Comprehensive Intravascular Ultrasound Assessment of Stent Area and Its Impact on Restenosis and Adverse Cardiac Events in 403 Patients Wit h Unprotected Left Main Disease

Article Summary

Insufficient stent expansion is the most common reason for restenosis and stent thrombosis following implantation of drug-eluting stents (DES). Minimum stent area (MSA) as determined by IVUS is known to be a useful pr edictor of restenosis and stent thrombosis. A 2011 study by Kang et al 2 therefore aimed to determine the optimum MSA cutoff value to predict both restenosis and long-tem clin ical outcomes. The study included 403 patients with LM disease who underwent im plantation of a sirolimus-eluting stent. After stenting, the MSA was assessed in 4 prespecifi ed segments: the LM proximal to the polygon of confluence (POC), the POC i tself, the left anterior descending artery (LAD), and the left circumflex artery (LCX). Of the patients undergoing PCI, 13% were ostial/midshaft and 87% were bifurcation lesions. Two thirds of the bifurcation lesions were treated with a 1-stent strategy, and one-t hird was treated with a 2-stent strategy (crush and T-stents).

Angiographic follow-up was performed at 9 months and s howed that 11.4% of participants had angiographic restenosis at 9 months: 4.5 % nonbifurcation lesions treated with a single-stent, 6.3% bifurcation lesions treated with single-stent crossover, and 25.4% of bifurcation lesions treated with 2 stent s, supporting a 1-stent strategy in LM bifurcation lesions. The MSA cutoffs that best predict ed in -stent retenosis were 5.0 mm 2 at the ostial LCX, 6.3 mm 2 at the ostial LAD, 7.2 mm 2 within the POC, and 8.2 mm 2 within the LM proximal to the POC.

Clinical follow-up was performed at 2 years and determi ned the incidence of major cardiovascular events (MACE), which was defined as death of cardiac cause, target lesion revascularization (TLR), and myocardial infarctio n (MI). At 2 years, survival free of MACE was significantly lower in patients with underexpan sion of at least 1 segment compared with lesions with adequate stent expansion (90± 3% versus 98±1%, log-rank p<0.001), and poststenting underexpansion was found to be an independent predictor for MACE, especially repeat revascularization (adjusted h azard ratio [HR], 5.56; 95% confidence interval, 1.99 – 15.49; p=0.001). Acute malapposition by IVUS in the LM was not related to either restenosis or 2-year MACE.

The findings of this study are important as they demon strate the importance of influence of smaller stent areas after PCI on adverse outcomes, fi ndings that are in line with other studies. 4 , 5 The authors concluded that correcting underexpansion wit h these optimal IVUS criteria using IVUS guidance during LM stenting pr ocedures may reduce cardiac events after DES treatment for LM disease.

Take-home message: larger poststent areas determined by IVUS are associated with better outcomes during LM DES implantation

Impact of IVUS guidance on long-term mortality in stenting for unprotected LM stenosis

In a 2009 analysis of the large multicenter registry of the revascularization for unprotected LM stenosis: COMparison of Percutaneous coronary Angioplasty versus surgical Revascularization (MAIN-COMPARE) study, Park et al compared the long term outcomes of IVUS-guided and conventional angiographi c stent implantation in patients with LM lesions. 6 The analysis included 975 patients, of whom 756 (77.5%) underwent IVUS-guided stenting and 219 (22.5%) underwent angiog raphy-guided procedures. Since patient and procedural characteristics differed bet ween groups, propensity score matching, a statistical technique that selects 2 similar g roups of patients with the same baseline characteristics within a study population, created 201 matched pairs of patients.

At 3-year follow-up, 102 patients (51%) undergoing IV US guidance and 116 patients (58%) undergoing angiography guidance had dropped out of the study. However, an analysis of the remaining patients showed that the use o f IVUS guidance during stent implantation was associated with a 46% lower risk of 3-yea r mortality compared with angiography guidance (6.0% vs. 13.6%, log-rank p= 0.063; HR , 0.54; 95% CI, 0.28 to 1.03). When the analysis was limited to 145 matched pa irs of patients receiving drug- eluting stents (DES) , the risk reduction in 3-year mortality was more striking: 61% with IVUS guidance compared with angiography guidance (4.7% v ersus 16.0%, log-rank p= 0.048; HR , 0.39; 95% CI, 0.15 to 1.02). However , in 47 matched patients receiving bare metal stent (BMS), the use of IVUS guidance did not reduce the risk of 3-year mortality (8.6% versus 10.8%, log-rank p= 0.35; hazard ratio, 0.59; 95% CI, 0.18 to 1.91). IVUS guided stenting did not affect the incidence of m yocardial infarction or target vessel revascularization. The use of DES has been associated with higher rates of late stent thrombosis than with BMS. It is therefore possible that IVUS guidance reduces the stent thrombosis risk.

This was the first study to show a mortality benefit for IVUS-guided procedures in LM CAD, and provided evidence to justify future large r andomized studies. This study is particularly important because at the time of publica tion, stent implantation in patients with unprotected LM disease was a rapidly growing procedure but represent ed a major clinical challenge. The authors concluded that the study p rovided evidence to recommend the routine use of IVUS in stent implantati ons in LM stenosis.