Comment
ATAAD is a critical illness with high mortality. In this study, 32 patients died within 30 days after surgery (10.2%), and the surgical mortality rate was lower than in previous studies. However, the surgical mortality of ATAAD remains unacceptable, so it is necessary to summarize the risk factors for surgical mortality that have been identified in patients with ATAAD in recent years. Large multicenter studies have analyzed the risk factors of mortality in ATAAD patients. The German Registry for Acute Aortic Dissection type A detected that longer operating times and comatose and resuscitated patients had the poorest outcomes (2). The International Registry of Acute Aortic (IRAD) concluded that surgical mortality was mainly related to unstable patients with preoperative organ malperfusion and time to surgery (3). However, a study from China showed that in-hospital adverse outcomes were associated with older age, presentation of lower limb symptoms prior to surgery and long CPBT (4). This retrospective study analyzed various parameters over 5 years and identified some risk factors for surgical mortality in ATAAD, with benefits for postoperative outcomes. Our findings showed that longer durations of surgery and CPBT, moderate to severe pericardial effusion, suprasternal branch involvement, and lower-extremity ischemia were independent risk factors for early postoperative mortality.
The multifactorial analysis in this study indicated that supraventricular branch involvement was a risk factor for postoperative mortality in patients with ATAAD. The extent of ATAAD involvement largely determined the preoperative state of the patients, and the postoperative outcome was greatly affected. In particular, involvement of the upper arch branch and the blood supply to the brain resulted in poor cerebral perfusion. In addition, anastomosis of branch vessels was required during surgery in these patients, prolonging the time of extracorporeal circulation and operation, which further affected cerebral perfusion. Some studies have shown that cerebral ischemia is a risk factor for in-hospital and postoperative mortality (5, 6). To prevent irreversible ischemic damage to the nervous system, it is of vital importance to administer timely and effective drug treatments and surgical treatments for patients who are unconscious or in a coma.
In this study, the proportion of patients with lower limb ischemia was significantly greater in the nonsurvivor group than in the survivor group. Multiple regression analysis showed that lower limb ischemia was a risk factor for early mortality in ATAAD patients, as in previous studies (7, 8). Poor perfusion of the lower extremities can lead to serious complications. ATAAD patients with lower limb ischemia present with no pulse or dysplasia and should be treated with appropriate attention. Uchida et al. improved the blood supply by draining the brachial arterial blood to the ischemic lower limb arteries, thereby significantly improving symptoms (9). However, Preece et al. conducted a literature analysis and concluded that inferior-limb ischemic artery reperfusion before aortic repair increased intraoperative mortality in ATAAD patients (10). Therefore, whether preoperative ischemic arterial perfusion of the lower extremities before aortic repair can improve the prognosis of surgery remains to be analyzed with additional sample data.
The duration of extracorporeal circulation was significantly longer in the nonsurvivor group than in the survivor group. The multivariable analysis showed that the duration of surgery and the duration of extracorporeal circulation were risk factors for early postoperative mortality. Our findings are consistent with previous studies (11). A long operation time reflects the severity of ATAAD in patients; moreover, a prolonged operation time affects organ perfusion. Therefore, longer duration of surgery is associated with unfavorable outcomes.
Echocardiography is an important tool for the diagnosis of ATAAD. There were 188 cases of ATAAD with medium to large amounts of pericardial effusion, and the proportion in the nonsurvivor group was significantly higher than that in the survivor group. Our findings revealed that moderate to severe pericardial effusion was a risk factor for postoperative death in patients with ATAAD. Moderate to severe pericardial effusion is a sign of hemodynamic instability and aortic rupture in ATAAD patients. Santi Trimarchi et al. demonstrated that pericardial tamponade was an independent predictor of postoperative mortality in patients with ATAAD (OR: 2.22)(7). The inner diameter of the ascending aorta of ATAAD patients was obtained by echocardiography and CTA measurements; the width was obviously increased, but the difference between the nonsurvivor group and the survivor group was not statistically significant. A report from the IRAD noted that the vast majority of ATAAD patients had an enhanced ascending aorta diameter, but the mortality in ATAAD patients was independent of the ascending aorta diameter (12). Kim et al. showed that moderate ascending aorta dilatation (inner diameter <50 mm) was moderately correlated with aortic dissection and/or rupture (R2=0.07) (13).
Our study revealed that the surgical technique had no significant effect on early postoperative mortality in patients with ATAAD; this finding could be related to selection bias in the surgical method choice. It could also be related to the interaction among various operating parameters. Goda et al. indicated that various surgical methods did not affect the early postoperative mortality rate of ATAAD patients (8). However, Ten et al. found that simultaneous aortic valve replacement or Bentall surgery in ATAAD patients was a protective factor against postoperative mortality (11).
Our study demonstrated that the admission blood potassium level in the nonsurvivor group was higher than that in the survivor group. However, multivariable analysis showed that potassium was not a risk factor for postoperative mortality in patients with ATAAD. This finding is inconsistent with the results of Chen et al., who found that the blood potassium level at admission (3.5-4.5 mmol/l) could be related to the increases in in-hospital mortality and long-term mortality in ATAAD patients (14). Our results might have been due to the small number of cases in the nonsurvivor group.
In this study, the proportion of patients with myocardial ischemia in the nonsurvivor group was greater than that in the survivor group. The proportion of patients with ATAAD combined with myocardial ischemia who underwent CABG was also greater in the nonsurvivor group than in the survivor group. When ATAAD was complicated with myocardial ischemia, chest pain was the main symptom, and coronary heart disease was easily misdiagnosed, resulting in a delayed diagnosis of ATAAD and delayed surgical treatment. When ATAAD affects both the left and right coronary arteries, it can lead to acute and severe myocardial ischemia and a poor prognosis. Santini et al. reported that myocardial ischemia is also a risk factor for in-hospital mortality in patients with ATAAD (15). Therefore, CABG should be performed to improve myocardial blood supply in patients with ATAAD complicated with myocardial ischemia. However, the multifactorial analysis in our study indicated that myocardial ischemia was not a risk factor for postoperative mortality; this result may have been related to the CABG operations in these patients. Myocardial ischemia was improved, and no adverse outcomes occurred during the observation period. Imoto et al. suggested that preoperative coronary stent implantation in ATAAD patients could improve the poor prognosis for such patients (16).