Comparative accuracy of mean pulmonary artery pressure estimation using transthoracic echocardiography versus phase-contrast MRI in healthy adults.

BACKGROUND: Non-invasive assessment of mean pulmonary artery pressure (MPAP) is crucial for clinical screening and longitudinal follow-up of pulmonary arterial hypertension (PAH). Transthoracic echocardiography (TTE) acts as the initial non-invasive modality, though it presents limited reliability in MPAP estimation. Phase-contrast magnetic resonance imaging (PC-MRI) allows direct and quantitative hemodynamic measurement, yet its comparative accuracy in healthy adults remains insufficiently explored. This study aimed to evaluate the accuracy of MPAP estimation in healthy adults using TTE compared to PC-MRI, with relevance to non-invasive assessment in settings such as pulmonary hypertension. METHODS: Twenty healthy volunteers underwent imaging with 3.0 Tesla PC-MRI to assess the main pulmonary artery (MPA) cross-sectional area (CSA) and forward peak velocity. MPAP was calculated using a previously validated formula. Within 48 hours, the same participants underwent TTE to obtain heart rate-adjusted pulmonary artery acceleration time (PAAT), from which MPAP was derived. The reference standard for MPAP was based on values obtained via right heart catheterization (RHC) in healthy adults. Agreement was defined as estimated MPAP falling within the 95% confidence interval (CI) of the RHC reference values. Between-modality differences were assessed using a paired t-test, with a two-tailed P value <0.05 considered statistically significant. RESULTS: All imaging studies were of diagnostic quality. MPAP estimated using PC-MRI (14.08±2.95 mmHg) fell within the 95% CI of the reference standard for all participant (100%). In contrast, TTE-derived MPAP (6.70±12.89 mmHg) demonstrated agreement in only 9 participants (45%), with 6 participants (30%) exhibiting non-physiological negative values. The difference in estimation agreement with established reference ranges between the two modalities was statistically significant (P<0.01). Mean deviation from the reference mean (14.0 mmHg) was +0.08 mmHg for PC-MRI and -7.30 mmHg for TTE. Bland-Altman analysis showed a mean bias of 7.38 mmHg (95% CI: 1.28 to 13.48 mmHg) with wide limits of agreement (-13.76 to 28.52 mmHg), indicating poor interchangeability. CONCLUSIONS: PC-MRI demonstrated superior agreement with established reference ranges and reproducibility compared to TTE for non-invasive MPAP measurement in healthy adults. The TTE-based PAAT method exhibited limited reliability in this population, frequently producing implausible results. PC-MRI may serve as a reliable non-invasive modality for quantitative evaluation of pulmonary artery pressure.