## 3 Results  
During the study period 538 patients underwent minimally invasive MV surgery at our institution. MAC was diagnosed preoperatively and assessed with the CT scan protocol in 27 (5%). Baseline characteristics are reported in Table 1. Mean age was 71 years and the majority of patients were women (20/27, 74%). The most common etiology was advanced [PERSON]'s disease or fibroelastic deficiency (18/27, 67%), whereas 4 cases were reoperations (15%). Long standing persistent atrial fibrillation was reported in 12 patients (44%). All the patients enrolled underwent CT scan examination. Intravenous non-ionic contrast agents for cardiac gating were used in 16 patients (59%). In the latter, the analysis was performed with a Revolution CT (GE Healthcare, General Electric) scanner. Eight patients (30%) underwent standard angio CT examination, while 3 patients (11%) underwent basal CT examination. The degree of MAC severity is reported in Table 2.  
Intraoperative data and postoperative outcomes are reported in Table 3. MV replacement was performed in 21 patients (78%), of whom 9 were diagnosed with severe MAC, whereas 12 showed a mild to moderate MAC. Bioprosthetic pericardial (Carpentier-Edwards Magna Ease, Edwards Lifesciences, Irvine, CA, USA) or porcine (MosaicTM, Medtronic Inc., Minneapolis, MN, USA) valves were used in almost all of the patients (20/21, 95%), confining mechanical MV replacement to a single case. The mean size in the implanted prosthetic valves was 27 \(\pm\) 2.6. In the 6 patients undergoing MV repair, two patients had a severe degree of MAC, while four had mild to moderate MAC. Annuloplasty alone was sufficient in 3 patients (50%) whereas leaflet resection or artificial chordae in ePTFE (W. L. Gore & Associates Inc., Flagstaff, AZ, USA) were used in the remaining. \begin{table}
\begin{tabular}{l c} \hline Age (Years) & 71 \(\pm\) 13 \\ Female & 20 (74) \\ BMI (kg/m2) & 23 \(\pm\) 5 \\ Euroscore II (\%) & 5 \(\pm\) 6 \\ Logistic Euroscore I (\%) & 10 \(\pm\) 11 \\ Diabetes & 5 (19) \\ eGFR (mL/min/1.73 m2) & 53 \(\pm\) 25 \\ Previous cardiac surgery & 4 (15) \\ LVEF (\%) & 62 \(\pm\) 9 \\ PAPs (mmHg) & 45 \(\pm\) 17 \\ MV dysfunction & \\ Re regurgitation & 20 (74) \\ Regurgitation and stenosis & 7 (26) \\ Moderate to severe tricuspid valve regurgitation & 9 (33) \\ MV disease etiology & \\ Barlow/FED & 18 (67) \\ Degenerative fibro-calcific & 4 (15) \\ Rheumatic & 3 (11) \\ Endocarditis & 1 (4) \\ Failure of previous repair & 1 (4) \\ \hline \end{tabular} SD: standard deviation; BMI: body mass index; eGFR: estimated glomerular filtration rate; LVEF: left ventricular ejection fraction; PAPs: pulmonary artery pressure, systolic; MV: mitral valve; FED: fibroelastic deficiency. Data are expressed as mean \(\pm\) SD or as n (\%).  
\end{table} 
Table 1: Preoperative characteristics (n = 27). \begin{table}
\begin{tabular}{l c} \hline \hline Calcium thickness & 4 (15) \\ 5-10 mm & 11 (41) \\ \(>\)10 mm & 12 (44) \\ Calcium distribution & \\ \(>\)180\({}^{\circ}\) & 10 (37) \\ 180\({}^{\circ}\)–270\({}^{\circ}\) & 12 (44) \\ \(>\)270\({}^{\circ}\) & 5 (19) \\ Trigones involved & \\ None & 20 (74) \\ One & 7 (26) \\ Two & – \\ Leaflets involved & – \\ None & – \\ One & 14 (52) \\ Two & 13 (48) \\ MAC CT grading & \\ Mild & 3 (11) \\ Moderate & 13 (48) \\ Severe & 11 (41) \\ \hline \hline MAC: mitral annular calcification; CT: computed tomography. Data are expressed as n (\%). \\ \end{tabular}
\end{table} 
Table 2: Calcium distribution and MAC CT grading (n = 27).