Study limitations
The present study did not validate the echocardiographic measurements against invasive gold standard evaluation of the pulmonary circulation by PAP, wedged PAP and cardiac output, and right ventricular function by indices derived from pressure-volume loops. Thus accuracy and precision were defined by comparison only with the core laboratory measurements. The number of patients studied was relatively small (n = 10). However, each of the 19 participating centers provided a total of 35 left and right heart echo-Doppler variables at rest, peak exercise and after 5 minutes of recovery. Finally, it should be underlined that contrast and/or agitated saline enhancement for tricuspid regurgitation (TR) Doppler signal was not performed. The additional use of contrast and/or agitated saline may further improve the reliability, particularly in less experienced centers.