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).