Intravascular Ultrasound Predictors of Subacute Vessel Closure after Balloon Angioplasty or Atherectomy

Vessel closure is a major complication after percutaneous coronary intervention (PCI) and is associated with a high rate of adverse clinical events.1,2 The occurrence of abrupt closure has been observed and evaluated mostly after stent implantation.3 Angiographic and intravascular ultrasound (IVUS) studies have shown that inadequate stent expansion is the main cause for this complication.4,5 In arteries treated with balloon angioplasty and atherectomy, however, the predictive factors of subacute closure have not been well established.6 IVUS provides unique tomographic and transmural imaging of coronary lesions pre- and post-intervention.7,8 The current study reviewed the pre- and post-intervention IVUS findings of lesions that developed angiographically documented subacute closure within 1 week after successful balloon angioplasty or atherectomy. We attempted to identify underlying IVUS predictors of this syndrome. Methods Patient Population. We included all patients who developed subacute closure after a de novo coronary narrowing was treated with balloon angioplasty or atherectomy during which IVUS imaging was performed. In our institution, IVUS is performed on a systematic basis in all PCIs, therefore, patients undergoing IVUS-guided PCI were not selected. The exclusion criteria were: 1) bailout stent implantation during the procedure; and 2) myocardial infarction within 1 month prior to the intervention. Baseline demographic and procedural variables and outcomes were recorded and entered prospectively in a pre-specified database by a dedicated data-coordinating center. All patients were interviewed by experienced research nurses at 30 days and 6 months after their procedure regarding the occurrence of cardiac events or the need for repeat coronary revascularization. All procedure complications and cardiac events were source-documented and adjudicated. All patients received daily aspirin pre- and post-procedure, but not ticlopidine or clopidogrel. Subacute vessel closure was defined as recurrent ischemia with angiographically documented vessel occlusion at the site of treatment within 7 days after successful index procedure. A successful index procedure was defined as a patent vessel at the treatment site with anterograde TIMI-3 flow and angiographic residual stenosis Qualitative analysis. IVUS characteristics were identified according to the criteria of the American College of Cardiology Clinical Expert Consensus Document on IVUS and confirmed by comparing pre- versus post-interventional IVUS studies.9 Atheroma were classified as soft, fibrous, calcific, and mixed according to the plaque echogenicity. Thrombus was recognized as a pedunculated echolucent intraluminal mass or channels into the plaque. Dissections were classified in intimal, medial, or adventitial. Ruptured plaque was defined as plaque ulceration with torn fibrous cap. Other unusual lesion morphologies were also noted. A calcified artery had at least 2 quadrants of calcium with calcium > 90° over half the lesion length. Quantitative analysis. Using planimetry software (TapeMeasure, INDEC Systems Inc.), the following lesion and reference measurements were made: external elastic membrane cross sectional area (CSA, mm2), lumen CSA area (mm2), plaque and media (external elastic membrane minus lumen) CSA, and plaque burden (plaque and media divided by external elastic membrane). The lesion site was the image slice with the smallest lumen CSA. The proximal and distal reference segments were the most normal-looking cross sections 1.0. Statistical analysis. Statistics were performed with StatView 5.0 (SAS Institute). Continuous variables were expressed as means ± 1 SD and compared with student’s t-test. Categorical data were expressed as frequencies and compared using chi-square statistics. Results Patients and procedures. During the 10-year study period, 3,403 patients were treated with balloon angioplasty or atherectomy with IVUS imaging during the procedure. There were 8 patients (0.2%) with documented vessel closure within 1 week after the procedure. Median time between index procedure and abrupt closure was 39 hours (14 to 72 hours). Patient characteristics are presented in Table 1. Average heparin dose during the procedure was 115 UI (100 UI to 150 UI). One patient with thrombus received intracoronary urokinase. No patient received a glycoprotein IIb/IIIa inhibitor. Clinical outcomes. At 30 days, death occurred in 1 patient (12.5%). In 5 patients (62%), creatine-kinase (CK) following vessel closure rose above 5 times the normal value, and Q-wave myocardial infarction occurred in 1 patient. At 6 months, the mortality rate was 12.5%. IVUS findings. IVUS findings are shown in Table 2. Subacute closure lesions (N = 8) are compared to a subset of matched lesions that did not develop subacute closure (N = 24). The most notable pre-intervention finding is that subacute closure lesions were not calcified. No lesion in either group had a pre-intervention thrombus. Vessels developing subacute closure were ordinary atherosclerotic lesions and did not present remarkable pre-intervention IVUS aspect as compared to matched controls. The most notable post-intervention finding is that subacute closure lesions typically had residual lumen dimensions that were smaller in comparison to the reference lumen than the matched group. Dissections were observed in 4 patients (50%). One was distal to the lesion, and 3 were mid-lesion; 2 had a mobile flap. The arc of dissection was Limitations. This study was retrospective. It was also an analysis of PCI performed with IVUS imaging. In general, IVUS information was used interactively during the procedure and may have influenced the results. Sub-optimal final lumen, dissections and thrombus were recognized by IVUS during the intervention but no further intervention was pursued since all patients had adequate lumen by angiogram with normal coronary flow. The main limitation of this study is that there were few subacute closure lesions. Therefore, the predictive value of the IVUS findings must be substantiated in larger patient numbers. Glycoprotein IIb/IIIa inhibitors were not used. Conclusions. This study showed that 87% of patients developing subacute vessel closure after successful balloon angioplasty or atherectomy had one or more abnormal findings as assessed by IVUS. Post-procedure lumen dimensions and dissections are the most important morphologies associated with subacute vessel closure.

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