Abstract
Myocardial Bridging (MB) refers to the band of myocardium that abnormally overlies a segment of a coronary artery. This paper quantitatively evaluates the influence of MB of the left anterior descending artery (LAD) on myocardial perfusion of the entire left ventricle. We studied 131 consecutive patients who underwent hybrid rest/stress 13N-ammonia positron emission tomography (PET) and coronary computed tomography angiography (CCTA) due to suspected myocardial ischemia. Patients with previous myocardial infarction and/or significant coronary artery disease (≥ 50% stenosis) were excluded. Myocardial perfusion measurements were compared between patients with and without LAD-MB. Additionally, we evaluated the relationship between anatomical characteristics (length and depth) of LAD-MB and myocardial perfusion measurements. 17 (13%) patients presented a single LAD-MB. Global myocardial perfusion reserve (MPR) was lower in patients with LAD-MB than in patients without LAD-MB (1.9 ± 0.5 vs. 2.3 ± 0.6, p < 0.01). Global stress myocardial blood flow (MBF) was similar in patients with and without LAD-MB (2.2 ± 0.4 vs. 2.3 ± 0.7 ml/g/min, p = 0.40). Global rest MBF was higher in patients with LAD-MB than in patients without LAD-MB (1.2 ± 0.3 vs. 1.0 ± 0.2 ml/g/min, p < 0.01). Global rest MBF, stress MBF, and MPR quantifications were similar in patients with superficial and deep LAD-MB (all p = NS). We did not find any correlation between length and global rest MBF, stress MBF nor MPR (r = − 0.14, p = 0.59; r = 0.44, p = 0.07; and r = 0.45, p = 0.07 respectively). Quantitative myocardial perfusion suggests that LAD-MB may be related to impaired perfusion reserve, an indicator of microvascular dysfunction. Anatomical characteristics of LAD-MB were not related to changes in myocardial perfusion.
Highlights
Right Coronary Artery (RCA) Right coronary artery positron emission tomography (PET) Positron emission tomography coronary computed tomography angiography (CCTA) Coronary computed tomography angiography myocardial perfusion reserve (MPR) Myocardial perfusion reserve myocardial blood flow (MBF) Myocardial blood flow coronary artery disease (CAD) Coronary artery disease SSS Summed stress score summed rest score (SRS) Summed rest score summed difference score (SDS) Summed difference score CAC Coronary artery calcium score
Mean global rest MBF was significantly increased in left anterior descending artery (LAD)-Myocardial bridging (MB) patients
Mean global stress MBF was similar in patients with and without LAD-MB
Summary
RCA Right coronary artery PET Positron emission tomography CCTA Coronary computed tomography angiography MPR Myocardial perfusion reserve MBF Myocardial blood flow CAD Coronary artery disease SSS Summed stress score SRS Summed rest score SDS Summed difference score CAC Coronary artery calcium score. Introduction hypothesized that anatomical characteristics of a LAD-MB, especially depth and length, are related to the clinical presentation, but this remains unclear [14]. There were three aims of this study: firstly, to compare global perfusion measurements of patients with and without LAD-MB; secondly, to compare regional perfusion measurements of the three vascular territories (LAD, LCx, and RCA) of patients with and without LAD-MB; thirdly, to evaluate the relationship of anatomical characteristics (length and depth) of LAD-MB, measured by CCTA, and quantitative perfusion measurements, as measured by PET. The clinical presentation of this coronary anomaly varies widely from asymptomatic patients to those with myocardial ischemia, myocardial infarction, and even sudden death [2,3,4,5,6]. It has been reported that patients with mild compression of the LAD-MB may show a normal distal flow of the LAD and septal ischemia, called “branch steal phenomenon”, due to high velocity within the MB segment and changes in perfusion pressure affecting septal branches of the LAD [9, 10]
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