Discussion
The role of echocardiography in detecting cardiovascular abnormalities
is increasing worldwide (4,
13). Considering the cost effectiveness
of non-invasive echocardiography modality , it could be an alternative
screening tool in detecting or excluding PHTN if it is proven to have
acceptable adequacy (4). The aim of this
study was to assess the properties of the hepatic vein Doppler signal as
an echocardiographic parameter in detecting PHTN. Because hepatic vein
is affected by RV function besides PHT; we divided our PHTN patients
into two groups based on RV dysfunction, including PHTN with significant
RV dysfunction and PHTN without significant RV dysfunction
The normal flow-pattern in the middle HV is phasic, in which the most
predominant velocities are antegrade. Pulsed-wave Doppler assessment
describes 3–4 distinct waveforms after atrial contraction: (1) large
systolic antegrade wave (negative velocity) (S-wave); (2) small
retrograde late systolic wave (positive velocity) (V-wave), (3) early to
mid-diastolic antegrade wave (D-wave), (4) late diastolic retrograde
wave (A-wave) (14).
In our study 13 cases in normal group, 16 cases in PHTN without
significant RV dysfunction and 11 cases in PHT with significant RV
dysfunction had all 4 distinct waveforms and 12 cases in normal group,
11 cases in PHT without significant RV dysfunction and 11 cases in PHT
with significant RV dysfunction had 3 distinct waveforms (absent V
wave). The findings of the current study revealed that A velocity , A/S
were significantly higher in PHT group with and without significant RV
dysfunction compared to normal group, while S/S+D and S/D were
significantly higher just in PHT with significant RV dysfunction
compared to normal group. It was previously reported that the systolic
wave is diminished in PHT and therefore S is reduced. A/S, A/(S+D),
AVTI/(SVTI+DVTI) were positively correlated with mPAP
(3). It was previously shown that PHT
group had higher A velocity ;VTI A ;VTI A/VTI S+VTI D were higher in
PHTN patients compared to healthy controls
(14). Inclusion of patients with PHTN
with and without significant RV dysfunction in this study enabled us to
evaluate the effect of RV dysfunction on PHTN.
The differences between the findings of our study and previous studies
is may be due to dividing the PHT patients based on RV function and also
exclude patients with severe TR(table2). Based on the findings of our
study, it can be hypothesized that increase in SPAP increased RV
afterload, which may lead in chamber remodeling and increased in muscle
mass. Increased RV end diastolic pressure (RVEDP) is the hemodynamic
consequence of RV hypertrophy. As RA pressure is not reduced at this
point, the duration of backflow in IVC and the HV persists will be
longer compared to the backflow across the Tricuspid valve. Therefore, a
large A-wave in terms of duration and velocity is observed in HV Doppler
assessment. Therefore, A/S also
increases to values higher than 1 in PHTN even at early stages.
This pattern was the main finding
on HV Doppler assessment in PHT with and without significant RV
dysfunction(table2). When RV longitudinal motion is significantly
reduced, the S wave is blunted or reduced in HV Doppler with consequent
re-emergence or increase in D velocity .Therefore, S/S+D and S/D could
only differentiate normal PAP from PHT with significant RV dysfunction
and thus may not be useful in differentiating normal SPAP from PHT
without RV dysfunction that is not an issue in previous echo study.
Furthermore, as evidenced by the findings of the current study,
increased D and decreased S values in PHT patients with RV dysfunction
magnifies the changes due to RV function and the S/D might detect
significant RV dysfunction earlier compared to other echocardiographic
parameters(table2).
The findings of this study revealed that A wave velocity and duration
could be a predictor for PHT patients regardless of RV dysfunction
although the result for the A wave duration was not statistically
significant in PHT patients. It was previously reported that in PHTN
patients, the peak A wave velocity significantly increases compared to
healthy individuals, which was in line with the findings of the current
study (7). As A velocity is a determinant
of RV filling function, combination of RV dysfunction and PHTN will
result in significant change in A velocity that may make it a better
marker for determining RV function in PHTN patients compared to other
echocardiographic parameters in the current study (table2)
(15). It was previously shown that the
use of parameters that are calculated based on dividing A, S, and D
including A/S, A/(S+D) and AVTI/(SVTI+DVTI) could be more sensitive in
detecting PHTN compared to A, S, and D alone
(6, 16,
17). This finding was in line with the
finding of the current study.
The findings of this study also revealed that hepatic venous systolic
filling fraction had an acceptable sensitivity in detecting normal SPAP
patients from PHT patients (80%), while its specificity was low (64%).
Similar sensitivity and specificity were found hepatic venous systolic
filling fraction in detecting normal RV function in PHT patients
(table2). It was previously reported that hepatic venous systolic
filling fraction less than 55% had 86% sensitivity and 90%
specificity in detecting PHTN (7). The
difference between the findings of this study and the finding of latter
studies may be due to the effect of RV function and TR severity on
echocardiographic parameters(table2). The high sensitivity of hepatic
venous systolic filling fraction in detecting normal PAP indicates that
this marker can be appropriate in ruling out PHTN but due to its low
specificity, this marker could not be used as a diagnostic marker for
PHT. There is a need for further studies to confirm these findings.