Non-Contrast Magnetic Resonance Angiography Outperforms Digital Subtraction Angiography in Detecting Hibernating Below-The-Knee Arteries and Downgrades TASC and GLASS Scores in CLTI Patients

Abstract

Introduction: Current imaging techniques are limited in their ability to accurately characterize below-the-knee diseased vessels. Digital subtraction angiography (DSA) remains the gold standard but may not visualize some vessels because it relies on nephrotoxic contrast that can fail to reach and opacify distal vessels. Quiescent-interval single shot (QISS) MRI images patients without exposure to nephrotoxic agents such as gadolinium or ionizing radiation and has been suggested to show "hibernating vessels" that are not visualized on DSA. The aim of this study is to evaluate whether QISS MRI would identify more patent vessels when compared to DSA, and whether this resulted in less severe Transatlantic Inter-Society Consensus (TASC) II and Global Limb Anatomic Staging System (GLASS) grades.

Methods: Patients with CLTI undergoing QISS MRI and DSA were included. Two examiners reviewed the imaging of each patient on both modalities. The vessels assessed were the popliteal and infrapopliteal arteries. All vessels were split into three sections (e.g Anterior tibial artery [ATA]1=proximal, AT2=middle, AT3=distal) and scored as either patent or occluded as individual segments (except the tibioperoneal and dorsalis pedis arteries which were counted as one segment each). Following this, TASC II and infrapopliteal GLASS scoring was performed and compared between QISS MRI and DSA.

Results: 41 patients were evaluated. Overall, 570 vessel segments were analyzed, with a significantly higher number of patent vessel segments found on QISS MRI compared to DSA (66% vs 58%, p<0.001). On single vessel analysis, there was a higher level of patency seen on QISS MRI compared to DSA in the peroneal (72% vs 61%, p=0.001), posterior tibial (54% vs 42%, p=0.001, anterior tibial (60% vs 52%, p=0.01) and dorsalis pedis arteries (65% vs 38%). Overall TASC II and GLASS scoring did not significantly differ when comparing DSA and QISS MRI. Subgroup analysis of TASC D and infrapopliteal GLASS 4 lesions showed that vessels were significantly more likely to be downgraded to lower grade lesions when interpreting images using QISS MRI in comparison to DSA.

Conclusion: QISS MRI can identify more patent vessel segments when compared to the current gold standard, DSA. This study also suggests that QISS MRI may result in lower grading on TASC II and GLASS scoring of the most severe spectrum of arterial disease. The improved visualization with QISS may expand the range of viable treatment options for patients with complex below-the-knee disease in CLTI.