Background: Coronary artery bypass graft (CABG) surgery is the most widely performed adult cardiac surgery in the US. Transesophageal echocardiography (TEE) is an ultrasound-based cardiac imaging modality used in CABG surgery for hemodynamic monitoring and management of complications related to cardiopulmonary bypass. However, there are no comparative effectiveness studies (randomized or non-randomized) that have investigated the relationship between TEE monitoring and clinical outcomes among patients undergoing CABG surgery. Because of this lack of evidence, recommendations for TEE in CABG surgery remain indeterminate (Class II). We aim to compare the clinical outcomes of patients undergoing CABG surgery with vs without TEE monitoring. This protocol will detail how we plan to investigate the hypothesis that TEE monitoring in CABG surgery will be associated with improved clinical outcomes. Methods and Analysis: This investigation will be an observational retrospective, comparative effectiveness, cohort study using Centers for Medicare and Medicaid Services (CMS) claims data from January 1, 2013 to October 15, 2015. The aim is to determine if TEE monitoring during CABG surgery is associated with improved 30-day survival, lower incidence of stroke, shorter length of hospitalization, and incidence of esophageal perforation. To alleviate the potential bias from unmeasured confounding, we propose leveraging hospitals' (or surgeons') preference for TEE in CABG surgery as an instrumental variable (IV). We will combine this IV technique with statistical-matching-based methods by pairing hospitals (or surgeons) with similar observed confounding variables but considerably different preference for TEE monitoring in CABG surgery. Our research design is meant to emulate a cluster-randomized encouragement experiment. The following a priori protocol will detail how we plan to execute this analysis.

中文翻译：

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回顾性比较研究冠状动脉旁路移植术（CABG）手术中使用的经食道超声心动图（TEE）监测与临床结果之间的关联的协议

背景：冠状动脉旁路移植术（CABG）手术是美国执行最广泛的成人心脏手术。经食道超声心动图（TEE）是一种基于超声的心脏成像方法，用于CABG手术，用于血液动力学监测和管理与体外循环有关的并发症。但是，尚无比较有效性研究（随机或非随机）研究了行CABG手术的患者中TEE监测与临床结果之间的关系。由于缺乏证据，CABG手术中TEE的建议仍然不确定（II类）。我们的目的是比较接受或不接受TEE监测的CABG手术患者的临床结局。该协议将详细说明我们如何计划调查CABG手术中的TEE监测与改善的临床结果相关的假设。方法和分析：本研究将采用2013年1月1日至2015年10月15日的医疗保险和医疗补助服务中心（CMS）索赔数据进行的观察性回顾性，比较有效性，队列研究。目的是确定CABG期间是否进行TEE监测手术与改善30天生存率，降低中风发生率，缩短住院时间以及食管穿孔的发生率有关。为了减轻不可估量的混杂因素带来的潜在偏差，我们建议利用医院（或外科医生）在CABG手术中偏爱TEE的手段变量（IV）。我们将这种IV技术与基于统计匹配的方法相结合，方法是将医院（或外科医生）与相似的观察到的混杂变量配对，但在CABG手术中对TEE监测的偏爱却大不相同。我们的研究设计旨在模拟集群随机激励实验。以下先验协议将详细说明我们计划如何执行此分析。