Cardiovascular Journal of Africa: Vol 27 No 3 (May/June 2016)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 3, May/June 2016

146

AFRICA

statistical error that could have been introduced because of

disease severity and procedure differences.

In this study, fewer postoperative complications and lower

mortality rate were detected in the subclavian artery group

(Table 2). Undoubtedly, the lower incidence of neurological

dysfunction could be attributed to selective cerebral perfusion

through subclavian cannulation.

We also found that subclavian

artery cannulation provided better perfusion for other visceral

organs (Table 2).

Two possible hypotheses may elucidate why. First, according

to the Hagen–Poiseuille law,

the pressure drops in a fluid flowing

through a long cylindrical pipe. So under constant blood flow,

cardiac and sternal perfusion may not be adequate with femoral

cannulation, especially when the aorta is dissected. Inevitably,

sternitis and myocardial injury would be higher in the femoral

cannulation group. Second, we assume that subclavian cannulation

would pump major blood flow into the true lumen, while femoral

cannulation pumps more blood into the false lumen.

Based on our evaluation, femoral cannulation introducedmore

retrograde dissection and exacerbated perfusion of the visceral

organs. Survivors who underwent subclavian cannulation had

better recovery during the postoperative hospital course, which

might be attributed to better perfusion of the visceral organs.

In other words, subclavian rather than femoral cannulation

could achieve a lower incidence of visceral malperfusion during

surgeries for AADA.

Our univariate analysis of hospital mortality revealed many

risk factors, including pre-operative respiratory failure, peri-

operative CPB time

200 min, postoperative acidosis, troponin

2.0 ng/dl, and acute renal failure (Table 3). Myocardial

injury has been thought to be a risk factor during major aortic

surgery, particularly when the thoracic aorta is involved.

7-8

Although femoral cannulation was eliminated as a risk factor by

multivariate analysis, it seemed to have a trend towards increased

mortality because it resulted in a higher postoperative troponin

I level, which leads to increased peri-operative cardiac injury,

which reached statistical significance in the multivariate analysis.

The significance could be confirmed if more patients are enrolled

in the future.

This study has several limitations. First, the cohort was

relatively small, but despite this, we still identified an advantage

in subclavian cannulation, which suggests a significant benefit

for simple reconstruction of the ascending aorta. Second, the

data were collected from 2003 to 2010. Surgical techniques and

general postoperative care may have improved in the latter part of

the study, which could explain the unusually high mortality rate

of femoral cannulation in the earlier phase. Third, the study was

retrospective and not randomised. More prospective, randomised,

controlled trials should be designed to support our hypothesis.

Conclusion

Cardiac failure and visceral malperfusion are both fatal

complications of AADA surgery.

9,10

In Christian and co-workers’

study, antegrade perfusion to the true lumen appeared to

be associated with superior long-term survival after hospital

discharge.

Based on our evaluation, we believe subclavian

cannulation could provide better perfusion, not only for the

brain but also for the myocardium and other visceral organs,

leading to lower mortality rates and better recovery following

AADA procedures.

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Table 3. Significant risk factors associated with hospital mortality

Univariate analysis

Survival

group

Mortality

group

value

Variables

(%)

Total number

40 (100)

11 (100)

Pre-operative

Respiratory failure

0.001

Peri-operative

Cardiopulmonary bypass time

200 mins

0.001

Post-operative

7.2

0.001

Troponin I

2.0 ng/dl

0.001

Acute renal failure

0.001

Multivariate analysis

Variables

OR 95% CI

value

Pre-operative

Respiratory failure

12.84 1.48–111.0 0.020

Peri-operative

CPB time

200 min

13.49 1.29–140.1 0.029

Post-operative

7.2

88.63 1.178–4.39 0.003

Troponin I

2.0

20.08 1.37–293.4 0.013

AR, aortic regurgitation; CRP, C-reactive protein; CI, confidence interval; OR,

odds ratio; CPB, cardiopulmonary bypass.