Division of Vascular and Endovascular Surgery, Massachusetts General Hospital, Boston, Mass, USA.
J Vasc Surg. 2011 Jul;54(1):22-9. doi: 10.1016/j.jvs.2010.12.052. Epub 2011 Mar 2.
The Evaluation of the Medtronic Vascular Talent Thoracic Stent Graft System for the Treatment of Thoracic Aortic Aneurysms (VALOR) trial findings noted superior 30-day and 1-year outcomes of the Talent thoracic endograft (Medtronic Vascular, Santa Rosa, Calif) compared with surgical repair of descending thoracic aneurysms (DTAs). Data from 195 prospective thoracic endovascular aneurysm repair (TEVAR) patients treated with the Talent device and 189 retrospective controls undergoing open surgical repair (OSR) from three centers of excellence were included in the trial after completion of TEVAR enrollment and compared. Such comparisons are biased by baseline differences among TEVAR vs OSR, however, propensity score (PS) analysis can reduce bias and validate such comparisons.
Logistic regression was used to generate a PS (range, 0-1) to identify baseline characteristics more likely in TEVAR. The PS estimated the probability that any patient would undergo TEVAR (eg, a PS of 0.99 represents a 99% chance a patient belongs to TEVAR). PSs were then generated for all patients, and TEVAR and OSR patients were divided into tertiles based on the PS to reduce up to 80% of inherent bias. Outcomes from the middle tertile (T2), patients equally likely (midrange PS) to be in TEVAR or OSR and therefore best matched, were compared using regression analysis and were also compared with the outcomes in the overall trial group.
Correlates of membership in TEVAR were smaller aneurysm (P < .001), anticoagulants (P < .01), no previous abdominal aortic aneurysm (AAA) repair (P < .01), no peripheral vascular disease (P = .001), statin use (P = .002), aspirin use (P = .002), older age (P = .028), race (P = .007), male gender (P = .02), and heart failure (P = .035). T2 included 68 TEVAR (PS, 0.58 ± 0.2) and 67 OSR patients (PS, 0.46 ± 0.2). VALOR overall reported differences in aneurysm size (56 mm TEVAR vs 69 mm open) and prior AAA repair (19% TEVAR vs 37% open), and this adjusted to no differences in T2 patients. In the well-matched T2 cohort, TEVAR patients had similar 30-day mortality (0% vs 3% OSR; P = .2) and improved 1-year aneurysm-related mortality rates (0% TEVAR vs 8% OSR; P = .05) compared with the OSR patients. This finding was in concurrence with the VALOR trial reporting similar benefit in TEVAR patients. The all-cause 1-year mortality showed a favorable trend for TEVAR in the VALOR trial; however, in T2 patients, 1-year all-cause mortality was similar in both groups of patients (17% TEVAR vs 15% OSR; P = .8). Age (P = .01), history of cerebrovascular accident (P < .05), antiarrhythmia medication (P = .04), and renal disease (P < .03) independently predicted all-cause and aneurysm-related mortality by regression analysis.
PS analysis is an important tool for elimination of bias inherent when retrospective controls are used. Its application to VALOR validates the long-term benefit in aneurysm-related mortality conferred by TEVAR in patients undergoing endovascular DTA repair.
美敦力血管天赋胸主动脉支架系统治疗胸主动脉瘤（VALOR）试验的评估结果指出，与胸主动脉瘤（胸主动脉瘤）的传统开放手术修复（OSR）相比，天赋胸主动脉内移植物（美敦力血管，加利福尼亚州圣罗莎）的 30 天和 1 年结果更优。在 TEVAR 入组完成后，从三个卓越中心纳入了 195 例前瞻性胸主动脉腔内修复术（TEVAR）患者使用天赋器械和 189 例回顾性对照接受开放手术修复（OSR）的数据，然后进行了比较。然而，TEVAR 与 OSR 之间的基线差异会导致此类比较存在偏倚，但是倾向评分（PS）分析可以减少偏倚并验证此类比较。
使用逻辑回归生成 PS（范围为 0-1），以识别更可能发生 TEVAR 的基线特征。PS 估计任何患者接受 TEVAR 的概率（例如，PS 为 0.99 表示患者属于 TEVAR 的概率为 99％）。然后为所有患者生成 PS，并根据 PS 将 TEVAR 和 OSR 患者分为三分位数，以减少高达 80％的固有偏差。使用回归分析比较中间三分位数（T2）中，在 TEVAR 或 OSR 中同等可能（中范围 PS）的患者的结果，并且还与整个试验组的结果进行了比较。
TEVAR 成员的相关性是较小的动脉瘤（P <.001），抗凝剂（P <.01），无先前的腹主动脉瘤（AAA）修复（P <.01），无外周血管疾病（P =.001），他汀类药物使用（P =.002），阿司匹林使用（P =.002），年龄较大（P =.028），种族（P =.007），男性（P =.02）和心力衰竭（P =.035）。T2 包括 68 例 TEVAR（PS，0.58 ± 0.2）和 67 例 OSR 患者（PS，0.46 ± 0.2）。VALOR 总体报告了动脉瘤大小（TEVAR 为 56mm，OSR 为 69mm）和先前的 AAA 修复（TEVAR 为 19％，OSR 为 37％）的差异，这与 T2 患者的差异相适应。在匹配良好的 T2 队列中，TEVAR 患者的 30 天死亡率相似（0％VS OSR 为 3％；P =.2），1 年与动脉瘤相关的死亡率降低（TEVAR 为 0％VS OSR 为 8％；P =.05）与 OSR 患者相比。这一发现与 VALOR 试验报告的 TEVAR 患者的类似益处一致。VALOR 试验中全因 1 年死亡率对 TEVAR 有有利趋势；然而，在 T2 患者中，两组患者的 1 年全因死亡率相似（TEVAR 为 17％，OSR 为 15％；P =.8）。年龄（P =.01），脑血管意外史（P <.05），抗心律失常药物（P =.04）和肾脏疾病（P <.03）通过回归分析独立预测全因和与动脉瘤相关的死亡率。
PS 分析是消除使用回顾性对照时固有偏倚的重要工具。它在 VALOR 中的应用验证了 TEVAR 在接受胸主动脉瘤腔内修复术的患者中与动脉瘤相关的死亡率的长期获益。
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