Decoding the volume–outcome relationship in Type A aortic dissection

Outcomes of type A aortic dissection in Australia

INTRODUCTION

Without surgical intervention, type A aortic dissection (TAAD) carries a high risk of life-threatening complications and mortality. Due to the low incidence of aortic dissection, case numbers vary significantly between institutions. This study reports outcomes for patients undergoing surgical TAAD repair in Australia between 2001 and 2021, and the impact of institution case numbers on mortality.

METHODS

Retrospective multicentre cohort study using the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) data, including consecutive adult patients undergoing surgery for TAAD. Patients were divided into groups based on 30-day mortality. Secondary morbidity outcomes are reported.

RESULTS

Between 2001 and 2021, 2604 patients (median age 65; 67% male) underwent operative intervention for TAAD. Over this period, the number of aortic dissections recorded in the database annually increased (from <50 to >200 cases per year), consistent with the increasing number of contributing institutions. Thirty-day mortality rates varied by unit from 0% to 100%, with an average over the period of 18%. Despite unit case numbers ranging from 1 or 2 to over 200 cases, funnel plot analysis demonstrated no units fell outside the accepted 99.7% control level for 30-day mortality. Individual surgeons showed decreased mortality with increased caseload. Non-survivors were more likely to have prior respiratory or cerebrovascular disease, previous myocardial infarction, or severe left ventricular dysfunction. Post-operative stroke, return to theatre for bleeding, renal failure and atrial fibrillation were more common in the non-survivors (P < 0.05).

CONCLUSION

Mortality outcomes for TAAD in Australia have improved over time, stabilizing at 18% over the last 5 years. Units performing fewer operations for TAAD showed equivalent mortality outcomes to high volume units, while surgeons performing fewer procedures displayed a higher mortality.

Transportation model for acute aortic dissection: implications for reduced treatment centres

OBJECTIVES

The objective of the present study was to model the effects of a reduced number of treatment centres for acute type A aortic dissection on preclinical transportation distance and time. We examined whether treatment in selected centres in Germany would be implementable with respect to time to treatment.

METHODS

For our transportation model, the number of aortic dissections and respective mean annual volume were collected from the annual quality reports (2015-2017) of all German cardiac surgery centres (n = 76). For each German postal code, the fastest and shortest routes to the nearest centre were calculated using Google Maps. Furthermore, we analysed data from the German Federal Statistical Office from January 2005 to December 2015 to identify all surgically treated patients with acute type A aortic dissection (n = 14 102) and examined the relationship between in-hospital mortality and mean annual volume of medical centres.

RESULTS

Our simulation showed a median transportation distance of 27.13 km and transportation time of 35.78 min for 76 centres. Doubling the transportation time (70 min) would allow providing appropriate care with only 12 medical centres. Therefore, a mean annual volume of >25 should be obtained. High mean annual volume was associated with significantly lower in-hospital mortality rates (P < 0.001). A significantly lower mortality rate of 14% was observed (P < 0.001) if a mean annual volume of 30 was achieved.

CONCLUSIONS

Operationalizing the volume-outcome relationship with fewer but larger medical centres results in lower mortality, which outweighs the disadvantage of longer transportation time.

Factors Affecting Outcomes in Acute Type A Aortic Dissection: A Systematic Review

Acute type A aortic dissection is a clinical emergency and is associated with significant morbidity and mortality rates if not managed promptly in specialised and high-volume centres. The mortality rate is increased by 1% for each hour delay in management; however, with advancement in clinical practice, diagnostic imaging and clinician awareness, this has been dramatically reduced to below 30% in most international centres. Not only timing of recognition of the pathology, but also other factors can significantly affect outcomes of such critical pathology. This includes, but is not limited to, age, extent of the pathology, existence of connective tissue disorders, hypertension, diabetes mellitus and surgeon experience. This narrative review will focus on current clinical practice and the evidence behind optimising each factor to minimise adverse outcomes in such high-risk cohort.

Volume-Outcome Relationships in Surgical and Endovascular Repair of Aortic Dissection

BACKGROUND

As surgical mortality decreases and endovascular utilization increases, it is unknown whether volume-outcome relationships exist in thoracic aortic dissection repair. We characterized volume-outcome relationships for surgical and endovascular management of thoracic aortic dissection.

METHODS

Patients aged more than 18 years undergoing repair of thoracic aortic dissection in the United States between 2010 and 2014 were identified in seven all-payer state inpatient administrative databases. Patients were divided into groups based on type of repair: surgical repair of type A dissection (TAAD), surgical repair of type B dissection (TBAD), and endovascular repair (TEVAR). Hierarchical logistic regression models evaluated the association between hospital volume and in-hospital mortality.

RESULTS

Overall in-hospital mortality rate was 13.4% (890 of 6650), highest after TAAD (463 of 2918, 15.9%), followed by TBAD (270 of 1934, 14.0%) and TEVAR (157 of 1798, 8.7%). Volume-outcome relationships for adjusted in-hospital mortality were demonstrated for TAAD and TBAD (P-trend < .001), but not TEVAR (P-trend = .11). Adjusted in-hospital mortality differed most for TAAD (fewer than 3 cases per year: 21%, 95% confidence interval, 18% to 24%; vs 11 or more cases per year: 12%, 95% confidence interval, 8% to 16%; P < .001) and TBAD (fewer than 2 cases per year: 18%, 95% confidence interval, 15% to 22%; vs 11 or more cases per year: 9%, 95% confidence interval, 5% to 12%; P < .001), whereas TEVAR did not differ between quartiles. Adjusted mortality was lower at centers with 26 or more overall annual thoracic dissection repairs, compared with any of the three lower-volume quartiles (P < .001).

CONCLUSIONS

This study demonstrated lower mortality at high-volume hospitals for overall repair of aortic dissection, persisting separately for surgical repair of TAAD and TBAD, but not TEVAR. As endovascular technology advances and practice patterns consequently change, analyses should focus on understanding the balance between procedural volume, mortality, and access to care for thoracic aortic dissection.