Background: Collaterals can maintain myocardial function or preserve viability in chronic total coronary occlusions (CTOs). It is unknown whether and to what extent collaterals regress after successful recanalization of a CTO.
Methods and results: In 103 patients with successful recanalization of a CTO collateral function was assessed by intracoronary Doppler and pressure recordings before and after recanalization, and again after 5.0+/-1.3 months. Doppler (CFI) and pressure-derived collateral function indexes (CPI) and collateral (RColl) and peripheral resistance indexes (RP) were calculated. In 10 patients with reocclusion, all without myocardial infarction during follow-up, collateral function had reached a similar level as before the first recanalization. In the other 93 patients with or without restenosis, collateral function was attenuated during follow-up. CPI had decreased by 23% immediately after recanalization (P<0.001) and decreased further by another 23% at follow-up (P<0.001). The RColl increased immediately after recanalization by 82% (P<0.001) and by a further 273% at follow-up (P<0.001). In contrast, RP increased only by 22% after recanalization (P<0.001) and by an additional 12% at follow-up (P<0.05). The initial size of the collaterals but not the incidence of a restenosis influenced the collateral regression. Only 18% of patients at follow-up had collaterals with a CPI >0.30, presumably sufficient to prevent ischemia during acute occlusion.
Conclusions: Collateral function regresses during long-term follow-up, especially in collaterals with a small diameter. In the majority of patients, collaterals are not readily recruitable in the case of acute occlusion. However, collaterals have the potential to recover in the case of chronic reocclusion.