Immediate impact of percutaneous transvenous mitral commissurotomy on right ventricular function

Background and Aims: Abnormal Right Ventricular (RV) function affects the long term outcome and clinical symptoms in patients with mitral stenosis (MS). This study evaluates the immediate effect of Percutaneous Transmitral Commisurotomy (PTMC) on RV function. Methods: An observational, cross sectional study was done on 50 patients with rheumatic MS who underwent PTMC at Shahid Gangalal National Heart Center from Dec 2015 –Dec 2016. All underwent clinical evaluation and echocardiogram before and immediately after PTMC. Results: There was female preponderance with 66% being female. The mean age was 37.26 ± 10.63 years. There was immediate increase in the mitral valve area (MVA) from 0.87 ± 0.12cm2 to 1.54 ± 0.27cm2(p< 0.001). There was significant decrease in mean mitral diastolic gradient from 16.4 ± 8.8mmHg to 5 ± 1.5mmHg (p< 0.001), in the pulmonary artery systolic pressure 53.6 ± 21.83mmHg to 39.5 ± 14.67mmHg (p< 0.001), in the RV Tei index from 0.56 ± 0.08 to 0.40 ± 0.08 (p< 0.001). There was significant increase in TAPSE from 16.0 ± 1.50 to 18.6 ± 1.70 mm, (p<0.001) and the longitudinal velocity of excursion of the RV at the tricuspid annulus (RV S’) from 13.69 ± 3.33 cm/sec to 15.31 ± 3.07 cm/sec (p< 0.001) Conclusions: Successful PTMC can improve RV function as shown by the improvement in PASP, RV Tei index, TAPSE and RV S’. Further larger population studies are required to confirm the findings. Long term studies are important to determine the prognostic significance of improvement in RV function.


Introduction
Mitral Stenosis (MS) is the commonest of all rheumatic heart disease. 1 It is a mechanical disorder and natural history is significantly altered with an improvement in mortality by intervention with Percutaneous Transmitral Commisurotomy (PTMC) or surgery. 2,3,4he RV function is an important determinant of clinical symptoms, exercise capacity, pre-operative survival and postoperative outcome in these patients. 5MS leads to increase in left atrial pressure due to the back pressure, results in passive rise in pulmonary venous and arterial pressures and causes RV dysfunction. 6RV dysfunction is also due to rheumatic process when it involves the myocardium, thus directly impairs RV function. 7he Echocardiographic parameters of RV function are RV ejection fraction, RV fractional area change, RV total ejection isovolume index (Tei index) and tricuspid annular plane systolic excursion. 8RVTei index may be more effective for analysis of global cardiac dysfunction than systolic and diastolic measure alone. 9ince its introduction in 1984 by Inoue et al. 10 PTMC is a safe and effective treatment for rheumatic MS and is treatment of choice in patients with a favorable anatomy. 11,12,13PTMC has been performed regularly in Shahid Gangalal National Heart Centre for the last 17 years. 14,15,16Till now there is no data regarding the impact of PTMC on the RV function in our population.Thus we aim to study the impact of PTMC on RV function.
This was a cross sectional single center hospital based study.The study population included 50 consecutive patients admitted in Shahid Gangalal National Heart Center with the diagnosis of Mitral Stenosis for PTMC.Ethical approval was taken prior to the conduct of the study and informed consent was taken.The study period was from December 2015 to June 2016.The sample size was calculated using the proportional formula.
The following were the inclusion and exclusion criteria

Study Protocol:
The ethical clearance was taken prior to conduct the study from the ethical committee.Informed consent was taken from all the patients before the procedure.Detail clinical evaluation and echocardiogram was done.All patients underwent following examination: 1. History, physical examination and cardiovascular examination 2. Electrocardiogram (ECG) 3. Chest roentgenogram 4. Baseline blood investigation 5. Echocardiogram Echocardiographic measurements Two-dimensional (2D) echocardiography and Doppler studies were performed before and immediately after PTMC within 24 hour.The same echocardiographer performed all measurements using the recommendations of the American Society of Echocardiography. 17Mitral valve area (MVA) was determined by planimetry in every patient.The peak and mean mitral valve transannular pressure gradients and late filling velocities were measured using the Bernoulli principle from continuous wave Doppler recordings through the centre of mitral inflow.Systolic pulmonary artery pressure was derived from the tricuspid regurgitant jet peak velocity using the modified Bernoulli equation (peak gradient 4V 2 , where V is the maximal velocity of the tricuspid regurgitant jet).
Tricuspid Annular Plane Systolic Excursion (TAPSE): It was determined by the difference in the displacement of the RV base during systole and diastole.TAPSE was acquired by placing an M-mode cursor through the tricuspid annulus and measuring the amount of longitudinal motion of the annulus at peak systole. 18 Tei Index: In apical 4 chamber view a sample volume (Pulsed wave Doppler) placed at the tricuspid valve.RVTei Index calculated as the sum of isovolumic contraction time (IVCT) and isovolumic relaxation time (IVRT) divided by ejection time (ET).

Percutaneous transveneous mitral commissurotomy
All patients underwent PTMC by the technique described by inoue et al by the antegradetranseptal approach. 20The nominal diameter was decided according to the height of the patient [i.e height (cm)/10 + 10 = balloon diameter]. 21

Statistical analysis
The calculations were done by Microsoft Excel 2007 and Statistical Package for Social Sciences, SPSS version 20; and the data were presented in the form of tables and diagrams.Categorical value was expressed as percentage.Continuous variable expressed as measured as mean +/-SD.Normal distribution of our population was checked by Shapiro-Wilk test and was found to be normally distributed.Significance of the results pre and post PTMC was analyzed employing student's paired t-test.A P-value <0.05 was considered statistically significant.

RESULT
The mean age was 37.26 ± 10.63years.Table 1 shows the baseline characteristics of the patients who underwent PTMC.Sixty six percent of the total was female and 34% were male.There was no significant difference with respect to height, weight, BMI and BSA among both sexes.The history of rheumatic fever prophylaxis was present in 39% of the total patients.Past history of surgery was present in 6% of the patients.Fourteen percent of them had previous PTMC.Atrial fibrillation was present in the presenting ECG in 46% of the patients.Nepalese Heart Journal 2017; 14(2): 19-24    Left heart parameters among the patient who underwent PTMC was shown in table 4.There was significant change in mean mitral valve area (0.87 ± 0.12 to 1.54 ± 0.27) cm2(p< 0.001) which turns out to be approximately 66% increase in the MVA.The mean transmitral gradient was decreased by 69% (16.4+8.8 to5+1.5)mmHg.The LVESd, LVEDd, LVEF, IVS remained stable which were statistically not significant.Table 5 shows the changes in the right heart dimension after PTMC.The decrease in RA area was not statistically significant.The decrease in RVOT and RV dimension was significant.
Hemodynamic changes and the changes in the RV parameters after PTMC was shown in Table 6.There was no any significant change in the right atrial pressure.There was significant reduction of the pulmonary artery systolic pressure (53.6 ± 21.83 to 39.5 ± 14.67) mmHg (p< 0.001) approximately by 26%.There was significant slight increase TAPSE from 16.0 ± 1.50mm to 18.6 ± 1.70 (p< 0.001).Doppler index for global right ventricular function immediately after PTMC showed significant reduction of the index (0.56 ± 0.08 to 0.40 ± 0.08) (p< 0.001).The longitudinal velocity of excursion of the right ventricle at the tricuspid annulus termed RV S' also showed significant improvement (13.69 ± 3.33 to 15.31 ± 3.07)cm/sec (p< 0.001).

Discussion
Right ventricular function impairment in mitral stenosis occurs both due to the myocardial disease process and increase in RV afterload.Abnormalities of the RV function play a significant role in the development of the overall symptoms and prognosis of mitral stenosis.Assessment of RV function is therefore an important in evaluation of mitral stenosis particularly after a procedure.Because of its trapezoid anatomy this assessment is particularly difficult.There are different techniques put forwarded for assessment however none of them is the gold standard.In practice most relies on the two modalities: two-dimensional echocardiography and DTI echocardiography.TAPSE is considered to reflect the global systolic function. 18,22,23The tei index reflects both systolic and diastolic function. 23he findings in our study show that patients with MS have depressed global and regional RV function as shown in table 4.These findings are in accordance with previous radionuclide and haemodynamic studies. 5There are no any conclusive explanation of such dysfunction and is controversial. 24ome studies conducted earlier and paper published suggests that the rheumatic pathologic process may directly affect the myocardium to cause dysfunction. 25,26There has been histomorphological studies of rheumatic heart disease which showed that intramyocardial branches of coronary vessels were involved in a form of active rheumatic vasculitis or inactive lesions characterized by medial hypertrophy and replacement fibrosis.They believe this might contribute to the dysfunction seen. 26he other factor that might cause RV functional impairment is the increase in LA pressure that acts passively to increase pulmonary artery pressure and reactive changes in pulmonary arteriolar resistance may lead to increased RV afterload and RV failure. 27ur study showed significant increase in TAPSE from 16.0 ± 1.50 to 18.6 ± 1.70 mm, p<0.001.This result is comparable to the study done by Ragab et al. 28 in which they found the TAPSE increased significantly after PTMC from 17.1 ± 2.1 to 19.1 ± 2.5, p<0.05.There has been mixed findings in other studies.The study done by Bensaid et al. 29 and Drighil et al. 8 noticed a non significant change in TAPSE after PTMC.
Our study shows there is significant decrease in RV Tei index (table 6) which shows improvement in both systolic as well as diastolic RV function post PTMC.We observed that the RV Tei index decreased after PTMC from 0.56 ± 0.08 to 0.40 ± 0.08, p< 0.001.This findings was comparable to the study done by Drighil et al 8 where they found RV Tei index decreased from 0.44 ± 0.25 to 0.29 ± 0.17(p<0.001)and Kundu et al. 30 found the decrease in RV Tei was from 0.50 ± 0.10 to 0.30 ± 0.10 Nepalese Heart Journal 2017; 14(2): 19-24 (p<0.001).In one of the study conducted by Borges et al. 31 who demonstrated an improvement in Tei index after vasodilatator therapy in patients with chronic pulmonary hypertension.

PASP:
Our study showed significant decrease in the PASP from 53.6 ± 21.83 to 39.5 ± 14.67 (p<0.001).the study conducted by Drighil et al 8 showed reduction of PASP from 46.4 ± 32.1 mmHg to 29.1 ± 13.4 mmHg ( P = 0.02).Kundu 30 et al showed reduction from 47.7 ± 7.9 to 28.2 ± 5.9 (p<0.001).Similar results were also seen in other studies conducted by Mohan JC et.al. 5 Systolic excursion velocity (RV S') In our study the there was significant improvement in the systolic excursion velocity from 13.69 ± 3.33 to 15.31 ± 3.07 (p<0.001).Bensaidet al. 29 observed a non-significant increase in tricuspid annular systolic myocardial velocity.Drighilet al. 8 found that systolic myocardial velocity did not change immediately after PTMC.
Small sample size and no long term follow up are the main limitation of this study.

Conclusion
The study shows that there is improvement in RV functions after the after load reducing procedure such as PTMC.Further studies with large population needs to be done to confirm the results of this study and also to assess its utility in follow up, prognosis and long term benefit.
Inclusion Criteria: Patients admitted in SGNHC, irrespective of age & sex with the diagnosis of symptomatic mitral stenosis that subsequently undergone PTMC (fulfilling criteria of indications).Exclusion criteria: • Patients with contraindication for PTMC • Systemic hypertension • Diabetes Mellitus • Patients with documented coronary artery disease requiring surgical revascularization • Chronic lung disease • New York Heart Association functional class IV.

Table 1 :
-Baseline characteristics of the patients with Mitral Stenosis undergoing PTMC

Table 2 :
Presenting complaints of the patients

Table 3
shows more than half of the patients were in NYHA functional Class III 26 (56.0%) followed by class II 22 (44.0%).After procedure, 14 (28.0%) of the show symptoms of class I, 20 (40.0%) in class II and 16 (32.0%) in class III.

Table 3 :
NYHA functional class pre and post PTMC

Table 5 :
-Echocardiographic data of right heart dimension of Pre and post PTMC

Table 6 :
Hemodynamic function and RV parameters between pre and post PTMC RA-right atrium, PASP-pulmonary artery systolic pressure, TAPSE-tricuspid annular plane systolic excursion