Transthoracic Doppler Echocardiography (TDE) is routinely used to estimate pulmonary artery systolic pressure (PASP) in patients suspected of having pulmonary hypertension (PH). However, there is conflicting data as to the accuracy of these pressure estimates when compared to right heart catheterization (RHC). We sought to determine the accuracy of TDE in estimating PASP and cardiac output (CO) among patients seen in a PH clinic.
We enrolled consecutive patients referred for RHC for the diagnosis or management of PH. Subjects underwent RHC followed within one hour by TDE performed by a dedicated echocardiographer blinded to RHC results. Measurements included right atrial pressure (RAP), PASP, and CO (determined by thermodilution for RHC and Doppler interrogation of the left ventricular outflow tract for TDE). Paired results from both studies were compared using Bland-Altman analysis. We calculated the average difference between RHC and TDE measurements (bias) and the expected range of differences for 95% of values (95% limits of agreement).
To date, 16 patients (94% female; median age 51 yrs) have completed the study. Seventy-five percent of patients had PH; the most common diagnoses were idiopathic pulmonary arterial hypertension (PAH) and PAH related to scleroderma. RHC yielded a median RAP of 8mmHg (range: 2-19), PASP of 70mmHg (range: 28-113), and CO of 4.1L/min (range: 1.6-8.7). TDE tended to overestimate RAP and PASP (bias 3.63mmHg and 8.22mmHg, respectively) with 95% limits of agreement of -4.3 to 11.6mmHg and -20.4 to 36.9mmHg, respectively. In 44% of patients, the TDE estimate of PASP had a difference of greater than ±10mmHg compared to RHC. TDE bias for CO estimates was 0.02L/min with 95% limits of agreement of -2.4 to 2.5L/min.
In patients with known or suspected PH, TDE estimates of RAP, PASP, and CO can vary significantly from RHC measurements.
While TDE plays an important role in the evaluation of PH, clinicians should not rely solely on TDE estimates to inform management decisions.
M.R. Fisher, None.