Systolic pulmonary artery pressure (sPAP) cannot always be assessed from Doppler-detected tricuspid regurgitation (TR), especially when sPAP is normal. The right ventricular isovolumic relaxation time (rIVRT) is related to sPAP, and assessment of rIVRT by tissular Doppler imaging (rIVRT') has recently been proposed as an alternative method for estimating sPAP in patients with pulmonary artery hypertension (PAH). We evaluated here its usefulness in everyday clinical practice.We conducted a prospective Doppler vs. catheterization study in 26 patients. TR was undetectable in 6 patients (32%) with normal sPAP and in one patient (14%) from those with PAH. rIVRT' was recordable in all patients. We found a strong correlation between rIVRT' and sPAP (r = 0.87; P < 0.0001). rIVRT' had a high sensitivity in detecting PAH, and a rIVRT' of 40 ms or less excluded PAH with a negative predictive value of 100%. We also found that a prolonged rIVRT' is not specific to PAH and that the rIVRT'-evaluated sPAP did not agree well with the catheter-evaluated value.Measurement of rIVRT' can help estimate sPAP in the absence of TR: A normal rIVRT' excludes PAH with a high negative predictive value. A prolonged rIVRT' is in favour of an elevated sPAP but cannot affirm it by itself.