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Type A Aortic Dissection: Optimal Annual Case Volume for Surgery
Quick Takes
- This study set out to establish the optimal annual case volume for acute type A aortic dissection (ATAAD) surgery. With the use of a novel volume–outcome meta-analytical approach, a relation was found between annual case volume, early mortality, and 10-year survival.
- Mortality in the lowest yearly volume quartile (Q1) was 16.2% versus 10.3% in the highest yearly volume quartile (Q4). Ten-year survival was 51% in Q1 versus 69% in Q4.
- The optimal annual hospital case volume was determined to be >38 cases/year.
Study Questions:
What is the optimal annual case volume for acute type A aortic dissection (ATAAD) surgery, and can a novel volume–outcome (V–O) meta-analytical approach help determine optimal thresholds for hospitals performing cardiovascular procedures like ATAAD?
Methods:
This volume–outcome meta-analysis used ATAAD as an illustrative, real-world example of a high-risk cardiovascular intervention potentially requiring centralization. Three databases were reviewed for all studies published between 2012–2023 that included number of consecutive ATAAD patients, years of inclusion, and primary outcome (in-hospital and/or 30-day mortality). Single-center studies were preferred. Multicenter studies were included only if the number of patients, years of inclusion, and outcomes were reported separately for each institution. Duplicate inclusions (i.e., data from the same center reported in >1 study) were avoided by including only the study describing the largest sample size of the center in question. Restricted cubic splines (RCS) were used to describe the V–O relation, and the elbow method was used to find the optimal case volume.
Results:
Data were included from 140 individual centers in 26 countries on five continents, for a total of 38,276 patients undergoing surgery for ATAAD; 66.1% of patients were males, with a mean age of 59.7 years (± 5.5 years). DeBakey Type 1 dissection was present in 82.4% of patients. The 140 centers were divided into quartiles, based on annual case volume: Q1 – 1-12 cases/year (35 centers representing n = 4,449 patients); Q2 – 12-17 cases (35 centers, n = 6,833 patients); Q3 – 17-29 cases (35 centers, n = 10,195 patients); Q4 – 29-152 cases (35 centers, n = 16,799 patients).
Early mortality differed significantly between the 4 quartiles, with mortality being lowest in Q4 (10.3%; 95% confidence interval [CI], 8.9-11.8%) and highest in Q1 (16.2%; CI, 14.0-18.7%). Differences between quartiles were even more pronounced for 10-year survival: 69% (95% CI, 66-71%) for Q4 versus 51% (95% CI, 48-55%) for Q1 (p < 0.01). RCS analysis revealed the optimal threshold for annual case volume to be 38 cases/year (95% CI, 37-40 cases/year).
Conclusions:
- With the use of a novel volume–outcome meta-analytical approach, a relation was found between annual case volume, early mortality, and 10-year survival.
- Mortality in the lowest yearly volume quartile (Q1) was 16.2% versus 10.3% in the highest yearly volume quartile (Q4).
- Ten-year survival was 51% in Q1 versus 69% in Q4.
- The optimal annual hospital case volume was determined to be >38 cases/year.
Perspective:
Prior studies have examined the relationship between case volume and outcome for common and elective procedures. The ability to establish volume–outcome relationships for relatively infrequent and very acute/high-risk cardiovascular interventions (such as ATAAD repair) has been limited. However, with the push toward centralization of cardiovascular interventions, this question is highly relevant. This article is impactful because it demonstrates that this V–O meta-analysis can inform us on optimal case volume thresholds, and the findings make intuitive sense.
We can expect to see this type of analysis becoming more commonplace for other high-risk cardiovascular (and noncardiac) procedures that may be amenable to centralization. However, it has all the limitations of a meta-analysis, with possible unknown confounders. In this particular study, an obvious confounder is “time to procedure.” One could imagine that in less densely populated areas, not only would there be a lower yearly case volume, but that a longer time to procedure could significantly impact outcomes. There should be caution in over-interpreting these results or using them to guide policy in the absence of further studies with different methodology.
Clinical Topics: Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention, Vascular Medicine, Interventions and Vascular Medicine
Keywords: Aneurysm, Dissecting, Cardiac Surgical Procedures
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