Among the many risk factors for poor prognosis following cardiac emergencies, accumulating research points to one that may be overlooked: the time of the week. Research has shown worse outcomes in cardiac patients presenting to the emergency department on the weekend vs during the week, and findings from several studies presented at the annual American College of Cardiology meeting in April 2022 add further support to this observation.1-3

Altujjar et al analyzed 6,020 records from the National Inpatient Sample (NIS) database to compare outcomes among patients who were hospitalized with aortic dissection on a weekday vs over the weekend.1 After adjusting for demographic factors and common comorbidities, such as myocardial infarction and heart failure, the authors found that weekend admissions were linked to higher in-hospital mortality (adjusted odds ratio [aOR], 1.27; P =.012) both in patients treated medically (OR, 1.32; P =.023) and in those treated surgically (OR, 1.36; P =.018).

Weekend admissions were also associated with lower odds of receiving surgical intervention (OR, 0.83; P =.003). In addition, patients with aortic dissection type B demonstrated higher mortality (OR, 1.7; P =.015) and longer time to surgery (2.83 vs 1.88 days; P =.0017) if they were admitted on the weekend compared to a weekday, while no such differences were observed in aortic dissection type A patients.1

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The same group conducted a similar study2 based on records of 5,535 patients hospitalized for cardiac arrest and observed higher in-hospital mortality in those with weekend vs weekday admission (77.13% vs 73.32%; aOR, 1.20; 95% CI, 1.04-1.39; P =.012).

Munshi et al examined NIS data to identify outcomes in weekday and weekend admissions in nearly 3 million cases of acute new onset non-ST elevation myocardial infarction (NSTEMI). Their analyses revealed higher odds of mortality (aOR, 1.04), longer length of stay (adjusted mean difference, 0.06 days), and numerous complications (aOR, 1.05) including acute renal failure, cardiac arrest, and acute respiratory failure (all P <.05) in patients presenting on the weekend. Odds of mortality (aOR 1.14; P <.05) and complications were further increased among those who were admitted on the weekend and received revascularization.3

Findings on this topic have been mixed overall, however. One recent study, for example, showed no evidence of elevated in-hospital mortality in patients hospitalized for acute myocardial infarction (AMI) on the weekend vs weekdays.4

We interviewed the following experts to discuss some of their own study results and thoughts about the weekend effect: Saraschandra Vallabhajosyula, MD, MSc, assistant professor of medicine at the Wake Forest School of Medicine in Winston-Salem, North Carolina, and medical director of the Cardiac Intensive Care Unit at the Congdon Heart and Vascular Center at the Atrium Health Wake Forest Baptist; and Ibrahim Sultan, MD, associate professor of cardiothoracic surgery at the University of Pittsburgh School of Medicine, director of the Center for Thoracic Aortic Disease at the University of Pittsburgh Medical Center, and surgical director of the UPMC Center for Heart Valve Disease.

What does the available evidence suggest thus far about the weekend effect and why it might occur? 

Dr Vallabhajosyula: ​The weekend effect is a complex phenomenon that denotes lower-quality care and potential delays in care for acute conditions on weekends, holidays, and off-hours. It is hypothesized to be due to differences in staffing patterns, emergency-only services with varying definitions of “emergency,” lesser availability of resources, and potentially higher rates of complications.

Dr Sultan: The weekend effect is the idea that outcomes of emergency surgery might be affected by the time when it is performed. Specifically, it is suggested that surgery performed outside of normal “business hours,” especially during the weekend, may result in suboptimal outcomes compared to surgery performed during business hours on a weekday. This is the so-called “weekend effect.” Data is admittedly conflicting, but it likely favors the existence of this phenomenon.

We have examined this phenomenon as it pertains to surgery for acute type A aortic dissection. While some studies suggest that 30-day mortality is higher for aortic surgery performed on the weekend, other studies have not found such a difference. However, a recent systematic review and meta-analysis by Toh et al suggests that pooled data from prior studies supports the existence of higher mortality when aortic surgery is performed on the weekend.5

Data explaining why the weekend effect might exist is more sparse. It is postulated that poor outcomes during the weekend may be due to limited staffing or expertise for such complex cases. It is also suggested that available staff are fatigued during the weekend. The latter is difficult to prove, while the former requires further investigation. 

What do you believe your recent study added to our understanding of this topic?

Dr Vallabhajosyula: Using a large national database of over 9 million acute myocardial infarction admissions in the United States between 2000 and 2016, we sought to assess if outcomes are truly different between patients admitted on weekends vs weekdays in the contemporary era.4 Our study did not demonstrate any differences in in-hospital mortality or rates of coronary angiography or percutaneous coronary interventions (PCI) in AMI. This is truly a tremendous finding since it consolidates the concentrated effort of various national initiatives for prompt care in this critically ill population. 

Dr Sultan: To our knowledge, our study is the largest series examining this effect. [Of 36,399 ED visits for aortic dissection, they found that 13% of patients admitted on the weekend died in the hospital compared to those admitted on a weekday.6]

The recent study by Toh suggests that the existing research may be biased.5 However, data from a single, large database such as the Nationwide Emergency Department Sample (NEDS) may be an opportune source for providing unbiased estimates of a phenomena such as the weekend effect. Second, existing single-institution studies include highly specialized tertiary academic centers in their analysis, while the NEDS database is far more inclusive in the types of hospitals included in the population. Thus, our study’s findings may be more generalizable to the larger patient population. 

Why is there such ongoing debate regarding the weekend effect? What are the main points of disagreement?

Dr Vallabhajosyula: Multiple studies prior to ours have shown that the weekend effect is prevalent in acute care, both within and outside of cardiovascular medicine. Specifically in AMI, there has been a perception that revascularization is delayed due to the weekend effect, which adversely effects outcomes. In our longitudinal study over 17 years, these differences were seen more often in the earlier years, but the gap narrowed over time. This is suggestive of higher uptake of national and societal guidelines on early and prompt angiography and revascularization in AMI. 

Dr Sultan: The main point of disagreement stems from interpreting the data in appropriate context. Experts who deny the existence of the weekend effect argue that specialized centers with dedicated staffing 24/7 may be able to achieve similar outcomes whether aortic surgery is performed on the weekend or on a weekday. Conversely, this may not be generalizable to the average patient presenting to the average hospital. Interpreted in this context, both are likely to be true.

As our study suggests, when considering all-comers presenting to any hospital, the weekend effect is likely to be true. But other studies, including a recent study by Arnaoutakis et al of the International Registry of Acute Aortic Dissection, which includes aortic centers of excellence at tertiary and quarternary care hospitals, found no difference in mortality whether surgery was performed on the weekend or during the week.7 Again, context matters when interpreting the data. 

What are the key considerations for clinicians regarding this topic?

Dr Vallabhajosyula: For STEMI patients, in the absence of significant contraindications, rapid coronary angiography and PCI is the norm and has been widely implemented across all centers in the US. For NSTEMI patients, which are a larger fraction in our practice, we must be careful and diligent in our care. These patients are often dynamic and evolve during their hospital course. We need to have a low threshold to consider early coronary angiography and PCI either on weekdays or weekends to provide optimal care. 

Dr Sultan: It is likely the case that optimal outcomes are attainable only at tertiary or quarternary referral hospitals with centers of excellence for the surgery of interest. However, data regarding the weekend effect highlights the importance of robust referral networks and the need for appropriate staffing and resources “on-call” 24-7, including neurophysiology and perfusion.  

What else is needed to improve outcomes related to this phenomenon? 

Dr Vallabhajosyula: The care provided for these patients needs a strong team of multidisciplinary providers led by the cardiologist/interventional cardiologist. We need a strong and vigilant team of nurses, respiratory therapists, ancillary staff, and caregivers who can provide holistic care. Systems of care need to be strong to rapidly evaluate and treat perturbations prior to clinical or hemodynamic deterioration. Use of best practice guidelines, consistent care independent of time of admission, and development of quality improvement initiatives that target best practices are important next steps to help these acute ill patients. 

Dr Sultan: Three things are likely necessary. First, we need to continue to define the gold standard of aortic surgery – for instance, when and how to repair the aortic root, the appropriate extent of the distal reconstruction, the need for concomitant elephant trunk procedures, the optimal cerebral protection strategy, etc. Once defined, intraoperative decision-making should be streamlined, whether on the weekday or weekend.

Second, hospitals ought to dedicate appropriate staffing and resources to be available 24/7 in order to improve outcomes on the weekend. This may be costly, but it may be necessary for optimizing outcomes. Finally, further research is necessary. In addition to investigating the optimal surgical approach, further data is necessary to clarify whether surgeon fatigue impacts emergent surgery for acute aortic dissection that is performed on the weekend.


1.  Altujjar M, Mhanna M, Bhuta S, et al. The weekend effect on outcomes in patients presenting with acute aortic dissection: a nationwide analysis. J Am Coll Cardiol. Published online April 1, 2022. doi:10.1016/S0735-1097(22)02733-4

2.  Altujjar M, Khokher W, Sajdeya O, et al. Weekend effect on patients presenting with cardiac arrest: a nationwide analysis. J Am Coll Cardiol. Published online April 1, 2022. doi:10.1016/S0735-1097(22)02031-9

3.  Munshi R, Pellegrini J, Nehru N, et al. “The weekend effect:” a nationwide analysis of difference in outcomes among patients with NON-ST elevation myocardial infarction admitted during the weekend. J Am Coll Cardiol. Published online April 1, 2022. doi:10.1016/S0735-1097(22)01882-4

4.  Vallabhajosyula S, Patlolla SH, Miller PE, et al. Weekend effect in the management and outcomes of acute myocardial infarction in the United States, 2000-2016. Mayo Clin Proc Innov Qual Outcomes. 2020;4(4):362-372. doi:10.1016/j.mayocpiqo.2020.02.004

5.  Toh S, Yew DCM, Choong JJ, Chong TL, Harky A. Acute type A aortic dissection in-hours versus out-of-hours: A systematic review and meta-analysis. J Card Surg. Published online October 1, 2020. doi:10.1111/jocs.15070

6.  Brown J, Usmani B, Arnaoutakis G, et al. 10-Year trends in aortic dissection: Mortality and weekend effect within the US Nationwide Emergency Department Sample (NEDS). Heart Surg Forum. 2021;24(2):E336-E344. doi:10.1532/hsf.36817.  Arnaoutakis G, Bianco V, Estrera AL, et al. Time of day does not influence outcomes in acute type A aortic dissection: Results from the IRAD. J Card Surg. Published online September 16, 2020. doi:10.1111/jocs.15017

This article originally appeared on The Cardiology Advisor