• Hypertension, Pulmonary
• Echocardiography

Echocardiography allows estimation of right ventricular (RV) systolic pressure by adding the estimated right atrial pressure (RAP) to the systolic pressure gradient between the RV and right atrium (RA) calculated from the tricuspid regurgitant (TR) Doppler velocity. RV systolic pressure is equivalent to pulmonary artery systolic pressure (PASP) in the absence of pulmonic valve stenosis. Some degree of TR is present in about 80% of patients undergoing echocardiography, often only a trace or mild amount but just enough to allow PASP estimation which is now a standard echocardiographic reporting element. Non-invasive estimates of PASP initially were validated in the 1980s,1 2 with demonstration of a close correlation between simultaneous invasive and non-invasive PASP measurements. Non-invasive PASP estimates are used widely to adjust medical therapy, determine the timing of interventions and provide prognostic information in patients with a range of cardiovascular conditions.

However, there currently is a misconception that non-invasive PASP estimates are not accurate when severe TR is present. One concern is that the simplified Bernoulli equation, the 4v² formula used to convert velocity to pressure gradient, assumes a narrow orifice between the two chambers whereas with severe TR, the area of backflow across the valve is quite large, often with nearly equal systolic and diastolic ‘to-and-fro’ flow across the tricuspid annulus. Another concern is the approach to estimating RAP based on the size and respiratory variation in the inferior vena cava (IVC) at the junction with the RA on two-dimensional echocardiography. It is likely that estimated categories of RAP, rather than a more precise measurement, may not adequately account for the elevated RAP seen when severe TR is present.

These concerns about potential inaccuracies in non-invasive estimation of PASP in patients with severe TR were addressed by Lemarchand and colleagues.3 In a single-centre study of 236 …