Aortic dissection type A requires immediate surgery. In general surgery populations, patients operated during weekends have higher mortality rates compared to patients operated on weekdays. The weekend effect in aortic dissection type A has not been studied in detail.

The Nordic Consortium for Acute Type A Aortic Dissection (NORCAAD) registry includes patients (N=1,159) who underwent type A dissection surgery at eight Nordic centers during 2005-2014. This study is based on data relating to surgery conducted during weekdays vs. weekends, and starting between 8 am and 8 pm ("daytime") vs. from 8 pm to 8 am ("nighttime"), as well as time from symptoms/admittance/diagnosis to surgery. The influence of timing of surgery on 30-day mortality was assessed using logistic regression analysis.

The 30-day mortality was 18% (204/1,159), with no difference in mortality between surgery performed on weekdays (17%, 150/889) and on weekends (20%, 54/270, p=0.45), or during nighttime (19%, 87/467) vs. daytime (17%, 117/680, p=0.54). Time from symptoms to surgery (median 7.0 hours vs. 6.5 hours, p=0.31) did not differ between patients who survived and those dead at 30 days. Multivariable regression analysis of risk factors for 30-day mortality showed no weekend effect (OR 1.04 [0.67-1.60], p=0.875), but nighttime surgery was a risk factor (OR 2.43 [1.29-4.56], p=0.006).

Thirty-day mortality in surgical repair of aortic dissection type A was not significantly affected by timing of surgery during weekends vs. weekdays. Nighttime surgery seems to predict increased 30-day mortality, after correction for other risk factors.