Risk of Post-Operative Stroke in Asymptomatic Patients with Known Extra-Cranial Carotid Artery Disease Undergoing Non-Cardiac Surgery

Few information regarding the risk of stroke in patients with preexisting extra-cranial carotid occlusive disease undergoing non-cardiac surgery is available in literature, however, preoperative assessment is a common reason for referral to a vascular specialist. Stroke is a devastating complication after surgical procedures, associated with a post-operative mortality rate up to 26%, compared to 12.6% in non-surgical patients [1,2]. The incidence after cardiac surgery ranges from 1.4% to 4.3%, with the most widely accepted mechanism related to embolization of aortic athermanous debris or calcified plaques [3]. Cardiothoracic, carotid and major vascular surgeries, especially if performed in emergency setting are associated with a higher risk of cerebrovascular events compared to non-vascular and less extensive elective surgeries [4-6]. Higher age, prior stroke, atrial fibrillation and HTN were associated with higher perioperative and post-operative stroke risk [5,7]. 

Data regarding post-operative stroke following abdominal, urogenital, gynecological and orthopedic surgeries or procedures is limited. In a retrospective study, Ng et al., reported a stroke incidence ranging from 0.05 to 7.4% following a variety of non-carotid, non-cardiac surgeries, in a non-homogenous population with variable cardiovascular risk [8].

Our study aimed to examine the incidence of post-operative cerebrovascular events in patients with asymptomatic extra-cranial carotid artery stenosis undergoing non-cardiac surgery. After Institutional Review Board approval was obtained, an Electronic Medical Records search was performed looking at hospital admissions and discharges and Vascular Laboratory Registry using ICD 10 codes (165.29, 165.23, 165.21, S15.009A) to identify individuals who had carotid disease and subsequently underwent a non-cardiac surgery or procedure within 2 years. 

All carotid artery studies were performed with IU 22 Philips Ultrasound units (Bothell, WA) in a laboratory accredited by the Intersectional Accreditation Commission (IAC) [9].All exams were performed by a certified Radiology Vascular Technologist using IAC recommended protocols. Carotid stenosis was classified and documented using University of Washington criteria ranging from < 19% up to 100% stenosis [10]. 

Patients were included only if they required general anesthesia for surgery or a procedure. Surgical procedures were classified as low, intermediate or high risk as defined in preoperative clearance literature [11]. The Electronic Medical Record was used to obtain demographic, clinical, operative information. Postoperative follow-up evaluation was conducted within 2 weeks with attention to neurological events including Transient Ischemic Attack (TIA) or stroke, validated based on the American Stroke Association diagnostic criteria [12]. Additional risk factors for neurological event including age, presence of atrial fibrillation, hypertension, diabetes, body mass index or previous TIA or stoke were recorded in control and in individuals with significant carotid stenosis of over 60%. 

Each carotid artery was enrolled as an independent variable and only a stroke or TIA in an ipsilateral cerebrum corresponding to same side stenotic carotid artery was recorded as an adverse neurological event after excluding for non-carotid related etiological factors for stroke. In the event that postoperative neurological events were noted, contributing factors such as hemodynamic instability, resuscitation or re-intubation were assessed.

We looked at selected individuals with associated demographics (Table 1). 

Table1: Baseline patient characteristics. Group comparisons were made using student t-test for continuous variable and Chi square or Fisher’s test for categorical variables.
BMI: Body Mass Index

Standard statistical analysis was performed using Windows version 3.3.2 software. Group comparisons were made using student t-test for continuous variable and Chi square or Fisher’s test for categorical variables. Prevalence of carotid stenosis of over 60% was significantly higher in older age, an increased BMI was associated with more frequent carotid stenosis reaching a statistical significance in left carotid artery.  

Our study demonstrated no stroke or TIA in 580 carotids with variable degree of stenosis undergoing non cardiac surgery. This included 117 carotids with stenosis of over 60% and 6 carotids with critical stenosis of 80-99 and 8 carotids with total occlusion with variable degree of stenosis in other carotid arteries.

Nine-hundred and twenty-two patients were identified. After exclusions for prior TIA or stroke, missing demographic information, suboptimal carotid ultrasound studies and inadequate postoperative documentation or neurological status, 472 patients were included in the study corresponding to 944 carotid arteries (Figure 1). From this group, 380 carotids which had <19% stenosis served as control group and 580 carotids had variable degree of occlusive disease (Figure 2). 

Figure 1: Patient selection flow diagram.

 Figure 2: Algorithm of study design and recruitment of carotid arteries without and with various degree of stenosis undergoing non-cardiac surgery.

Among the carotids with significant occlusive features 8 had total occlusion and 7 had critical stenosis (Tables 2 and 3) undergoing low, intermediate and high risk surgical procedure. All individuals had clinical follow-up in two weeks and there were no neurological events (TIA or stroke) were reported. 

 Table 2: Characteristic of surgeries in patients with total occlusion of carotids and with various degree of stenosis in contralateral carotid artery.

ICA: Internal Carotid Artery. 

Table 3: Characteristic of surgeries in patients with critically stenotic carotids (80-99%) with various degree of stenosis in contralateral carotid artery.

ICA: Internal Carotid Artery.

Limitations to our study include the retrospective nature of investigation and the small sample size of patients with critical stenosis or total occlusion undergoing surgeries. Although still a small sample size to determine the risk of an infrequent event, this study provides some reassurance to the expectation that TIA or stroke following non-carotid, non-cardiac surgery is rare, in part due to differing pathophysiology.

No TIA or stroke was observed in asymptomatic patients with known extracranial carotid artery stenosis undergoing a variety of non-cardiac surgeries suggesting that no intervention is required during preoperative assessment by a vascular specialist.

There are 5 authors involved in producing this article. All authors contributed in designing, data collection and writing of the article. All authors had direct access to data which was collected in Redcap a secure web application to manage surreys and database. There has been no industry found to use for the preparation of our manuscript. There has been no financial or personal interest that may affect objectivity and therefore outcome of the study (A separate COI letter was signed previously and attached to publisher web already).

The study was supported by research fund from Vascular Medicine Department at Cleveland Clinic Florida.