Multidetector Computed Tomography for Detection and Characterization of Pulmonary Hypertension in Consideration of WHO Classification:

Prognostic value of cardiac CT-derived RV dysfunction in lung transplantation candidates: A single-center retrospective study

BACKGROUND

There are no specific criteria for listing and prioritizing lung transplantation (LTx) candidates based on the severity of right ventricular (RV) dysfunction. We evaluated the prognostic value of cardiac CT-derived right ventricular ejection fraction (RVEF) in LTx candidates.

METHODS

This retrospective study included patients who were listed for LTx and underwent cardiac computed tomography (CT) between September 2019 and December 2023. Patients were categorized into 3 groups based on CT-derived RVEF and survival analyses were performed among these groups: normal RVEF (≥45%), mild-to-moderate RV dysfunction (25%-45%), and severe RV dysfunction (<25%).

RESULTS

In the 203 patients (median age, 61 years [interquartile range [IQR], 54-64]), the most common indication for LTx was interstitial lung disease (79.3%). Patients were followed for a median duration of 297 days (IQR, 140-632), and the 1-year survival rates were 85.2% for those with normal RV, 69.3% for those with mild-to-moderate RV dysfunction, and 55.6% for those with severe RV dysfunction (p < 0.001). Severe RV dysfunction (hazard ratio [HR] 6.72, p = 0.020), age (HR 1.1, p = 0.010), and 6-minute walking distance (HR 0.62, p = 0.010) were associated with an increased risk of 1-year mortality.

CONCLUSIONS

Severe RV dysfunction identified on cardiac CT was a significant prognostic factor for 1-year mortality in LTx candidates. Patients with severe RV dysfunction should be prioritized for LTx and classified as urgent due to their elevated short-term mortality risk. Cardiac CT may provide valuable prognostic information during the pretransplant evaluation process.

Determining pulmonary artery diameter on CT scans as basis for performing transthoracic echocardiography to screen for pulmonary hypertension in patients with pulmonary artery enlargement

BACKGROUND

The current guidelines recommend patient stratification based on transthoracic echocardiography (TTE) to identify individuals with potential pulmonary hypertension (PH). We validated the relationship between PH and the pulmonary artery diameter (PAD) on computed tomography (CT) with peak tricuspid regurgitant velocity (TRV) measured by TTE for referral of patients with suspected PH for TTE screening.

METHODS

We performed a retrospective analysis of CT-based PAD of 2356 patients who underwent TTE from February 2, 2013 to December 25, 2019 at our institution. The thresholds for suspected PH based on TRV were determined using receiver operating characteristic curves based on PAD. Pearson's rank correlation coefficient was used to assess the relationship between PAD and TRV.

RESULTS

The area under the curve (AUC) of the PAD for suspected PH was statistically greater or comparable to others. The sex-specific PAD threshold for high PH probability were 29.4 mm (male: AUC, 0.86; sensitivity, 84.9%; specificity, 72.3%) and 27.8 mm (female: AUC, 0.83; sensitivity, 78%; specificity, 75.6%). Pearson's rank correlation coefficient showed a correlation between the PAD and TRV (male: ρ = 0.40, P < 0.001, female: ρ = 0.43, P < 0.001).

CONCLUSIONS

The main PAD on CT findings served as a suitable marker for referral of patients with suspected PH for TTE screening. Patients exceeding the CT-derived PAD threshold, even incidentally, should undergo additional TTE for a comprehensive PH assessment.

Efficacy of computed tomography in diagnosing pulmonary hypertension: A systematic review and meta-analysis

Objective

This study seeks to evaluate the diagnostic value of computed tomography (CT) in pulmonary hypertension.

Method

PubMed, Embase, Scopus, and Web of Science databases were searched to obtain the relevant English literature, and the retrieval time until June 2022. The quality of the included studies is evaluated using the QUADAS-2 tool. The quality of the included studies was assessed, followed by a meta-analysis, analyze heterogeneity, summarize sensitivity and specificity, draw the comprehensive subject working characteristics (sROC) curve, calculate the area under the curve and conduct subgroup analysis and sensitivity analysis to find the source of the heterogeneity.

Results

A total of 12 articles were included, all with pulmonary artery diameter/liter aortic diameter >1 or 1 as the diagnostic criteria for pulmonary hypertension, and a total of 1,959 patients were included. Deek’s funnel plot analysis suggests that there is no significant publication bias (P = 0.102). The combined sensitivity was 0.652 (95% CI: 0.579, 0.719), combined specificity was 0.830 (95% CI: 0.796, 0.880), positive likelihood ratio was 3.837 (95% CI: 3.215, 4.579), negative likelihood ratio was 0.419 (95% CI: 0.346, 0.507), diagnostic odds ratio was 9.157 (95% CI: 6.748, 12.427) and area under the summary receiver operating characteristic (SROC) curve was 0.84 (95% CI: 0.81, 0.87).

Conclusion

The CT examination of pulmonary artery diameter/aortic artery hypertension is worthy of clinical application.

Prognostic value of main pulmonary artery diameter to ascending aorta diameter ratio in patients with advanced heart failure

OBJECTIVES AND BACKGROUND

In this study we assessed the prognostic value of main pulmonary artery diameter and its ratio to ascending aorta diameter (P/Ao ratio) in advanced heart failure patients.

METHODS

Patients with advanced heart failure who were candidates for heart transplantation were retrospectively evaluated. The clinical information, cardiac catheterisation results, and computed tomography images were gathered from institutional database system. The observed and predicted probabilities for survival were analysed in a nomogram.

RESULTS

The P/Ao ratio was found to be a strong predictor for MACE both in traditional multivariable Cox proportional hazard regression modelling (increase in P/Ao ratio per 2 SD, HR:2.72, 95% CI 1.14-6.48, p = 0.024) and ridge regression analysis (increase in P/Ao ratio per 2SD, HR:3.45, 95% CI 1.53-7.74, p = 0.003). Prediction model showed statistically significant correlation between the observed and predicted probabilities for 1-year survival.

CONCLUSION

In patients with advanced heart failure, computed tomography derived P/Ao ratio might be a prognostic predictor during follow up.

Main pulmonary artery enlargement predicts 90-day readmissions in Chinese COPD patients

BACKGROUND

Numerous studies have shown pulmonary artery enlargement when measured by chest computed tomography (CT) could predict a worse outcome in chronic obstructive pulmonary disease (COPD) patients. Herein, we studied the prognostic implication of main pulmonary artery diameter (MPAD) in Chinese COPD patients.

METHODS

This is an observational case-control study. Patients with 90-day readmissions are case group and those without 90-day readmission are control group. The study comprised of 417 COPD patients who underwent chest CT in their initial admission due to acute exacerbation of COPD (AECOPD). We analyzed their clinical characteristics such as MPAD, arterial blood gas (ABG) results, other chest CT findings and comorbidities to identify the cause of readmission within 90 days.

RESULTS

Median age of our study population is 75 years old, and 79.6% of them are male. The median MPAD is 2.8 cm and 80.6% were also diagnosed with community acquired pneumonia (CAP) in their first admission. The median MPAD in patients with 90-day readmission was 3.1 cm while patients without 90-day readmission had median MPAD of 2.8 cm. Through multivariate logistic regression analysis CAP (P=0.019, OR: 3.105, 95% CI: 1.203-8.019) and MPAD (P<0.001, OR: 2.898, 95% CI: 1.824-4.605) were statistically significant. In the second stage of analysis, subgroup of patients diagnosed with CAP and AECOPD (pAECOPD) were analyzed, MPAD remained statistically significant (P<0.001, OR: 3.490, 95% CI: 1.929-6.316) and receiver operative characteristic (ROC) curve for pAECOPD patients; area under the curve (AUC) was 0.704 (95% CI: 0.631-0.778) with a MPAD cut off value of 2.9 cm (sensitivity 72%, specificity 53%).

CONCLUSIONS

Enlarged MPAD and pAECOPD in initial admission are independent risk factors for 90-day readmission. In our pAECOPD patient population, MPAD >2.9 cm are at increased risk of 90-day readmission.

Imaging of Pulmonary Hypertension in Adults: A Position Paper from the Fleischner Society

Pulmonary hypertension (PH) is defined by a mean pulmonary artery pressure greater than 20 mm Hg and classified into five different groups sharing similar pathophysiologic mechanisms, hemodynamic characteristics, and therapeutic management. Radiologists play a key role in the multidisciplinary assessment and management of PH. A working group was formed from within the Fleischner Society based on expertise in the imaging and/or management of patients with PH, as well as experience with methodologies of systematic reviews. The working group identified key questions focusing on the utility of CT, MRI, and nuclear medicine in the evaluation of PH: (a) Is noninvasive imaging capable of identifying PH? (b) What is the role of imaging in establishing the cause of PH? (c) How does imaging determine the severity and complications of PH? (d) How should imaging be used to assess chronic thromboembolic PH before treatment? (e) Should imaging be performed after treatment of PH? This systematic review and position paper highlights the key role of imaging in the recognition, work-up, treatment planning, and follow-up of PH. This article is a simultaneous joint publication in Radiology and European Respiratory Journal. The articles are identical except for stylistic changes in keeping with each journal's style. Either version may be used in citing this article. © 2021 RSNA and the European Respiratory Society. Online supplemental material is available for this article.

Imaging of pulmonary hypertension in adults: a position paper from the Fleischner Society

Pulmonary hypertension (PH) is defined by a mean pulmonary artery pressure greater than 20 mmHg and classified into five different groups sharing similar pathophysiologic mechanisms, haemodynamic characteristics, and therapeutic management. Radiologists play a key role in the multidisciplinary assessment and management of PH. A working group was formed from within the Fleischner Society based on expertise in the imaging and/or management of patients with PH, as well as experience with methodologies of systematic reviews. The working group identified key questions focusing on the utility of CT, MRI, and nuclear medicine in the evaluation of PH: a) Is noninvasive imaging capable of identifying PH? b) What is the role of imaging in establishing the cause of PH? c) How does imaging determine the severity and complications of PH? d) How should imaging be used to assess chronic thromboembolic PH before treatment? e) Should imaging be performed after treatment of PH? This systematic review and position paper highlights the key role of imaging in the recognition, work-up, treatment planning, and follow-up of PH.

[Current Aspects of Definition and Diagnosis of Pulmonary Hypertension]

At the 6th World Symposium on Pulmonary Hypertension (WSPH), which took place from February 27 until March 1, 2018 in Nice, scientific progress over the past 5 years in the field of pulmonary hypertension (PH) was presented by 13 working groups. The results of the discussion were published as proceedings towards the end of 2018. One of the major changes suggested by the WSPH was the lowering of the diagnostic threshold for PH from ≥ 25 to > 20 mmHg mean pulmonary arterial pressure, measured by right heart catheterization at rest. In addition, the pulmonary vascular resistance was introduced into the definition of PH, which underlines the importance of cardiac output determination at the diagnostic right heart catheterization.In this article, we discuss the rationale and possible consequences of a changed PH definition in the context of the current literature. Further, we provide a current overview on non-invasive and invasive methods for diagnosis, differential diagnosis, and prognosis of PH, including exercise tests.

Performance of pulmonary artery dimensions measured on high-resolution computed tomography scan for identifying pulmonary hypertension

Background

On high-resolution computed tomography (HRCT), pulmonary artery (PA) dimensions may hint at the presence of pulmonary hypertension. We aimed to determine how accurately various measures of the PA, as viewed on HRCT, predict right heart catheterisation (RHC)-confirmed pulmonary hypertension.

Methods

We retrospectively reviewed patients who had HRCT and RHC between 2010 and 2018. Analyses considered respiratory cycle, pulmonary hypertension diagnostic criteria, time between HRCT and RHC, and subgroup analysis in interstitial lung disease (ILD) and chronic obstructive pulmonary disease (COPD).

Results

Of 620 patients, 375 had pulmonary hypertension. For pulmonary hypertension (defined as mean PA pressure (mPAP) ≥25 mmHg) and from HRCT performed within 60 days of RHC, main PA diameter (MPAD) ≥29 mm had a sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 88%, 42%, 0.70 and 0.70, respectively, while ratio of the diameter of the PA to the diameter of the ascending aorta (PA:Ao) ≥1.0 showed 53%, 85%, 0.84 and 0.54, respectively. In general, results were similar when the interval between HRCT and RHC varied from 7 to 60 days and when measured on expiratory images. In ILD, the sensitivity of MPAD was higher; in COPD, the specificity of PA:Ao was higher. There was moderately positive correlation between mPAP and inspiratory MPAD, PA:Ao, right PA diameter (RPAD), left PA diameter (LPAD) and (RPAD+LPAD)/2 (r=0.48, 0.51, 0.34, 0.34 and 0.36, respectively), whereas there was weak negative correlation between mPAP and PA angle (r= -0.24).

Conclusions

Findings on HRCT may assist in the diagnosis of RHC-confirmed pulmonary hypertension. MPAD ≥29 mm had high sensitivity and PA:Ao ≥1.0 had high specificity. Compared with the entire cohort, MPAD had greater sensitivity in ILD and PA:Ao had higher specificity in COPD.

Clinical outcome and survival in 30 pulmonary hypertension patients with high severity indices and advanced functional class

BACKGROUND

Pulmonary hypertension (PH) is an idiopathic or secondary disorder associated with many systemic illnesses. Long-term survival in PH depends on the severity and functional class. Several new drugs are now available to treat PH, but their impact on clinical outcome and survival are not well established.

OBJECTIVES

Evaluate severity parameters and the impact of current recommended therapy on survival in PH.

DESIGN

Cross-sectional.

SETTINGS

Tertiary care center.

PATIENTS AND METHODS

The study included adult patients who had undergone right heart catheterization since 2012 and were diagnosed with pulmonary hypertension. Survival was recorded after 6 years, at the end of the study. Nine severity variables for PH were assessed including right ventricular size by echocardiogram and pulmonary artery diameter (PA diameter) and the ratio of pulmonary artery diameter to ascending aorta diameter (PA/Ao ratio) by CT.

MAIN OUTCOME MEASURES

Evaluation of severity parameters.

SAMPLE SIZE

30 patients.

RESULTS

Twenty-five patients were positive for 8/9 severity parameters. Eight of 30 (26.6%) patients died. In nonsurvivors, right ventricular size was increased by 25% ( P=.427), pulmonary vascular resistance increased by 29.4% in nonsurvivors ( P=.302), the 6-minute walk distance decreased by 21% ( P=.875), median brain natriuretic peptide increased by 96% ( P=.890), median GGT and alkaline phosphatase were 3 times higher in nonsurvivors ( P=.893 and P=.047, respectively) and PA/Ao was nonsignificantly decreased in nonsurvivors ( P=.373), Survival was decreased by a median of 2.3 years in nonsurvivors.

CONCLUSION

Our study identified a subgroup of PH patients with NYHA functional class III and above with worsening severity indicators who were labeled as a high-risk group. These patients showed continuous deterioration in their clinical status despite escalation of therapy with current guidelines. We recommend these high-risk group patients be referred for early lung transplantation.

LIMITATIONS

Low sample size and only a single center. Needs confirmation with a larger multicenter trial.

CONFLICT OF INTEREST

None.

Evaluation of the CT imaging findings in patients newly diagnosed with chronic thromboembolic pulmonary hypertension

PURPOSE

The aim of this study was to evaluate the vascular and parenchymal CT imaging findings, including vessel and cardiac chamber diameter measurements, in patients newly diagnosed with chronic thromboembolic pulmonary hypertension (CTEPH). The CT imaging findings were correlated with hemodynamic measurements and patient outcome.

METHODS

Vascular and parenchymal CT findings were assessed on retrospectively ECG-gated MDCT angiography scans in 76 patients newly diagnosed with CTEPH. The diameters of the right and left ventricle (dRV, dLV), the right and left atrium (dRA, dLA), the ascending aorta (dAA), the right and left pulmonary arteries (drPA, dlPA), and the main pulmonary artery (dPA) were measured on axial CT scans. The CT imaging findings were correlated with demographic and hemodynamic data and adverse patient outcome due to right heart failure (RHF).

RESULTS

The majority of patients showed chronic PE, mosaic perfusion, disparity in segmental vessel size, parenchymal densities, bronchial dilatation, and bronchial collaterals in CT. Mean pulmonary artery pressure (mPAP) was not significantly different in patients with and those without chronic PE, mosaic perfusion, disparity in segmental vessel size, parenchymal densities, bronchial dilatation, and bronchial collaterals. Mean PAP showed significant correlations with the CT metrics of dRV/dLV ratio, dRA, dRV, dPA and dPA/dAA ratio, but no correlation with the central thrombi score. By backward linear regression, the dPA/dAA ratio independently correlated with mPAP. Patients who died of RHF tended to have a higher frequency of exclusively chronic peripheral PE and greater dRV/dLV ratios on presenting CT scans compared with survivors.

CONCLUSION

The majority of patients newly diagnosed with CTEPH show vascular signs of chronic PE, mosaic perfusion, parenchymal densities, disparity in segmental vessel size, bronchial dilatation, and bronchial collaterals on presenting CT scans. Particularly CTEPH patients with exclusively chronic peripheral PE and increased dRV/dLV ratios seem to be at risk of adverse outcome due to RHF.

A four-tier classification system of pulmonary artery metrics on computed tomography for the diagnosis and prognosis of pulmonary hypertension

BACKGROUND

We aimed to develop a severity classification system of the main pulmonary artery diameter (mPA) and its ratio to the ascending aorta diameter (ratio PA) for the diagnosis and prognosis of pulmonary hypertension (PH) on computed tomography (CT) scans.

METHODS

In 228 patients (136 with PH) undergoing right heart catheterization (RHC) and CT for dyspnea, we measured mPA and ratio PA. In a derivation cohort (n = 114), we determined cutpoints for a four-tier severity grading system that would maximize sensitivity and specificity, and validated it in a separate cohort (n = 114). Cutpoints for mPA were defined with ≤27 mm(F) and ≤29 mm(M) as the normal reference range; mild as >27 to <31 mm(F) and >29 to <31 mm(M); moderate≥31-34 mm; and severe>34 mm. Cutpoints for ratio PA were defined as normal ≤0.9; mild>0.9 to 1.0; moderate>1.0 to 1.1; and severe>1.1.

RESULTS

Sensitivities for normal tier were 99% for mPA and 93% for ratio PA; while specificities for severe tier were 98% for mPA>34 mm and 100% for ratio PA>1.1. C-statistics for four-tier mPA and ratio PA were both 0.90 (derivation) and both 0.85 (validation). Severity of mPA and ratio PA corresponded to hemodynamics by RHC and echocardiography (both p < 0.001). Moderate-severe mPA values of ≥31 mm and ratio PA>1.1 had worse survival than normal values (all p ≤ 0.01).

CONCLUSION

A CT-based four-tier severity classification system of PA diameter and its ratio to the aortic diameter has high accuracy for PH diagnosis with increased mortality in patients with moderate-severe severity grades. These results may support clinical utilization on chest and cardiac CT reports.

Transesophageal Echocardiographic Assessment of Pulmonary Artery-to-Ascending Aorta Ratio for the Detection of Pulmonary Hypertension in Cardiac Surgical Patients

OBJECTIVE

The objective of the study was to investigate if the main pulmonary artery (mPA)-to-ascending aorta (AscAo), (mPA:AscAo) ratio could serve as a screening tool in identifying pulmonary artery hypertension (PAH).

DESIGN

A prospective observational study.

SETTING

Tertiary care center, university hospital.

PARTICIPANTS

Fifty-four adult patients undergoing off-pump coronary artery bypass grafting surgery (OPCAB).

INTERVENTIONS

mPA and AscAo transverse diameters were measured by transesophageal echocardiography (TEE) and the mean pulmonary arterial pressures (mPAP) were recorded simultaneously using a pulmonary artery catheter.

MEASUREMENTS AND MAIN RESULTS

mPA:AscAo ratio demonstrated significant linear correlation with mPAP measured by pulmonary artery catheterization (ie, r = 0.61, confidence interval [CI] = 0.5352-0.6736, p < 0.0001). Receiver operating characteristic curves were performed to evaluate sensitivity and specificity of mPA:AscAo ratio ≥1 for diagnosing PAH (mPAP ≥25 mmHg). Area under the curve for mPA:AscAo ratio was 0.91 (95% CI, 0.869-0.936, p < 0.0001), with a sensitivity of 84.27%, specificity of 83.92%, positive-predictive value of 87.6% and negative-predictive value of 81.1% for a mPAP ≥25 mmHg.

CONCLUSIONS

The ratio of mPA:AscAo is a simple, reliable, and reproducible method that can be obtained through TEE, which guides the clinician to screen patients with PAH.

Multidetector computed tomography shows reverse cardiac remodeling after double lung transplantation for pulmonary hypertension

OBJECTIVE

To use multidetector computed tomography (MDCT) to evaluate the structural changes in the right heart and pulmonary arteries that occur in patients with severe pulmonary hypertension treated by double lung transplantation.

MATERIAL AND METHODS

This was a retrospective study of 21 consecutive patients diagnosed with severe pulmonary hypertension who underwent double lung transplantation at our center between 2010 and 2014. We analyzed the last MDCT study done before lung transplantation and the first MDCT study done after lung transplantation. We recorded the following variables: diameter of the pulmonary artery trunk, ratio of the diameter of the pulmonary artery trunk to the diameter of the ascending aorta, diameter of the right ventricle, ratio of the diameter of the left ventricle to the diameter of the right ventricle, and eccentricity index. Statistical analysis consisted of the comparison of the means of the variables recorded.

RESULTS

In all cases analyzed, the MDCT study done a mean of 24±14 days after double lung transplantation showed a significant reduction in the size of the right heart chambers, with improved indices of ventricular interdependency index, and reduction in the size of the pulmonary artery trunk (p<0.001 for all the variables analyzed).

CONCLUSION

Patients with pulmonary hypertension treated by double lung transplantation present early reverse remodeling of the changes in the structures of the right heart and pulmonary arterial tree. MDCT is useful for detecting these changes.

CT-base pulmonary artery measurement in the detection of pulmonary hypertension: a meta-analysis and systematic review

To summarize the performance of CT-based main pulmonary artery diameter or pulmonary artery to aorta ratio (PA:A ratio) measurement in detection of pulmonary hypertension by a systematic review and meta-analysis. A comprehensive literature search was performed to identify studies determining diagnostic accuracy of main pulmonary artery diameter or PA:A ratio measurement for pulmonary hypertension. The Quality Assessment of Diagnostic Accuracy Studies tool was used to assess the quality of the included studies. A bivariate random-effects model was used to pool sensitivity, specificity, positive/negative likelihood ratio (PLR/NLR), and diagnostic odds ratio (DOR). Summary receiver operating characteristic (SROC) curves and area under the curve (AUC) were used to summarize overall diagnostic performance. This meta-analysis included 20 publications involving 2134 subjects. Summary estimates for main pulmonary artery diameter measurement in the diagnosis of pulmonary hypertension were as follows: sensitivity, 0.79 (95% CI 0.72-0.84); specificity, 0.83 (95% CI 0.75-0.89); PLR, 4.68 (95% CI 3.13-6.99); NLR, 0.26 (95% CI 0.20-0.33); DOR, 18.13 (95% CI 10.87-30.24); and AUC 0.87. The corresponding summary performance estimates for using the PA:A ratio were as follows: sensitivity, 0.74 (95% CI 0.66-0.80); specificity, 0.81 (95% CI 0.74-0.86); PLR, 3.83 (95% CI, 2.70-5.43); NLR, 0.33 (95% CI 0.24-0.44); DOR, 11.77 (95% CI 6.60-21.00); and AUC 0.84. Both main pulmonary artery diameter and PA:A ratio are helpful for diagnosing pulmonary hypertension. Nevertheless, the results of pulmonary artery measurement should be interpreted in parallel with the results of traditional tests such as echocardiography.

Increased pulmonary artery diameter on chest computed tomography can predict borderline pulmonary hypertension

Pulmonary hypertension (PH) often leads to dilatation of the pulmonary artery (PA), which can be measured on chest computed tomography (CT). While the predictive capability of PA dilatation is useful to distinguish PH (mean PA pressure ≥25 mmHg) from normal (mean PA pressure ≤ 20 mmHg), CT characteristics of borderline PH (mean PA pressure 21-24 mmHg) have not been described. We aimed to investigate whether patients with borderline PH already show PA dilatation and to assess the diagnostic accuracy of PA dilatation for borderline PH diagnosis. Between April 2003 and September 2008, consecutive symptomatic patients with a mean PA pressure below 25 mmHg on right heart catheterization who had a chest CT available were retrospectively included. PA diameters from chest CT were correlated with hemodynamic measurements and analyzed with respect to their accuracy of predicting borderline PH. Main PA diameters were significantly larger in 26 patients with borderline PH compared with 52 patients without PH (3.16 ± 0.53 vs. 2.78 ± 0.43 cm, P = 0.001). The main PA diameter on CT correlated with mean PA pressure (r = 0.496, P < 0.001) and pulmonary vascular resistance (r = 0.445, P < 0.001), and predicted borderline PH with sensitivity, specificity, negative and positive predictive values of 77%, 62%, 84%, and 50%, respectively, using a cutoff ≥2.9 cm. This first systematic investigation of CT parameters in symptomatic patients with mean PA pressures less than 25 mmHg could show that, even in patients with borderline PH, significant PA dilatation can be present, which was related to PA pressure and pulmonary vascular resistance. This can be useful for identification of patients with borderline PH for further study and to prompt further diagnostic work-up of possible underlying diseases.