Aortic replacement in cardiac surgery

WHAT ARE THE RISKS WITH ASCENDING AORTIC REPAIR?

The condition of the patient at presentation has become the strongest predictor of surgical risk. An improved understanding of these associations can improve our prediction of risks and the decision about when to operate. Patients needing aortic replacement can present with a broad spectrum of pathologies. For example, a patient who presents with acute type A dissection is quite different from a patient with an enlarging ascending aneurysm who had a previous aortic valve replacement for bicuspid aortic valve stenosis as a young adult. Further, both are different from the elderly patient with the complex constellation of coronary disease, multivalve disease, atrial fibrillation, and an ascending aneurysm—an increasingly common presentation.

Guidelines supporting the decision to replace the aorta in patients with chronic asymptomatic aortic disease are limited by a lack of data on surgical risk and long-term effectiveness.

A study from the Society of Thoracic Surgeons database assessed outcomes in patients who had surgical replacement of the ascending aorta, with or without root repair.³ The operative mortality (either in-hospital or within 30 days of surgery) was 8.3% and ranged from 3.5% for elective surgery to 9.1% for urgent surgery, and 21.5% for emergencies. End-stage kidney disease and reoperation were also shown to be independent predictors of risk in that study.

Outcomes at Cleveland Clinic for elective ascending aortic procedures are much better than these national averages. Outcomes data are important to patients when making a decision about prophylactic surgery. In a study analyzing 1,889 patients undergoing elective ascending replacement at Cleveland Clinic between 2006 and 2010, the operative mortality was only 0.5% for those undergoing isolated ascending replacement and 2% for those requiring a multicomponent operation. In the multicomponent group, 87% included aortic valve replacement, 29% coronary bypass, and 25% underwent more than 2 different combined procedures.⁴

Patient risk factors

A comparison of patient risk factors for the 2 groups showed that the isolated replacement group had larger aortic diameters, more extensive disease with dilated descending aortas, and were more frequently undergoing a reoperation than the multicomponent group.

To further define the risks, we conducted a propensity-matching study of 197 pairs of these patients, comparing 62 variables including aortic morphology data gathered from 3-dimensional analysis of computed tomography scans. Results showed no differences in survival rates between the groups during 4 years of follow-up.⁴ A comparison of the risk of other perioperative complications—death, stroke, need for dialysis, respiratory failure, and bleeding—also showed no differences between the groups.

Does adding ascending aortic replacement to other cardiac procedures increase the surgical risk?

To answer this question, we collected data on Cleveland Clinic patients between 2006 and 2011 who had aortic surgery in combination with cardiac surgery (N = 1,677) and compared them against a similar cohort who only had cardiac surgery (N = 12,617).⁵ The objectives were to determine the risk of adding aortic surgery to an elective cardiac operation. A second objective was to determine the impact of circulatory arrest on outcomes.

Comparison 1. We identified 1,284 matched pairs from the 2 groups. Data showed a slightly higher risk of stroke in patients who had cardioaortic surgery (2.4%) compared with those who had cardiac surgery alone (1.7%); however, the mortality rate was not significantly different between the groups.

Does circulatory arrest affect the stroke rate?

From the matched pairs of patients who underwent cardioaortic surgery, we identified a subset of patients who had circulatory arrest and compared them with those who did not have circulatory arrest. The circulatory arrest group had worse outcomes. Mortality rates were 4.1% vs 1.0%, respectively, and stroke rates were 3.9% vs 0.9%. 

This raised the question of whether circulatory arrest was the cause of the worse outcomes or a marker of patients with more advanced disease.

The decision to use circulatory arrest is primarily based on 2 factors:

• Patient-specific factors, such as those with advanced aortic disease in whom circulatory arrest is unavoidable.
• Surgeon preference/technical decision. For example, in a patient with a bicuspid valve, the surgeon may choose to use a brief period of circulatory arrest instead of clamping the proximal arch.

Comparison 2. To further define the impact of circulatory arrest, we grouped the patients who underwent cardioaortic surgery (N = 1,677) into those who had circulatory arrest (n = 728) or no arrest (n = 949). From those groups, we identified 324 matched pairs of patients and compared the outcomes.

Our results showed no differences associated with the use of circulatory arrest in rates of mortality (1.2% with and 0.6% without) or stroke (1.5% for both groups) when comparing patients with similar disease characteristics. These results suggest that the need for circulatory arrest was probably not the culprit but more likely a marker of patients with more complex disease. It is their more advanced disease that puts them at higher risk.

Comparison 3. To determine whether circulatory arrest has an overall impact on cardiac surgery, we took the population of matched cardioaortic patients from comparison 2 regardless of whether they had circulatory arrest and compared them to the larger group of 12,617 cardiac surgery-alone patients. Again, results indicated that the addition of aortic surgery had no real impact on outcomes. Both groups had similarly low risks for both mortality (0.9% with aortic replacement vs 0.5% without) and stroke (1.4% with aortic replacement vs 1.1% without).

Clinical implications

This multistepped comparison study found that adding ascending aortic replacement to cardiac surgery had essentially no impact on mortality or stroke. These data provide evidence indicating that cardiac surgeons should be more proactive in deciding whether to add ascending aorta replacement to cardiac surgery when treating a patient with a dilated ascending aorta. It must be noted, however, that patients with more advanced aortic disease are a higher risk population. All of these findings highlight the importance of managing thoracic aortic disease within an experienced multidisciplinary center.