Impact of post-percutaneous mitral balloon valvuloplasty mitral valve area indexed for the body size on long-term outcomes in rheumatic mitral stenosis: a 20-year retrospective analysis
Authors: Songsangjinda T , Chichareon P , Suwanugsorn S , Nilmoje T , Thungthienthong M , Manoret P , Chamnarnphol N , Jintapakorn W 
Published: November 2023

Abstract

Introduction
Percutaneous mitral balloon valvuloplasty (PBMV) remains one of the standard treatments for symptomatic rheumatic mitral stenosis (MS)(1). The procedural success criteria are generally defined as a post-procedural mitral valve area (MVA) of more than 1.5 cm2 without significant mitral regurgitation or in-hospital complications(2, 3). However, the effect of body size on the post-procedural MVA is not well examined.

Purpose
This study intended to investigate the association between the different methods of indexing post-PBMV MVA for the body size parameters and event-free survival compared to the absolute MVA in rheumatic MS patients treated with PBMV.

Methods
We retrospectively enrolled clinically significant rheumatic MS patients (MVA ≤1.5 cm2) who underwent PBMV with Inoue balloon between June 2002 and February 2021. The patients who experienced in-hospital complications (stroke, emergency surgery, or death) were excluded. A final number of 584 out of 618 patients were included in the analysis. Post-procedural MVA was assessed using echocardiographic 2D planimetry or pressure half-time if planimetry was not available. Post-PBMV MVA was indexed by body surface area (BSA), body mass index (BMI), body weight or height. The median value of absolute MVA and indexed MVA was used to stratify patients into two groups. The primary outcome was the composite of death, repeat PBMV, and mitral valve surgery. We performed Cox regression analyses to assess the association between groups and outcomes. C-index was calculated to assess the discriminative ability of each index.

Results
The mean age was 41.5 (±11.9) years, and 490 patients (82.8%) were female. The prevalence of atrial fibrillation was 39.5%. The median Wilkin score was 8 (interquartile range of 7-9). The mean pre-procedural and post-procedural MVA was 0.92 (±0.24) and 1.57 (±0.28) cm2, respectively. The average pre-procedural and post-procedural mean pressure gradient was 13.1 (±6.3) and 5.7 (±3.0) mmHg, respectively. The prevalence of post-procedural MR in a moderately severe to a severe degree was 3.8%. Over a median follow-up of 3.9 years, 194 composite events occurred. Patients with post-procedural indexed MVA of any type greater than a median were not associated with a significantly lower risk of primary outcome compared to those with indexed MVA less than the median (Picture 1). Moreover, absolute MVA greater than a median (1.55 cm2) was independently associated with a lower risk of primary outcome after adjusting with age and gender (Hazard ratio [95% CI] = 0.658 [0.493-0.879], p = 0.005). The discriminative ability of the absolute MVA was highest than the indexed MVA (Picture 2).

Conclusion
Indexing post-procedural MVA did not provide additional benefit on long-term risk stratification after PBMV compared with the absolute MVA.