Echocardiographic Assessment
Most echocardiograms were performed on a Philips IE33 system (Philips Medical Systems, Andover, Mass. USA) with an age and size appropriate probe (S8 or S12). The small remainder were performed on GE Vivid Q (General Electric Corporation, Milwaukee, USA) with an age and size appropriate probe. Atrial septal Doppler assessment was performed from a subcostal view; pulmonary artery band Doppler interrogation were usually obtained using a high parasternal view and interrogated with continuous wave Doppler.
On each of the echocardiograms, the atrial septal Doppler along with each pulmonary artery band Doppler was reviewed. The atrial septal Doppler wave was traced over two cardiac cycles to calculate the mean transatrial gradient (IAS) (Figure 1). The pulmonary artery band Doppler for the right (RPA) and left (LPA) pulmonary artery bands was traced over two cardiac cycles. The mean velocity and VTI were measured as well as the peak systolic velocity (S vel) and diastolic velocity (D vel) (Figure 2). The systolic to diastolic velocity ratio (S vel: D vel) was calculated, along with the pulsatility index ((systolic velocity minus diastolic velocity) divided by the mean velocity, PI). Additionally, the shape of the traces was recorded as either sawtooth or pulsatile, along with the presence of any notching of the descent (Figure 3).
One operator performed all measurements (HBR). Intra-user variability was tested by the same operator measuring the parameters on 5 echocardiograms >3 weeks after the initial measurements. Another operator (EK) measured the parameters on the same 5 echocardiograms to assess inter-user variability.