Myocardial Bridging in Absence of Coronary Artery Disease: Proposal of a New Classification Based on Clinical-Angiographic Data and Long-Term Follow-Up

Abstract

Background: There is no widely accepted classification to guide therapy in patients with symptomatic myocardial bridging (MB). Methods: A retrospective analysis of 157 patients with chest pain, angiographic MB of the left anterior descending artery without obstructive coronary artery disease (CAD) was performed. Patients were evaluated for clinical symptoms, objective signs of ischemia by stress test, intracoronary Doppler flow measurement and coronary flow reserve. 100 patients without CAD or MB served as controls. Results: There was no difference in clinical symptoms and objective signs of ischemia between controls and patients with MB. The length of MB was 22.6 ± 7.8 mm, maximal systolic luminal diameter reduction 71 ± 16%, and maximal mid-diastolic luminal reduction 34.7 ± 13% as demonstrated by quantitative coronary angiography (QCA). Intracoronary Doppler showed significantly increased average peak flow velocity (APV), average systolic peak velocity (ASPV), average diastolic peak flow velocity (ADPV), and maximal peak velocity (MPV) in MB versus proximal and distal segments at rest and after maximal vasodilatation (p < 0.001 for all parameters). Coronary flow reserve was significantly higher proximally (2.9 ± 0.9) compared with segments distal to the MB (2.0 ± 0.6, p < 0.01). We propose a new MB classification for symptomatic patients with MB:Type A:incidental finding on angiography, no objective signs of ischemia; Type B: objective signs of ischemia, and Type C: with or without objective signs of ischemia and altered intracoronary hemodynamics (by QCA/CFR/intracoronary Doppler). 5-Year follow-up data based on this classification showed that types B and C responded well to β-blockers or calcium channel antagonists. Patients with type C refractory to medical therapy were treated with stenting of the MB. Conclusion: Patients with MB without CAD did not have a higher prevalence of chest pain or abnormal non-invasive stress tests compared to patients without CAD or MB. Intracoronary hemodynamic measurement is a novel approach that may be valuable in defining the functional significance of MB. We propose a classification of symptomatic patients with MB without CAD using non-invasive and invasive parameters to guide therapeutic choices.

Significance of the Anatomical Properties of a Myocardial Bridge in Coronary Heart Disease

“…Coronary angiography shows that patients with ischemic symptoms generally demonstrate systolic narrowing >70-75% at the bridged segment at rest without nitrate administration 9 and/or hemodynamic abnormality, 21 and their abnormal blood flow should be improved by appropriate treatment. The anatomical properties of the MB also influence the method of treatment and the patient's outcome.…”

Coronary artery myocardial bridging: Is it benign or not?

“…In agreement with a recent proposal of new functional classification [37], additional efforts should be made in order to check better for hemodynamic significance of MB, especially in patients with no coronary artery disease. Physical stress or exercise may play a triggering role for arrhythmias or symptoms [9,27], so that a stress-testing should be performed in each patient as a part of the diagnostic workup.…”

Attenuation Drop of Intra-Mural Coronary Segment Observed at Diastolic Phase of Coronary CT Angiography Predicts Significant Systolic Compression of Myocardial Bridge

“…Although MB is generally considered a benign anomaly, it may be associated with clinical manifestations that have been linked to dynamic compression [5][6][7][8][9][10][11]. The treatment strategy is guided by the presence of reduced myocardial perfusion, which is closely related to extent of dynamic compression [18,19]. Therefore, it is clinically important to iden- tify the presence of significant dynamic compression to select proper candidates for medical treatment.…”