Results
Baseline characteristics
The baseline data of the patients were shown in Table 1. Compared with the mechanical MVR group, the bioprosthetic MVR group had a larger left atrium (49.5 [IQR, 46.0-55.5]mm vs. 46.0 [IQR, 40.3-48.9]mm, p<0.05), a larger thickness of the left interventricular septum (11.0 [IQR, 10.0-11.8]mm vs. 10.0 [IQR, 9.0-10.8]mm in the mechanical MVR group, p<0.05), and a smaller mitral ring area (2.3 [IQR, 2.0-2.6]mm2vs. 2.6[IQR, 2.4-2.9]mm2, p<0.05). There were no significant differences in left ventricular ejection fraction, left ventricular end-diastolic diameter and left ventricular end-systolic diameter between the two groups. There were no statistically significant differences in gender, age, blood pressure, BMI, laboratory parameters and co-morbidities between the two groups.
Electrophysiology study and ablation
The ablation strategies and results of the two groups were shown in Table 2. In the bioprosthetic MVR group, all the 12 patients underwent CPVA. The bilateral PVI rate was 100%. Seven patients underwent MI ablation with bidirectional MI block in 5 of the 7 patients (71.4%). Nine patients underwent CTI ablation with a 100% CTI block rate. In the mechanical MVR group, all the 58 patients underwent CPVA. Bilateral PVI was achieved in all the patients. MI ablation was performed in 36 cases (64.3%). Bidirectional MI block was achieved in 21 of the 36 cases (58.3%). Unidirectional mitral block was achieved in one case, and MI block was not verified in one case. Forty-seven patients (83.9%) underwent CTI ablation, bidirectional CTI line block was achieved in 44/47 (93.6%) patients. CTI block was not verified in one case. The prevalence of ethanol infusion in vein of Marshall was significantly higher in the bioprosthetic MVR group than in the mechanical MVR group (33.3%vs.0.0%, p<0.001). There was no significant difference of MI block rate between the two groups. There were 2 cases (3.4%) of pseudoaneurysm and 1 case of acute cerebral infarction in the mechanical MVR group. No complication was observed in the bioprosthetic MVR group.
Follow-up results
After a follow-up of median 23.4 (6.1, 36.5) months, the incidence of the endpoint events (33.3% vs. 30.4%) was not significantly different between the two groups (log-rank p = 0.48, Fig.1). One case (8.3%) had early recurrence in the bioprosthetic MVR group, and two cases (3.4%) had early recurrence in the mechanical MVR group (p = 0.964). As shown in Table 3, Cox univariate and multivariate regressions were used to identify risk factors for AF recurrence. Univariate analysis showed that blood glucose level was related to the recurrence of AF after catheter ablation (p = 0.039). However, there was no significant risk factor related to the endpoint event in multivariate analysis.
Eight patients had bleeding events with clinical symptoms in the mechanical MVR group, mainly manifested as hematuria and nasal hemorrhage, all of which used warfarin. The INR values were between 2.37 and 4.0 at occurrence of the bleeding events. No significant clinical bleeding events were observed in the bioprosthetic MVR group (p = 0.368).