Pulmonary hypertension (PH) is defined by elevated pressures within the pulmonary circulation and, if unrecognized, progresses to right ventricular (RV) dysfunction, biventricular failure, and death. Regardless of etiology—idiopathic pulmonary fibrosis, left ventricular dysfunction, parenchymal lung disease, chronic thromboembolism, or multifactorial mechanisms—early detection is essential to prevent irreversible vascular remodeling and enable timely therapeutic intervention. Over the past two decades, therapeutic strategies for PH have advanced substantially, offering safer and more effective treatments. To date, right heart catheterization (RHC) remains the gold standard for diagnosis but is unavailable in many parts of the world, particularly in resource-limited settings.1 Given the increased mortality, emphasis on early detection has become increasingly important by leveraging noninvasive modalities to identify patients at risk for PH.
Transthoracic echocardiography remains the first-line noninvasive assessment for suspected PH. The most commonly used approach applies the principles of the Bernoulli equation to find the estimated pulmonary artery systolic pressure (ePASP) from the tricuspid regurgitant (TR) jet velocity.2 However, ePASP may be underestimated or overestimated in various clinical scenarios, especially in patients affected by valvular diseases.3 Furthermore, in more than a third of patients with PH, ePASP is indeterminable due to insufficient TR jet on echocardiography.4 Hence, conventional assessment for PH using only ePASP may be limited.
To address instances when TR jet is insufficient, recent work by Bagherzadeh and colleagues introduced novel reference limits for main pulmonary artery (PA) diameter size on echocardiography that factor in body size, sex, and age.5 These z score equations enabled standardized reporting and were able to identify outliers suggestive of PH, even when there was insufficient TR jet to find the ePASP. Using echocardiography, the investigators showed that the main PA diameter in diastole had a high diagnostic OR for identifying patients with group 1, group 2, and group 3 PH.5 These findings further confirmed prior guidelines proposed by the European Society of Cardiology recommending a 25-mm PA diameter threshold for identifying patients at risk for PH.6
While enlargement of the main PA has also been a frequent finding on chest CT scans in patients with PH, a recent study by Cao and colleagues also suggested that longitudinal measurements of the main PA diameter may further inform prognosis.7–9 In their work, they demonstrated that progressive PA enlargement occurred with worsening hemodynamic burden and RV dysfunction, whereas stabilization was associated with therapeutic response.9 The study supported using both baseline main PA diameter and progression as dynamic predictors of outcome.9
Noninvasive imaging approaches, particularly echocardiography-based and CT scan-based main PA diameter assessment, offer complementary insights into early PH detection and risk stratification. However, they can be used only for screening purposes; diagnostic confirmation still requires RHC.6 Will we ever reach a point of a noninvasive identification of PH that is more accessible, especially in resource-limited settings? It is uncertain—although we may be closer than we think in bridging gaps where RHC is unavailable to assist with timely clinical decision-making.
References
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2. Parasuraman S, Walker S, Loudon BL, et al. Assessment of pulmonary artery pressure by echocardiography—a comprehensive review. Int J Cardiol Heart Vasc. 2016;12:45-51. doi:10.1016/j.ijcha.2016.05.011
3. Rich JD. Counterpoint: can Doppler echocardiography estimates of pulmonary artery systolic pressures be relied upon to accurately make the diagnosis of pulmonary hypertension? No. Chest. 2013;143(6):1536-1539. doi:10.1378/chest.13-0297
4. O’Leary JM, Assad TR, Xu M, et al. Lack of a tricuspid regurgitation Doppler signal and pulmonary hypertension by invasive measurement. J Am Heart Assoc. 2018;7(13):e009362. doi:10.1161/JAHA.118.009362
5. Bagherzadeh SP, Celestin BE, Santana EJ, et al. Novel reference equations for pulmonary artery size and pulsatility using echocardiography and their diagnostic value in pulmonary hypertension. Chest. 2024;166(5):1184-1196. doi:10.1016/j.chest.2024.06.3805
6. Humbert M, Kovacs G, Hoeper MM, et al; ESC/ERS Scientific Document Group. 2022 ESC/ERS guidelines for the diagnosis and treatment of pulmonary hypertension. Eur Respir J. 2023;61(1):2200879. doi:10.1183/13993003.00879-2022
7. Ratanawatkul P, Oh A, Richards JC, Swigris JJ. Performance of pulmonary artery dimensions measured on high-resolution computed tomography scan for identifying pulmonary hypertension. ERJ Open Res. 2020;6(1):00232-2019. doi:10.1183/23120541.00232-2019
8. Shen Y, Wan C, Tian P, et al. CT-base pulmonary artery measurement in the detection of pulmonary hypertension: a meta-analysis and systematic review. Medicine (Baltimore). 2014;93(27):e256. doi:10.1097/MD.0000000000000256
9. Cao JY, Abdo RM, Wang N, et al. Prognostic value of main pulmonary artery diameter in pulmonary arterial hypertension. Chest. 2025;168(2):476-487. doi:10.1016/j.chest.2025.02.012
