Discussion
In the present research, we observe that cirrhotic patients without PAH
have higher PAS values than healthy subjects, which may indicate an
early change in the pulmonary vascular bed among these cases. To our
knowledge, this should be the first study demostarating higher PAS
values in cirrhotic patients.
Nowadays, the average life expectancy of cirrhotic patients is prolonged
due to early diagnosis and effective treatment modalities. However,
complications related to portal hypertension, which is the main cause of
mortality, are frequently observed. (1-4). Portal hypertension is
included in the WHO PAH group I; PAH caused by portal hypertension is
termed PoPH. Even though the underlying pathophysiologic mechanisms of
PoPH are somewhat complex and not fully understood, it is hypothesized
that the passage of some vasoconstrictive substances, mainly serotonin
and endothelin-1, into the lung circulation with portosystemic
collaterals and shunts is the main mechanism of developing PoPH (14).
Another possible explanation is that thrombi caused by venous
thromboembolism can enter the lung circulation through shunts, thereby
resulting in PAH (15, 16). Furthermore, hyperdynamic circulation in
cirrhotic patients can cause excessive blood flow to the lung
circulation, which may promote PAH formation (15). All in all, it is
still not clear why PoPH develops in a small proportion of cirrhotic
cases with PH.
In previous studies, although different rates have been reported, PoPH
was detected in 1-2% of cases with PH and in 5-10% of cases who were
candidates for liver transplantation (7, 16). These findings highlight
that cirrhotic patients should be evaluated more carefully for the
development of PoPH and that a screening plan is needed. In a recent
analysis, the importance of early recognition for PAH was noted, and
some echocardiographic parameters, including PfAT, RV isovolumic
relaxation time and Tei index, were suggested (17). However, measuring
such parameters is quite time consuming. In a prospective study that
included patients waiting for liver transplantation, 7 out of 17
patients with an echocardiographic diagnosis of PAH were demonstrated by
right heart catheterization (RHC) to not show PoPH. In that study, there
was a 10 mmHg greater difference between RHC and echocardiographic sPAP
(18). In this reseach, there was also no significant dissimilarities
between the groups in terms of sPAP. Because the pulmonary vascular bed
has high capacitance property, sPAP does not usually develop until the
loss in microcirculation reaches 60-70%. After this threshold is
exceeded, clinical findings occur and sPAP increases (19). Therefore, we
consider that using only echocardiographic measurements of sPAP may be
misleading for early diagnosis among these patients.
PAS, which is a simple and easy echocardiographic parameter to
determine, is found to be linked with a worse survival in PAH patients
(20). In addition, an independent and significant relationship between
PAS and RV dysfunction has been demonstrated (21). Previously, PAS was
shown to be an significant determinant in the occurrence of PAH in
subjects with chronic lung disease (10), as well as an early
prognosticator of RV dysfunction in patients with systemic lupus
erythematosus and HIV (9,12). However, to our knowledge, no prior
research has examined the PAS in cirrhotic patients. This might be the
first study to show that the PAS values are significantly elevated in
subjects with cirrhosis comparing in healthy participants. Moreover, PAS
was an independent predictor that was associated with cirrhosis disease
according to multivariate logistic regression analysis. Additionally, we
detected a positive correlation between PAS and sPAP values and a
negative correlation between PfAT and sPAP values, while observing that
there was no difference in terms of PAS values between clinically
compensated and decompensated cirrhotic patients.
Our study results are important and valuable in terms of clinical
perspectives. Because most cirrhotic patients are usually asymptomatic
at the time of recognition of PAH, early diagnosis facilitates treatment
as well as reduces the mortality risks in such patients. Similarly, no
clear PAH was observed among the cases we investigated; however, the
cirrhosis group had higher PAS values. Therefore, we believe that PAS
may show us transitions in the pulmonary vascular region before the
development of significant PAH.