DISCUSSION
To the best of our knowledge, this is the first study to evaluate the
accuracy of multiple echocardiographic algorithms to estimate
PAPM and study diagnostic performance to identify PH in
the specific setting of HF. All 4
DE algorithms demonstrated reasonable association with RHC and good
agreement on Bland-Altman analysis, with generally lower bias seen in
methods interrogating the TR signal. Of the 4 methods, the Chemla et al
algorithm demonstrated comparable diagnostic performance with
TRVmax, both when employing ROC and sensitivity
analysis. However, none of the DE algorithms outperformed
TRVmax.
The accuracy of DE to estimate pulmonary artery pressures has been a
matter of debate. Earlier studies suggest that DE frequently over- or
underestimates invasive pulmonary pressures and should not be relied
upon.15 16 More recent studies, however, have
emphasized results of Bland-Altman analyses that display low bias
between echocardiographic PAPM and RHC, suggesting that
Doppler estimates are highly accurate.17 Our data
suggests that accuracy of DE estimates may also vary based on approach
utilized. Minimal bias was observed in methods that incorporated
TRVmax, corroborating an earlier study employing
high-fidelity catheters that suggests that such an approach, despite
being routinely used as an estimate of PAPS, provides
the most accurate estimate of PAPM.18Higher systemic bias with RHC and lower precision reflected in wider
limits of agreement employing both PI (Abbas et al7)
and RVOTAT (Dabestani et al12) seen in
this study may, at least in part, be attributable to smaller patient
cohorts (n = 23 and 39 respectively) and less severe clinical
presentations in the original studies. As seen in the Bland-Altman
plots, a greater dispersion of points is observed at higher mean values
of PAPM, suggesting that these methods may be less
reliable in the setting of severe PH. The cohort examined by Abbas et al
demonstrated a PAPM = 25 (range 10-57) mmHg and
PAWPM =15 (range 2-38) mmHg, suggesting a milder
hemodynamic presentation compared with the present
cohort.7 Dabestani et al do not present corresponding
values in their cohort, but suggest a PAPM range that is
relatively lower than that in our study with lower PH cut-off
(20mmHg).12 Additionally, the empirical algorithms
presented using this method may demonstrate limited utility in the
setting of severely elevated PAPM, as alluded to in
certain comparative studies evaluating multiple echocardiographic
approaches.13
Importantly, despite displaying relatively lower precision and agreement
with invasive measurements, both the above-mentioned methods
demonstrated good diagnostic ability to identify PH in our cohort.
Uninterpretable TR signals are frequent in HF,19 have
been reported in as many as 39% of subjects and may present a
limitation to echocardiographic evaluation of PH.20 In
our study, TRVmax could not be adequately assessed in
14% and VTI in 19% of patients, suggesting a potential diagnostic role
for methods that do not necessitate TR jet interrogation.
Early identification of PH in HF has direct consequences on treatment
and prognosis. Despite reasonable diagnostic ability demonstrated by all
echocardiographic algorithms, only the approach postulated by Chemla et
al8 demonstrated diagnostic ability comparable with
recommended 2.8m/sec TRVmax cut-off in both ROC and
sensitivity analysis. However, none of the methods outperformed
TRVmax. This finding is contrary to a recent comparative
report where the chosen DE algorithms showcased generally superior
performance as compared with TRVmax.13The authors suggest in the abovementioned study that DE algorithms that
consider estimates of right atrial pressure in addition to
TRVmax demonstrate generally stronger correlation with
invasive measurements and superior diagnostic performance when compared
with TRVmax. This was substantiated by data from their
study where right atrial pressure > 15mmHg estimated by
echocardiography demonstrated highest odds ratio for invasively
confirmed PH. In the setting of HF, echocardiographic estimates of right
atrial pressure are frequently falsely elevated and sole reliance on the
IVC to estimate RAP may be misleading.21 In our study,
30% of patients with echocardiographically estimated
RAPM = 15mmHg demonstrated normal corresponding invasive
pressures, suggesting that these estimates are frequently inaccurate and
may not necessarily contribute to stronger performance of derived
PAPM variables as suggested in certain derivation
cohorts7 and the comparative
study.13 Echocardiographic estimates of
RAPM have been incorporated into empirical derivations
of PAPM in all but one selected PAPMalgorithms in this study. This may play a role in the observed lower
performance when compared with TRVmax alone, but needs
to be further examined.
The use of fluid-filled catheters instead of high-fidelity
manometer-tipped catheters for pressure measurement might introduce
additional error and may be considered a limitation in this study.
Retrospective analysis of echocardiographic data did not permit a closer
inspection factors leading to lower feasibility of certain algorithms
included in this comparative analysis. Finally, we did not employ
agitated saline bubble contrast to strengthen TR jet signal as this is
not part of routine protocol in our laboratory.