Impact of successful and failed revascularization of chronic total occlusion on left ventricular function and infarct size

Introduction

Non-randomised studies have reported a prognostic advantage with percutaneous coronary intervention (PCI) in the treatment of chronic total occlusions (CTO). Failure to cross and successfully open a CTO confers a worse clinical outcome, however most trials have included occlusions of short duration (7-30 days). PCI success rates are inversely related to the age of vessel occlusion reflecting temporal, cellular changes within a CTO, namely progressive collagen deposition.

Purpose

To assess the medium-term cardiac outcomes of PCI in the treatment of true CTO (endorsed by an expert consensus panel, requiring Thrombolysis In Myocardial Infarction [TIMI] flow grade 0 on angiography and ≥12 weeks duration) using quantitative cardiac magnetic resonance (CMR) imaging.

Methods

23 patents (mean age 60 ± 11, 82% male) referred for PCI to a single vessel de novo CTO underwent CMR examination within one week prior to and 6 months after their procedure. PCI success was defined as recanalisation of the occluded vessel and stent implantation with a final residual diameter stenosis <30%. Left ventricular (LV) function and transmural extent of infarction (TEI) were assessed using standard SSFP and T1-weighted imaging on a 1.5 T MRI system. LV volumes and mass were quantified using a dedicated software package (QMass). Segmental wall thickening (SWT) was calculated by (end systolic - end-diastolic wall thickness)/end-diastolic wall thickness × 100%. Myocardial segments were considered dysfunctional if SWT was ≤45%. Viable segments included dysfunctional myocardium with TEI <25%.

Results

TIMI 3 flow was successfully achieved in 13 of the 23 patients (59%), all treated with drug eluting stents. Baseline demographics were well matched in each group (Table 1). Opening a CTO did not result in improvement in either regional or global systolic function however it was associated with a significant increase in SWT in dysfunctional but viable segments (Table 2). Failed PCI was not associated with a worse cardiac outcome in terms of LV remodelling and infarct size as compared to patients with an open artery however one patient experienced a peri-procedural myocardial infarct (MI).

Table 1 Baseline demographics

Table 2 Results

Conclusion

In this single-centre pilot study failed revascularisation of true CTOs was not associated with worse cardiac outcomes compared to successful PCI. Despite a lack of improvement in global systolic function opening a CTO improved SWT within dysfunctional but viable segments. Larger, randomised studies are required to assess the long-term benefits and morbidity of PCI in the treatment of CTOs.