal ABI and no history of lower extremity vascular intervention.
Table of Contents
INTRODUCTION...............................................................1
BACKGROUND.................................................................3
METHODS......................................................................8
RESULTS......................................................................13
DISCUSSION.................................................................17
REFERENCES.................................................................22
FIGURES......................................................................25
TABLES.......................................................................33
APPENDIX....................................................................37
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