Cardiac cycle weighted ΜQFR for the assessment of functional relevance of the myocardial bridge

Myocardial bridging (MB) causes coronary artery compression in systole, potentially resulting in angina and arrhythmias. Stent implantation in patients with MB may offer short-term improvement of symptoms, but carries a high risk of restenosis. We present a symptomatic patient with MB who was assessed by a novel angiography-based functional index that incorporates both the diastolic and systolic phases of the heart cycle - termed "cardiac cycle weighted µQFR" (µQFRccw). In addition to the observed dynamic systolic narrowing of the left anterior descending artery (LAD), a fixed stenotic (atherosclerotic) component was suspected due to mild diastolic diameter reduction. Invasive physiological measurements during adenosine and dobutamine provocation were also performed. Following administration of 200 µg ic. adenosine, the FFR was measured as 0.74, while during a 40 µg/bwkg/min dobutamine iv. infusion it was measured as 0.83. The measured FFR during adenosine-induced hyperemia was found to be very close in value to the calculated µQFRccw (0.74 vs. 0.75). This case demonstrates the potential utility of the image-based cardiac-cycle weighted µQFR in MB evaluation. In our opinion, the discordance between the significant invasive adenosine FFR and the non-significant dobutamine FFR results may indicate a fixed atherosclerotic component of the lesion, which could support the consideration of stenting despite the potential risk of restenosis.