Introduction
Pulmonary hypertension is a rare disease that can have many long term
consequences including significant disability and
death1. Traditionally, echocardiography has been used
to identify patients with this disease because of its non-invasive
nature. Various indirect parameters demonstrated with echocardiography
can indirectly help quantify right ventricular systolic pressure
(tricuspid regurgitant velocity, ventricular septal defect velocity) or
mean pulmonary artery pressure (patent ductus arteriosus velocity, early
pulmonary regurgitation velocity); however for many patients, these jets
are insufficient or absent for quantification. In particular, the
tricuspid valve regurgitant velocity cannot be obtained in 30-54% of
pediatric echocardiograms performed for assessment of pulmonary
hypertension2-6. Qualitative assessment of the
position of the interventricular septum has been used to gauge whether a
right ventricle is “sub-systemic, half-systemic, or
supra-systemic”7-10. In patients with normal right
ventricular systolic pressures (RVSP), the septum bows towards the right
ventricle and the left ventricle is rounded in short axis during systole
(Figure 1B); whereas, in those with elevated RVSP, the septum is
flattened and can even bow into the left ventricle in suprasystemic RVSP
conditions. While used frequently, this qualitative assessment may yield
significant inter-reader and intra-reader
variability11. Another recently published
echocardiographic measure, the eccentricity index, which is the ratio of
the LV dimension parallel to the septum to the LV dimension
perpendicular to the septum is limited by dependence upon a normal left
ventricular geometry, precise placement of a perpendicular line through
the septum, and precision in timing the measurement within the cardiac
cycle12. Catheter-based measurements are the
gold-standard for assessment of RVSP because of their direct
measurements, however these procedures are invasive and have known and
potentially catastrophic complications13.
Given that septal position is frequently the only available method for
non-invasive assessment for elevated right ventricular pressures in many
children, a quantitative assessment of that curvature could be useful to
assist in the diagnosis and medical management of patients with
pulmonary hypertension. Some quantifications of septal position like the
left ventricular end-diastolic eccentricity index12and the septal flattening angle14 have been compared
with other echocardiographic measures of right ventricular systolic
pressure such as the tricuspid regurgitant jet velocity. The only other
quantifications of septal position to compare with gold-standard
catheterization direct-pressure measurements is the normalized septal
curvature9 and the eccentricity
index12.
The aim of this study was to create a novel semi-quantitative
measurement of septal positioning that was easy to perform,
reproducible, and accurate in identifying significant pulmonary
hypertension.