Collateral formation in patients after percutaneous myocardial revascularization: a mechanism for improvement?

Percutaneous myocardial revascularization (PMR) has emerged as a novel therapeutic strategy for patients with ischemic heart disease not amendable to traditional revascularization approaches. Despite the symptomatic improvement documented in clinical trials, underlying mechanism remains unknown.We assessed the coronary angiograms of 25 patients before and 6 months after the PMR procedures for collateral vessel formation. The Rentrop scoring system was used to score the extent of collateral vessel formation. The angiograms were analyzed by 2 independent reviewers. The change in Rentrop score and improvement in angina status was correlated.During follow-up period of 6 months, no patient died or suffered from myocardial infarction. Overall the mean Canadian Classification Society (CCS) class among the study patients was significantly improved from 3.5 to 2.4; mean difference = 1.08 (p < 0.0001). Among these, 8 (32%) had improvement of > 2 CCS classes (p = 0.003) (improvement group). The rest of the patients had either no change (n = 8; 32%) or improvement of 1 CCS class (n = 9; 36%) (no improvement group). The Rentrop score improved in 3 (12%), remained unchanged in 22 (88%) and deteriorated in 0 patient. Overall, there was no significant change in Rentrop score at 6-month follow-up; mean difference 0.13 (p = 0.08). There was also no correlation between the change in extent of collateral vessel formation and the improvement in angina status (correlation coefficient r = 0.09) at 6 months after PMR.Improvement in collateral vessel formation is unlikely to be a mechanism responsible for symptomatic improvement in patients after PMR.