DISCUSSION
In the study from the International Registry of Acute Aortic Dissection (IRAAD) reported by Sultan I et al [6], which represented the largest study to date assessing the impact of CM at the time of presentation for patients with TAAAD, 15.1% of patients presented with CM. Our study also reveals that the incidence of CM in TAAAD is 15.9%, ranged from 6.5% to 26.1%. Despite the surgical techniques, the anesthesiology and perioperative management have greatly improved over the last years, and the mortality rate has improved significantly in the surgical treatment for TAAAD patients with CM, the mortality remains high. A report by Fann JI, et al in 1989 demonstrated that the surgical results of such patients showed a high mortality rate of 57%[20]. In 2007, the report from University of Pennsylvania by Geirsson A, et al[21] showed that the mortality rate was 50% in surgical repair for TAAAD with CM patients. A report from Japan by Okita Y, et al in 2021 showed that the mortality rate is 28%[12]. From our investigation, the mean in-hospital mortality is 20.1%. However, the outcomes is variable. In a few studies, the mortality was 0 and the long time survival was acceptable. Although the number of cases in these studies was not so enough, the results was encouraging in this critically ill cohort of patients. TAAAD patients with CM should not preclude surgical candidacy.
In the case of acute ischemic cerebrovascular pathology, the interval from onset of neurological symptoms to return of cerebral blood flow is key factor in determining the severity and recovery of cerebral injury. The 2015 guidelines of the Healthcare Professionals from the American Heart Association/American Stroke Association reported the efficacy of endovascular treatment within 8 hours of symptom onset for patients with acute ischemic stroke [22]. Data from our review show that the mean time from presentation of neurological symptoms to surgical intervention is 13.3 hours. Multiple studies shown patients who initially underwent early surgical repair or reperfusion of brain had good outcomes [5, 8, 9, 18, 23,24]. The mortality in the group which surgery underwent within 10 hours was significantly lower than that of patients over 10 hours. Tsukube et al. [18] performed immediate surgery within 5h for TAAAD patients with coma, which resulted in full recovery of consciousness in 86% and hospital mortality of 14%. Estrera et al [9] reported the operative results of 16 patients with TAAAD complicated by preoperative stroke. The median time from onset of stroke to surgery was 9 hours, and 80% of patients who underwent surgical repair within 10 hours had improvement in neurologic status, whereas none improved if operated on beyond 10 hours. Sasaki H et al [8] reported that hemiplegia and hemiparesis improved significantly after immediate aortic repair in which the time from onset of symptoms to operating room was 7.2 ± 2.4 h, with hospital mortality of 0% and overall survival at 24 months after operation of 100%. Morimoto et al [5] also reported that 9.1 hours was an optimal cutoff value for predicting lack of neurologic improvement-if surgery was performed within 9.1 hours, 88% improved neurologically, with dramatically improved 5-year survival (84% vs. 33%). Those present researches indicate that early surgical repair within 10 hours may improve the outcomes. However, multicenter controlled clinical trials with large samples are needed.
Cerebral malperfusion time plays a role in determining outcomes in TAAAD patients, and expeditious revascularization was crucial in the management strategy of TAAAD with CM. Early reperfusion and extra-anatomic revascularization may reduce the risk of neurological complications. A number of institutions have adopted strategies to minimize cerebral malperfusion time and reperfuse the cerebral blood flow sooner, including extra-anatomic revascularization [8, 14, 16], direct carotid artery cannulation [12, 13, 25, 26], or percutaneous endovascular carotid artery stenting [25]. Immediate central aortic repair and primary entry tear resection is the most widely practiced early reperfusion strategy, wherein the goals are to expand the true lumen by redirecting flow into it and to decompress the false lumen by resecting the entry tear, and has been shown to improve outcomes in patients with malperfusion [9, 27, 28]. Arterial cannulation sites are determined according to a patient’s status, preoperative involved supra-aortic branch vessels and the preference of the surgeon. The right axillary artery is the most frequent choice because it will allow for uninterrupted ACP during arch reconstruction. RCP, another bran protection strategy, is also performed in many centers, which can flush out air and atheromatous debris within the arch vessels[5, 6, 9, 12, 19,25,29,30]. The extent of aortic replacement is determined on the position of the primary entry, and ascending aorta combined with hemi-arch replacement with or without root replacement or repair is performed in most patients. It is necessary to investigate the correlation between outcomes and operation strategies, such as the extent of aortic replacement and selective cerebral perfusion, in TAAAD with CM patients.
Coma is the common presentation following TAAAD complicated with CM, and its definition is varied among studies. There has controversial with regards to the surgical management required cardiopulmonary bypass, full anticoagulation with hypothermic circulatory arrest for a patient in coma. The threat of use of high-dose heparin, hemorrhagic conversion of the ischemic infarction, cerebral reperfusion leading to worsening of neurologic outcome exists. For this reason, Fukuda et al. advocated intentional delay of surgical repair [31]. Fukuhara S and colleagues [25] found that all patients developed severe cerebral edema and herniation syndrome died regardless of the surgical management. Caution is necessary because the differentiation of coma is vitally important, and is difficult also. Cranial computed tomographic scanning often does not identify early acute ischemic infarction, however, is the best means to rule out acute bleeding [32]. Patients with the evidence of intracranial hemorrhage have been an absolute contraindication to immediate surgical repair.
Several limitations to our study exist. This is a retrospective systematic review of published reports on surgical treatment of TAAAD complicated with CM. The inherent limitations of a retrospective study and review should be acknowledged. There could be a risk of publication bias because several data are missing during the investigation. There is a degree of heterogeneity in the pathology, the operative and cerebral protection strategy for TAAAD patients with CM among different institutions. In addition, there is a lack of standardization in evaluation of the neurological presentations and outcomes. Lastly, the prognosis of TAAAD is determined on many factors, and malperfusion of other organ systems is common in TAAAD patients with CM and potential significant bias by this fact may exist. Further investigation and clinical research using standardized methodology is highly warranted to validate our results.