In daily clinical practice, in-stent restenosis (ISR) is defined

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1 Impact of In-Stent Minimal Lumen Area at 9 Months Poststent Implantation on 3-Year Target Lesion Revascularization Free Survival A Serial Intravascular Ultrasound Analysis From the TAXUS IV, V, and VI Trials Hiroshi Doi, MD, PhD; Akiko Maehara, MD; Gary S. Mintz, MD; Neil J. Weissman, MD; Alan Yu, MS; Hong Wang, MS; Lazar Mandinov, MD; Jeffrey J. Popma, MD; Stephen G. Ellis, MD; Eberhard Grube, MD; Keith D. Dawkins, MD; and Gregg W. Stone, MD Background Intravascular ultrasound (IVUS) is used to assess intermediate lesions in native coronary arteries; minimum lumen area (MLA) 4.0 mm 2 is accepted as a cutoff for a significant stenosis. We evaluated the IVUS in-stent MLA at 9-month follow-up that best predicted subsequent target lesion revascularization (TLR) free survival in patients from the TAXUS IV, V, and VI studies. Methods and Results In the combined TAXUS IV, V, and VI randomized trials, 9-month IVUS was available in 635 patients (331 treated with paclitaxel-eluting stents [PES] and 304 treated with bare-metal stents [BMS]) who did not require TLR in the first 9 months postintervention and who were followed for 3 years. The in-stent MLA that best predicted 3-year TLR-free survival was determined. At 9-months follow-up, IVUS-measured in-stent MLA was mm 2 in the PES group and mm 2 in the BMS group. Between 9 months and 3 years, TLR was required in 4.9% of patients who were treated with PES and 6.7% of patients who were treated with BMS. Multivariate analysis identified MLA at 9 months as a significant predictor of late TLR (hazard ratio, 0.63 [ ]; P 0.02). The ability of MLA to predict late TLR was further assessed using receiver operating characteristic analysis. MLA was found to be an acceptable discriminator for both PES (c ) and BMS (c ). Finally, the optimal thresholds of MLA that best predicted subsequent TLR-free survival were determined to be 4.2 mm 2 for PES and 4.0 mm 2 for BMS. Conclusion In the combined IVUS analysis of TAXUS IV, V, and VI, patients who did not require TLR within the first 9 months had a high subsequent TLR-free survival rate whether treated with PES or BMS. MLA measured by IVUS at 9 months predicted subsequent TLR with a cutoff similar to intermediate, de novo lesions in native coronary arteries. (Circ Cardiovasc Intervent. 2008;1: ) Key Words: intravascular ultrasound restenosis stents In daily clinical practice, in-stent restenosis (ISR) is defined angiographically, and patients with 50% angiographic diameter stenosis typically undergo a repeat intervention. Although coronary angiography has been accepted as the gold standard for the quantification of coronary artery disease, including ISR lesions, several reports have shown its limitation in the assessment of intermediate lesions. 1 3 Intravascular ultrasound (IVUS) and invasive physiological analyses such as Doppler FloWire (Volcano Corporation, Rancho Cordova, Calif) and coronary pressure wire were developed, in part, to assess intermediate lesions. 4 Among these techniques, the IVUS-measured minimum lumen area (MLA), the Doppler FloWire measured coronary flow reserve, and the pressure wire measured fractional flow reserve (FFR) have been used to identify a significant de novo stenosis. 5 7 However, the application of these techniques has not been reported for intermediate ISR lesions. Editorial see p 90 Clinical Perspective see p 118 To address this issue, we used data from the major paclitaxel-eluting stent (PES) versus bare-metal stent (BMS) Received April 6, 2008; accepted August 13, From the Cardiovascular Research Foundation, New York, NY (H.D., A.M., G.S.M., G.W.S.); Columbia University Medical Center, New York, NY (H.D., A.M., G.S.M., G.W.S.); Washington Hospital Center, Washington, DC (N.W.W.); Boston Scientific Corporation, Natick, Mass (A.Y., H.W., L.M., K.D.D.); St Elizabeth Medical Center, Boston, Mass (J.J.P); Cleveland Clinic, Cleveland, Ohio (S.G.E.); and Heart Center Siegburg, Siegburg, Germany (E.G.). Correspondence to Gary S. Mintz, MD, 611 Pennsylvania Ave, SE #386, Washington, DC gsm18439@aol.com 2008 American Heart Association, Inc. Circ Cardiovasc Intervent is available at DOI: /CIRCINTERVENTIONS

2 112 Circ Cardiovasc Intervent October 2008 randomized TAXUS IV, V, and VI trials These trials included substudies of patients who underwent 9-month follow-up IVUS imaging and 3-year clinical follow-up. We hypothesized that 9-month IVUS can predict 3-year target lesion revascularization (TLR) free survival in patients receiving PES and BMS. Methods Patient Population and Protocol TAXUS IV, TAXUS V, and TAXUS VI were prospective, double-blind, BMS-controlled trials in which patients with a single de novo native coronary artery lesion were randomly assigned to treatment with a PES or an otherwise identical BMS (Boston Scientific, Natick, Mass) The TAXUS IV and V studies used the TAXUS slow-release formulation (commercially available), whereas TAXUS VI used the TAXUS moderaterelease formulation (not commercially available). IVUS substudy data from these trials were analyzed at a single core laboratory (Medlantic Research Institute, Washington Hospital Center, Washington, DC) as described previously. 11 Of the 2918 patients enrolled in the 3 trials, the first 956 patients enrolled at prespecified IVUS substudy sites underwent serial volumetric IVUS analysis and were included in the IVUS cohort, including 268 from TAXUS IV, 509 from TAXUS V, and 179 from TAXUS VI. In the IVUS cohort, 635 patients (331 PES and 304 BMS) did not require TLR in the first 9 months post stent implantation, including the day of the 9-month angiography/ivus follow-up and were followed for 3 years. TLR was defined as any ischemia-driven repeat percutaneous intervention of the target lesion or bypass surgery of the target vessel. All TLR throughout follow-up (up to and including the 3-year follow-up) were adjudicated by the Clinical Events Committee (Harvard Clinical Research Institute, Boston, Mass). If the lesion diameter stenosis was 70%, no additional clinical evidence of ischemia was needed. If the lesion diameter stenosis was 50% but 70%, one of the following pieces of evidence was needed: (1) positive functional study corresponding to the area served by the target lesion, (2) ischemic ECG changes at rest in a distribution consistent with the target vessel, or (3) ischemic symptoms referable to the target lesion. If the lesion diameter stenosis was 50%, a markedly positive functional study or ECG changes corresponding to the area served by the target vessel was needed. The authors had full access to and take full responsibility for the integrity of the data. All authors have read and agreed to the manuscript as written. Angiography Analysis Two or more angiographic projections of the stenosis after intracoronary nitroglycerin were acquired with repetition of identical angiographic projections of the lesion at the time of follow-up angiography. With the contrast-filled catheter as the calibration source, quantitative angiographic analysis was performed using a validated automated edge-detection algorithm (MEDIS Medical Imaging System, Maastricht, The Netherlands) by a technician who was unaware of the clinical or IVUS findings and who was blinded to the treatment arm. IVUS Protocol and Analysis Clinical sites were selected based on their IVUS experience and volume. Volumetric IVUS was performed immediately after stent implantation and at 9-month follow-up in patients at the IVUS substudy sites of each trial until the prespecified enrollment numbers in each trial were obtained. IVUS imaging was performed after intracoronary administration of 0.1 to 0.2 mg of nitroglycerin using motorized transducer pullback (0.5 mm/s) and contemporary, commercial scanners. Images were continuously recorded throughout the stent, including 5-mm segments distal and proximal to the stent. Images were recorded onto s-vhs videotape, compact discs, or magneto-optical discs for offline analysis at a single, independent core laboratory by a technician who was unaware of treatment assignment or patient clinical outcomes. With the use of computerized planimetry (TapeMeasure, Indec Systems, Mountain View, Calif.), stent and lumen borders were manually traced, and stent, lumen, and intimal hyperplasia (stent lumen) areas were calculated every 1 mm within the stented segment. Volumes were calculated using the Simpson rule. Percentage of intimal hyperplasia (%IH) was defined as intimal hyperplasia volume divided by stent volume. MLA was defined as the smallest lumen area within the length of the stent. Minimum stent area was defined as the smallest stent area within the length of the stent. Statistical Analysis Categorical variables were summarized as frequencies and percentages and were compared between groups using 2 tests or Fisher exact tests, as appropriate. Continuous variables were presented as mean SD and compared between groups using 2-tailed, unpaired t tests;if parameters were not normally distributed per Kolmogorov- Smirnov test, then the Wilcoxon 2-sample test was used. Multivariate analysis was used to determine predictors of late TLR (between 9 months and 3 years). All covariates were modeled univariately for each outcome and multivariately using a stepwise procedure in the Cox regression model. Baseline patient and lesion characteristics and 9-month IVUS variables were included. Statistical significance was set at P For each outcome, predictors were listed in ascending order of probability value. Coefficients with probability values 0.05 were not listed. Receiver operating characteristic (ROC) analysis was used to measure the ability of MLA and %IH at 9-months follow-up to discriminate between those subjects who experienced TLR within the subsequent follow-up (between 9 months and 3 years) compared with those who did not. The ROC curves plot the probability of detecting true signals (sensitivity) against false signals (1 specificity) over an entire range of possible cut points. Acceptable discrimination is considered if the c statistic is 0.7 but 0.8; excellent and outstanding discrimination are considered for c statistics 0.8 but 0.9, and 0.9, respectively. To determine the optimal IVUS cutoff value for each treatment group to best predict late (3-year) TLR, the cross point of sensitivity and specificity curves was used. The Kaplan-Meier product-limit method and log-rank tests were used to assess time-to-event end points between treatment groups. Differences were considered to be statistically significant when the probability value was Results This study consisted of 635 patients with IVUS data (331 PES and 304 BMS) who did not require TLR in the first 9 months post stent implantation, who were not staged for intervention after the 9-month coronary angiography and IVUS, and who were subsequently followed for 3 years. Between the 9-month and 3-year follow-up visits, TLR was necessary in 16 patients who were treated with PES (4.9%) and 20 patients who were treated with BMS (6.7%). The time from 9-month follow-up IVUS to the late TLR event was days in the PES group and days in the BMS group. TLR-free survival curves are shown in Figure 1 and were not different between the 2 groups. Only 1 patient in each group developed stent thrombosis between 9 months and 3 years. Patients and Lesion Characteristics Baseline clinical and lesion characteristics of late-tlr patients were similar to those of TLR-free patients in the PES

3 Doi et al Nine-Month In-Stent MLA and 3-Year TLR %; P ), and a smaller external elastic membrane area ( versus mm 2 ; P ) as compared with patients treated with PES who did not undergo TLR during the follow-up period (Table 3). Figure 1. Kaplan-Meyer TLR-free survival curves in 635 patients (331 treated with PES and 304 treated with BMS) who did not require TLR in the first 9 months post stent implantation and who were followed for 3 years. At 3 years, TLR-free survival rates in the PES- and BMS-treated groups were 95.1% and 93.3%, respectively. and BMS groups (Tables 1 and 2). In addition, baseline clinical and lesion characteristics were similar between the PES and BMS groups (Tables 1 and 2). Thus, baseline clinical characteristics, including incidence of diabetes mellitus and lesion severity, did not affect the magnitude of late TLR. IVUS Findings at 9 Months in the PES Group At 9 months, patients treated with PES who required revascularization within 3 years had a smaller minimum stent area ( versus mm 2 ; P ), a smaller MLA ( versus mm 2 ; P ), a greater in-stent volume obstruction (%IH volume, % versus Table 1. Clinical and Angiographic Findings in the PES Group Total (N 331) IVUS Findings at 9 Months in the BMS Group At 9 months, patients treated with BMS who required revascularization within 3 years had a smaller MLA ( versus mm 2 ; P ) and a greater in-stent volume obstruction (%IH volume, % versus %; P ) as compared with patients treated with BMS who did not undergo TLR during the follow-up period. However, there was only a trend toward a smaller minimum stent area ( versus mm 2 ; P ) and smaller external elastic membrane area ( versus mm 2 ; P ) between the 2 groups (Table 4) in patients with late TLR versus TLR-free patients. IVUS-Measured MLA and %IH Predicted Late TLR Multivariate analysis identified MLA (hazard ratio, 0.63 [ ]; P 0.02) and %IH volume (hazard ratio, 1.07 [ ]; P ) as the only predictors of late TLR. We performed ROC analysis of the MLA and %IH to ascertain and compare their ability to predict patients who would receive late TLR versus those with no late TLR. The ROC analysis of MLA showed that the c statistics in the TAXUS and BMS groups were and , respectively (Figure 2). In addition, ROC analysis of %IH volume Late TLR (N 16) No Late TLR (N 315) P value Age, years Female, n (%) 84 (25) 4 (25) 80 (25) 1.00 Diabetes, n (%) 86 (26) 2 (13) 84 (27) 0.26 Hypertension, n (%) 225 (68) 11 (69) 214 (68) 1.00 Hyperlipidemia, n (%) 232 (70) 10 (67) 222 (71) 0.77 Smoking, n (%) 74 (22) 3 (19) 71 (23) 1.00 Prior MI, n (%) 104 (31) 6 (38) 98 (31) 0.59 Unstable AP, n (%) 108 (33) 2 (13) 106 (34) 0.10 Ejection fraction, % Vessel LAD, n (%) 139 (42) 8 (50) 131 (42) 0.61 LCX, n (%) 96 (29) 5 (31) 91 (29) 0.79 RCA, n (%) 94 (29) 3 (19) 91 (29) 057 Baseline angiographic findings Type C lesion, n (%) 117 (35) 5 (31) 112 (36) 0.80 Lesion length, mm RVD, mm MLD, mm DS, % MI indicates myocardial infarction; AP, angina pectoris; LAD, left anterior descending artery; LCX, left circumflex artery; RCA, right coronary artery; RVD, reference vessel diameter; MLD, minimum lumen diameter; DS, diameter stenosis.

4 114 Circ Cardiovasc Intervent October 2008 Table 2. Clinical and Angiographic Findings in the BMS Group Total (N 304) Late TLR (N 20) No Late TLR (N 284) P value Age, years Female, n (%) 87 (29) 6 (30) 81 (29) 1.00 Diabetes, n (%) 72 (24) 5 (25) 67 (24) 1.00 Hypertension, n (%) 198 (65) 15 (75) 183 (64) 0.47 Hyperlipidemia, n (%) 208 (68) 10 (50) 198 (70) 0.08 Smoking, n (%) 50 (16) 4 (20) 46 (16) 0.75 Prior MI, n (%) 89 (29) 4 (20) 85 (30) 0.45 Unstable AP, n (%) 94 (31) 4 (20) 90 (32) 0.33 Ejection fraction, % Vessel LAD, n (%) 125 (41) 12 (63) 113 (40) LCX, n (%) 79 (26) 4 (21) 75 (27) 0.79 RCA, n (%) 97 (32) 3 (16) 94 (33) 0.13 Baseline angiographic findings Type C lesion, n (%) 103 (34) 4 (20) 99 (35) 0.32 Lesion length, mm RVD, mm MLD, mm DS, % MI indicates myocardial infarction; AP, angina pectoris; LAD, left anterior descending artery; LCX, left circumflex artery; RCA, right coronary artery; RVD, reference vessel diameter; MLD, minimum lumen diameter; DS, diameter stenosis. showed that the c statistics in TAXUS and BMS groups were and , respectively (Figure 3). Using the cross points of the sensitivity and specificity curves for 9-month MLA and %IH as discriminators for 3-year TLR probability, the best cutoff values were 4.2 mm 2 (PES) and 4.0 mm 2 (BMS) for MLA (Figure 4) and 24.5% (PES) and 23.9% (BMS) for %IH volume. The rate of late TLR in PES-treated patients with a 9-month MLA 4.0 mm 2 was 2.9% as compared with 11.6% in patients with an MLA 4.0 mm 2 (P ). Although 9-month MLA 4.0 mm 2 demonstrated a high predictive value for TLR-free survival of 97.2%, MLA 4.0 mm 2 had only an 11.4% predictive value Table 3. IVUS and Angiographic Findings at 9-Month Follow-Up in PES-Treated Patients of late TLR. In the BMS cohort, the late-tlr rate in patients with 9-month MLA 4.0 mm 2 was 3.5% as compared with 11.1% in patients with MLA 4.0 mm 2 (P ). Similar to PES, the predictive value of an MLA 4.0 mm 2 for TLR-free survival in BMS patients was 96.6%, whereas the predictive value of MLA 4.0 mm 2 for late TLR was only 10.9%. Discussion The major findings of this study were as follows: (1) in the combined IVUS analysis of TAXUS IV, V, and VI, patients who did not require TLR within the first 9 months Total Late-TLR No Late-TLR P value IVUS findings (N 331) (N 16) (N 315) MSA, mm (4.6, 6.3, 8.1) (4.5, 5.2, 6.1) (4.8, 6.2, 7.8) 0.10 MLA, mm (4.0, 5.5, 7.2) (1.7, 3.0, 5.2) (4.2, 5.5, 7.2) IH volume, % (2.3, 8.9, 18.4) (10.7, 18.4, 40.5) (2.1, 8.5, 18.1) EEM area, mm (11.6, 15.0, 19.1) (10.1, 11.6, 13.7) (12.1, 15.2, 19.1) Angiographic findings (N 322) (N 14) (N 308) In-segment MLD, mm (1.8, 2.1, 2.4) (1.1, 1.4, 1.9) (1.8, 2.1, 2.4) In-segment DS, % (16.8, 23.0, 33.3) (35.1, 49.4, 58.3) (16.5, 22.9, 32.1) In-segment binary restenosis (%DS 50), % 5.3 (17/322) 50.0 (7/14) 3.3 (10/308) * P values are from Wilcoxon 2-sample tests for continuous data. Data are presented as mean SD (1st quartile, median, 3rd quartile). MSA indicates minimal stent area; IH, intimal hyperplasia; EEM, external elastic membrane; MLD, minimum lumen diameter; DS, diameter stenosis. *P value is from Fisher exact test.

5 Doi et al Nine-Month In-Stent MLA and 3-Year TLR 115 Table 4. IVUS and Angiographic Findings at 9-Month Follow-Up in BMS-Treated Patients Total Late TLR No Late TLR P value IVUS findings (N 304) (N 20) (N 284) MSA, mm (4.5, 6.1, 8.4) (3.6, 5.2, 6.7) (5.1, 6.6, 8.5) MLA, mm (2.9, 4.6, 6.3) (1.5, 2.2, 4.9) (3.1, 4.7, 6.4) IH volume, % (20.3, 29.4, 39.2) (32.3, 49.4, 60.8) (19.1, 28.4, 37.9) EEM area, mm (12.1, 15.1, 18.4) (10.5, 13.4, 14.9) (12.1, 15.3, 18.4) 0.07 Angiographic findings (N 290) (N 16) (N 274) In-segment MLD, mm (1.4, 1.8, 2.2) (0.8, 1.0, 1.4) (1.5, 1.9, 2.2) In-segment DS, % (24.6, 33.2, 45.1) (45.8, 60.6, 65.5) (24.0, 32.3, 42.5) In-segment binary restenosis (%DS 50), % 19.3 (56/290) 62.5 (10/16) 16.8 (46/274) * P values are from Wilcoxon 2-sample tests for continuous data. Data are presented as mean SD (1st quartile, median, 3rd quartile). MSA indicates minimal stent area; IH, intimal hyperplasia; EEM, external elastic membrane; MLD, minimum lumen diameter; DS, diameter stenosis. *P value is from Fisher exact test. had a very low 3-year TLR rate regardless of whether they were treated with PES (3-year TLR rate of 4.9%) or BMS (3-year TLR rate of 6.7%); and (2) in-stent MLA measured by IVUS at 9 months predicted TLR-free survival during subsequent follow-up in both PES- and BMS-treated groups, and the MLA cutoffs (4.2 and 4.0 mm 2, respectively) were virtually identical. In patients with an MLA 4.0 mm 2, late TLR rates in patients treated with PES or BMS were especially low (2.9% and 3.5%, respectively). Thus, just as IVUS is useful in assessing intermediate de novo lesions, IVUS is also useful in assessing intermediate ISR lesions; patients with intermediate ISR lesions (MLA 4.0 mm 2 ) can be treated medically with good long-term outcomes. Several studies have reported a strong correlation between anatomic data obtained from IVUS and physiological data obtained using coronary flow reserve, FFR, or radionuclide angiographic stress testing. Abizaid et al 5 studied 112 de novo lesions in 86 patients with both IVUS and coronary flow reserve; an IVUS lumen cross-sectional area of 4.0 mm 2 predicted a coronary flow reserve of 2.0 with a diagnostic accuracy of 89%. Nishioka et al 12 reported that an IVUS MLA 4.0 mm 2 correlated with abnormal stress myocardial single-photon emission computed tomography (sensitivity of 88% and specificity of 90%). Takagi et al 13 examined 51 lesions in 42 patients using both IVUS and pressure wire; although an MLA of 3.0 mm 2 best predicted an abnormal FFR, regression analysis of individual data points showed that an IVUS MLA of 4.0 mm 2 best correlated with an FFR of 0.75 to The use of IVUS to assess intermediate, native, de novo lesions has been validated clinically. Abizaid et al 14 studied 357 intermediate lesions in 300 patients in whom intervention was deferred based on IVUS findings; TLR was required in 6% of the patients at a mean follow-up of 13 months. Moreover, patients with an MLA 4.0 mm 2 by IVUS had only a 2.8% rate of TLR, although the TLR rate was higher in diabetics as compared with nondiabetics. There have been preliminary reports on the use of IVUS to assess intermediate ISR lesions. Nishioka et al 15 studied 150 intermediate ISR lesions in 142 patients. Repeat intervention was deferred if the MLA measured by IVUS was 3.5 mm 2 ; in these patients, the 2-year event-free survival rate was high (96.5%). Lee et al 16 evaluated the long-term clinical outcome of asymptomatic patients with moderate ISR after repeat intervention was deferred; during a mean follow-up of 26 months, TLR (3% and 2%, respectively) and major adverse cardiac event -free survival (87% and 85%, respectively) were similar to a group of patients without ISR. As in the study by Abizaid et al 14 of native artery lesions, the presence of diabetes mellitus Figure 2. ROC analysis of MLA at 9-month follow-up for predicting 3-year TLR. The areas under the curve in ROC analysis in the PESand BMS-treated groups were and , respectively.

6 116 Circ Cardiovasc Intervent October 2008 Figure 3. ROC analysis of the %IH at 9-month follow-up for predicting 3-year TLR. The areas under the curve in ROC analysis in the PES- and BMS-treated groups were and 0.803, respectively. influenced late events in ISR lesions. 16 However, because of the small number of patients who required 3-year TLR in the current study, we were unable to assess the impact of diabetes mellitus (or other risk factors) on long-term outcome. Intracoronary physiology has also been used to assess ISR lesions. Compared with reversible perfusion defects on myocardial scintigraphy, an FFR 0.75 predicted hemodynamically significant ISR with a sensitivity of 92%. Krüger et al 17 studied 42 intermediate ISR lesions. In 22 patients with an FFR 0.75, there were no adverse coronary events related to the stented lesion in the subsequent 6 months. Thus, similar to IVUS, the FFR threshold for a significant ISR lesion was similar to de novo lesions. Kimura et al 18 demonstrated that in-stent luminal diameter measured by quantitative angiography in patients treated with the Palmaz-Schatz stent improved from 1.95 to 2.09 mm between 6 months and 3 years postimplantation. In a subsequent report, Kimura et al 19 analyzed late clinical and angiographic outcomes after Palmaz-Schatz stent implantation. Among the 405 patients in this second study, quantitative angiographic analysis of 179 lesions in 173 patients showed a minimum lumen diameter of 2.62 mm postprocedure, 2.00 mm at 6 months, 2.19 mm at 3 years, and 1.85 mm beyond 4 years. These data indicated a triphasic BMS luminal response, characterized by early restenosis, intermediate-term neointima regression (from 6 months to 3 years), and late renarrowing (beyond 4 years). In support of intermediate-term neointima regression after BMS implantation, Kuroda et al 20 reported that intimal hyperplasia area measured by IVUS decreased from 3.0 mm 2 at 6 months to 2.2 mm 2 at 12 months. Also using IVUS, Hong et al 21 showed that there was intimal hyperplasia regression in most BMS-treated lesions (76%), with an overall mean decrease in intimal hyperplasia area from 2.6 mm 2 at 6 months to 2.3 mm 2 at 2 years. The longest available IVUS follow-up after PES implantation is also 2 years. In an IVUS substudy from TAXUS II, Aoki et al 22 showed that there was a modest increase in %IH in the PES group as compared with a decreased in %IH in the BMS group between 6 months and 2 years. In another long-term IVUS substudy from ASPECT (a study that used a nonpolymeric paclitaxel stent), Park et al 23 demonstrated a late catch-up of intimal hyperplasia growth from 6 to 18 months, especially in the high-dose group. These differences between PES and BMS led to the hypothesis that the 9-month MLA cutoff predicting late TLR would be larger in PES as compared with BMS because a larger MLA would be necessary to accommodate ongoing neointimal hyperplasia in PES-treated lesions. In fact, this was not the case; the MLA cutoffs were nearly identical. This finding, along with virtually identical event-free survival curves, also suggested that any late intimal hyperplasia would have little clinical consequence. Figure 4. Sensitivity and specificity curves for 9-month follow-up MLA predicting 3-year TLR.

7 Doi et al Nine-Month In-Stent MLA and 3-Year TLR 117 Study Limitations First, in this study, we evaluated only PES; however, the late intimal hyperplasia growth patterns in other drug-eluting stents might be similar to those in PES. Second, the results in this study are limited to vessel diameters, stent lengths, and lesion complexities in the TAXUS IV, V, and VI trials. Third, the TAXUS trials were not undertaken to evaluate the efficacy of IVUS for decision-making in intermediate ISR lesions. Since an MLA 4.0 mm 2 had low predictive value for late TLR, and given the lack of evidence that treatment of these lesions would benefit patients without objective evidence of ischemia, these findings should not be taken as a prescription to routinely treat patients with MLA 4.0 mm 2. Fourth, comparisons between groups are not powered and are used either for descriptive purpose or to show consistency with the predictive analysis, which is the major focus of this article. Finally, these results are based on IVUS analysis only and cannot be extrapolated to any angiographic data because of lack of correlation between angiographic and IVUS measures. Conclusions and Clinical Implications In the combined IVUS analysis of TAXUS IV, V, and VI, patients who did not require TLR within the first 9 months had a low subsequent (3-year) TLR rate whether treated with PES or BMS. In-stent MLA measured by IVUS at 9 months predicted subsequent 3-year TLR-free survival in both the PES and BMS groups, with cutoffs virtually identical to and event rates as low as in intermediate, de novo, native artery lesions. The low late-tlr rates in patients with MLA 4 mm 2 at 9 months brings uncertainty to the practice of intervening on moderate lesions at routine follow-up, even in the absence of symptoms mostly due to the oculostenotic reflex. Conversely, patients with intermediate ISR lesions (MLA 4.0 mm 2 ) can be treated medically with good long-term outcomes. Thus, IVUS may also be a useful modality for decision-making in intermediate ISR lesions. Disclosures Drs Mintz and Stone are consultants for Boston Scientific Corporation. Alan Yu, Hong Wang, and Drs Mandinov and Dawkins are employees of Boston Scientific Corporation. Dr Popma is a member of the Advisory Board and the Speaker s Bureau for Boston Scientific Corporation and has received research grants from Boston Scientific Corporation. References 1. Glagov S, Weisenberg E, Zarins CK, Stankunavicius R, Kolettis GJ. Compensatory enlargement of human atherosclerotic coronary arteries. N Engl J Med. 1987;316: Tobis JM, Mallery J, Mahon D, Lehmann K, Zalesky P, Griffith J, Gessert J, Moriuchi M, McRae M, Dwyer ML. Intravascular ultrasound imaging of human coronary arteries in vivo. Analysis of tissue characterizations with comparison to in vitro histological specimens. Circulation. 1991;83: Hodgson JM, Reddy KG, Suneja R, Nair RN, Lesnefsky EJ, Sheehan HM. 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8 118 Circ Cardiovasc Intervent October Kuroda N, Kobayashi Y, Nameki M, Kuriyama N, Kinoshita T, Okuno T, Yamamoto Y, Komiyama N, Masuda Y. Intimal hyperplasia regression from 6 to 12 months after stenting. Am J Cardiol. 2002;89: Hong MK, Lee CW, Kim YH, Lee BK, Kim MK, Yang TH, Song JM, Han KH, Kang DH, Song JK, Kim JJ, Park SW, Park SJ. Two-year follow-up intravascular ultrasound analysis after bare metal stent implantation in 120 lesions. Catheter Cardiovasc Interv. 2005;65: Aoki J, Colombo A, Dudek D, Banning AP, Drzewiecki J, Zmudka K, Schiele F, Russell ME, Koglin J, Serruys PW. Persistent remodeling and neointimal suppression 2 years after polymer-based, paclitaxel-eluting stent implantation: insights from serial intravascular ultrasound analysis in the TAXUS II study. Circulation. 2005;112: Park DW, Hong MK, Mintz GS, Lee CW, Song JM, Han KH, Kang DH, Cheong SS, Song JK, Kim JJ, Weissman NJ, Park SW, Park SJ. Two-year follow-up of the quantitative angiographic and volumetric intravascular ultrasound analysis after nonpolymeric paclitaxel-eluting stent implantation: late catch-up phenomenon from ASPECT Study. J Am Coll Cardiol. 2006;48: CLINICAL PERSPECTIVE In treating patients with complex coronary artery disease, physicians are often faced with deciding which lesions to treat and which lesions to leave alone. This can be especially difficult when a patient has had a prior intervention. Intravascular ultrasound (IVUS) can be used to assess de novo intermediate lesions in native coronary arteries; a minimum lumen area (MLA) 4.0 mm 2 is accepted as a cutoff for a significant stenosis. However, the use of IVUS to assess intermediate in-stent restenosis lesions has not been reported. In the current study, we used the IVUS substudy data from TAXUS IV, V, and VI to assess the 9-month IVUS in-stent MLA that best predicted subsequent target lesion revascularization (TLR) free survival. Nine-month IVUS data were available for 635 patients (331 treated with paclitaxel-eluting stents and 304 treated with bare-metal stents) who did not require TLR in the first 9 months postintervention and who were followed for a total of 3 years. Multivariate analysis identified the 9-month IVUS MLA as a significant predictor of late TLR. The MLA that best predicted subsequent TLR-free survival was 4.2 mm 2 for paclitaxel-eluting stents and 4.0 mm 2 for bare-metal stents. The late TLR rate of patients with a 9-month IVUS MLA 4.0 mm 2 was lower as compared with the late TLR rate in the setting of an MLA 4.0 mm 2 in both treatment groups (paclitaxel-eluting stents: late TLR,2.9%, versus no late TLR, 11.6% [P ]; bare-metal stents: 3.5% versus 11.1% [P 0.009]). Patients with intermediate in-stent restenosis lesions (MLA 4.0 mm 2 ) can be treated medically with good long-term outcomes. Thus, IVUS is a useful modality for decision-making in intermediate in-stent restenosis lesions similar to de novo lesions.