3. RESULTS
The baseline characteristics and pre-operative TTE data, including MR
etiologies, are listed in Table 1. The mean age was 62 ± 13 years, and
105 (61%) patients were men. The mean value of the LV ejection fraction
was 64.6 ± 8.7%. A large proportion (87%) had a prolapse of the
anterior and/or posterior mitral leaflets due to fibroelastic deficiency
as the main etiology of MR. Fifteen patients experienced new onset AA
events, including paroxysmal or persistent AF and AT during the
post-operative follow-up period, with a median of 35.7 months (range,
0.5 to 132 months). No significant difference was found in baseline
characteristics between patients who experienced post-operative AA
events and those who didn’t. Table 2 shows the data for the surgical
procedure. There were no significant differences in any pre-operative
TTE parameter between the two groups, including the MR etiology, extent
of mitral valve lesions and aorto-mitral angle (135 ± 11 degrees vs. 131
± 12 degrees, P = 0.29). The cardiopulmonary bypass (CPB) time was
longer in patients who had post-operative AA events than in patients who
didn’t (195 ± 69 min vs. 168 ± 53 min, P = 0.035). The post-operative
TTE data are listed in Table 3. The patients who experienced
post-operative AA events had a smaller aorto-mitral angle at the
post-operative TTE than the patients who didn’t (119 ± 6 degrees vs. 125
± 10 degrees, P = 0.003). There was no significant difference in the
grading of residual MR or the mean TMPG between the two groups.
The univariate Cox proportional hazards analyses revealed that the CPB
time and the aorto-mitral angle at the post-operative TTE were
significant predictors of the post-operative AA events
among all demographic, procedural
and echocardiographic parameters. A multivariate Cox proportional
hazards analysis revealed that the CPB time (odds ratio 1.12 per 10
minutes; 95% CI 1.03-1.21; P = 0.008) and the aorto-mitral angle at the
post-operative TTE (odds ratio 0.92; 95% CI 0.86-0.98; P = 0.014) were
the independent predictors of the new onset AA events (Table 4). The
area under the ROC curve of the aorto-mitral angle to predict the new
onset AA event was 0.717 (Figure 2). One-hundred and seventeen degrees
was the optimal cutoff value of the post-operative aorto-mitral angle
for predicting the post-operative AA events with a sensitivity of 57%
(95% CI, 29-82%) and a specificity of 80% (95% CI, 73-86%). Figure
3 shows the Kaplan-Meier event-free curves in patients stratified based
on the post-operative aorto-mitral angle. The post-operative AA
event-free rate was higher in patients with the post-operative
aorto-mitral angle > 117 degrees than in patients with the
post-operative aorto-mitral angle ≤ 117 degrees.
We additionally analyzed the determinants of the small post-operative
aorto-mitral angle (≤ 117 degrees). TMPG > 3mmHg (odds
ratio 2.53; 95% CI, 1.19-5.37, P = 0.016) was the only determinant of
the small post-operative aorto-mitral angle among the post-operative
echocardiographic parameters.