Myocardial ischemic burden and angiographic assessment of collateral network in patients with chronic total coronary occlusion

Background Chronic total coronary occlusion (CTO) myocardial territories maintain perfusion via collateral circulation from adjacent vessels, thereby preventing transmural myocardial infarction and partially preserving ventricular function. The collateral network may be categorized based on its angiographic characteristics, using either Rentrop or Werner classification, which may be used to evaluate the need for revascularization. Nevertheless, their relationship with myocardial ischemic burden is not entirely established. Purpose To assess whether collateral angiographic characteristics of patients with CTO have an impact on quantitative myocardial ischemic burden, evaluated by [13N]NH3 positron emission tomography computed tomography (PET-CT). Methods We conducted a single-centre observational prospective study on patients with CTO who had angiographic characteristics assessed by coronariography and quantitative myocardial perfusion in CTO territory measurements assessed by [13N]NH3 PET-CT, using the quantification software PCARDP (PMOD Cardiac PET Analysis Tool). Patients with insufficient data were excluded. Well developed (WD) collaterals were defined as a concomitant angiographic Rentrop grade 3 and Werner collateral connection score 2 or 3, whereas the remaining were categorized as poorly developed (PD). Results A total of 15 patients, with a mean age of 66.8 years (±4.2) and a male prevalence (80%) were included. The most affected artery was the right main coronary artery (60%). Regarding collateral evaluation, 9 patients (60%) had WD collateral circulation. When comparing myocardial ischemic burden using quantitative parameters, no statistically significant differences were observed between patients exhibiting WD and PD collateral circulation (hyperaemic myocardial blood flow, measured in mL.min-1.g-1: WD 1.24±0.53 vs. PD 1.25±0.38, p=0.971; rest myocardial blood flow, measured in mL.min-1.g-1: WD 0.66±0.17 vs. PD 0.74±0.32, p=0.513; myocardial flow reserve: WD 1.91±0.59 vs. PD 1.91±0.81, p=0.893). Conclusion The angiographic evaluation of collateral network and subsequent categorization in WD and PD collaterals in patients with CTO revealed no significant association with the observed myocardial ischemic burden in these patients. Therefore, its utility to guide decisions concerning percutaneous intervention benefit should be used cautiously.