Unbalanced Atrioventricular Septal Defect: A CHSS Inception Cohort Study (2010-2011)
David M. Overman, MD
Children’s Hospital & Clinics of Minnesota
Unbalanced atrioventricular septal defect (uAVSD) is one of the most challenging lesions that pediatric cardiac surgeons confront today. Despite tremendous progress in reducing mortality associated with surgical treatment other complex congenital heart defects, mortality for repair of uAVSD remains unacceptably high. Unbalanced AVDS presents with varying amounts of severity. When uAVSD is mild, surgical treatment is aimed at restoring normal, biventricular physiology. When uAVSD is severe, single ventricle palliation is necessary to achieve survival. What confounds surgeons and cardiologists alike is reliably determining when biventricular repair must be abandoned in favor of single ventricle palliation to achieve optimal outcomes. The relatively low incidence of uAVSD and its wide spectrum of anatomic variations make informed decision making very difficult for any single institution. This difficulty is compounded by the fact that firm diagnostic criteria do not exist for uAVSD. Thus, a prospective, multi-institutional study is required to create the basis for establishing anatomic and physiologic criteria that, when applied, will optimize outcomes for every uAVSD patient. In order to create a reliable method for diagnosis of uAVSD, a retrospective, multi-intuitional “lookback” study was conducted. This study established an echocardiographic measurement called the atrioventricular valve index (AVVI) as a reliable means of diagnosing uAVSD. Additional echocardiographic measures have been analyzed to enhance the ability of AVVI to discriminate uAVSD from the more common “balanced” AVSD (for which surgical repair is straightforward and carries very low mortality risk). The lookback also measured the incidence of uAVSD at member institutions and the mortality associated with surgical repair. With this information, we are now able to design a prospective study with a reliable and reproducible way to enroll patients, and we are also able to predict with reasonable certainty both the number of patients and the length of enrollment necessary to be able to statistically discern important differences in outcomes amongst various anatomic varieties and selected surgical strategies.
Patients will be enrolled at member institutions using AVVI as the arbiter of the presence or absence of unbalance in AVSD. Prior to participation, each institution will be required to undergo echocardiography training to ensure proper performance of the AVVI as well as additional important echo measurements to be obtained in the study. IRB approval must be obtained at each institution. The diagnostic echo and its interpretation, patient demographic information, and clinical records including any surgical intervention will be collected by the member institution and sent securely to the Congenital Heart Surgeons Society (CHSS) Data Center for storage and subsequent analysis. Updated patient information, including any subsequent hospitalizations or interventions, will be obtained by Data Center personnel working with each member institution. All echocardiograms will be reviewed by a team of echocardiographers who will constitute the “echo core lab” in order to confirm diagnosis, perform an independent AVVI, and to perform additional measurements relevant to the study. Subsequent data analysis and manuscript preparation will be performed, together with echo core lab personnel, by an UAVSD Working Group of the CHSS, to be convened at the upcoming Annual Meeting of the CHSS in Chicago. This working group will include surgeons, cardiologists, statisticians, as well as research fellows and data center personnel, and will meet periodically at the data center to shepherd the project through to completion as well as to perform subsequent analysis and follow-up studies. Patients are typically followed for fifteen years or more by annual follow-up data requests from member institutions and/or follow-up interviewed with patient families by Data Center personnel.
We hypothesize that diagnostic criteria used to identify uAVSD are varied and inconsistent, and that this inconsistency results in inappropriate treatment decisions, which incurs suboptimal outcomes for patients with uAVSD. We further hypothesize that AVVI will consistently delineate uAVSD from balanced forms of AVSD and that are other echocardiographic features that are important determinants of outcome as well. The principle aim of the study, therefore, is to define anatomic criteria which, when applied, result in optimal treatment outcomes for each patient with uAVSD resulting in improved survival and diminished need for reintervention. Additional study aims include defining other important clinical factors, such as patient demographics, coexisting conditions, and chromosomal abnormalities, which impact outcomes and thus may affect treatment strategy.
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