Normal limits for the right ventricle-pulmonary circulation exercise echocardiography: a meta-analysis

Normal limits for exercise Doppler echocardiography (ex-TTE) measurements of the right ventricle (RV), pulmonary artery (PA) and left atrial (LA) unit remain inadequately defined. This meta-analysis aims to establish normal limits for measurements of the RV-PA-LA unit. A comprehensive literature search of Medline, Web of Science and Scopus (1 January 1999-December 2024) was performed. We included ex-TTE studies performed using a supine/semi-recumbent cycle ergometer in healthy subjects that reported the following parameters: tricuspid regurgitation velocity (TRV), systolic pulmonary artery pressure (sPAP), mean pulmonary artery pressure (mPAP), mPAP/cardiac output (CO) slope, mitral Doppler E to tissue Doppler e' ratio (E/e'), tricuspid annular plane excursion (TAPSE) and TAPSE/sPAP. Summary mean estimates were calculated using a restricted maximum-likelihood random-effects model. Lower and upper limits of normal (LLN and ULN) were defined as the 5th and 95th percentiles. Between-study heterogeneity was assessed using the Q-statistic and quantified with the inconsistency index. Data on 1122 healthy subjects (mean±sd age: 42.8±18.3 years) across 19 eligible studies were analysed. The pooled mean estimates and limits of normal for ex-TTE measurements were as follows: TRV 2.5 m·s^-1 (ULN 3.4), sPAP 38.5 mmHg (ULN 57.8), mPAP 29.8 mmHg (ULN 43.0), mPAP/CO slope 1.4 mmHg·min·L^-1 (ULN 3.0), E/e' 7.1 (ULN 11.5), TAPSE 31.8 mm (LLN 24.6), TAPSE/sPAP 0.8 mm·mmHg^-1 (LLN 0.4). Despite notable heterogeneity for several measurements, the present meta-analysis provides a robust framework for defining normal reference limits for ex-TTE measurements of the RV-PA-LA unit.