Aims: This study evaluated associations between coronary collaterals and myocardial viability assessed by quantitative cardiac magnetic resonance (CMR) imaging in patients with a chronic coronary total occlusion (CTO).
Methods and results: 218 patients with a CTO who underwent CMR between 2013-2018 were included. A concomitant collateral connection (CC) score 2 and Rentrop grade 3 defined well-developed collaterals in 146 (67%) patients, whereas lower CC scores or Rentrop grades characterized poorly-developed collaterals. Dysfunctional myocardium (<3mm segmental wall thickening (SWT)) and ≤50% late gadolinium enhancement defined viability. Extensive scar (LGE>50%) was observed in only 5% of CTO segments. In the CTO territory, SWT was higher (3.72±1.51 vs. 3.05±1.60mm, p<0.01) and extent of scar was lower (7.0 [0.1-16.7] vs. 13.1% [2.8-22.2], p=0.048) in patients having well-developed vs. poorly-developed collaterals. Viability was more prevalent in CTO segments among patients with poorly-developed vs. well-developed collaterals (44% vs. 30% of segments, p<0.01), predominantly due to higher prevalence of dysfunctional myocardium (51% vs. 34% of segments, p<0.01) in the poorly-developed collateral group.
Conclusions: The infarcted area in myocardium subtended by a CTO is generally limited. Well-developed collaterals are associated with less myocardial scar and enhanced preserved function. However, viability was regularly present in patients with poorly-developed collaterals.