The Influence of the Presence of the Ramus Intermedius on Atherosclerosis Plaque Deposition in the Left Bifurcation Region in Low-Risk Individuals.

Background: Additional bifurcations at the left main coronary artery (LMCA) could modify the geometry of the left coronary system, disturbing haemodynamic flow patterns and potentially altering endothelial shear stress (ESS). A low ESS has been implicated in atherogenesis. The emergence of the ramus intermedius (RI) from the LMCA creates additional branching, but the specific role of the RI in plaque deposition at the left coronary system remains unclear. This study sought to elucidate the potential effects of the RI on plaque formation at the LMCA and its bifurcation.

Methods: A retrospective cross-sectional single-centre study was conducted using data from 139 female patients who were identified to have low risk of cardiovascular disease. These patients underwent cardiac computed tomography angiography between January 2017 and December 2018. Contrasted multiplanar coronary images taken during the best diastolic phase were analysed for the presence (experimental group) or absence (control group) of the RI. Measurements of plaques were done at the LMCA and at a 10 mm distance from the ostia of daughter arteries. Plaque data at the left bifurcation region were analysed using descriptive statistics, chi-square, and binary logistic regression tests. A p-value of <0.05 was considered statistically significant.

Results: Amongst these low-risk patients, 33.8% (n = 47) had an RI. In the presence of RI, there was an eight-fold increased risk of plaque deposition at the LMCA (adjusted odds ratio, aOR = 8.5) and a three-fold increased risk of plaque deposition at the proximal left anterior descending (pLAD), especially on its lateral wall (aOR = 3.5). However, the RI did not influence plaque deposition at the distance of 10 mm from the ostium of the proximal left circumflex artery.

Conclusions: These findings suggest that the RI increases the risk for atherosclerosis plaque deposition by three to eight-fold at the pLAD artery and the LMCA.