We performed a prospective case control study from December 2014 to November 2016. Twenty-nine patients satisfying the inclusion criteria were studied and underwent detailed echocardiographic assessment pre- and post-balloon mitral valvotomy. Sample size was calculated with alpha of 1%, clinical significant difference (d) of 2, and power of 90% using the following equation:
$$ ``n-2\left(z1-\alpha /2+z1-\upbeta \right)2\ \delta 2/\mathrm{d}2" $$
A sample size of 29 was reached based on the above formula.
Patients with severe rheumatic mitral stenosis in normal sinus rhythm with valve suitable for BMV and who underwent successful BMV were included in the study. Patients in atrial fibrillation (during hospitalization for BMV or history of AF or paroxysmal AF), more than mild mitral regurgitation (MR), aortic regurgitation (AR), diabetes mellitus, hypertension, and renal failure were excluded from the study. Control group included 30 age- and sex-matched healthy volunteers.
Balloon mitral valvotomy
Indications for BMV in mitral stenosis included symptomatic severe mitral stenosis (New York Heart Association class II–IV and mitral valve area calculated by planimetry ≤ 1.5 cm2), less than grade 2+ mitral regurgitation, and favorable morphology of mitral valve. All patients underwent balloon mitral valvuloplasty using Inoue balloon method. Successful BMV procedure was defined as achieving either a final MVA > 1.5 cm2 or increase in MVA by 40% and mitral regurgitation grade ≤ 3+ [1]. None of the patients who underwent BMV had any peri-procedural or post-procedural complications.
Echocardiographic examination
The measurements were performed echocardiographically using the Philips Epiq 7c system. All the parameters were taken by a single person to avoid observer bias. The area of mitral valve was calculated using 2D planimetric method. Continuous-wave Doppler was used to measure the gradients across the mitral valve and pulmonary artery systolic pressure.
Post-BMV mitral valve area, pulmonary artery pressure, mean mitral gradient, and global LA strain were measured 24–48 h after procedure. Delta (Δ) was used to define the absolute changes in the valve area and gradients across the mitral valve pre- and post-BMV.
$$ {\displaystyle \begin{array}{l}\varDelta \mathrm{Mitral}\ \mathrm{valve}\ \mathrm{area}=\mathrm{post}-\mathrm{BMV}\ \mathrm{MVA}\ \mathrm{value}-\mathrm{pre}-\mathrm{BMV}\ \mathrm{MVA}\ \mathrm{value}\\ {}\varDelta \mathrm{Mean}\ \mathrm{mitral}\ \mathrm{gradient}=\mathrm{post}-\mathrm{BMV}\ \mathrm{MMG}\ \mathrm{value}-\mathrm{pre}-\mathrm{BMV}\ \mathrm{MMG}\ \mathrm{value}\end{array}} $$
Speckle tracking
For speckle tracking, apical four-, three-, and two-chamber views were obtained using standard 2D gray scale echocardiography with breath hold and stable electrocardiographic recording. The average of three cardiac cycles was recorded. The frame rate was set at 60–80 frames/s. These settings are recommended to combine temporal resolution with adequate spatial definition and to enhance the probability of the frame-frame tracking technique [2]. During offline image analysis of 2D cine loops with deformation study, 2D left atrial wall in apical four-, two-, and three-chamber views were tracked in semi-automated method. Offline analysis of the recorded images was analyzed by a single experienced echocardiographer who was not involved in image acquisition and had no knowledge of other echocardiographic variables using Philips automated cardiac motion quantification (ACMQ) software.
First, the endocardial left atrial surface was traced manually using the point and click method in apical four-, three-, and two-chamber views, following which epicardial surface was traced automatically by the software system creating a region of interest involving the entire myocardial thickness. Lastly, the system generates two strain curves for each atrial segment. In total, 12 segments were analyzed after acquiring decent image quality (Fig. 1). In sinus rhythm, atrial strain shows two distinct wave forms, peak atrial longitudinal strain (PALS) and peak atrial contraction wave. In the present study, we measured global PALS, i.e., average of PALS in all segments of left atrium (Fig. 2). According to the current American Society of Echocardiography/European Association of Echocardiography Consensus, the global positive PALS was measured at the end of the reservoir phase using a 12-segment model and QRS onset as the reference point before and after the procedure.
Statistical analysis
SPSS.v.16.0 software was used for analyzing statistics. Continuous variables were expressed as mean +/− SD. Categorical data were analyzed using chi-square test. Differences between groups (case vs control) were evaluated with independent t test. Differences between the cases (pre-BMV vs post-BMV) were compared using paired t test. p value, i.e., level of statistical significance, was set at < 0. 05.
