Cardiovascular Journal of Africa: Vol 31 No 2 (March/April 2020)

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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 2, March/April 2020 AFRICA 79
mPAP, cardiac output and cardiac index, have been shown to
be significant predictors of survival time in PAH. In addition,
a range of other factors that reflect RV structure and function,
including echocardiographic parameters, exercise capacity and
serum biomarkers, have been shown to be of prognostic value.10-12
PwD is an easily calculated ECG parameter that has been found
to have a strong correlation with the haemodynamic parameters
shown to be of prognostic value. Our study also showed that PwD
is an independent predictor of functional status in PAH patients.
The 6MWD is currently the only exercise end-point accepted
by the Food and Drug Administration and European Agency
for the Evaluation of Medicinal Products for studies evaluating
treatment effects in PAH.13 It is a good indicator of prognosis 11
and has been shown to decrease in proportion to the severity
of World Health Organisation functional class, and to correlate
with cardiac output, total pulmonary resistance14 and changes in
PVR.15 A 6MWD ≥ 500 m should be the goal of therapy, while
a 6MWD ≤ 300 m should prompt intensification of treatment.13
Since we have a formula, we can easily calculate the 6MWD to
estimate the adequacy of treatment and prognosis of the patient.
In the setting of PAH and RV failure, when RV end-diastolic
volumes and pressures increase, increased RV wall stress leads to
reduced RV stroke volume. Elevated RV end-diastolic volumes
also cause tricuspid annular dilatation, which worsens tricuspid
valve insufficiency and increases atrial wall tension. Mercurio
et al. demonstrated that during the course of PAH, atrial
fibrillation is a predictor of a poor prognosis.16 PwD is a good
predictor of atrial fibrillation.5
Although there has been significant development in our
understanding of PAH and its management over the years, there
is a need for further studies. In particular, despite its importance,
the right ventricle has been less well studied, as have the processes
underlying pulmonary vascular remodelling and strategies to
modify it. There is still much to learn about the assessment of
right heart function, and we have not identified ideal alternate
markers for PAH. Catheterisation remains the gold standard, but
is invasive and complex. Evidence is accumulating for additional
measurements for predicting prognosis of PAH patients. PwD
is a more robust method of predicting prognosis in patients and
may be a directive to treatment.
Our study has some limitations. One is the small number of
patients because of the exclusion criteria of our study. However,
it was important for the correct patient selection to exclude
compounding factors and strengthen the study. In addition,
our study did not include follow up of patients to reveal their
prognosis. Finally, the correlations between echocardiography
and ECG (P-wave dispersion) were in some cases very low.
P-wave dispersion reflects the ‘invasive state’ of patients.
Conclusion
To the best of our knowledge, our study is the first investigating
the relationship between PwD, functional capacity and
haemodynamic parameters in PAH. PwD and mPAP obtained
by RHC were found to be independent predictors of functional
capacity in PAH patients. PwD is easily calculated from surface
ECG to indirectly estimate the invasive status and prognosis of
patients.
Special thanks go to Samet Emet for the English editing of our manuscript.
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