Extensive aortic surgery in acute aortic dissection type A on outcome – insights from 25 years single center experience

We operated consecutively 407 patients for AADA from 1988 to 2012 at the Department of Cardiac Surgery of the University Hospital Heidelberg. The patients were treated by different surgeons during that period. The cohort was divided into subgroups according to the surgical approach and all subgroups were compared with the supracommissural replacement group (SCR; n = 141; 45%). These groups included aortic valve sparing techniques (AVS; n = 29; 7%), Composite replacement (COMP; n = 119; 29%), COMP with total arch replacement (COMP+TAR; n = 27; 7%) and SCR with TAR (n = 75; 18%). Wheat operation (n = 7) and AVS with TAR (n = 6) were excluded from statistical comparison due to small cohorts. Other nonspecific techniques were used in 3 patients. Seventeen patients (4%, COMP n = 2, SCR n = 15) underwent Frozen elephant trunk (FET, Jotec® prosthesis, Jotec, Hechingen, Germany) while the classic Elephant-Trunk procedure was accomplished in 16 patients (4%, COMP n = 2, SCR n = 14). In total, almost a third of the cohort (n = 115, 28%) received TAR. Aortic valve-sparing methods were David technique (n = 20, 5%) and Yacoub technique (n = 15, 4%) and four patients received nonspecific aortic valve reconstruction (1%). Concomitant CABG and concomitant mitral valve operations were performed in 4 patients each (1%).

Diagnosis of AADA was confirmed by computed tomography scans, angiography and transthoracic/transesophageal echocardiograms. Mostly, AADA was diagnosed in external centers and patients were transferred to our institution for emergency surgery. If diagnostic studies were incomplete the diagnosis was confirmed in our emergency department. The whole cohort was divided into subgroups according to the surgical approaches. Results of each group were compared to standard SCR group defined as the most conservative but limited surgical approach. Perioperative data, incidence of neurological complications, early mortality and morbidity, cause and risk factors for aortic re-interventions and long-term survival were evaluated. The Ethics Committee of the University of Heidelberg authorized this study (S-286/2010). We have obtained all clinical data retrospectively by reviewing hospital records.

Cardiogenic shock was defined as inadequate tissue perfusion due to reduced cardiac output (cardiac index < 2.2 l/min/m2), manifested low systolic pressure (< 90 mmHg for longer than 30 min). General malperfusion was defined as clinical condition with reduced central and peripheral hypoperfusion caused by longstanding haemodynamic instability causing multiple organ failure. Multi organ failure was assessed by laboratory parameters and clinical signs of organ dysfunction (cold extremities, oliguria or altered mental condition). Acute renal failure was defined as AKIN stage 2 or 3 (AKIN 2: increase of serum creatinine > 200 a 300% (> 2 a3x) or < 0.5 mL/kg/h in 12 h) according to the Acute Kidney Injury Network (AKIN) classification. Stroke was specified as the presence of new neurological symptoms or was verified by computed tomography scan or magnetic resonance imaging of the head.

Follow-up data was obtained from the patient directly, or by contacting the local population administration office, home doctors or patient’s family. Completeness of follow-up was 97% with a mean follow-up time of 4.5 ± 5.6 years (up to 25 years).

At the first years of the study period, femoral arterial and venous cannulation was the most often used approach for establishment of extracorporeal circulation. With beginning of the second millennium, standard surgical approach was median sternotomy with direct arterial cannulation of the ascending aorta and venous cannulation by a two-stage right-atrial cannula. In case of hemodynamic instability or suspected large thoracic aneurysm, the femoral artery and femoral vein were further used for cannulation and initiation of extracorporeal circulation (ECC). In more recent times, axillary arterial cannulation was applied most often as the standard cannulation technique. After systemic administration of heparin, ECC was established (targeted activated clotting time > 400 s). For decompression of the left ventricle, a vent catheter was inserted via the upper right pulmonary vein. After initiation of ECC, the patient was cooled to target body temperature. After aorta was cross-clamped and ascending aorta was transected above the commissures, cardioplegic solution was administrated selectively in antegrade fashion or retrograde perfusion via the coronary sinus was implemented. The decision for the surgical approach was taken individually depending on the clinical status of the patient and on the intraoperative findings, which included the location of the intimal tear and the inspection of aortic root and aortic valve. The surgical decision (e.g. for aortic arch replacement) depended also on the existence of a patent intimal entry or reentry within the aortic arch. We aimed to resect all aortic segments that contained an intimal tear and to restore the native aortic circulation. Surgical techniques varied from simple SCR to a complete replacement of the aortic root or a complete aortic arch replacement with or without applying a hybrid frozen elephant procedure as surgical solution for an affected descending thoracic aorta.

We used Gelatine-resorcinol-formaldehyde (GRF) glue to readapt the dissected distal aortic wall layers. Deep systemic hypothermic circulatory arrest was also applied when necessary. In the more recent cases, moderate hypothermic circulatory arrest with antegrade cerebral perfusion was used during the inspection of the aortic arch or, if required, during replacement of the aortic arch. Cerebral oximetry (INVOS™, Medtronic, Dublin, Ireland) and in the early years common electroencephalography were used routinely to monitor cerebral blood oxygen saturation during or electrical brain activity during AADA repair. In the case of circulatory arrest, once distal aortic anastomosis was accomplished, the Dacron prosthesis was cannulated, clamped proximally and full reperfusion and rewarming was started. During active rewarming, the proximal anastomosis was completed and concomitant procedures could be performed. After completion of the proximal anastomosis the lungs were manually re-inflated and the de-airing was performed before aortic cross-clamp was released. Atrial and ventricular pacemaker electrodes were placed to ensure a heart rate between 70 and 100 beats/min. Once the patient was rewarmed to a body core temperature above 36 °C and after sufficient reperfusion time and generation of optimal preload, weaning from ECC was performed in the usual manner. Thorax drainages were placed and the chest was closed after meticulous hemostasis was accomplished.

For data description and analysis, SPSS statistic software was used (IBM®SPSS®22, 2013, Chicago, USA). Variables are described as quantity and percentages or as means and standard deviations. Statistical analysis was performed using Student’s T-test, if variances were not equal (tested by Leven’s test) Mann-Whitney-U-Test was performed. Chi-squared test (Fisher exact tests if n ≤ 5) was used for categorical variables. To determine perioperative risk factors for early mortality and re-operations, logistic regression testing were performed. The impact of perioperative variables on long-term survival was analyzed by multivariable cox proportional hazards model. For adjusting the logistic and cox proportional hazards model to relevant baseline parameters, the variables age, sex and the individual operation methods (SCR, SCR + TAR, COMP, COMP + TAR, AVS) were included into the multivariate model. First, possible relevant risk factors were tested with this adjusted model by backward LR stepwise selection (LR, Likelihood Ratio, selection and significance criteria p < 0.1 and p < 0.05 respectively). Final models were calculated by entering all selected variables en bloc in a single step (Enter mode). Kaplan–Meier analysis was used to estimate survival. Two-tailed significance level was determined 5%.

The overall cohort included 132 (32%) female and 285 male patients with a mean age of 58 years (Table 1). Thirty percent (n = 123) were type 2 dissection according to DeBakey classification (DeBakey type 3 were not included). Male gender was clinically more frequent in COMP groups (n = 89, 75% in COMP and n = 21, 78% in COMP+TAR. Relevant secondary diagnoses were bicuspid aortic valve (n = 21, 5.2%) and Marfan syndrome (n = 15, 3.7%). Twelve AADA cases (n = 3% = were caused iatrogenically, 12 occurred after trauma (n = 3%) and eight during pregnancy (2%). Forty-nine patients (12%) had a history of cardiothoracic surgery and 42 had already experienced myocardial infarction at the time of presentation (10.3%). Sixty-three patients (16%) presented in cardiogenic shock or had required cardiopulmonary resuscitation (n = 22, 5.4%). As clinical correlate for bad medical condition patients suffered general malperfusion (n = 80, 20%), coronary malperfusion (n = 42, 10.3%) or showed new neurological symptoms (n = 57, 14%). In comparison with SCR patients were younger in COMP (61y vs. 56y, p = 0.017) and COMP+TAR (61y vs. 51y, p = 0.001) group. Proportion of male patients was higher in AVS than in SCR-group (n = 24, 82% vs. n = 87, 61%, p = 0.025). Additionally, patients of COMP group presented more frequently in cardiogenic shock (n = 18, 13% vs. n = 27, 23%, p = 0.032, Table 1).

Peripheral cannulation of the femoral vessels for initiation of extra corporal circulation (ECC) was carried out in 209 patients (52%) while direct aortic cannulation was performed in 170 patients (42%) and subclavian artery or axillary artery cannulation was performed in 26 patients (6%). Overall, mean bypass time was 221 min with a mean cross-clamp time of 115 min (Table 2). Selective cerebral perfusion technique was used in 136 patients (33%). Operative procedures took longer if TAR was accomplished (SCR + TAR 337 min vs. 387 min, p = 0.005 and COMP+TAR 337 min vs. 420 min, p = 0.003 compared to SCR). ECC and cross-clamp times were longer in SCR + TAR (199 min vs. 255 min, p < 0.001 and 95 min vs. 123 min, p < 0.001 respectively) and COMP+TAR (199 min vs. 263 min, p = 0.002 and 95 min vs. 137 min p < 0.001 respectively) than in SCR. However, circulatory arrest time was only significantly longer in SCR + TAR (22 min vs. 42 min, p < 0.001, compared to SCR). Circulatory arrest times were the shortest in COMP and AVS operations (16mins and 15 min respectively). If COMP or AVS were performed, such as David or Yacoub operation, longer aortic cross-clamp times (95 min vs. 124 min, p < 0.001 and 95 min vs. 122 min, p = 0.002, respectively) but comparable ECC-times were required compared to SCR alone (199 min vs. 218 min, p = 0.068 and 199 min vs. 202 min, p = 0.860, respectively). Overall, intraoperative mortality was 7.3% (n = 29) with the highest mortality in COMP+TAR group (n = 4, 15%, p = 0.018 compared to SCR).

The median stay on intensive care unit was 4 days (interquartile range 1–9 days) with a mean mechanical ventilation time of 91 h (standard deviation ±208 h) (Table 2). Stay on intensive care unit was shorter after COMP compared to SCR (median 4d (1–4) vs 3d (1–6.5), p = 0.036). Sixty-nine patients (17%) developed renal failure postoperatively and 57 (14%) required temporary hemodialysis. Postoperative neurological complications such as stroke (not reported preoperatively) occurred in 52 (12%) cases. Patients undergoing AVS required significant more re-explorations with re-thoracotomy due to postoperative bleeding compared to patients receiving SCR (n = 9, 7% vs. n = 8, 29%, p < 0.001). Our cohort had an overall 30-day mortality of 21% without statistically significant differences between surgical subgroups. However, 30-day mortality was observed markedly higher after COMP than after AVS (n = 29, 25% vs. n = 4, 14%, p = 0.32). By analyzing the number of operated patients over the course of years we observed an increase of operations for AADA per year and improvement of early mortality during the last 8 years (Fig. 1).

Kaplan-Meier survival curve analysis revealed an estimated-overall survival for 1, 5 and 10 years of 69, 58.9 and 42% respectively (Fig. 2 and Table 3). The 5-years survival estimated by Kaplan Meier function was the highest after AVS (69.9%) and the lowest after SCR + TAR (46.1%, Table 3, Fig. 3). In the overall cohort, freedom from re-operation was 92% over the total follow-up, with an estimated 5-year survival of 78% after redo operation (64.4–94.2, 95% CI).

Multivariable logistic regression revealed long circulatory arrest time as strong independent risk factor for early mortality (Odds Ratio = 13, death within 30 days post-surgery). Other variables were also identified as independent factors influencing the early mortality, such as general malperfusion and bypass- and operation times (Table 4).

Numerous variables impacting the overall survival were found by Cox regression. Multivariable analysis confirmed age, circulatory arrest, preoperative general malperfusion, postoperative need for hemodialysis and bypass time as independent factors influencing the overall survival (Table 5). Subanalysis identified younger age (p = 0.003, HR (hazzard ratio) 0.95; 0.92–0.98, 95% CI) and Marfan syndrome (p = 0.001; OR 8.72, 2.40–31.6 95%) as independent risk factors for root re-operation (multivariable logistic regression analysis, not shown).

Our single-center study has an exploratory character and based exclusively on retrospective analysis of surgical strategies used in AADA repair. An important limitation is the long study period over 25 years that included the change and development of surgical techniques during the study period. Moreover, our patient cohort is inhomogeneous due to the natural individual characteristic of AADA. Furthermore, surgical technique was chosen individually according to clinical presentation and, more dominantly, according to surgeon’s preference. The influence impact of the surgeon per se was not measured.