Usefulness of preprocedural coronary lesion morphology as assessed by intravasuclar ultrasound in predicting Thrombolysis In Myocardial Infarction frame count after percutaneous coronary intervention in patients with Q-wave acute myocardial infarction

Abstract

T remains some concern regarding coronary blood flow deterioration in patients after percutaneous coronary intervention (PCI). The corrected Thrombolysis In Myocardial Infarction (TIMI) frame count (cTFC) is a quantitative index of coronary blood flow, it reflects microcirculatory damage, and it predicts clinical and functional outcomes after acute infarct intervention.1–3 Intravascular ultrasound (IVUS) assesses lesion morphologies in a way not possible using other techniques. We hypothesized that IVUS would identify morphologic features predictive of the final post-PCI cTFC in patients who had an acute infarction. • • • From 1998 to 2001, we studied infarct related arteries in 43 consecutive patients with IVUS-imaged ST-segment elevation acute myocardial infarction who met the following criteria: (1) native coronary arteries; (2) 72 hours from onset of symptoms to IVUS and intervention; (3) optimum assessment by IVUS and angiography; (4) no angiographic distal embolization or TIMI grade 0 or 1 flow at the end of procedure; and (5) no significant residual stenosis, inflow or outflow disease, or evidence of coronary perforation or flow-limiting dissection by IVUS or angiography. The study included 28 men and 15 women (62 14 years of age). Fifteen patients had received intravenous thrombolysis. Stenosis location was in the left anterior descending coronary artery in 15 patients, left circumflex artery in 8, and right coronary artery in 20. Five patients were treated with balloon alone and 38 with stenting. One patient was treated with thrombectomy before stenting. Nine stents were inserted without predilation and 28 after balloon predilation. Glycoprotein IIb/IIIa inhibitors were used in 8 patients during angioplasty. Angiograms were reviewed blinded to the IVUS results. Quantitative coronary angiography was performed using the CAAS II system (Pie Medical, Maastricht, The Netherlands) on images after intracoronary nitroglycerin in single planes that identified the greatest stenosis severity. Films were recorded at 30 frames/s. The frame count was measured with a frame-counting cine viewer. cTFC was obtained using the technique described by Gibson et al1,2 IVUS was performed with a commercially available system (Boston Scientific Corp./SciMed, Maple Grove, Minnesota) after the intracoronary administration of 100 to 200 g of nitroglycerin. The IVUS catheter was advanced approximately 10-mm distally to the lesion and withdrawn automatically (0.5 mm/s) to the aorto-ostial junction. Studies were recorded on 1/2-in high-resolution s-VHS tapes for off-line analysis. Quantitative analysis was performed using computerized planimetry (TapeMeasure; Indec Systems, Capola, California). Measurements included proximal and distal reference, lesion external elastic membrane (EEM), lumen, plaque and media (EEM minus lumen) cross-sectional areas (mm) and plaque burden (plaque and media divided by EEM). Remodeling index was lesion EMM divided by mean reference EEM. Qualitative assessment was performed according to 2 previously published consensus documents.4,5 When it appeared to be present, thrombus was classified as (1) a low-echoic smooth mass with a distinct interface with the underlying plaque, (2) attached to the vessel wall, or (3) mobile. Statistical analysis was performed using StatView 5.0 (SAS Institute, Cary, North Carolina). Continuous variables are expressed as mean 1SD; categoric variables are expressed as frequencies. Variables were compared using Student’s t test, categoric analysis of variance, and correlation coefficients. Multivariate linear regression analysis was used to assess predictors of cTFC. A p value 0.05 was considered significant. Angiographic findings are listed in Table 1. Heart rate was 80 15 beats/min, systolic blood pressure was 118 19 mm Hg, and diastolic blood pressure was 70 14 mm Hg. Preprocedural IVUS findings are listed in Table 2. Stenosis length was 17 9 mm. There was no difference in stenosis length (p 0.2), plaque media area (p 0.3), and the presence of thrombus (p 0.5) between patients treated with and without preinterventional thrombolysis. Final cTFC correlated with preinterventional stenosis EEM area (r 0.45, p 0.0022), plaque From the Cardiovascular Research Institute, Washington Hospital Center, Washington, DC; and the Cardiovascular Research Foundation, New York, New York. Dr. Weissman’s address is: Washington Hospital Center, 110 Irving Street, NW, Suite 4B-1, Washington, DC 20010. E-mail: Neil.J.Weissman@medstar.net. Manuscript received November 1, 2002; revised manuscript received and accepted December 3, 2002.