Impact of myocardial bridging on coronary artery plaque formation and long-term mortality after heart transplantation

Objectives: This study aimed to explore the impact of myocardial bridging (MB) on early development of cardiac allograft vasculopathy and long-term graft survival after heart transplantation.

Background: MB has been reported to be associated with acceleration of proximal plaque development and endothelial dysfunction in native coronary atherosclerosis. However, its clinical significance in heart transplantation remains unclear.

Methods: In 103 heart-transplant recipients, serial (baseline and 1-year post-transplant) volumetric intravascular ultrasound (IVUS) analyses were performed in the first 50 mm of the left anterior descending (LAD) artery. Standard IVUS indices were evaluated in 3 equally divided LAD segments (proximal, middle, and distal segments). MB was defined by IVUS as an echolucent muscular band lying on top of the artery. The primary endpoint was death or re-transplantation, assessed for up to 12.2 years (median follow-up: 4.7 years).

Results: IVUS identified MB in 62% of the study population. At baseline, MB patients had smaller intimal volume in the distal LAD than non-MB patients (p = 0.002). During the first year, vessel volume decreased diffusely irrespective of the presence of MB. Intimal growth diffusely distributed in non-MB patients, whereas MB patients demonstrated significantly augmented intimal formation in the proximal LAD. Kaplan-Meier analysis revealed significantly lower event-free survival in patients with versus without MB (log-rank p = 0.02). In multivariate analysis, the presence of MB was independently associated with late adverse events [hazard ratio 5.1 (1.6-22.2)].

Conclusion: MB appears to relate to accelerated proximal intimal growth and reduced long-term survival in heart-transplant recipients.