A modeled outcome-based spoke-and-hub paradigm of transcatheter aortic valve implantation (TAVI) care, when compared with a simulated volume threshold, was associated with improved national outcomes at the cost of reduced geographic access to care, according to a recent study published in JAMA Cardiology.

Adam J. Nelson, MBBS, et al., included 166,248 patients (mean age 79.5 years, 47.3% female, 4.2% Black) from the STS/ACC TVT Registry in the study. Patients undergoing TAVI from July 2017 to June 2020 were used to establish a baseline for site volume and outcomes. Outcomes from July 2020 to March 2022 were modeled as though patients were treated at the nearest higher volume site (≥50 TAVIs per year) and then the best outcome site within a hospital referral region. The primary outcome was the absolute difference in events between the adjusted observed and modeled 30-day composite of death, stroke, major bleeding, stage III acute kidney injury and paravalvular leak.

Of the overall study cohort, 95% were treated in higher volume sites while 45% were treated in the best outcome sites. The volume threshold model showed no significant reduction in estimated adverse events (–34; 95% Bayesian credible interval [CrI], –75-8), and median (IQR) driving time from the existing to alternate site was 22 (15-66) minutes. The composite outcome model, which transitioned care to the best outcome site, saw an estimated 1,261 fewer adverse outcomes (95% CrI, 1,013-1,500), with the median driving time from original to best site amounting to 23 (15-41) minutes. Similar results were observed when selecting for Black patients, Hispanic patients or patients residing in rural areas.

Nelson, et al., acknowledge multiple study limitations including their choice to use 30-day outcomes, which may not encompass care from other clinicians and health care systems following discharge; their disregard of factors like patient preference and insurance status when estimating TAVI access; and the fact that certain aspects of patient risk may not be fully captured in their risk adjustment. Given these limitations, the authors note their modeled evaluation is not “a repudiation of previous volume-outcome analyses of TAVI, but rather a specific investigation of a proposed cut point.”

“Reassigning care based on a direct measure of quality resulted in substantial absolute reductions in national 30-day adverse events,” write the authors. “With the exception of acute kidney injury, improvements across the remaining measured 30-day complications including death were observed, all of which are of increasing importance as TAVI expands to lower-risk cohorts where tolerance for adverse outcomes is lower.”

Keywords: Kidney, Health Services Accessibility, Referral and Consultation, Cardiology, Hemorrhage, Registries, Bayes Theorem, Patient Discharge, STS/ACC TVT Registry, National Cardiovascular Data Registries

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