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.