Long-term outcomes of common carotid artery cannulation for elective aortic surgery—a follow-up study

Introduction

Elective ascending and aortic arch surgeries have become standardized procedures performed with acceptably low mortality and morbidity in a multitude of centers (1). However, the choice of arterial cannulation is mostly an individual choice based on the surgeon’s experience and surgical strategy. One practical and convenient cannulation site is the right common carotid artery (CCA). Initially described in the late 90s (2-4) and promoted through the work of Urbanski et al. (5), cannulation of the CCA for arterial blood return during extracorporeal circulation (ECC) is still under debate. The benefits of using this cannulation site are its accessibility, direct antegrade perfusion of the brain, and a clean and controlled environment, while arguments opposing the utilization of the right CCA include potential risks such as embolic events, stroke, and local dissection. No long-term follow-up of the cannulation site and the patient’s clinical outcomes has been published so far. Hence, the aim of this study was to present the short- and long-term mortality and morbidity after cannulation of the right CCA in elective aortic surgery, the fate of the cannulation site, and the hemodynamic profile during hypothermic circulatory arrest. We present this article in accordance with the STROBE and STROCSS reporting checklists (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-735/rc).

Methods

Study design

This observational retrospective study prospectively collected preoperative, intraoperative, and postoperative data with active cross-sectional follow-up in patients undergoing elective aortic surgery with or without partial or total aortic arch replacement.

Patients

A total of 343 patients with proximal thoracic aortic aneurysms with or without involvement of the aortic valve underwent surgery at our center between April 2013 and March 2020. Here, we present the first 100 cases of elective aortic surgery using the right CCA as the sole arterial cannulation site for blood return from the heart-lung machine (Table 1).

Preoperative clinical records, operative reports, hemodynamic parameters, and intensive care unit (ICU) records were obtained from an electronic clinical database. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013) and was approved by the institutional ethics committee of University of Würzburg (No. 88/19-sc), individual consent for this retrospective analysis was waived. The study was registered in the German clinical trials register. Follow-up data were collected via a structured follow-up questionnaire mailed to patients and included a clinical interview after obtaining informed consent. For those who did not respond to the letter, data were collected by reviewing their records from recent clinic visits. Information about deceased patients was gathered through phone calls with the patient’s primary care practitioner or cardiologist.

Cohort description

A total of 100 consecutive patients underwent elective proximal thoracic aortic surgery with or without partial or total aortic arch replacement, using the right CCA as the sole arterial cannulation site. Of these, 83 (83%) patients underwent moderate hypothermic circulatory arrest (MHCA) with unilateral selective antegrade cerebral perfusion (uSACP) and the remaining 17 (17%) underwent surgery on a cross-clamped aorta. There were 4 (4%) redo surgeries (two after previous aortic valve replacement, and two after previous surgery for acute aortic dissection—one case of pseudoaneurysm on the proximal suture line, and other progressions of aortic arch aneurysm after dissection). The concomitant procedures are detailed in Table 2. The carotid arteriotomy used as the cannulation site was closed with patch repair in 75% of the patients, with the remaining 25% having directly closed arteriotomy with interrupted 5-0 prolene sutures.

Surgical technique and rationale

The decision to use the carotid artery was based on surgeon preference. For this study, the CCA was the only arterial cannulation site, so we used it for cooling, uSACP, and rewarming after hypothermic circulatory arrest. Preoperative assessment of the patients started with a physical examination, contrast-enhanced computed tomography (CT) of the aorta, including the supraaortic branches, and vascular ultrasound with color Doppler assessment of the carotid arteries.

Blood pressure monitoring during the operation was performed through arterial lines in the right radial and left femoral arteries. Cerebral monitoring was achieved using continuous near-infrared spectroscopy (NIRS). A temperature measurement probe was placed in the bladder, esophagus, and tympanum (6).

The carotid artery was exposed and prepared through a 3–4-cm incision in the neck along the medial marking of the sternocleidomastoid muscle, separate from the midline sternotomy skin incision. After heparinization and continuous NIRS monitoring, the right CCA was cross-clamped, a half-circumference transverse incision was made and an 8-mm vascular sealed polyester graft was anastomosed to the artery with a continuous 5-0 polypropilene suture. The angle between the prosthetic graft and distal CCA should not exceed 90°. In all cases we used a 24-Fr elongated one-piece arterial (EOPA) cannula from Medtronic^Ò (Meerbusch, Germany) introduced into the 8 mm graft a few centimeters distal to the carotid anastomosis (Figure 1). Venous drainage is usually enabled through the femoral vein (the most common RAP^TM 22 Fr from LivaNova^Ò, London, UK). In larger patients, we aimed to cannulate the right atrium using a two-stage cannula (VC2 from Medtronic^Ò).

Figure 1 Central image—the actual operative site with carotid cannulation and exposure of the aorta through an upper-hemisternotomy approach.

Perfusion strategy

We started the perfusion with a 100-mL bolus and gradually increased it to full flow. Usually, we utilize supraphysiological flow (110–115% of full flow) to countersteer the need for vasoplegic drugs. We then started cooling with maximal intensity. The goal temperature for hypothermic circulatory arrest (HCA) and uSACP in our clinic is between 24 and 28 ℃, by agreement (mean esophageal temperature for the 83 patients at which HCA was initiated was 27.1±5.1 ℃, with uSACP cold blood perfusion at 24.4±2.8 ℃). At the commencement of HCA, we decreased the flow to 10 mL/kg and clamp the right CCA proximally. Hemiarch or total arch reconstruction was then performed. After deairing, our preference is to replace the clamp and progressively increase arterial flow with the first 5 min of cold perfusion, and finally reestablish flow at 110% full flow (median 5 L/min) during the period of rewarming with an arteriovenous temperature gradient of 10 ℃ (arterial line peak temperature at 38.5 ℃ to venous blood return as core temperature surrogate gradient). We used alpha-stat throughout the entire operation, monitored NIRS, and reacted with perfusion adjustments (Table 3).

End points

The primary endpoints of this study were as follows: (I) postoperative death from neurological causes; (II) clinical stroke during follow-up; and (III) the fate of the cannulation site on the CCA during follow-up. The secondary endpoint was the identification of clinical factors for death and stroke during follow-up.

Statistical analysis

We screened the relevant variables using a univariate Cox proportional hazard model, in which we assessed the model quality using Harrel’s concordance index (7), that is, the proportion of all usable patient pairs in which the predictions and outcomes are concordant. Usable patient pairs were pairs in which at least one patient died or had a stroke. If the predicted outcomes were in the correct time order, they were concordant. We then selected the 20 variables with the highest concordance index and built models based on the best subset with a maximum of three variables in each model. The best model is assessed with an out-of-sample concordance index using 5-fold cross-validation with stratified sampling, that is, the treatment proportions in each group are preserved (8). Missing data is imputed with canonical variate analysis implemented in the Hmisc R package with the function ‘transcan’. After model selection, the coefficients were estimated with bootstrapping using stratified sampling with a final model concordance of 0.68±0.07. Other techniques were used to verify the model selection. Both the cross-validated least absolute shrinkage and selection operator (LASSO) using concordance index as a quality metric and stepwise Cox regression using Akaike information criterion (AIC) as a quality metric yielded the same result. Kaplan-Meier plots compare mortality in the treatment group with population mortality in a proximal geographical area (the state of Bavaria, Germany), implemented with the same sex ratio and age as in our treatment group (Bavarian State Office for Statistics, Fuerth, Germany, Data licence Germany, www.govdata.de/dl-de/by-2-0). We used the log-rank test to compare treatment group mortality with general population mortality.

Results

Preoperative demographics

The preoperative patient characteristics are presented in Table 1. Details of proximal reconstruction, concomitant procedures, and operative times are presented in Table 2. Detailed hemodynamic profiles as well as perfusion specifications during ECC and HCA and blood gas analysis are presented in Table 3.

Follow-up

The follow-up data were 100% complete, with a median duration of 5.4 years (mean duration 4.8±1.7 years, range 0.3 to 7.6 years), and was closed on September 9, 2022.

Hospital outcomes

One death (1%) was directly related to disabling left-sided stroke within the first 30 days. On postoperative day (POD), an 80-year-old male with a history of ipsilateral cerebro-vascular accident (CVA) developed sudden right-sided hemiparesis after a short hypertensive crisis. Emergency CT angiography revealed an almost complete occlusion of the left CCA in the proximity of the carotid bulbus due to a dislodged atherosclerotic plaque. An emergent thromboendarterectomy could not prevent massive left-sided stroke, which is incompatible with life. The patient died the same day.

Rates of transient and permanent neurologic deficit or dysfunction

Clinically evident stroke occurred in 4 patients (4%), with half of the patients recovering almost completely by the time of the first scheduled postoperative control in our outpatient care facility. One patient suffered from occlusion of the retinal artery and had blurred vision, the second suffered infarction with secondary bleeding in the left partial middle cerebral artery territory, and the third suffered spastic hemiparesis on the left side with predominantly arm weakness. In addition to bleeding in the infarcted region, no other imaging correlation was found on the CT scans in these patients.

Three patients (3%) suffered from transient ischaemic attack (TIA) with complete resolution within 24 hours, and 13 (13%) of the patients awoke delirium, agitation, confusion, or symptoms of decreased level of consciousness. Probably unrelated to central neuropathology, one patient had left vocal cord paresis.

Postoperative magnetic resonance imaging (MRI) imaging

Randomly assigned 14 patients received cranial MRI postoperatively (mean on POD 3.8, range from 0 to 15). None of these patients had a positive neurological result prior to imaging. The rationale for immediate postoperative brain imaging was to assess the hyperperfusion of the right hemisphere. However, no evidence of this association was found. Three patients had accidental findings: minor thromboembolic infarctions; minor cerebellar bleeding without any clinical correlation; and lesions in the right temporal, occipital, and cerebellar territories, as well as left frontal territories without any neurologic clinical correlation.

Postoperative course and complications

The average ventilation time in the ICU was 19.3±18.3 hours (range, 3–148.8 hours), with 13 patients (13%) having prolonged ventilation (>24 hours). Five patients (5%) returned to the operating room for bleeding, four patients (4%) developed third-degree atrioventricular block (AV-block), and three patients (3%) received a permanent pacemaker postoperatively in the same course. The average ICU stay was 2.2±2.0 days (range, 1–13 days), and the average hospital stay was 10±5 days.

No new postoperative renal failure requiring temporary renal replacement therapy was observed, with one patient already on dialysis preoperatively. No hepatic insufficiency was observed (Figure 2A,2B, Table 4).

Figure 2 Laboratory analysis (hepatic function tests and kidney parameters). (A) Hepatic laboratory studies showing initial increase in hepatic enzymes and subsequent normalization towards discharge. (B) Kidney parameters in the postoperative course: decline in GFR followed by normalization towards discharge. AP, alkaline phosphatase; LDH, lactate dehydrogenase; AST, aspartate aminotransferase; ALT, alanine aminotransferase; GFR, glomerular filtration rate.

Color Doppler ultrasound of the carotid artery in follow-up

No local dissections or hematomas of the CCA associated with cannulation were observed. A total of 78 patients (87% of the survivors) after an average of 2.3 years after the operation underwent a control color Doppler ultrasound examination of the right CCA specifically for detecting changes in the cannulation site. No pathological findings were observed in any of the patients examined.

Long-term survival and comparison with an age- and gender-matched normal population

Multivariable analysis revealed that age at surgery was the only significant predictor of late stroke or death [hazard ratio (HR) =1.083; 95% confidence interval (CI): 1.013, 1.158; P=0.01; c-index 0.683]. If only death and not stroke is used as the response variable (with 10 events in follow-up, after median 5.4 years), the same result is obtained with age as the only significant predictor (HR =1.147; 95% CI: 1.039, 1.266; P=0.006, c-index 0.806). If only stroke was used as the response, no predictors were significant due to the low number of events in this category (seven events in follow-up).

The 1-, 3-, and 6-year survival rates were 97%, 95%, and 92%, respectively. Kaplan-Meier and log-rank tests were used to compare the survival of the entire cohort with an age- and sex-matched normal population in Bavaria, Germany. There was no significant difference in survival between the groups (P=0.50, Figure 3). Event-free survival rates at 1-, 3-, and 6-year were 94%, 92%, and 87%, respectively (Figure 4).

Figure 3 Kaplan-Meier survival curve for patients after elective aortic surgery using the right common carotid artery as an arterial cannulation site and comparison with age- and gender-matched population in Bavaria, Germany.

Figure 4 Kaplan-Meier event-free survival curve for composite event of stroke and death in follow-up.

Discussion

Cannulation of the right CCA is a safe, feasible, and practical adjunct for proximal aortic surgery. At a median of 5.4 follow-up years, the patients had no significant overt mortality compared to the general population and had a low incidence of stroke. Furthermore, after a median of 2.3 follow-up years, the patients had no signs of pathological change at the cannulation site on the carotid artery, corroborated through postoperative vascular ultrasound control examination.

The use of carotid artery cannulation as an adjunct cannulation technique in cardiac surgery for proximal aortic and aortic arch replacement has been a topic of discussion for over two decades. Here, we present the first 100 elective aortic cases that utilized the right CCA as the sole arterial cannulation site. We see a few advantages of this technique, which have also been appreciated by other groups (2,3,5). First, there was continuous uninterrupted antegrade cerebral perfusion throughout the surgery. Hence, CCA cannulation obviates the need for a second or additional cannulation during the operation. This can also be achieved by cannulation of the axillary (AxA) and innominate arteries (IAs) (9). Nonetheless, the advantage of carotid cannulation over the others is that it is a fast and simple approach, especially in obese patients, where AxA access can be challenging. Second, CCA is rarely affected by the atherosclerotic process; thus, peripheral debris and cerebral embolization are assumed to be smaller than manipulation of the IA, especially in the heavily atheromatous aortic arch (10). Furthermore, when utilizing CCA cannulation, uSACP exclusively involves brain perfusion without “steal” perfusion in the arm.

The literature consistently supports the use of CCA as a safe and effective adjunctive cannulation technique. However, probably due to its proximity to the brain and fear of potential detrimental effects, such as pathological changes in the carotid wall at the cannulation site, this technique is not widely accepted. However, morbidity and mortality were consistent with other published data. Immediate neurological outcomes are comparable among the few published reports on carotid artery cannulation. While Neri et al. (3) and Kuniyoshi et al. (2) reported no early stroke, Urbanski (11) reported perioperative stroke rates between 1.0% and 4.9% depending on the urgency of surgery. Compared to other commonly used cannulation sites, carotid artery cannulation seems to be safer. Using the AxA, Zierer et al. (12) reported 3% stroke, Leshnower et al. (13) reported permanent and temporary neurologic deficits of 2.5% and 7.2%, respectively, whereas Preventza et al. (9) reported an average of 2.8% of stroke for a mixed urgency collective. Using IA as the cannulation site, Jassar et al. (14) reported 1% stroke, whereas Preventza et al. (15) reported 1.9% and 3.4% permanent and temporary neurologic deficits, respectively. In our series, we observed permanent and temporary neurologic deficits in 4% and 3% of patients, respectively. With regard to mortality, the results were again comparably satisfactory. In our series we lost one patient (1%) in the first 30 days due to a detrimental stroke in a patient with a history of CVA. By applying multivariable logistic regression, we found that only age at surgery was an independent risk factor for stroke or death during follow-up. While Neri et al. (3) and Kuniyoshi et al. (2) reported no mortality, Urbanski et al. reported 2.1 an early mortality (11). Jassar et al. 1% (14), Preventza et al. 4.9% (15), and Leshnower et al. 4.5% mortality for elective cases (13). A recent randomized trial directly comparing AxA versus IA cannulation for aortic arch surgery presented similar outcomes, in which all patients were postoperatively MRI-screened (16). Finally, Svensson et al. (17) reported 0.8% early mortality and 0.8% stroke, but what is more important in their seminal paper from 2015 is that imaging studies alone, as well as in combination with clinical diagnostics, are not sensitive enough to detect neurologic deficits. Similarly, we found pathological changes on MRI without clinically evident neurological defects, and vice versa. Hence, his group recommends using both brain imaging (CT and MRI) and neurocognitive studies for a more complete evaluation of neurological function (17).

Many studies in the past have supported unilateral perfusion without hesitation. Ayad et al. (18) described the suboccipital carrefour in 1998, showing that there are other intra- and extracranial collaterals and a circle of Willis. Urbanski et al. (19) performed a prospective study showing no side-related differences during the uSACP. Similar results were shared by other surgical teams (15,20,21). Depending on the cannulation site, the approach toward endoluminal blocking or snaring of the left carotid and subclavian arteries also has advantages and disadvantages (2,3).

Finally, whole-body perfusion and rewarming through the right CCA after moderate HCA are achieved without difficulties and lasting complications. At the end of the operation, the lactate level was just above the reference limit, and we observed no new renal failure or liver impairment, findings comparable with those of other published reports (3,5,12,22-24). For this study, we asked the referring centers or general practitioners to perform a follow-up color Doppler ultrasound examination in all patients who underwent surgery using the right CCA as the sole cannulation site. We observed no local pathological changes at the cannulation site and no hemodynamic compromise downstream of the carotid. In summary, utilization of the right CCA for uSACP during mild hypothermia and for whole-body perfusion and rewarming did not negatively impact visceral or cerebral organ protection.

Limitation

The present study had several limitations. A retrospective study bears a selection bias. Second, we did not have a comparison group to correlate our findings; therefore, we used other published results as a proxy comparison. Another limitation is the relatively small sample size. Finally, only a few randomly chosen patients underwent postoperative MRI instead of imaging the entire cohort.

Conclusions

Cannulation of the right CCA is a safe, feasible, and practical solution for proximal aortic surgery, with comparable short- and long-term results. Careful patient selection and appropriate techniques are essential to minimize the risk of complications. A prospective study concerning the question of the optimal cannulation site is of immense importance. This should include standardized perioperative neurological imaging and functional neurological tests during follow-up.

Acknowledgments

We would like to thank Mrs. Magdalena Burkard and Mrs. Franziska Döll for their assistance with, and selfless commitment to the execution of the follow-up for this study.

Funding: None.

Footnote

Reporting Checklist: The authors have completed the STROBE and STROCSS reporting checklists. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-735/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-735/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-735/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-735/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013) and was approved by the institutional ethics committee of University of Würzburg (No. 88/19-sc), individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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