The extent of repair in type A aortic dissection is highlighted as a knowledge gap in this year’s exceptional clinical guidelines on aortic disease, which have been previously discussed on this blog.

Resection of the primary entry tear is a procedural principle, yet this can be challenging in patients with entry tears located in the descending thoracic aorta. This article focuses on analyzing a pertinent question: What is the significance of residual primary entry tears in the descending thoracic aorta following surgery? Are there age-related differences?

This year, Kawaito et al. published in Annals of Thoracic Surgery an analysis on the impact of primary entry tears in the descending thoracic aorta in over 1000 patients who underwent type A aortic dissection repair in two high-volume Japanese centers, with a median follow-up of 16 years.

The authors reviewed patients over a 28-year period, dividing them into two age groups (older or younger than 70 years), further categorized based on the presence of a primary entry tear in the descending thoracic aorta.

The surgical intervention generally followed the tear-oriented approach recommended by guidelines:

• Hemiarch replacement if the entry tear was located in the ascending aorta (E1), lesser curvature (E2, lesser curvature), or if no entry tear was observed in the root, ascending aorta, or arch (E0 or E3).
• Total arch replacement (TAR) if the entry tear was found in the arch or supraaortic vessels (E2, greater curvature).

Myocardial protection was achieved with cold blood cardioplegia, applied retrograde or antegrade. For perfusion and organ protection, deep hypothermia at 20ºC was used until 2008, and subsequently either deep or moderate hypothermia (20-28ºC) with selective cerebral perfusion (either unilateral or bilateral) was applied. The patient group distribution for each method was not reported in the article.

In the younger group, there were 191 patients with a residual entry tear in the descending thoracic aorta (E3, 28%) and 490 patients without a residual entry tear (72%), compared to 74 patients (E3, 18%) and 348 patients (82%) in the older group under the same categories. Propensity score matching using the nearest neighbor method without replacement resulted in 179 and 71 pairs, respectively, in each age and entry presence category.

The primary outcome was a composite event termed “DAE” (distal aortic events), encompassing malperfusion, recurrence of new distal dissection, rupture, reintervention, or death due to an aortic event.

Short-term outcomes reported an overall in-hospital mortality of 7.4%, with no differences between age groups. Hospital morbidity was also similar across groups.

Regarding the type of surgery, TAR was more frequent in patients without residual entry tears across both age groups. Among those with residual entry tears in the descending thoracic aorta, 89% of younger patients and 96% of older patients underwent hemiarch or ascending aorta replacement. Root surgery was uncommon, with no cases in patients over 70 years and less than 5% in younger patients.

Patients with residual entry tears had shorter cardiopulmonary bypass (CPB) times (139 vs. 207 min in patients under 70 years), likely due to the reduced surgical extent. No differences were observed in morbidity or mortality between groups.

Long-term follow-up, with a median of 16.8 years and an exceptional follow-up rate of 98.7%, showed similar 10-year survival rates between groups with and without residual entry in those under 70 (72% vs. 74%) and those over 70 (53% vs. 52%). Deaths at 10 years from non-aortic causes were more frequent in patients over 70 years (37.3% vs. 14.2%; p < .001).

Distal aortic events (DAEs) were more frequent in younger patients (80 vs. 13 cases). Younger patients with residual entry tears had more frequent DAEs at 10 years compared to those without (35% vs. 22%; p < .001). However, no differences were observed in the older group at 10 years (11% vs. 9%).

COMMENTARY:

This is not the first time that Kawahito et al.’s group has published on this topic; however, this analysis focuses on primary entry tears in the descending thoracic aorta. Importantly, we are not referring to reentries in the descending thoracic aorta, but to patients without observable entry tears in the arch or ascending aorta in type A dissections or whose entry tear is in the descending thoracic aorta. This phenomenon, termed by some as non-iatrogenic retrograde aortic dissection, may lead to persistent pressurization of the residual false lumen, potentially resulting in an increase in late aortic events.

Although rare, type A dissections originating from an entry tear in the descending thoracic aorta (A,E3) may account for approximately 7% of all type A dissections, as indicated by the International Registry of Acute Aortic Dissection (IRAD).

This study compares patients with primary entry tears in the ascending aorta or arch against those with entry tears in the descending thoracic aorta, categorized by age.

The study’s main conclusion is clear: residual primary entry tears in the descending thoracic aorta do not affect 10-year mortality but do increase the frequency of distal aortic events in patients under 70.

Various factors should be considered:

Definitions: The terminology used may cause confusion as patients are classified based on preoperative CT scans and intraoperative findings, comparing classic type A dissections (A, E1-2) with retrograde dissections (A, E3). Thirty patients in the residual entry group underwent arch surgery, but details on the false lumen patency and whether the elephant trunk technique was applied remain unknown.

Age: An arbitrary cutoff of 70 years was used, yet younger patients with aortic dissection may have a genetic predisposition. Detailed descriptions of patients experiencing late aortic events, including age and associated pathology, are missing.

Repair Extent: The tear-oriented approach to ascending aorta and arch is recommended in the 2024 guidelines. Most patients with residual entry tears underwent ascending aorta replacement or hemiarch, with no information on the frozen elephant trunk technique. This study may prompt age-based stratification for frozen elephant trunk technique.

Postoperative Structural Changes: This study lacks information on false lumen status, residual aorta diameters, and new distal reentries, all factors associated with late aortic events.

Survival and Follow-up Duration: Survival appears unaffected by descending aorta entry tears. The low DAE frequency in older patients (under 10%) supports a conservative approach in this group.

Mortality: Type A dissection mortality in Asian studies is typically low, with this study reporting only 7%, whereas registries like German (16%), British (17%), and international (18%) report higher rates. The study’s results may not be broadly applicable to clinical practice.

In summary, recent data prompt us to reconsider management for retrograde type A dissections (entry in descending thoracic aorta or E3), especially in patients over 70. Aggressive treatment and close follow-up for those under 70 may be justified based on these findings.

REFERENCES:

Kawahito K, Aizawa K, Kimura N, Yamaguchi A, Adachi H. Influence of residual primary entry following the tear-oriented strategy for acute type A aortic dissection. Eur J Cardiothorac Surg. 2022;61:1077-1084.

Nauta FJH, Kim JB, Patel HJ, Peterson MD, Eckstein HH, Khoynezhad A, et al. Early Outcomes of Acute Retrograde Dissection From the International Registry of Acute Aortic Dissection. Seminars in Thoracic and Cardiovascular Surgery. 2017;29(2):150–9.

Inoue Y, Matsuda H, Matsuo J, Shijo T, Omura A, Seike Y, et al. Efficacy of entry exclusion strategy for DeBakey type III retrograde Stanford type A acute aortic dissection. European Journal of Cardio-Thoracic Surgery. 2021 Jan 29;59(2):481–9.

Benedetto U, Dimagli A, Kaura A, Sinha S, Mariscalco G, Krasopoulos G, et al. Determinants of outcomes following surgery for type A acute aortic dissection: the UK National Adult Cardiac Surgical Audit. European Heart Journal. 2021 Dec 28;43(1):44–52.

Kallenbach K, Büsch C, Rylski B, Dohle DS, Krüger T, Holubec T, et al. Treatment of the aortic root in acute aortic dissection type A: insights from the German Registry for Acute Aortic Dissection Type A. European Journal of Cardio-Thoracic Surgery. 2022 Jun 15;62(1):ezac261.

Harris KM, Nienaber CA, Peterson MD, Woznicki EM, Braverman AC, Trimarchi S, et al. Early Mortality in Type A Acute Aortic Dissection: Insights From the International Registry of Acute Aortic Dissection. JAMA Cardiol. 2022 Oct 1;7(10):1009.