P915Clinical characteristics, natural history and predictors of disease progression in patients with degenerative mitral stenosis
Authors: Kuyama N , Hamatani Y , Okada A , Yanagi Y , Jo Y , Amano M , Takahama H , Amaki M , Hasegawa T , Kanzaki H , Yasuda S , Izumi C 
Published: October 2019

Abstract

Background
Mitral annular calcification (MAC) is a common echocardiographic finding and an increasingly recognized cause of degenerative mitral stenosis (DMS). However, little is known about the natural history and predictors of disease progression of DMS, especially compared with rheumatic mitral stenosis (RMS).

Purpose
To compare the clinical characteristics and disease progression among patients with DMS and those with RMS, and to investigate the determinants of disease progression in DMS patients.

Methods
We retrospectively reviewed consecutive MS patients with a trans-mitral mean gradient ≥2 mmHg who underwent echocardiography at our institution between January 2014 and December 2017. We selected patients who had an initial and follow-up echocardiography with a ≥3-month interval and without prior and interim mitral valve intervention. DMS was defined as MS with MAC with normal or minimally reduced leaflet motion without tips restriction. RMS was defined as MS with tip restriction, thickening and restriction of leaflet mainly. We defined MAC severity as mild (focal), moderate (marked density >1/3 but <1/2 of the mitral annulus) and severe (marked density involving >1/2 of the mitral annulus) based on previous reports. We calculated disease progression from the annual increase rate of trans-mitral mean gradient. First, we compared the backgrounds and disease progression between DMS group and RMS group. Second, we investigated the predictors of disease progression in DMS group.

Results
We enrolled 111 patients (64 in DMS group and 47 in RMS group) with a mean follow-up period of 2.1 years. Patients in DMS group were significantly older (79±9 vs. 70±10 years; P<0.01), had higher prevalence of hypertension (P<0.01) and coronary artery disease (P=0.02), and had higher plasma BNP level (P<0.01) than those in RMS group. Baseline trans-mitral mean gradient was slightly lower in DMS group than in RMS group (3.9±1.9 vs. 4.7±1.8 mmHg; P=0.02). There were wide variations among individuals in progression rate (range: 0 to 3.5 mmHg/year in DMS group and 0 to 5.8 mmHg/year in RMS group, respectively), and the progression rate was comparable between DMS group and RMS group (0.49±0.79 vs. 0.61±1.37 mmHg/year; P=0.59). In DMS group, higher prevalence of dyslipidemia (P=0.01) and lower baseline trans-mitral mean gradient (P<0.01) were significantly associated with disease progression even after adjustment for age and sex. Unexpectedly, there was no significant difference in the disease progression regardless of the MAC severity among DMS group (Picture).
MAC severity and disease progression

Conclusions
Progression in DMS group is highly variable, but generally slow as that in RMS group. Initial mean gradient was inversely associated with disease progression in DMS group. Furthermore, baseline MAC severity did not correlate with the progression, suggesting the importance of follow-up echocardiography in spite of the MAC severity and initial mean gradient.