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Interact CardioVasc Thorac Surg 2009;9:209-212. doi:10.1510/icvts.2008.201558 © 2009 European Association of Cardio-Thoracic Surgery
Clinical significance of anastomotic leak in ascending aortic replacement for acute aortic dissectionDepartment of Cardiovascular, Thoracic, and Pediatric Surgery, Kobe University Hospital, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe, Japan Received 29 December 2008; received in revised form 26 April 2009; accepted 27 April 2009
*Corresponding author. Tel.: +81 78 382 5942; fax: +81 78 382 5959.
‘Anastomotic leak’ after ascending aortic replacement for acute aortic dissection, which is determined as direct forward blood flow into the false lumen at the distal anastomosis, prevents the false lumen from being thrombosed. The aim of this study is to determine whether the leak influences on residual aortic growth. Between October 1999 and May 2006, 100 patients presenting for acute type A aortic dissection underwent surgery at our institution. Among the population, 34 patients who underwent ascending aortic replacement and have been followed by computed tomography (CT) for over 6 months were reviewed. On the follow-up CT, maximum diameter of aortic arch and descending aorta were measured and the presence of anastomotic leak was determined. The growth rates of aortic arch and descending aorta in patients diagnosed as having anastomotic leak were greater than patients not having leak (P=0.003, P<0.001, respectively). Initial maximum diameter just after ascending aortic replacement was greater in patients with anastomotic leak than without anastomotic leak in aortic arch and descending aorta (P=0.013, P=0.06). Anastomotic leak after ascending aortic replacement for acute type A aortic dissection contributed to remnant aortic growth. More sophisticated method for reapproximation of dissected aorta should be dictated.
Key Words: Aortic dissection; Aorta
Surgical results for acute type A aortic dissection have been improved with mortality of 10–25% [1, 2], thus the number of reoperations of residual dissecting aortic aneurysm has increased. Bachet et al. [3] and Halstead et al. [4] reported that patent false lumen influenced the growth of the residual aorta after ascending aortic replacement and the direct forward flow at the distal anastomotic site would contribute to patent false lumen left in the remnant aorta. Subsequent surgery often has to be extended to aortic replacement including arch, descending, and thoracoabdominal aorta, and the high mortality rate has been reported [5, 6]. Although mortality for the initial surgery for acute type A aortic dissection is still not low, for the patients who survive through the operation, we need to determine the prognostic factors for residual aortic growth, and which patient requires us to do careful follow-up after ascending aortic replacement.
From October 1999 to May 2006, one hundred patients presenting for acute type A aortic dissection underwent surgery at our institution. Sixty-two patients underwent ascending aortic replacement, 30 total arch replacement, and eight partial arch replacement (one or two arch branches were reconstructed). In the patients who underwent ascending aortic replacement, 12 patients died in the hospital (19.3%). Thirty-four patients who had been followed-up by computed tomography (CT) for >6 months were reviewed. The mean age at the primary replacement was 66.0±12.0 ranging 22–88 years old. Median follow-up period was 1.92 ranging 0.5–6.0 years. Preoperatiave types of DeBakey classification were type I in 22 patients and type II in 12. Study population is shown in Table 1. On the follow-up two-phase CT, maximum diameters of aortic arch and descending aorta were measured and the presence of ‘distal anastomotic leak’ was determined.
On the other hand, nine patients underwent subsequent thoracic aortic replacement after the initial ascending aortic replacement for acute type A aortic dissection at the same time period. Three of them were included in the patients who had the primary hemiarch replacement in our hospital, and the others were referred to us from other cardiac centers for residual aortic growth. ‘Anastomotic leak’ was found in seven of these patients on preoperative CT, and ‘no anastomotic leak’ was diagnosed in the others. We reviewed the intraoperative findings for these cases to confirm that the diagnosis on CT was correct. 2.1. How to diagnose ‘distal anastomotic leak’ on CT As our routine follow-up CT, the patients are scanned at 30 (early phase) and 100 (late phase) seconds after injection of contrast media. If no patent false lumen is shown, of course, we diagnose it as ‘no anastomotic leak’. If the false lumen in the arch is enhanced in the early phase, our diagnosis is ‘astomotic leak’ (Fig. 1a). If the false lumen in the arch is enhanced only in the late phase, our diagnosis is ‘no anastomotic leak’ (Fig. 1b). In the latter cases, most of them have an intimal tear in the proximal descending aorta.
We applied these methods to the reoperation cases, and determined the specificity and sensitivity of CT for diagnosis of distal anastomotic leak by referring to intra-operative findings. 2.2.1. Primary surgery for acute type A aortic dissection After establishing cardiopulmonary bypass by arterial cannulation through femoral artery and axillary artery if needed, a patient is cooled down to 20 °C. During cooling, a cross-clamp is placed at the distal ascending aorta and then transects the aorta at the level of 1 cm distal to the sino-tubular junction. Proximal reapproximation is performed with Teflon felt outside and Gelatin–Resorcin–Formalin (GRF) glue inside the false lumen with 4-0 prolene (Ethicon, USA) running sutures. Hypothermic circulatory arrest is obtained and ascending aorta and aortic arch is opened. The primary intimal tear and other visible intimal tears if they exist are meant to be resected. If arch reconstruction is necessary, we use selective cerebral perfusion for cerebral protection and reconstruct arch vessels with four-branched graft using the elephant trunk technique. In cases of ascending aortic replacement, distal aortic reapproximation is commonly performed as follows: Teflon felt outside the adventitia is fixed by three 4-0 prolene sutures and reapproximated by running suture. We usually apply only outside Teflon felt to reinforce the anastomosis, but in the cases of extremely fragile aortic tissue, GRF glue in the false lumen (5/34) and adventitial inversion technique (3/34), which was first described by Floten et al. [7], were applied. Connecting the graft to the distal aortic stump, the patient is rewarmed and the graft is anastomosed to the proximal aortic stump.
2.2.2. Reoperation for arch and descending aneurysm after hemiarch replacement
The existence of anastomotic leak and the distal aortic reapproximation methods are shown in Table 2. Eighteen patients had our current routine reapproximation technique described above (only outside Teflon felt without GRF glue or adventitial inversion) at distal anastomosis. Seven of them (39%) were diagnosed as having anastomotic leak after surgery.
Figs. 2 and 3 show change of the maximum diameter of the aortic arch and the descending aorta after the initial hemiarch replacement. Three patients who had distal anastomotic leak had reoperation because of dilatation of the proximal descending aorta. Figs. 4 and 5 show comparisons of the change of the diameter in the aortic arch and descending aorta between the patients with and without anastomotic leak. In this group, we excluded the patients with DeBakey type II. There were significant differences between the two groups by repeated measured ANOVA (P=0.003, in aortic arch, P<0.001, in descending aorta).
Seven of nine patients diagnosed as having anastomotic leak by preoperative CT had entry to the false lumen at the distal anastomossis observed at surgery, which meant ‘suture cutting’ at the initial surgery. The others had an entry in the aortic arch and descending aorta apart from the distal anatomosis of the primary surgery. Therefore, the sensitivity of CT as a diagnostic modality for anastomotic leak was 88% and the specificity was 100%. There was one hospital mortality (1/9, 11%) in these reoperations, and no stroke.
As the surgical results of acute type A aortic dissection, have been improving the long-term fate of the residual false lumen has been discussed. The factors which influence the growth rate and the reoperation rate of the remnant aorta have been reported as the initial diameter after primary surgery, patent false lumen [8, 9], and primary methods of surgery (ascending aorta or total arch replacement) [10]. The factors which could be controlled by surgeons at primary surgery would be:
Performing total arch replacement with the elephant trunk technique is an ideal method to establish these tasks [10]. However, the results of surgery for acute type A aortic dissection still demonstrate mortality of 10–25%, and total arch replacement is a complicated procedure and associated with higher mortality rate [11], therefore, applying total arch replacement for all cases is over-indicated if hemiarch replacement is enough to establish these tasks. Some kinds of reapproximation methods have been introduced, however, which method is best for the false lumen to be thrombosed has not been widely dictated. Tanaka reported that adventitial inversion technique for the distal aortic anastomosis in hemiarch replacement induced the false lumen in the arch and proximal descending aorta to be thrombosed in 12 of 12 cases postoperatively. Despite a small number of cases, the method using autologous tissue could be a better alternative. According to the previous reports, the ratio of patent false lumen after hemiarch replacement is 30–50% [12, 13] which is similar to the present report, even no details of reapproximation methods were noted. Ohtsubo reported that the incidence of postoperative patent false lumen in the descending thoracic aorta did not differ among the three groups (ascending aortic replacement, hemiarch replacement, and total arch replacement); however, the ratio of the patent false lumen showed relatively low rates of 28.5% (10/41), 26.3% (5/23), and 14.2% (2/24), respectively, in which there was a tendency although no significant difference [11]. Reoperation after ascending aortic replacement for aortic dissection is inclined to be extensive thoracic aortic replacement because of the exceeding growth of aortic arch and proximal descending aorta, thus we need more sophisticated methods for reapproximation of acute dissected aorta to avoid these procedures. Although two-stage repair combined total arch replacement through median sternotomy with descending aortic replacement, endovascular treatment, and a hybrid therapy are advocated, our current strategy is a single-stage arch and descending aortic replacement through left thoracotomy using selective cerebral perfusion, and achieves an acceptable result. In two-stage repair, some percentage patients would be lost during the interval because of aortic events. If there is anastomotic leak in the distal aortic anastomosis after hemiarch replacement, leaving the entry and the aortic arch involved in aortic dissection, and grafting only the proximal descending aorta, could bring a catastrophic complication in the arch and its branches [14]. Therefore, our current strategy is a single-stage radical repair for residual aortic dissected aneurysm after hemiarch replacement for acute type A dissection. In conclusion, anastomotic leak after ascending aortic replacement for acute type A aortic dissection contributes to remnant aortic growth and could be a risk factor for subsequent aortic surgery. A more sophisticated method for reapproximation of dissected aorta should be dictated to avoid subsequent aortic surgery.
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Abstract
1. Introduction
