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Published on: March 26, 2018
Aortic valve replacement: using a statewide cardiac surgical database identifies a procedural volume hinge point
Himanshu J Patel1, Morley A Herbert, Daniel H Drake
1University of Michigan Medical Center, Ann Arbor, Michigan.
Insights
Hospital volume significantly impacts aortic valve replacement (AVR) outcomes, particularly for high-risk patients. High-volume hospitals demonstrate lower mortality and complication rates compared to low-volume facilities.
Area of Science:
- Cardiac Surgery
- Health Services Research
- Patient Outcomes
Background:
- Aortic stenosis therapies are expanding, necessitating evaluation of conventional surgical approaches.
- Conventional aortic valve replacement (AVR) and AVR with coronary artery bypass grafting (CABG) outcomes require assessment, especially for high-risk patients.
Purpose of the Study:
- To analyze the relationship between hospital/surgeon volume and outcomes for AVR and AVR/CABG procedures.
- To identify predictors of early mortality and postoperative complications in patients undergoing AVR.
Main Methods:
- Analysis of 6,270 AVR or AVR/CABG procedures in Michigan (2008-2011) using a statewide cardiothoracic surgical database.
- Assessment of hospital and surgeon volume-outcome relationships, including mortality and complication rates.
Main Results:
- Hospital volume was an independent predictor of early mortality; high-volume hospitals (HVH) had lower mortality (2.41%) than low-volume hospitals (LVH, 4.34%).
- HVHs showed improved outcomes for high-risk patients (predicted risk of mortality > 4.7%) and reduced rates of prolonged ventilation, transfusion, pneumonia, and organ failure.
- No significant surgeon-volume outcome relationship was identified.
Conclusions:
- Volume-outcome relationships exist for AVR, primarily driven by hospital procedural volume.
- High-risk patients undergoing AVR benefit most from procedures performed in high-volume hospital settings.
- Findings suggest a review of approaches for high-risk AVR patients, considering system experience and resource availability.
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.
