Closing of a Patent Tear Above the Aortic Hiatus and Type A Aortic Dissection Outcomes

Abstract

Background

A strategy combining tear-oriented initial surgical procedure and subsequent thoracic endovascular aortic repair (TEVAR) can be adopted for acute type A aortic dissection (ATAAD). This study investigated this strategy’s outcomes and the role of the aortic hiatus (AH).

Methods

Overall, 192 consecutive patients with ATAAD who underwent initial surgery between 2012 and 2021 were assessed in this observational retrospective study. The reintervention rate, the relationship of the residual tear location above or below the AH, and the outcomes of subsequent TEVAR and redo distal open repair were assessed.

Results

The initial surgery’s in-hospital death rate was 8.3%; the subsequent TEVAR and redo distal open repair rates were 28% and 3%, respectively. Reintervention was performed in 93% and 0% of patients with tears above and below the AH, respectively, with a 0% mortality rate.

Conclusions

In false lumen expansion cases, timely detection and closure of the residual intimal tear above the AH with subsequent TEVAR might improve ATAAD outcomes.

In Short.

• ▪Our strategy, which combined tear-oriented initial surgery with subsequent thoracic endovascular aortic repair for acute type A aortic dissection, produced satisfactory outcomes.
• ▪Timely detection and closure of the residual intimal tear above the aortic hiatus can result in better outcomes and help prevent open thoracoabdominal repair in patients with type A aortic dissection.

Although the exact surgical approach for acute type A aortic dissection (ATAAD) is controversial,¹ 1 study claimed that replacing or sealing the dissected aorta yields better results with the single extended strategy.² However, another study claimed that compact surgery based on tear orientation is sufficient and reintervention can be performed (the combination strategy) for ATAAD if necessary.³

Approximately 20% of patients with ATAAD require reintervention for postoperative false lumen expansion (FLE) of the distal dissected aorta.^3,4 However, this single extended strategy may cause overindication for total arch replacement (TAR) or more extensive repair. Moreover, whether every patient's residual tear causes FLE cannot be accurately predicted at the onset. Therefore, minimizing the complication risks due to overly large replacements in patients without FLE is necessary. Conversely, patients with postoperative FLE should be treated promptly and less invasively.

The role of the aortic hiatus (AH), the sole rigid structure surrounding the distal aorta, in FLE is poorly documented.⁵ Here, we report our combination strategy’s outcome and explore the relationship between the residual intimal tear’s location, above or below the AH, and distal reintervention.

Patients and Methods

The institutional review board of Iwate Prefectural Central Hospital approved this observational retrospective study (approval number: 631), which conformed to the Declaration of Helsinki. The informed consent requirement was waived.

Between June 2012 and December 2021, 192 consecutive patients with ATAAD underwent aortic replacement or primary thoracic endovascular aortic repair (TEVAR) at our institute (Supplemental Table 1). Initial surgery for ATAAD was defined as surgery performed within 14 days after symptom onset (179 patients [93%] within 48 hours). Distal reintervention was defined as redo open repair or endovascular intervention on the aorta distally after the initial surgery.

All prosthetic graft replacements were routinely performed under hypothermic cardiopulmonary bypass using antegrade cerebral perfusion with an open distal anastomosis. Ascending aorta replacement was performed without aortic clamping. Hemiarch (without arch vessel reconstruction) or partial arch replacement (with the reconstruction of 1 or 2 proximal arch vessels), known as non-TAR, was performed in patients with intimal entry tears in the arch proximally and partially. Furthermore, TAR was performed with a short elephant trunk in patients with intimal entry tears mostly localized along the arch.

Surviving patients were regularly followed up for clinical and multidetector computed tomography (CT) reviews. Figure 1 presents patient characteristics with a median follow-up period after the initial surgery of 4.6 years (interquartile range, 2.7-7.5 years). The intimal flap movement was fierce, confirming that the residual tear's location in the acute phase was challenging. However, its movement gradually decreased, and the patent intimal tear’s location was easily detected by contrast-enhanced CT 3 months after the initial surgery. Patients were categorized into 4 groups based on the residual patent tear location as follows: no residual tear, tears only above the AH, tears only below the AH, and tears above and below the AH.

Figure 1.

Flowchart for patient selection. (CT, computed tomography; TEVAR, thoracic endovascular aortic repair.)

Timely detection of FLE was the strategy’s most important aspect, and the target intimal tears that caused FLE were confirmed in every case. FLE was defined as an expansion of >5 mm/6 months of the false lumen, as observed on contrast-enhanced CT, which aligned with the reintervention indication for subsequent TEVAR and redo distal open repair. Contrast-enhanced CT was performed at weeks 1, 2, and 3; at months 1, 3, 6, and 12; and subsequently every 6 months for 3 years after the initial surgery. The annual CT examination was continued.

Meticulous TEVAR planning confirmed the optimal device length and diameter critical for safe installation. Prolonged sealing, which might cause paraplegia, was avoided. Careful surgery under intravascular ultrasound guidance and precise positioning and angulation of the devices were crucial. Zenith TX2 (Cook Medical) and Gore C-TAG (W. L. Gore & Associates) were used. Redo distal open repairs were performed when the anatomic conditions were unsuitable for TEVAR.

Continuous variables are presented as medians (interquartile range) for age and days from the initial surgery and means (SD) for time- and volume-related values. Categorical variables are presented as counts and percentages and were compared using the χ² test. Fisher exact test was used for small group sizes (n < 5). P values were not presented for n = 0 in the subgroups. Multivariable logistic regression was applied for reintervention risk factor analysis. The significance level was set at P < .05. All statistical calculations were performed with JMP software, version 16.2.0 (SAS Institute).

Results

The primary entry exclusion rate for the initial surgery was 81.3% (156/192; Supplemental Table 2). The in-hospital mortality rate was 8.3% (16/192). Of 131 patients with complete follow-up data, 90 showed no FLE or distal reinterventions. The reintervention, subsequent TEVAR, and redo distal open repair rates were 31% (41/131), 28% (37/131), and 3% (4/131), respectively (Figure 1).

The residual tear's existence and location were important for the patient's fate after the initial surgery. The relationship between the residual tear's location and the AH was particularly crucial. Reintervention was unnecessary in 69 patients without residual tears or tears only below the AH (Supplemental Table 3). In 18 patients with tears only below the AH, 1 or more branches of the abdominal aorta (AA) were directly connected to the false lumen, and they received blood flow through the patent intimal tear. Of 14 patients with tears only above the AH, reintervention was performed in 13 (93%). One patient with tears only above the AH had no FLE; therefore, several intercostal arteries were connected to the false lumen, similar to visceral arteries. Of 48 patients with tears at both sites, reintervention was performed in 28 (58%). In 20 patients with tears at both sites without FLE, 1 or several intercostal arteries were similarly connected to the false lumen. The χ² test showed significant differences between these 4 groups (P < .001).

No significant difference was observed between TAR and non-TAR (P = .07; Supplemental Table 4); a significant difference was observed between DeBakey type I and type III retrograde aortic dissection (P < .001; Supplemental Table 5). Fisher exact test showed a significant difference between the groups with tears at both sites and tears only above the AH (P = .023). Multivariate logistic regression revealed the retrograde DeBakey III aortic dissection (P < .001) and tears only above the AH (P = .002) as significant risk factors (Supplemental Table 6).

Supplemental Table 7 presents the subsequent perioperative details of TEVAR (n = 37). Of all cases, the in-hospital mortality and postoperative paraplegia rates were 0%. Distal stent graft–induced new entry occurred in 2 Zenith TX2 cases; consequently, additional TEVAR was performed with Gore C-TAG. With these 2 exceptions, no additional TEVAR or redo distal open thoracoabdominal repair was needed.

Supplemental Table 8 presents redo distal open repair cases (n = 4), without tears observed in the thoracic aorta; hence, subsequent TEVAR was not performed. During the initial surgery, isolated ascending aorta replacement was performed. The target tears that caused FLE were at the arch vessels in all cases. Blood flow through these tears poured into the false lumen of the aortic arch and thoracic descending aorta (TDA). Therefore, redo distal open repair was performed in these patients. The in-hospital mortality rate was 0%, and the postoperative courses were uneventful. No thoracoabdominal repair was needed.

Comment

We demonstrated our combination strategy’s outcomes for ATAAD. The initial surgery's results were acceptable. Overall late outcomes were acceptable because of the redo distal open repair’s extremely low rate (3%). Because these results were favorable compared with those of previous reports,1, 2, 3 we hypothesized that the role of the AH in FLE needs further consideration.

Reintervention was unnecessary in the groups without residual tears and tears only below the AH. It was also necessary in the groups with tears only above the AH and tears at both sites in more than half of the cases. In cases without FLE and a tear above the AH, 1 or more arteries were connected to the false lumen, and blood flow was supplied through the patent tear. FLE occurrence may depend on the balance between inflow from the tear and outflow through the arteries directly originating from the false lumen. Although the residual tear exists, closure of the tear is unnecessary in preventing FLE and may be advantageous to prevent paraplegia.

The false lumen of the TDA may expand more easily than that of the AA for the following reasons. The AA is surrounded by numerous tightly placed lymph nodes and plexuses (Figure 2A),^6,7 which may protect it from FLE. Multiple visceral and lumbar arteries may prevent easy expansion. In the AA, an intimal tear is mostly pierced by these arteries. Therefore, the multiple and thick branches from the false lumen may prevent the sharp increase in the false lumen blood pressure. The TDA is inadequately surrounded by tough tissues and has only small-caliber branches, making the false lumen of the TDA expand easily (Figure 2B). Early closure of the tears that cause FLE is critical in patients with tears only above the AH. However, the mechanism of FLE is more complex in patients with tears at both sites (Figure 2C). The AH may serve as a tight loop between the false lumen of the TDA and the AA. In cases of FLE, if the tears above the AH are not closed or delayed, the communication between the false lumen of the TDA and the AA increases, leading to AH enlargement (Figure 2C, right arrow). Intimal flaps may become thick and fixed, and the narrow true lumen may become irreversibly obliterated. In such cases, the retrograde blood from the tears below the enlarged AH may cause massive FLE of the thoracoabdominal aorta. Conversely, when the tears above the AH are promptly closed, the true lumen at the level of the AH enlarges, leading to rapid shrinkage of the false lumen. Therefore, the communication between the thoracic and abdominal aortic false lumen drastically decreases (Figure 2C, left arrows).

Figure 2.

Presumed mechanisms of false lumen expansion influenced by tear location above or below the aortic hiatus (AH). (A) Group of patients with tears only below the AH: no need for subsequent thoracic endovascular aortic repair (TEVAR). (B) Group of patients with tears only above the AH: subsequent TEVAR was mostly needed. (C) Group of patients with tears at both sites: subsequent TEVAR was required in more than half of the cases. Large right arrow: no subsequent TEVAR in the case of false lumen expansion. Large left arrows: subsequent TEVAR was performed promptly. Small arrows in each figure means bloodstream direction.

Our study suggested the retrograde DeBakey III aortic dissection to be a significant risk factor for reintervention, whereas non-TAR was not a significant risk factor. Tears only above the AH might be a significant risk factor, although this factor’s CI was wide in this study.

This study had some limitations. First, it was a single-institution, observational, retrospective study with a small cohort and a 5-year median follow-up period. Therefore, larger studies with longer follow-up data should provide more insights into this topic.

Conclusively, our strategy, which combined tear-oriented initial surgery with subsequent TEVAR, when necessary, produced satisfactory outcomes. Therefore, for FLE occurring after initial surgery, timely detection and closure of the residual intimal tear above the AH may lead to better outcomes for type A aortic dissection.

The Supplemental Tables can be viewed in the online version of this article [https://doi.org/10.1016/j.atssr.2023.05.014] on http://www.annalsthoracicsurgery.org.