Discussion
Our findings confirm that RV systolic function was diminished in MS patients. S’, FAC, TAPSE, and RVFWS values were significantly reduced in MS cases compared with the control group. Furthermore, average PAP values were substantially increased in MS patients. In addition, S’ and TAPSE values were considerably lower in very severe MS patients compared with severe patients, which not only verify the relationship between MS and RV dysfunction, but also indicate that the severity of MS correlates with the extent of RV dysfunction and its echocardiographic markers.
Various imaging modalities have been utilized in order to diagnose MS patients with pre-symptomatic and subclinical RV failure. Tanboga et al. employed TDI and two-dimensional speckle tracking echocardiography in order to assess 59 MS cases (33 mild and 26 moderate patients)17. Even though they found no connections between FAC values of healthy controls and MS patients, markers such as RVFWS and strain rate demonstrated strong evidence of RV dysfunction in MS cases17. However, their subgroup analysis on mild and moderate patients did not show any correlations between the severity of the disease and the level of RV dysfunction. It is important to note that Tanboga et al. studied mild and moderate MS cases, whereas our study selected severe to very severe patients. The duration and degree of severity of the disease can affect the process of RV dysfunction, which might justify this divergence in findings. Thus, further studies on various degrees of severity and duration of MS with larger samples are required to shed more light on the relation of severity of MS with the degree of RV dysfunction. Similar studies have consistently demonstrated that declined TAPSE, S’, and RVFWS values are good predictors of early RV dysfunction but have not discussed the effects of severity of MS 4,6,18,19.
Even though our findings agree with previous studies, the pathophysiology of RV dysfunction is still debatable. Some studies have speculated that the initial rheumatic heart disease and its subsequent scarring process might directly damage the RV myocardium in MS patients, which could possibly lead to RV dysfunction and reduced RV ejection performance 20,21. On the other hand, according to recent studies, MS patients tend to have a passive elevated left atrial pressure, which results in pulmonary venous hypertension3,22. As a complication of longstanding MS, a retrograde passive increase in pressure contributes to elevated pulmonary arterial pressure 3. In time, this phenomenon alongside pulmonary arteriolar vasoconstriction and changes in the pulmonary microvasculature would subsequently lead to pulmonary artery hypertension, which increases RV afterload and results in RV dysfunction and right sided heart failure 3,22. A study by Ozdemir et al. provided evidence for the latter hypothesis by examining RV systolic function in 45 mild to moderate pure MS patients against 21 healthy individuals 6. Their results demonstrated that global RV strain and S’ are decreased in MS patients. They divided global RV strain into two regional components of interventricular septum (IVS) and RVFWS and showed that the rheumatic process does not influence the contractility of the RVFWS. In addition, their findings implied that RV dysfunction was more likely due to mild increase in PAP and its subsequent increased afterload. Even though we initially aimed to investigate the correlation of the degree of MS severity and echocardiographic parameters of RV function through multivariate analysis, irrespective of PAP values, our sample size restricted our analysis, and consequently multivariate analysis could not be performed distinctively on severe and very severe subgroups, in order to exclude the effect of PH and PAP. However, our results indicated that PAP has a significant correlation with RVFWS in MS patients, which was similar to the findings of Ozdemir et al. Many studies on PH have proven the correlation of increased PAP with RV dysfunction and have also shown the relation of echocardiographic impairments such as RVFWS with PAP and MS 12,23-28. Thus, RVFWS can be used as an early indicator of RV dysfunction in MS patients.
PH in MS patients is potentially reversible. Several studies have shown rapid improvements in echocardiographic variables such as TAPSE, FAC, and RVFWS after interventions such as percutaneous transvenous mitral commisurotomy, balloon mitral valvuloplasty, or mitral valve repair in MS patients 29-33. Future studies could investigate the possibility of early interventions in MS patients as soon as echocardiographic markers start to deteriorate (before the remodeling of RV and the appearance of clinical signs and symptoms), in pursuit of increased survival and quality of life in these individuals.