A Cardiac Computed Tomography-Based Score to Categorize Mitral Annular Calcification Severity and Predict Valve Embolization

Objectives: This study aims to establish a computed tomography (CT)-based scoring system for grading mitral annular calcification (MAC) severity and potentially aid in predicting valve embolization during transcatheter mitral valve (MV) replacement using balloon-expandable aortic transcatheter heart valves.

Background: Transcatheter MV replacement is emerging as an alternative treatment for patients with severe MAC who are not surgical candidates. Although cardiac CT is the imaging modality of choice in the evaluation of candidates for valve-in-MAC (ViMAC), a standardized grading system to quantify MAC severity has not been established.

Methods: We performed a multicenter retrospective review of cardiac CT and clinical outcomes of patients undergoing ViMAC. A CT-based MAC score was created using the following features: average calcium thickness (mm), degrees of annulus circumference involved, calcification at one or both fibrous trigones, and calcification of one or both leaflets. Features were assigned points according to severity (total maximum score = 10) and severity grade was assigned based on total points (mild ≤3, moderate 4 to 6, and severe ≥7 points). The association between MAC score and device migration/embolization was evaluated.

Results: Of 117 patients in the TMVR in MAC registry, 87 had baseline cardiac CT of adequate quality. Of these, 15 were treated with transatrial access and were not included. The total cohort included 72 (trans-septal = 37, transapical = 35). Mean patient age was 74 ± 12 years, 66.7% were female, and the mean Society of Thoracic Surgery risk score was 15.4 ± 10.5%. The mean MAC score was 7.7 ± 1.4. Embolization/migration rates were lower in higher scores: Patients with a MAC score of 7 had valve embolization/migration rate of 12.5%, MAC score ≥8 had a rate of 8.7%, and a MAC score of ≥9 had zero (p = 0.023). Patients with a MAC score of ≤6 had 60% embolization/migration rate versus 9.7% in patients with a MAC score ≥7 (p < 0.001). In multivariable analysis, a MAC score ≤6 was in independent predictor of valve embolization/migration (odds ratio [OR]: 5.86 [95% CI: 1.00 to 34.26]; p = 0.049).

Conclusions: This cardiac CT-based score provides a systematic method to grade MAC severity which may assist in predicting valve embolization/migration during trans-septal or transapical ViMAC procedures.