Echocardiographic variables measured on study echocardiograms
| Index name | Description | Measurement | Study specific |
| Pulmonary artery acceleration time (PAAT) (Primary index) | A marker of pulmonary vascular resistance (inversely related). | Interval between the onset of ejection and peak flow velocity measured from a pulse wave Doppler tracing obtained by placing a 2 mm sample volume in the middle of the main pulmonary artery, at the tip of pulmonary valve leaflets. | In addition, the ratio of total right ventricular (RV) ejection time to PAAT is also measured as a heart rate independent measure of PVR (directly related). |
| Tricuspid annular plane systolic excursion (TAPSE) (primary index) | A marker of RV longitudinal systolic function. | Measure of the downward displacement of tricuspid annulus during contraction. | From an apical four-chamber view by placing M-mode cursor through the tricuspid valve annulus. |
| Two-dimensional peak global end-systolic longitudinal strain (pLS)—right ventricle (secondary index) | A measure of myocardial deformation expressed as percentage change in length in systole from the baseline at end diastole. | Performed offline using software, which uses frame to frame tracking of the unique ultrasound speckles within the myocardial wall. | Longitudinal strain will be calculated for RV lateral and inferior wall from RV apical four chamber and three chamber views, respectively. |
| Fractional area change (FAC-4C) % (secondary index) | A surrogate to ejection fraction and indicative of overall ‘pump function’. | Manual tracing of the RV endocardial borders at respective phases of the cardiac cycle. | From an apical four chamber view the end systolic area (ESA) and end diastolic area (EDA) are measured. FAC-4C (%) =((EDA-ESA)/EDA)x 100 |
| Tissue Doppler imaging (TDI) (secondary index) | Allows measurement of velocities directly from the myocardium to assess longitudinal systolic and diastolic RV function. | Measure the peak systolic and diastolic velocities, and duration of various phases of a cardiac cycle. | Measurements obtained at the RV basal segment. |
| RV peak systolic pressure (RVsP) (secondary index) | A direct measure of pulmonary artery systolic pressure. | Calculated by measuring peak velocity (v) of tricuspid regurgitation using the modified Bernoulli equation. RVsP=4v2+right atrial pressure. | Calculated whenever feasible. Right atrial pressure is predefined as 5 mm Hg in all cases. |
| Assessment of shunts (secondary index) | Patent ductus arteriosus and patent foramen ovale/ atrial septal defect. | Visualised on colour Doppler assessment. | Shunt diameter in millimetre and flow direction documented. |
| Flow patterns in main and branch pulmonary arteries (secondary index) | Presence of notching is considered a marker of high downstream resistance | Visualised on pulse wave Doppler | Presence or absence of midsystolic notching in the Doppler profile. |
PVR, pulmonary vascular resistance.