Association between myocardial bridge with transthoracic doppler echocardiography-defined physiological indices and fractional flow reserve before and after elective percutaneous coronary intervention

Abstract

Abstract Background A myocardial bridge (MB) is a coronary variant in which an epicardial coronary artery courses through myocardium. MB can be identified by computed tomographic coronary angiography (CTCA) or invasive coronary angiography (ICA), which is known to be common in left anterior descending artery (LAD). Transthoracic Doppler echocardiography (TDE) noninvasively provides coronary flow information. Purpose We aimed to investigate the physiological impact of myocardial bridge on coronary flow dynamics assessed by adenosine-induced stress-TDE before and after elective percutaneous coronary intervention (PCI). Methods We examined 93 consecutive patients treated with fractional flow reserve (FFR)-guided elective PCI who underwent pre-PCI CTCA and pre- and post-PCI stress-TDE. We compared patient characteristics, angiographic, physiological data, and stress-TDE-defined coronary flow parameters in patients with versus without MB. Results We identified MB in 40 (43.0%) and 15 (16.1%) patients by CTCA and ICA, respectively. All MBs diagnosed by ICA were identified by CTCA. Longer MB was associated with the detectability by ICA. Older age and higher frequency of diabetes mellitus were observed in patients with CTCA-defined MB compared with those without. Pre-PCI FFR was similar in patients with versus without CTCA-defined MB (0.69 [0.61-0.73] vs. 0.69 [0.61-0.75], P=0.92), while post-PCI FFR was significantly lower in patients with versus without CTCA-defined MB (0.82 [0.78-0.86] vs. 0.84 [0.82-0.88], P=0.01). Pre- and Post- PCI hyperemic systolic peak flow velocity (SPV) by stress-TDE was higher in patients with versus without MB by CTCA (36 [26-43] m/s vs. 30 [23-34] m/s, P=0.03 and 38 [32-52] m/s vs. 33 [20-39] m/s, P=0.02, respectively). Pre-PCI hyperemic diastolic peak flow velocity (DPV) by stress-TDE was not significantly different between the 2 groups (49 [39-64] m/s vs. 45 [34-55] m/s, P=0.12), while post-PCI hyperemic DPV was higher in patients with versus without CTCA-defined MB (73 [60-85] m/s vs. 63 [50-81] m/s, P=0.03). Conclusion In patients undergoing elective PCI for LAD, a presence of CTCA-defined MB was associated with higher pre- and post-PCI hyperemic SPV and an acceleration of hyperemic DPV after the PCI. Impact of systolic compression by MB on hyperemic DPV at the distal segment accelerated by the treatment of upstream stenosis may lead to lower post-PCI FFR compared with patients without MB.