Introduction

A strategy to positively impact aortic remodeling and false lumen perfusion, the PETTICOAT (Provisional Extension to Induce Complete Attachment), technique has evolved to support the delaminated segments of the thoracoabdominal aorta [6-8]. This approach utilizes an uncovered stent with low radial force deployed into the false lumen of the thoracoabdominal aorta, generally in the visceral segments. The purpose of this investigation is to determine the early clinical outcomes and changes in aortic morphology by managing the abdominal aorta with the PETTICOAT technique and report our experience in patients with acute and chronic thoracoabdominal aortic dissection.

Methods

Patients

This retrospective study was approved by the institutional review board at Cleveland Clinic, and informed consent was waived as IRB #20-979 on September 15, 2020. From April 1, 2019 to April 5, 2021, 73 patients underwent endovascular aortic repair for thoracoabdominal dissection with the PETTICOAT technique. The FDA-approved Zenith® Dissection Endovascular Stent (Cook Medical; Bloomington IN) was used in conjunction with commercially available covered thoracic aortic stent grafts. Acute dissections were defined as those <14 days, subacute 14-30 days, and chronic >30 days. Patients were identified using the implant log of the Zenith® Dissection Endovascular Stent since its availability at our institution and the electronic medical record, from which patient data was abstracted.

Of the 73 patients in our study group, 20 patients had Debakey class IIIb dissection (6 acute, 1 subacute, 13 chronic). The remaining 53 patients had Debakey class I dissection (16 acute, 37 chronic). Surgical indications included complicated acute Debakey IIIb dissection, an increase in the adventitia-to-adventitia diameter of the descending thoracic aorta >5.5cm, or an increase in the growth rate of the descending thoracic aorta by >0.5mm/year.

Demographic and pre-operative characteristics are presented in Table 1. (Option B: Table 1 stratified by Debakey classification).

Table 1. Patient Characteristics
Group Characteristic N N = 73
Pre-Operative Age 73 58.00 (19.00)
Sex 73
Female 25.0 (34.2%)
Male 48.0 (65.8%)
BMI 73 28.60 (8.69)
Debakey Classification 73
I 53.0 (72.6%)
III 20.0 (27.4%)
Dissection Chronicity 73
Acute 22.0 (30.1%)
Subacute 1.0 (1.4%)
Chronic 50.0 (68.5%)
Indication for Surgery 73
Growth 51.0 (69.9%)
Size 11.0 (15.1%)
Compression 11.0 (15.1%)
Time to Surgery 73 351.00 (1,787.00)
Length of Stay 73 8.00 (7.00)
Procedure Time 26 170.00 (79.00)
Contrast Volume 22 46.00 (44.00)
Fluoroscopy Time 22 27.50 (20.00)
Coronary Artery Disease 73 16.0 (21.9%)
Peripheral Vascular Disease 73 19.0 (26.0%)
Stroke (within 30 days) 73 0.0 (0.0%)
Chronic Obstructive Pulmonary Disease 73 8.0 (11.0%)
Hypertension 73 61.0 (83.6%)
Diabetes 70 5.0 (7.1%)
Hyperlipidemia 73 31.0 (42.5%)
Chronic Renal Failure 73 13.0 (17.8%)
Aortic Surgery 73 45.0 (61.6%)
Connective Tissue Disorder 73 8.0 (11.0%)
Type A Dissection 73 38.0 (52.1%)
Malperfusion 73 10.0 (13.7%)
Post-Operative Type 1 Endoleak 73 11.0 (15.1%)
Type 2 Endoleak 73 8.0 (11.0%)
Other Endoleak 73 14.0 (19.2%)
Reintervention 73 10.0 (13.7%)
Mortality 73 4.0 (5.5%)
Paraparesis 73 3.0 (4.1%)
Mesenteric Ischemia 73 5.0 (6.8%)
Limb Ischemia 73 3.0 (4.1%)
Stroke 73 3.0 (4.1%)
1 Continuous data is displayed as Median (IQR); Categorical data is displayed as N (%)

Follow up

Follow-up of patient clinical status and the presence of surveillance imaging was obtained by chart review. Imaging was performed prior to endovascular intervention and per routine post-operative surveillance strategy. Post-operative data was grouped into five timepoints for analysis: pre-operative, <30 days, 3-6 months, 1 year, and >1 year. If a patient underwent two imaging studies during one time period, the later study was analyzed.

Imaging Analysis

Multi-phase (noncontrast, arterial phase, and delayed venous phase) contrast-enhanced CT angiography were analyzed using 3D reconstructive software (Aquarius; TeraRecon, San Mateo, CA). Centerline measuresments of total aortic area, false lumen area, false lumen area, and the presence of patent, partially thrombosed, or thrombosed false lumen at zones 0 to 9 of the aorta were collected. All scans were reviewed by a single interpreter, and measurements confirmed by a second reviewer.

For each time point, area fraction was calculated for the false and false lumen by dividing the summed lumen area by the summed total area for dissected segments. False lumen patency was quantified by dividing the number of patent zones by the total number of dissected zones. Mean values for each time point are displayed in Table 2.

Table 2.
Characteristic Pre-Op, N = 73 Post-Op, N = 63 3-6mo, N = 43 1y, N = 17 >1y, N = 9
Post-Operative Day 0 (0, 0) 3 (2, 4) 123 (98, 149) 330 (252, 352) 463 (441, 555)
Mean Aortic Area 906 (748, 1,127) 970 (821, 1,220) 1,017 (886, 1,182) 962 (880, 1,068) 906 (782, 1,090)
Mean Dissected Aortic Area 1,014 (745, 1,206) 1,061 (857, 1,360) 1,102 (905, 1,321) 1,037 (895, 1,100) 985 (771, 1,151)
Mean True Lumen Area 371 (280, 466) 601 (528, 687) 644 (542, 785) 651 (589, 718) 584 (495, 783)
Mean False Lumen Area 550 (434, 806) 419 (267, 622) 406 (235, 583) 330 (199, 465) 250 (176, 291)
True Lumen Area Fraction 0.37 (0.30, 0.43) 0.59 (0.50, 0.67) 0.60 (0.53, 0.72) 0.64 (0.59, 0.80) 0.74 (0.59, 0.77)
False Lumen Area Fraction 0.62 (0.56, 0.68) 0.40 (0.33, 0.49) 0.38 (0.26, 0.47) 0.36 (0.20, 0.42) 0.24 (0.22, 0.34)
Patent Fraction 0.83 (0.56, 1.00) 0.50 (0.33, 0.67) 0.43 (0.25, 0.57) 0.43 (0.00, 0.50) 0.38 (0.28, 0.50)
Thrombosed Fraction 0.00 (0.00, 0.29) 0.43 (0.20, 0.50) 0.50 (0.33, 0.61) 0.50 (0.43, 0.60) 0.46 (0.33, 0.52)

Data Analysis and Statistics

The surgery was considered a technical success if there was satisfactory positional deployment of the stent grafts in the false lumen without obstruction of branch vessels, no evidence of type 1 or 3 endoleaks, and survival at 24 hour post-operatively.

To account for variation in the affected aortic area between patients as well as changes in total area over time, aortic remodeling was assessed via (1) true lumen area fraction, and (2) patent fraction for each follow-up visit. Changes in area and patency fraction over time were assessed with a variable dispersion beta regression model, a standard maximum likelihood model well suited for regression with proportional data. Covariates included ***. Only clinically and statistically significant variables were included in the final model for each dependent variable. Group differences were assessed via the Wilcoxon signed-rank test.

Categorical variables are summarized as n (%). Continuous data that follow a Gaussian distribution are described as mean ± standard deviation; non-normal data are described as median ± interquartile range. Statistical significance was set at p = 0.05.

Results

Post-Operative Outcomes

Technical success was achieved for all 73 patients undergoing TEVAR + PETTICOAT stenting, and post-operative complications are presented in Table 2. There were 2 in-hospital deaths resultant from multi-system organ failure after presenting with acute Debakey class I dissections and malperfusion. Additionally there was another mortality after acute Debakey class IIIb with malperfusion occurring at 30 days, and of unknown etiology. Similarly, both patients requiring hemodialysis for acute renal failure presented with acute Debakey class I dissections. Retroperitoneal bleeding occurred after TEVAR+PETTICOAT procedure in 2 patients. One patient was managed non-operatively with surveillance, and the other was diagnosed during exploratory laparotomy for mesenteric ischemia after presenting with intestinal malperfusion that eventually resulted in death.

Patients were followed up for a median of 104$$298 days.

During the study period, a total of 5 (7%) patients died and 11 (15%) required reintervention. No patient who underwent reintervention died. By the study endpoint, 16 (22%) patients had not yet reached 1 year post-op.

Aortic Remodeling

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There were 67 patients that had CT angiography at 3 months follow-up (92%) and 20 at 1 year (27%). Those patients that did not have CT scans at those intervals died, chose to pursue care elsewhere, have not reached the 1-year follow-up yet, or were lost to follow-up.

Longitudinal volumetric analysis over time, and total aortic area and luminal area from pre-op to most recent imaging are displayed in Figure 1. While total aortic area did increase significantly between baseline and last follow up (953±267 mm2 vs. 1015±261 mm2, p<.001), the true lumen area increased to a greater degree (374±150 mm2 vs. 659±155 mm2, p<.001) as evidence by a significant increase in true lumen fraction (0.38±0.13 vs. 0.62±0.14 p<.001) and decrease in false lumen fraction (0.62±0.13 vs. 0.37±0.14, p<.001). Aortic remodeling is shown in Figure 2, with largely positive remodeling at 3 months, 1 year, or most recent scan; 84%, 95%, 87%, respectively. The fraction of dissected zones were patent from baseline to most recent imaging is seen in Figure 3.

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There were 67 patients that had CT angiography at 3 months follow-up (92%) and 17 at 1 year (23%). Those patients that did not have CT scans at those intervals died, chose to pursue care elsewhere, have not reached the 1-year follow-up yet, or were lost to follow-up.

Median pre-operative cross sectional area was 1014 mm\(^{2}\) for the dissected aorta, 371 mm\(^{2}\) for the true lumen, and 550 mm\(^{2}\) for the false. Median area fraction was 0.35 for the true lumen and 0.62 for the false lumen, and 83% of all dissected zones had patent flow. By the post-operative scan, true lumen area fraction was 0.59 and 50% of dissected zones were patent.

Results of the beta regression models are shown in []. Post-operative day was significantly associated with increased true lumen area fraction (\(\beta\)=1.69e-3, p=1.03e-7) and decreased patent fraction (\(\beta\)=-1.79e-3, p=.013). In addition to post-operative day, increased age, Debakey type I classification, acute dissection, decreased pre-operative dissected aortic area, and decreased pre-operative patent fraction were significantly associated with increased true lumen fraction. Debakey type I classification and subacute chronicity were positively correlated with patent fraction, while

Post-operative day, Debakey type III classification, a history of malperfusion, and pre-operative true lumen area fraction were significantly associated with decreased patent fraction, while subacute chronicity and a history of COPD were positively correlated.

Median time between pre- and post-operative scan was 3 days. In this interval, true lumen area fraction increased significantly (0.37 vs 0.59, p<.001) while patent fraction decreased significantly (0.83 vs. 0.50, p<.001). Over the following year these changes continued, with a significant difference observed between post-operative and 1-year follow-up scans for both true lumen area fraction (0.59 vs. 0.64, p=.018) and patent fraction (.50 vs. .43, p=.018).

Covariates in Beta Regression Model of True Lumen Area Fraction
Variable estimate std.error statistic p.value
(Intercept) 0.4331754 0.2371653 1.8264701 0.0677795
POD 0.0016927 0.0003181 5.3208770 0.0000001
Age 0.0147104 0.0032305 4.5535293 0.0000053
Debakey [Type III] -0.3202795 0.0951879 -3.3647070 0.0007662
Total Dissected Area -0.0000663 0.0000164 -4.0373097 0.0000541
Patent Fraction -0.6666350 0.1456014 -4.5784932 0.0000047
Chronicity [Subacute] 0.5561946 0.3111039 1.7878099 0.0738067
Chronicity [Chronic] -0.3630733 0.1018345 -3.5653269 0.0003634
Time to Surgery (Days) -0.0000215 0.0000273 -0.7864797 0.4315865
Covariates in Beta Regression Model of Patent Fraction
Variable estimate std.error statistic p.value
(Intercept) 1.3144844 0.7217204 1.8213206 0.0685581
POD -0.0017937 0.0007266 -2.4686830 0.0135611
Age 0.0037545 0.0075821 0.4951858 0.6204690
BMI 0.0173979 0.0158541 1.0973817 0.2724745
Debakey [Type III] -0.8012352 0.2114309 -3.7895847 0.0001509
Chronicity [Subacute] 1.3131114 0.6466998 2.0304807 0.0423077
Chronicity [Chronic] -0.1810181 0.2292430 -0.7896344 0.4297413
Total Dissected Area 0.0000299 0.0000356 0.8395887 0.4011390
Patent Fraction -3.1090463 0.6160203 -5.0469867 0.0000004
Time to Surgery (Days) -0.0001043 0.0000566 -1.8447839 0.0650690
History of COPD -0.5779007 0.1976354 -2.9240753 0.0034548
History of Malperfusion 0.5754349 0.1901195 3.0267014 0.0024724