Between January 2016 and December 2020, consecutive patients aged $\ge$18 years who underwent surgical repair for ATAD in this center were reviewed. Eligibility criteria for surgery included: (1) presenting with intraoperative iATAD; and (2) receiving immediate aortic repair. In this study, intraoperative iATAD was defined as an iATAD occurring due to a cardiac surgical procedure and during the course of the cardiac surgical procedure. Intraoperative iATAD was diagnosed via intraoperative vision and by using transesophageal echocardiographic (TEE) assessment of the aorta. Exclusion criteria included dissection occurring after cardiac surgery, dissection appearing after cardiac catheterization procedures, and iATAD associated with procedures other than cardiac surgery. This study did not include patients with spontaneous type A aortic dissection.

The surgical objectives for intraoperative iATAD repair were resection of the primary aortic entry tear with the dissected aorta as much as possible and restoration of flow into the true lumen. Rapid suspension of CPB was performed as soon as the diagnosis was confirmed. The true lumen within the aortic arch was the preferred option of the location of arterial recannulation. We could perform this procedure by direct vision into the aorta or by repeated needle puncture guided by TEE. Then the guidewire followed by a cannula was guided into the true lumen. It may be difficult to differentiate the true from the false lumen, especially when the dissection involved the entire aorta. A femoral artery, alternatively, was utilized to re-establish CPB using a Seldinger technique. Femoral cannulation was preferred over subclavian or other peripheral arteries, as it was easy and fast to expose with enough workspace available for the second surgeon [8].

After completion of recannulation, CPB was restarted and deep hypothermia technique was applied in order to assess the extent of the dissection and repair it with individualized operation methods during a short circulatory arrest time while the aorta was exposed. Before the circulatory arrest, core body temperature was controlled to 18–25 ${}^{\circ }$C rectally, varying from different surgeons. INVOS 5100C monitor (Somanatics Corporation, Troy, MI, USA) was used to real-time assess the cerebral oxygenation during the cooling stage. According to the left cerebral oxygenation, right antegrade cerebral perfusion via direct cannulation of the brachiocephalic trunk or bilateral antegrade cerebral perfusion via direct cannulation of both the brachiocephalic trunk and the left common carotid artery was conducted at a flow rate of 10 mL/kg/min.

TEE evaluation and the operative findings were valued on the determination of the extent of aortic repair. Arch reconstruction was performed in patients whose dissected intima extended into or beyond the arch. When there is a primary entry or secondary re-entry tear in the aortic arch, total arch reconstruction was arranged. Partial arch reconstruction was reserved for the rest. Proximal aortic root procedures were carried out during the rewarming stage in patients receiving arch reconstruction. The ascending aorta was replaced by a vascular prosthesis with sutures in all patients. Our technique for reinforcing the distal and proximal anastomoses was to place individual pledgetted mattress sutures along the circumference of the anastomosis over the first suture line. When there was a primary entry or secondary re-entry tear in the aortic sinus wall, aortic root repair or replacement may be required. In case of coronary malperfusion, coronary artery bypass grafting may be considered. In fact, coronary malperfusion was difficult to diagnose intraoperatively. When the dissection membrane extended into coronary ostium, coronary malperfusion should be suspected when any of the following were observed: localized wall motion abnormalities on transesophageal echocardiography; and the presence of an epicardial hematoma adjacent to the coronary ostium.

In-hospital outcomes included mortality, new-onset stroke, low cardiac output syndrome, prolonged mechanical ventilation, acute kidney injury requiring hemodialysis, sepsis, reoperation for bleeding, and gastrointestinal complications. In-hospital mortality was defined as any death during the same hospitalization or within 30 days after the procedure [9]. New-onset stroke was defined as any new focal or global, temporary or permanent neurological deficit with new radiologic findings [10]. Low cardiac output syndrome was defined as the requirement for mechanical circulatory support and/or inotropic support for inability to discontinue CPB or for longer than 30 min after the patient was returned to intensive care unit to maintain the systolic blood pressure $>$90 mmHg and the cardiac index $>$2.2 L/min/m${}^2$ [11]. Prolonged mechanical ventilation was defined as the duration of mechanical ventilation of more than 48 hours or reintubation following cardiac surgery [10]. In addition, length of intensive care unit (ICU) stay and length of postoperative hospital stay were also recorded.

Follow-up data included intermediate-term survival, reoperation, New York Heart Association (NYHA) functional class, and the appearance of the residual aortic false lumen with or without perfusion. Intermediate-term survival was defined as survival at 3 years after surgical repair of intraoperative iATAD. The appearance of the residual aortic false lumen with or without perfusion was determined by using a computed tomographic (CT) scan.

This is a single-center, retrospective-prospective observational study. The study protocol was approved and supervised by the Ethics Committee of Zhongshan Hospital Fudan University (No. B2021-274R). All the procedures during the study were consistent with the Declaration of Helsinki. Baseline characteristics of included patients, features of dissection (time of discovery, localization of tear, and extent of dissection), operative data (initial cardiac surgical procedures, extent of aortic surgery, aortic cross-clamp time, CPB time, and cerebral protection strategy), and in-hospital outcomes were retrieved from our electronic medical records database and were registered using a standard case reporting form. Patients were routinely followed up at three and six months after surgery, as well as at 6-month intervals after that. Follow-up data were gathered by clinic visits, online feedbacks, short message service or telephone interviews. The datasets were then double-checked for plausibility by an independent database-monitoring center. Only completed and verified datasets were used for statistical analysis.

Statistical analysis was performed with SPSS statistical software version 22.0 (SPSS Inc., Chicago, IL, USA). Categorical variables were expressed as frequency distributions and single percentages. The normality distribution of the variables was determined by using the quantile-quantile (QQ) plot. Normally distributed continuous variables were expressed as the mean and standard deviation and non-normally distributed continuous variables were expressed as median and inter-quartile range (IQR). The cumulative survival curve was conducted by the Kaplan–Meier method.

A total of 23,143 adult patients underwent cardiac surgical procedures in our institution during the study period. As presented in Fig. 1, 21 (0.09%) eligible patients were finally analyzed. The baseline characteristics of this series are shown in Table 1 (Ref. [12]). There were slightly more male (52.4%) than female patients (47.6%) with a median age of 65.0 (IQR, 56.5–73.0) years. No instance of chronic kidney disease and/or hemodialysis before surgery was recorded. It was noteworthy that dilated ascending aorta (the maximum diameter of ascending aorta of more than 40 mm measured by using transthoracic echocardiography or CT imaging) was observed in 14 (66.7%) patients with intraoperative iATAD.

Fig. 1.

Flow chart for the selection of study population. 21 of 23,143 patients who underwent cardiac surgical procedures in our institution during the study period were selected for intraoperative iatrogenic ATAD study. pts., patients; ATAD, acute type A aortic dissection.

All 21 patients received elective initial cardiac surgical procedures. No patients were in critical preoperative state before initial cardiac surgical procedures. One patient with previous cardiac procedure (mechanical prosthesis replacement for both mitral and aortic valves) who was diagnosed with perivalvular leakage of mitral valve underwent a repeated mitral valve surgery and developed intraoperative iATAD. Intraoperative iATAD occurred before the onset of CPB in 5 (23.8%) patients, during CPB in 8 (38.1%) patients, and after the discontinuation of CPB in 8 (38.1%) patients. The most frequent origin of the dissection was aortic cannula itself (47.5%, n = 10), followed by cardioplegia cannulation (38.1%, n = 8). The dissected intima extended proximally into the ascending aorta in all patients; and it extended distally into the aortic arch in 14 (66.7%) patients, into the supra-aortic vessels in 4 (19.0%), and beyond proximal thoracic aorta in 8 (38.1%). The features of dissection are listed in Table 1.

Regarding proximal injury, an ascending aorta replacement was performed in all patients, and a CABG (aorta-vein graft-right main coronary artery) was conducted in one patient with coronary malperfusion resulted from the dissection extending into coronary ostium and the right main coronary artery. No aortic root repair or replacement was recorded. Regarding distal aortic repair, a partial arch reconstruction was performed in 10 (47.6%) patients and a total aortic arch reconstruction in 4 (19.0%).

The cumulative aortic cross-clamping time and cumulative CPB time was 105.5 (IQR, 94.3–140.0) minutes and 217.5 (IQR, 156.0–257.0) minutes, respectively. Circulatory arrest was performed in 14 (66.7%) patients with a mean duration of 16.8 minutes. The mean lowest rectal temperature was 22.6 centigrade. Among 14 patients undergoing circulatory arrest, 13 received antegrade cerebral perfusion (right in 11 patients and bilateral in 2 patients). One patient with ascending aorta replacement plus partial arch reconstruction, who received a circulatory arrest time of 8 minutes and a lowest rectal temperature of 19.9 centigrade, did not receive antegrade or retrograde cerebral perfusion. Surgical data of this case series are summarized in Table 2.

Two (9.5%) patients died of the rupture of aortic root on the first day following surgery and of the rupture of abdominal aortic dissection on the fifth day after surgery, respectively. New-onset stroke was observed in 4 (19.0%) patients, including 3 with temporary neurological deficit lasting less than 3 weeks and one (4.8%) with neurologic deficit that persisted at the time of hospital discharge. As shown in Table 3, other perioperative complications included low cardiac output syndrome in 2 (9.5%) patients, prolonged ventilation and/or re-intubation in 9 (42.9%), acute kidney injury requiring hemodialysis in 5 (23.8%), and sepsis in 3 (14.3%). Fifteen (71.4%) patients received blood transfusion. The median ICU stay was 4.0 (IQR, 2.0–15.5) days. Nineteen (90.5%) patients recovered and were discharged, with a median length of postoperative hospital stay of 11.0 (IQR, 7.5–31.0) days.

A total of 18 patients, accounting for 94.7% of discharged patients, received a follow-up visit. As presented in Fig. 2, Kaplan–Meier curves revealed that all 18 follow-up patients survived during the median duration of 36.0 (IQR, 16.5–45.0) months. No repeated surgery was recorded. Seventeen out of 18 follow-up patients were classified as NYHA class I–II. A follow-up CT examination at 3–6 months after discharge was available in 16 patients (84.2% of survivors) and showed a residual false lumen in the aortic arch in 3 (18.8%) patients, in the descending aorta in 8 (50.0%), and in the abdominal aorta in 4 (25.0%). The residual false lumen perfusion (the descending aorta and the abdominal aorta) was recorded in one (6.3%) patient, but the maximum diameter of the aorta was less than 40 mm. We classified the patient as NYHA class II and proceeded with dynamic evaluation and CT examination. No residual false lumen was found in the ascending aorta.

Fig. 2.

Cumulative survival after surgery. One patient died of the rupture of aortic root on the first day after surgery and one patient died of the rupture of abdominal aortic dissection on the fifth day after surgery (black arrow).