a b s t r a c t

Introduction: Type A Aortic Dissection (TAAD) is a surgical emergency with a time-dependent rate of mortality. We hypothesized that a direct-to-operating room (DOR) Transfer program for patients with TAAD would reduce time to intervention.

Methods: A DOR program was started at an urban tertiary care hospital in February 2020. We performed a retrospective study of adult patients undergoing treatment for TAAD before (n = 42) and after (n = 84) imple- mentation of DOR. Expected mortality was calculated using the International Registry of Acute Aortic Dissection risk prediction model.

Results: Median time from acceptance of transfer from emergency physician to operating room arrival was 1.37 h (82 min) faster in DOR compared to pre-DOR (1.93 h vs 3.30 h, p < 0.001). Median time from arrival to operating room was 1.14 h (72 min) faster after DOR compared to pre-DOR (0.17 h vs 1.31 h, p < 0.001). In-hospital mor- tality was 16.2% in pre-DOR, with an observed-to-expected (O/E) ratio of 1.03 (p = 0.24) and 12.0% in the DOR group, with an O/E ratio of 0.59 (p < 0.001).

Conclusion: Creation of a DOR program resulted in decreased time to intervention. This was associated with a de- crease in observed-to-expected operative mortality. The transfer of patients with Acute type A aortic dissection to centers with direct-to-OR programs may result in decreased time from diagnosis to surgery.

(C) 2023

1. Introduction

Acute type A aortic dissection (TAAD) is a surgical emergency in which mortality increases in a time-dependent manner. The estimated risk of death has historically been 1-2% per hour without surgical man- agement, with significantly better outcomes achieved through surgical intervention within the first 4 h [1-3]. For hospitals that do not have the capabilities to provide definitive surgical care, it is imperative that rapid transfer out of the emergency department occur as soon as the

Abbreviations: DOR, direct-to-operating room; ICU, intensive care unit; IQR, interquartile range; O/E, observed-to-expected; TAAD, Type A Aortic dissection.

* Corresponding author at: Division of Cardiac Surgery, NorthWestern medicine, 676 N. St Clair St, Arkes Pavilion, suite 730, Chicago, IL 60611, USA.

E-mail address: [email protected] (C.K. Mehta).

initial evaluation and treatment has happened. Once diagnosis, resusci- tation, and transport has occurred, time spent on arrival in receiving hospital locations other than the operating room (such as an intensive care unit (ICU) or a second emergency department) adds little value to the care of patients needing definitive surgical treatment and can contribute to delays. Streamlining processes to allow patients to go directly from a referring hospital emergency department to the receiv- ing hospital operating room could improve outcomes. We started a direct-to-OR (DOR) external transfer program for aortic emergencies with the aim to reduce time from diagnosis by emergency physicians to definitive surgical care. We hypothesized that this program would reduce time from diagnosis to surgery and expedite interfacility transfer of patients with TAAD. In this study, we evaluated the results of TAAD repair before and after implementation of our DOR program.

https://doi.org/10.1016/j.ajem.2023.05.036

0735-6757/(C) 2023

1. Materials and methods
   1. Patient population and data collection

This is a single-center Observational retrospective cohort study of adult patients undergoing surgical or medical treatment for acute TAAD at an urban tertiary care hospital. This institution has over 900 beds and serves the greater Chicago area and surrounding counties.

A multidisciplinary comprehensive aortic dissection program and aortic dissection quality outcomes database were started in January 2019, and the DOR program implemented in February 2020. We studied consecutively treated patients from January 2019 to November 2021, comparing patients before and after initiation of DOR (pre-DOR: January 2019 - January 2020; DOR: February 2020 - November 2021).

Preoperative, intraoperative, and postoperative data were obtained from our prospectively maintained institutional database. This study was approved January 6, 2022 [Institutional Review Board (STU00215889)] which includes waiver of consent. Patients were excluded if they devel- oped intraoperative aortic dissection at the time of cardiac surgery. Society of Thoracic Surgery definitions were used for post-operative complica- tions. Time metrics from our aortic dissection quality outcomes database developed in 2019 were data pulled from discrete fields documented in the electronic medical record.

Surgically managed patients included all patients for whom there was an intention to operate, including patients who died during attempted Life-saving interventions. Medically managed patients were either patients deemed as prohibitive surgical risk or patients who refused surgery.

• 1. Direct-to-OR program

The DOR pathway at our institution allows emergency physicians at outside hospitals to connect directly with cardiac and vascular surgeons when an acute aortic syndrome is diagnosed (Fig. 1). The program is operational 24 h/day, 365 days/year. Attending cardiac and vascular surgeons are immediately paged to a secure conference line with the re- ferring emergency physician to discuss the case. The radiology images (and report if available) are reviewed in real time via an image sharing platform in combination with the clinical history from emergency physicians to confirm the diagnosis. Using this bridge line emergency physicians and surgeons can discuss optimal early management strate- gies to mitigate the risk of aortic morbidity and mortality. A determina- tion is then made by the accepting physician in coordination with the emergency department physician to transfer patients emergently directly to the operating room (DOR) or to the intensive care setting. Patients are brought to the ICU first if they require further evaluation

regarding surgical candidacy, require complex pre-operative aortic surgery planning, or if they refuse surgery. Physician accept time is doc- umented in the electronic medical record allowing time metrics to be monitored. A DOR activation triggers surgical, anesthesia, nursing, and perfusion teams to prepare an operating room while patients are being transferred. The transfer process involves coordination by our transfer center to facilitate ground ambulance or Air ambulance (either hospital-contracted or fastest available) transfer from the referring emergency department. Once at our facility, the patient is registered and a name band applied and the surgical and anesthesia team trans- port the patient directly to the OR with the Emergency Medical Techni- cians. The transfer pathway bypasses the intensive care unit (ICU) and emergency department alleviating these resources in order to transfer patients directly to the operating room.

• 1. Outcome measures

The primary outcome was time to intervention and secondary outcomes were operative mortality and postoperative complications. Operative mortality was defined as either intraoperative or postopera- tive mortality within 30 days or during index hospitalization. Complica- tions defined by the Society of Thoracic Surgery included readmission within 30 days, stroke, respiratory failure, renal failure requiring dialysis, reoperation for bleeding, and abdominal complications.

• 1. Statistical methods

Data summaries include mean, median, standard deviation, first/ third quartiles (Q1/Q3), frequencies and percentages. Group compari- sons are based on two-sample test, Wilcoxon’s rank sum test, or Fisher’s exact test. Expected mortality was calculated using the International Registry of Acute Aortic Dissection risk prediction model considering only pre-operative factors [4]. We then calculated our observed mortal- ity compared to expected mortality (O/E) fpr pre-DOR and DOR. Statis- tical significance was declared at two-sided 5% alpha level and no multiplicity corrections were made. All analyses were conducted in SAS v 9.4 (SAS Institute, Cary, NC).

1. Results
   1. Demographics

In total, 42 patients were accepted for management of type A aortic dissection in the pre-DOR group and 84 patients in the DOR group. Age, gender, body mass index, race, and relevant past medical history were not different between the two groups (Table 1).

Fig. 1. Workflow schematic for Direct-to-OR transfer process. OR = operating room.

Baseline demographics in all patients.

Variable	Entire Cohort (N = 126)		Pre-DOR (N = 42)		DOR (N = 84)		P-value
Age	61.8	+- 14.61	61.0	+- 12.96	62.2	+- 15.43	0.656
Gender (male)	85	(67.5)	30	(71.4)	55	(65.5)	0.501
Body mass index	28.4	+- 6.85	27.7	+- 5.61	28.7	+- 7.40	0.461
Race Asian	6	(4.8)	2	(4.8)	4	(4.8)	0.123
Black or African American	40	(31.7)	8	(19.0)	32	(38.1)
Hispanic or Latino	8	(6.3)	2	(4.8)	6	(7.1)
Other	1	(0.8)	1	(2.4)	0	(0.0)
Caucasian Smoker Current	71 34	(56.3) (27.2)	29 10	(69.0) (23.8)	42 24	(50.0) (28.9)	0.050
Former	52	(41.6)	13	(31.0)	39	(47.0)
Never	39	(31.2)	19	(45.2)	20	(24.1)
Prior cardiac surgery	6	(4.8)	4	(9.6)	2	(2.4)	0.322
Bicuspid aortic valve	8	(6.3)	1	(2.4)	7	(8.3)	0.196
Connective tissue disorder	5	(4.0)	3	(7.1)	2	(2.4)	0.197
Hypertension	103	(81.7)	35	(83.3)	68	(81.0)	0.744
Chronic kidney disease	26	(20.6)	6	(14.3)	20	(23.8)	0.213
Diabetes	12	(9.5)	3	(7.1)	9	(10.7)	0.520
COPD	33	(26.2)	11	(26.2)	22	(26.2)	1.000
Congestive heart failure	16	(12.7)	7	(16.7)	9	(10.7)	0.344

Values are n (%). COPD = chronic obstructive pulmonary disease. DOR = direct-to-operating room.

• 1. Time to operating room

In both groups, patients were accepted for type A aortic dissection through the external transfer system at or through our hospital’s emer- gency department (Fig. 2). In the pre-DOR group, 8 patients presented through our emergency department, and in the DOR group, 6 presented through the emergency department. These patients were excluded from calculations of time metrics.

The remainder of patients were accepted under the external transfer system. No patients with TAAD were refused for transfer. The median time from physician acceptance to operating room was 3.30 h (inter- quartile range (IQR) 2.20, 4.60) in the pre-DOR group versus 1.93 h (IQR 1.38, 2.78) in the DOR group (p < 0.001) (Table 2; Fig. 3). The median time from arrival at our hospital to arrival in the operating room was 1.31 h (IQR 0.65, 2.47) in the pre-DOR group vs. 0.17 h (IQR 0.08, 0.50) in the DOR group (p < 0.001) (Table 2; Fig. 3). After

Fig. 2. Breakdown of patients Pre-DOR and DOR with TAAD by management approach, admission destination and repair type. DOR = direct-to-operating room, ICU = Intensive Care Unit, TAAD = type A aortic dissection.

Table 2

Preoperative characteristics in all patients.

Variable		Entire Cohort (N = 126)		Pre-DOR (N = 42)		DOR (N = 84)	P-value
DeBakey Classification							0.725
DeBakey I	107	(84.9)	35	(83.3)	72	(85.7)
DeBakey II	19	(15.1)	7	(16.7)	12	(14.3)
Expected operative mortality	19.6	+-16.68	16.1	+- 10.60	21.4	+- 18.82	0.094
Time from acceptance to OR? (hours)	2.05	(1.53,3.35)	3.33	(2.20, 4.62)	1.93	(1.38, 2.78)	<0.001
Time from hospital arrival to OR? (hours)	0.32	(0.12, 1.15)	1.31	(0.65, 2.47)	0.17	(0.08, 0.50)	<0.001
Pre-operative chest compressions	12	(9.5)	3	(7.1)	9	(10.7)	0.520
Myocardial malperfusion	10	(7.9)	4	(9.5)	6	(7.1)	0.641
Limb malperfusion	32	(25.4)	13	(31.0)	19	(22.6)	0.311
Mesenteric malperfusion	15	(11.9)	4	(9.5)	11	(13.1)	0.560
Cerebral malperfusion	30	(23.8)	12	(28.6)	18	(21.4)	0.375
Tamponade	26	(20.6)	8	(19.0)	18	(21.4)	0.756

Values are n (%), mean +- SD, or median (interquartile range). DOR = direct-to-operating room, OR = operating room.

* Patients who presented to the emergency department and medically managed patients were excluded from time calculations.

implementation of DOR, the median time from hospital arrival to arrival in the operating room was 1.35 h faster for patients brought directly to the operating room (65 patients) compared to those brought to the ICU for evaluation prior to surgery (11 patients) (0.15 h vs 1.78 h).

The 11 patients first brought to the ICU included the following: 2 pa- tients who were unsure whether they wanted surgery, 2 patients brought first to the ICU due to early surgeon reluctance to activate direct-to-OR pathway, 1 patient deemed prohibitive risk who under- went ascending Endovascular repair, and 6 patients that required more thoughtful surgical planning (redo cardiac surgery, questionable surgical candidacy, and ascending intramural hematoma initially medically managed).

One patient died while in transport to our hospital and was excluded from the analysis. There were only two DOR activations in which the pa- tient did not actually have a type A aortic dissection as confirmed by transesophageal echocardiogram; no intervention was performed and these patients were excluded.

• 1. Pre- and intra-operative characteristics

Overall, there were no significant differences in the pre-operative characteristics between the pre-DOR and DOR groups (Table 2). There were no differences in mean cardiopulmonary bypass time, aortic

Fig. 3. In all surgically managed patients, crude operative mortality was lower in the DOR group compared to pre-DOR. In the DOR group, the observed mortality was 41% lower than expected (O/E ratio 0.59). DOR = direct-to-operating room.

cross clamp time, circulatory arrest time, or frequency of extended aortic arch resections.

• 1. Operative mortality

In the pre-DOR group, there was one intra-operative mortality. In the DOR group, there were three intra-operative mortalities. In pre-DOR, one patient died of rupture prior to sternotomy in the OR. In DOR, one patient arrested on anesthesia induction and two other patients arrested en route to the operating room. All of these patients underwent salvage emergency sternotomy but were unsuccessfully rescued.

The operative mortality (including these salvage cases) was 16.2% in pre-DOR, with an observed-to-expected (O/E) ratio of 1.03 (p = 0.24) and 12.0% in the DOR group, with an O/E ratio of 0.59 (p < 0.001) (Fig. 3).

• 1. Medical management

Medically managed patients had similar mortality rates in the pre-DOR and DOR groups. In the pre-DOR group, 5 patients (11.9%) underwent medical management and 2 survived to discharge (60% mortality). In the DOR group, 8 patients (9.5%) underwent medical management and 4 survived to discharge (50% mortality).

• 1. Post-operative length of stay and morbidity

Post-operative length of stay was similar between pre-DOR and DOR groups (median 12.5 vs 11.0 days, p = 0.99). Rates of respiratory failure, renal failure, stroke, and readmission were similar in both groups (Table 3).

Table 3 Postoperative characteristics in surgically managed patients. Analysis below is individuals that survived surgery.

	Variable			Pre-DOR (N = 36)			DOR (N = 73)		P-value
	Operative Mortality		5	(13.9)		6	(8.2)		0.732
	Respiratory failure		5	(13.9)		5	(6.8)		0.231
	Renal failure		5	(13.9)		3	(4.1)		0.066
	Stroke		8	(22)		8	(11.0)		0.118
	Reoperation for bleeding		1	(2.8)		3	(4.1)		0.140
	Abdominal complications		5	(13.9)		12	(16.4)		0.345
	Length of stay (days)		12.50	(6.00, 18.00)		11.00	(6.50, 18.50)		0.997
	Readmission		9	(25)		14	(19.2)		0.531

Values are n (%) or median (interquartile range). DOR = direct-to-operating room.

1. Discussion

The implementation of a DOR external transfer program at a high-volume urban tertiary care referral hospital resulted in reduced time from emergency department diagnosis to transfer to definitive surgical care. The main advantages of this program are a reduction in diagnosis to surgery time, easier access for emergency physicians to cardiac surgery, and facilitation with arranging expedited ground or air emergency medical transportation. To our knowledge, this is the first study to report outcomes before and after implementation of a direct-to-operating room program for TAAD.

Although acute Type A aortic dissection requires immediate surgical treatment, delays to surgery are common. Several factors account for these delays including lack of immediate availability of trained surgical personnel and transfer to Tertiary care centers. Hospital Inpatient units at these centers are often at full capacity, leading to overcrowded emer- gency departments [5]. Attempting to transfer patients to a receiving hos- pital inpatient unit or emergency department prior to emergency surgery can result in delay of care. Direct transfer to the operating room can obvi- ate the need for an immediate ICU bed. A DOR pathway provides extra time to procure an ICU bed while transport and surgery take place.

In the United States, transfer of patients with acute Type A aortic dissection is reported from 40 to 75% [6,7]. In their study of Medicare beneficiaries, Goldstone et al. noted a reduction in operative mortality in patients transferred to high volume centers despite a delay in time to surgery. After implementation of DOR, we were able to provide defin- itive surgical care 1.37 h (82 min) faster than pre-DOR. Our median time from transfer acceptance to surgery was 1.93 h, well below the published mean interval of 4.30 h in the International Registry of Acute Aortic Dissection database [8]. After arrival at our hospital door, the median time to operating room was 10.2 min (0.17 h) compared to 78.6 min (1.31 h) prior to DOR, which represents an 87% relative re- duction in door time to operating room. This was 2.43 h faster and a 94% relative reduction in time when compared to the 2.6-h median time from hospital arrival to operating room entry reported in the recent re- port from the Society of Thoracic Surgery adult cardiac surgery data base by Lee et al. [9]. In our study, of the total reduction of 1.37 h, 1.14 h were saved in the time spent from hospital arrival to operating room entry. This finding highlights the reduction in door-to-operating room time associated with bypassing an ICU stay.

This decrease in time to intervention was associated with an improved observed-to-expected operative mortality using the Interna- tional Registry of Acute Aortic Dissection prediction model. Our observed operative mortality was 41% lower than expected following DOR. Crude operative mortality went from 16.2% to 12.0%, results comparable to published mortality rates at other high-volume aortic centers [3,10-12]. While certainly encouraging, this finding is only hypothesis-generating, as the primary outcome measure was not oper- ative mortality.

• 1. Limitations

Several limitations of this study must be acknowledged. First, as a retrospective study, there may be unknown confounding factors. Sec- ond, the results of our program may not be generalizable to all Hospital systems. Those requiring significant times in regional transport may not be able to achieve the end-result time from acceptance-to-operating room. Third, although observed-to-expected operative mortality im- proved after DOR, long term survival data and larger multicenter studies are needed to better understand the relationship between time to oper- ating room and mortality.

1. Conclusion

Patients with TAAD are commonly transferred to other hospitals for management, which delays time from diagnosis to definitive surgical

care [6,7]. Strategies to reduce time to surgery can lead to meaningful improvements in TAAD mortality [2]. Our study found a reduced time to intervention. This was associated with a decrease in observed-to- expected operative mortality for patients with TAAD after starting a DOR external transfer program at an urban tertiary care hospital. In con- clusion, direct-to-operating room programs may allow for more expedi- tious definitive surgical care in patients diagnosed with TAAD.

Funding

No outside funding sources.

Institutional review board

Northwestern University STU00215889 (approved 1/6/2022) which includes waiver of consent.

CRediT authorship contribution statement

Christopher K. Mehta: Writing - review & editing, Writing - original draft, Visualization, Validation, Supervision, Methodology, Formal analysis, Data curation, Conceptualization. Stephen Chiu: Writing - review & editing, Writing - original draft, Data curation, Conceptualization. Andrew W. Hoel: Writing - review & editing, Writing - original draft, Validation, Methodology, Conceptualization. Patricia Vassallo: Conceptualization, Methodology, Validation, Writing - original draft. Beth Whippo: Writing - review & editing, Writing - original draft, Project administration, Formal analysis, Data curation, Conceptualization. Adin Cristian Andrei: Writing - review & editing, Writing - original draft, Validation, Methodology, Formal analysis, Data curation. Michael J. Schmidt: Writing - review & editing, Methodology, Investigation, Data curation. Duc Thinh Pham: Writing - review & editing, Writing - original draft, Validation, Methodology, Data curation, Concep- tualization. Douglas R. Johnston: Writing - review & editing, Visualiza- tion, Resources, Conceptualization. Andrei Churyla: Writing - review & editing, Resources, Investigation, Data curation. S. Chris Malaisrie: Writing - review & editing, Resources, Investigation, Data curation.

Declaration of Competing Interest

Christopher K. Mehta, MD: Gore: Speaker and Educational Funding. Duc Thinh Pham, MD: Abbott, Medtronic, Abiomed: Speaker and

Advisory Panel.

Douglas R. Johnston, MD: Advisor: Abbott, Edwards Lifesciences, Terumo, Livanova, HD Medical.

S. Chris Malaisrie, MD: Edwards Lifesciences: Consultant; Medtronic, CryoLife, Atricure, Terumo Aortic: Consultant and Speaker.

All other authors have nothing to disclose.

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