Elsevier

The Annals of Thoracic Surgery

Volume 96, Issue 5, November 2013, Pages 1560-1566
The Annals of Thoracic Surgery

Original article
Adult cardiac
Aortic Valve Replacement: Using a Statewide Cardiac Surgical Database Identifies a Procedural Volume Hinge Point

Presented at the Forty-ninth Annual Meeting of The Society of Thoracic Surgeons, Los Angeles, CA, Jan 26–30, 2013.
https://doi.org/10.1016/j.athoracsur.2013.05.103Get rights and content

Background

Expanding therapies for aortic stenosis have focused on high-risk and inoperable patients, suggesting that an evaluation of outcomes of conventional aortic valve replacement (AVR) or AVR and coronary artery bypass grafting (CABG) is timely and warranted.

Methods

Outcomes for 6,270 AVR (3,487) or AVR/CABG (2,783) procedures performed in Michigan (2008–2011) were analyzed using a statewide cardiothoracic surgical database. Hospital and surgeon volume-outcome relationships were assessed.

Results

Independent predictors of early mortality (all p < 0.05) included age, female sex, predicted risk of mortality, and hospital volume, with a hinge point of a 4-year volume of 390 procedures (high-volume hospital [HVH], 2.41% versus low-volume hospital [LVH], 4.34%; p < 0.001). At this hinge point, observed to expected ratio (O/E) for operative mortality after AVR was lower in HVHs for patients with a predicted risk of mortality (PRoM) greater than 4.7%. In contrast, no surgeon-volume outcome relationship was identified, even when stratified by preoperative patient-risk profile. With respect to other measures, HVHs reported lower rates of prolonged ventilation (24.9% versus LVH, 30.9%; p < 0.001), postoperative transfusion (46.1% versus LVH, 59.0%; p < 0.001), pneumonia (6.6% versus LVH, 9.0%; p = 0.01), and multisystem organ failure (0.7% versus LVH, 1.8%; p = 0.012).

Conclusions

This population-based analysis suggests that volume-outcome relationships exist for AVR. The predominant effect on mortality appears based on the setting of the procedure and occurs primarily in the high-risk patient. These results provide an opportunity to review approaches for high-risk patients undergoing AVR, including resource availability and system experience as the spectrum of treatment options expands to transcatheter therapies.

Section snippets

Material and Methods

The Michigan Society of Thoracic and Cardiovascular Surgeons Quality Collaborative is a multidisciplinary group consisting of all 33 hospitals performing adult cardiac operations in the state of Michigan. The structure, data collection systems, and auditing processes have been previously described [13]. Briefly, all data submitted to the Society of Thoracic Surgeons (STS) database is simultaneously submitted to the Michigan Society of Thoracic and Cardiovascular Surgeons Quality Collaborative.

Results

The median age of the entire cohort was 72 years (63.1% male patients). The median PRoM was 2.57%. Frequent comorbidities included history of stroke (7.1%), hypertension (83.2%), diabetes (33.7%), moderate or severe chronic obstructive lung disease (10.2%), and previous CABG (9.4%), valve (4.5%), or percutaneous coronary (57.7%) procedures. The predominant aortic valve disease was aortic stenosis (87.9%), although 14.4% of participants had severe aortic insufficiency.

Early mortality was

Comment

Previous studies have suggested that important determinants of early mortality after AVR included age, urgency of presentation, diagnosis, and prolonged cardiopulmonary bypass times 1, 2, 3. In 2000, Astor and colleagues [4] from the US Food and Drug Administration used the Nationwide Inpatient Sample to suggest that hospital volume served as an important variable in predicting mortality after AVR.4 This supported a growing body of literature examining the association of improved outcomes with

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