Aortic Dissection in Patients With Bicuspid Aortic Valve-Associated Aneurysms

Abstract

Background: Data regarding the risk of aortic dissection in patients with bicuspid aortic valve and large ascending aortic diameter are limited, and appropriate timing of prophylactic ascending aortic replacement lacks consensus. Thus our objectives were to determine the risk of aortic dissection based on initial cross-sectional imaging data and clinical variables and to isolate predictors of aortic intervention in those initially prescribed serial surveillance imaging.

Methods: From January 1995 to January 2014, 1,181 patients with bicuspid aortic valve underwent cross-sectional computed tomography (CT) or magnetic resonance imaging (MRI) to ascertain sinus or tubular ascending aortic diameter greater than or equal to 4.7 cm. Random Forest classification was used to identify risk factors for aortic dissection, and among patients undergoing surveillance, time-related analysis was used to identify risk factors for aortic intervention.

Results: Prevalence of type A dissection that was detected by imaging or was found at operation or on follow-up was 5.3% (n = 63). Probability of type A dissection increased gradually at a sinus diameter of 5.0 cm--from 4.1% to 13% at 7.2 cm--and then increased steeply at an ascending aortic diameter of 5.3 cm--from 3.8% to 35% at 8.4 cm--corresponding to a cross-sectional area to height ratio of 10 cm(2)/m for sinuses of Valsalva and 13 cm(2)/m for the tubular ascending aorta. Cross-sectional area to height ratio was the best predictor of type A dissection (area under the curve [AUC] = 0.73).

Conclusions: Early prophylactic ascending aortic replacement in patients with bicuspid aortic valve should be considered at high-volume aortic centers to reduce the high risk of preventable type A dissection in those with aortas larger than approximately 5.0 cm or with a cross-sectional area to height ratio greater than approximately 10 cm(2)/m.

Fig 1

Each point represents the risk-adjusted probability of immediate dissection. Curves are the smoothed relationships. Loess smooth curve indicates the trend of increased risk with diameter. (A) Sinus diameter (cm). (B) Ascending diameter (cm). (C) Classification receiver operating characteristic (ROC) curve for ascending aortic dissection by diameter (cm). (D) Sinus cross-sectional area to height ratio (cm²/m). (E) Ascending cross-sectional area to height ratio (cm²/m). (F) Classification ROC curve for ascending aortic dissection by cross-sectional area-to-height ratio. (AUC = area under the curve; FPR = false prediction rate; TPR = true prediction rate.)

Fig 2

Risk of aortic intervention among 380 surveillance patients. (A) Years from index computed tomographic scan. Each symbol represents an aortic operation positioned on the vertical axis by the Kaplan-Meier estimator, and vertical bars are confidence limits equivalent to ± 1 standard error (SE). Solid line is parametric risk of aortic intervention estimate enclosed within dashed 68% confidence band equivalent to ± 1 SE. (B) Predicted risk at 1 (blue), 5 (green), and 10 (red) years by age. Solid lines are parametric risk of aortic intervention estimates enclosed within dashed 68% confidence band equivalent to ± 1 SE. This nomogram is based on multivariable equation in Table 3. Nomogram of risk is for patient with 5.0-cm ascending aorta diameter (z value = 12), date of presentation of July 2008, and body surface area of 2.1 m². (C) Predicted risk at 1 (blue), 5 (green), and 10 (red) years by ascending aorta diameter. Solid lines are parametric estimates of risk of aortic intervention estimates enclosed within dashed 68% confidence bands equivalent to ± 1 SE. This nomogram is based on multivariable equation in Table 3. Risk of aortic intervention is for 55-year-old patient with the same characteristics noted in B.

Fig 3

Instantaneous risk of aortic intervention (hazard function). Solid line is parametric hazard estimate enclosed within dashed 68% confidence band equivalent to ± 1 standard error. (CT = computed tomography.)