CT derived left atrial size identifies left heart disease in suspected pulmonary hypertension: Derivation and validation of predictive thresholds

Clinical-radiological-pathological correlation in pulmonary arterial hypertension

Pulmonary hypertension (PH) is defined by the presence of a mean pulmonary arterial pressure >20 mmHg. Current guidelines describe five groups of PH with shared pathophysiological and clinical features. In this paper, the first of a series covering all five PH classification groups, the clinical, radiological and pathological features of pulmonary arterial hypertension (PAH) will be reviewed. PAH may develop in the presence of associated medical conditions or a family history, following exposure to certain medications or drugs, or may be idiopathic in nature. Although all forms of PAH share common histopathological features, the presence of certain pulmonary arterial abnormalities, such as plexiform lesions, and extent of co-existing pulmonary venous involvement differs between the different subgroups. Radiological investigations are key to diagnosing the correct form of PH and a systematic approach to interpretation, especially of computed tomography, is essential.

Pulmonary hypertension associated with lung disease: new insights into pathomechanisms, diagnosis, and management

Patients with chronic lung diseases, particularly interstitial lung disease and chronic obstructive pulmonary disease, frequently develop pulmonary hypertension, which results in clinical deterioration, worsening of oxygen uptake, and an increased mortality risk. Pulmonary hypertension can develop and progress independently from the underlying lung disease. The pulmonary vasculopathy is distinct from that of other forms of pulmonary hypertension, with vascular ablation due to loss of small pulmonary vessels being a key feature. Long-term tobacco exposure might contribute to this type of pulmonary vascular remodelling. The distinct pathomechanisms together with the underlying lung disease might explain why treatment options for this condition remain scarce. Most drugs approved for pulmonary arterial hypertension have shown no or sometimes harmful effects in pulmonary hypertension associated with lung disease. An exception is inhaled treprostinil, which improves exercise capacity in patients with interstitial lung disease and pulmonary hypertension. There is a pressing need for safe, effective treatment options and for reliable, non-invasive diagnostic tools to detect and characterise pulmonary hypertension in patients with chronic lung disease.

Fully automatic cardiac four chamber and great vessel segmentation on CT pulmonary angiography using deep learning

Introduction

Computed tomography pulmonary angiography (CTPA) is an essential test in the work-up of suspected pulmonary vascular disease including pulmonary hypertension and pulmonary embolism. Cardiac and great vessel assessments on CTPA are based on visual assessment and manual measurements which are known to have poor reproducibility. The primary aim of this study was to develop an automated whole heart segmentation (four chamber and great vessels) model for CTPA.

Methods

A nine structure semantic segmentation model of the heart and great vessels was developed using 200 patients (80/20/100 training/validation/internal testing) with testing in 20 external patients. Ground truth segmentations were performed by consultant cardiothoracic radiologists. Failure analysis was conducted in 1,333 patients with mixed pulmonary vascular disease. Segmentation was achieved using deep learning via a convolutional neural network. Volumetric imaging biomarkers were correlated with invasive haemodynamics in the test cohort.

Results

Dice similarity coefficients (DSC) for segmented structures were in the range 0.58-0.93 for both the internal and external test cohorts. The left and right ventricle myocardium segmentations had lower DSC of 0.83 and 0.58 respectively while all other structures had DSC >0.89 in the internal test cohort and >0.87 in the external test cohort. Interobserver comparison found that the left and right ventricle myocardium segmentations showed the most variation between observers: mean DSC (range) of 0.795 (0.785-0.801) and 0.520 (0.482-0.542) respectively. Right ventricle myocardial volume had strong correlation with mean pulmonary artery pressure (Spearman's correlation coefficient = 0.7). The volume of segmented cardiac structures by deep learning had higher or equivalent correlation with invasive haemodynamics than by manual segmentations. The model demonstrated good generalisability to different vendors and hospitals with similar performance in the external test cohort. The failure rates in mixed pulmonary vascular disease were low (<3.9%) indicating good generalisability of the model to different diseases.

Conclusion

Fully automated segmentation of the four cardiac chambers and great vessels has been achieved in CTPA with high accuracy and low rates of failure. DL volumetric biomarkers can potentially improve CTPA cardiac assessment and invasive haemodynamic prediction.

Diagnostic accuracy of automated 3D volumetry of cardiac chambers by CT pulmonary angiography for identification of pulmonary hypertension due to left heart disease

OBJECTIVES

To assess diagnostic accuracy of automated 3D volumetry of cardiac chambers based on computed tomography pulmonary angiography (CTPA) for the differentiation of pulmonary hypertension due to left heart disease (group 2 PH) from non-group 2 PH compared to manual diameter measurements.

METHODS

Patients with confirmed PH undergoing right heart catheterisation and CTPA within 100 days for diagnostic workup of PH between August 2013 and February 2016 were included in this retrospective, single-centre study. Automated 3D segmentation of left atrium, left ventricle, right atrium and right ventricle (LA/LV/RA/RV) was performed by two independent and blinded radiologists using commercial software. For comparison, axial diameters were manually measured. The ability to differentiate group 2 PH from non-group 2 PH was assessed by means of logistic regression.

RESULTS

Ninety-one patients (median 67.5 years, 44 women) were included, thereof 19 patients (20.9%) classified as group 2 PH. After adjustment for age, sex and mean pulmonary arterial pressure, group 2 PH was significantly associated with larger LA volume (p < 0.001), larger LV volume (p = 0.001), lower RV/LV volume ratio (p = 0.04) and lower RV/LA volume ratio (p = 0.003). LA volume demonstrated the highest discriminatory ability to identify group 2 PH (AUC, 0.908; 95% confidence interval, 0.835-0.981) and was significantly superior to LA diameter (p = 0.009). Intraobserver and interobserver agreements were excellent for all volume measurements (intraclass correlation coefficients 0.926-0.999, all p < 0.001).

CONCLUSIONS

LA volume quantified by automated, CTPA-based 3D volumetry can differentiate group 2 PH from other PH groups with good diagnostic accuracy and yields significantly higher diagnostic accuracy than left atrial diameter.

KEY POINTS

• Automated cardiac chamber volumetry using non-gated CT pulmonary angiography can differentiate pulmonary hypertension due to left heart disease from other causes with good diagnostic accuracy. • Left atrial volume yields significantly higher diagnostic accuracy than left atrial axial diameter for identification of pulmonary hypertension due to left heart disease without time-consuming manual processing.

Animal models of pulmonary hypertension due to left heart disease

Pulmonary hypertension due to left heart disease (PH‐LHD) is regarded as the most prevalent form of pulmonary hypertension (PH). Indeed, PH is an independent risk factor and predicts adverse prognosis for patients with left heart disease (LHD). Clinically, there are no drugs or treatments that directly address PH‐LHD, and treatment of LHD alone will not also ameliorate PH. To target the underlying physiopathological alterations of PH‐LHD and to develop novel therapeutic approaches for this population, animal models that simulate the pathophysiology of PH‐LHD are required. There are several available models for PH‐LHD that have been successfully employed in rodents or large animals by artificially provoking an elevated pressure load on the left heart, which by transduction elicits an escalated pressure in pulmonary artery. In addition, metabolic derangement combined with aortic banding or vascular endothelial growth factor receptor antagonist is also currently applied to reproduce the phenotype of PH‐LHD. As of today, none of the animal models exactly recapitulates the condition of patients with PH‐LHD. Nevertheless, the selection of an appropriate animal model is essential in basic and translational studies of PH‐LHD. Therefore, this review will summarize the characteristics of each PH‐LHD animal model and discuss the advantages and limitations of the different models.

Impact of the new definition of pulmonary hypertension according to world symposium of pulmonary hypertension 2018 on diagnosis of post-capillary pulmonary hypertension

BACKGROUND

The World Symposium on Pulmonary Hypertension (WSPH) in 2018 recommended new definitions of pulmonary hypertension (PH). We investigated the impact of the updated definition on prevalence of PH due to left heart disease (PH-LHD).

METHODS

The data of right heart catheterizations in patients with suspected PH-LHD between January 2008 and July 2015 was retrospectively analyzed applying different definitions. The number of patients diagnosed by the updated WSPH hemodynamic criteria of a mean pulmonary artery pressure (mPAP) > 20 mmHg was compared to the number of patients using mPAP ≥ 25 mmHg. The differentiation between patients with isolated post-capillary (Ipc) and combined post-capillary and pre-capillary (Cpc) PH was analyzed comparing the ESC/ERS guidelines, the recommendation of Cologne Consensus Conference (CCC) and WSPH.

RESULTS

Of the 726 patients with a suspected PH, 58 patients met the diagnostic criteria of the ESC/ERS guidelines for PH-LHD with 32.8% Ipc-cases, 34.4% Cpc-PH-cases and 32.8% unclassifiable cases. Overall, 58 patients were diagnosed by the CCC criteria, with 34.5% classified as Cpc-PH and 65.5% as Icp-PH. Using the criteria of WSPH, the number of PH-LHD rose by one patient. According to the new definition, 64.4% of the patients were classified as Cpc-PH and had a significantly higher right to left atrial area (RA/LA) ratio than Ipc-PH patients.

CONCLUSION

Applying the new recommendation, the number of diagnosed patients with PH-LHD increases marginally. There is, however, a relevant shift in the number of Cpc-PH cases. An elevated RA/LA ratio might help to identify patients for invasive diagnostic work-up.

Early Triage of Cardioembolic Sources Using Chest Spectral Computed Tomography in Acute Ischemic Stroke

OBJECTIVES

The present study investigated the potential usefulness of delayed-phase, low-dose, non-gated, chest spectral CT scans (DSCT) for the early triage of cardioembolic (CE) sources in patients admitted with acute ischemic stroke (AIS), and for the simultaneous detection of myocardial disease and thrombotic complications.

MATERIAL AND METHODS

Since July 2020 and promoted by the COVID-19 pandemic, we implemented the use of DSCT after cerebrovascular CT angiography (CTA) among patients with AIS using a dual-layer spectral CT. We explored the presence of CE sources, as well as late myocardium iodine enhancement (LIE) and pulmonary thromboembolism. Among patients further undergoing transesophageal echocardiogram (TEE) or cardiac CTA, we explored the diagnostic performance.

RESULTS

Fifty consecutive patients with AIS who underwent DSCT after cerebrovascular CTA comprised the patient population. The confidence degree for excluding cardiac thrombi was significantly higher than for LIE (4.4±0.8 vs. 3.4±1.3, p<0.0001). DSCT identified a CE source in 4 (8%) and LIE in 24 (48%) patients. The iodine ratio of CE sources was significantly lower compared to the left atrial appendage of patients with no CE sources (0.25±0.1 mg/mL vs. 0.91±0.2 mg/mL, p<0.0001). TEE/cardiac CT, performed in 20 (40%) patients, identified a CE source in 5 (25%) cases, whereas DSCT identified 4 (20%), leading to a sensitivity and specificity of 80% (95% CI 28-99%) and 100% (95% CI 78-100%) respectively (kappa 0.86).

CONCLUSIONS

In this pilot study, we identified DSCT as a potential unsophisticated approach for the early triage of CE sources among patients with AIS undergoing CTA upon admission.

Cardiac Magnetic Resonance-Derived Indexed Volumes and Volume Ratios of the Cardiac Chambers Discriminating Group 2 Pulmonary Hypertension From Other World Health Organization Groups

OBJECTIVE

The aims of the study were to assess the performance of cardiac magnetic resonance (CMR)-derived cardiac chamber volumes and volume ratios to identify group 2 pulmonary hypertension (PH) patients and to determine their cutoff values with the highest sensitivity and specificity.

METHODS

One hundred six patients underwent CMR, 2 months after the diagnosis of PH by right heart catheterization. We classified patients with pulmonary capillary wedge pressure of greater than 15 mm Hg as group 2 PH. Cardiac chamber volumes indexed to the body surface area and volume ratios were correlated to the type of PH. Their sensitivity and specificity to detect group 2 PH were examined at various cutoff points.

RESULTS

The most appropriate cutoff values to designate group 2 PH patients with high sensitivity and specificity were as follows: left atrium volume index of 54.72 mL/m2 or greater, right ventricle volume/left atrium volume of 2.07 or less, and right atrium volume/left atrium volume of 1.61 or less.

CONCLUSIONS

Cardiac magnetic resonance-derived cardiac chamber volume indices and volume ratios can determine group 2 PH diagnosis with high sensitivity and specificity.

A machine learning cardiac magnetic resonance approach to extract disease features and automate pulmonary arterial hypertension diagnosis

AIMS

Pulmonary arterial hypertension (PAH) is a progressive condition with high mortality. Quantitative cardiovascular magnetic resonance (CMR) imaging metrics in PAH target individual cardiac structures and have diagnostic and prognostic utility but are challenging to acquire. The primary aim of this study was to develop and test a tensor-based machine learning approach to holistically identify diagnostic features in PAH using CMR, and secondarily, visualize and interpret key discriminative features associated with PAH.

METHODS AND RESULTS

Consecutive treatment naive patients with PAH or no evidence of pulmonary hypertension (PH), undergoing CMR and right heart catheterization within 48 h, were identified from the ASPIRE registry. A tensor-based machine learning approach, multilinear subspace learning, was developed and the diagnostic accuracy of this approach was compared with standard CMR measurements. Two hundred and twenty patients were identified: 150 with PAH and 70 with no PH. The diagnostic accuracy of the approach was high as assessed by area under the curve at receiver operating characteristic analysis (P < 0.001): 0.92 for PAH, slightly higher than standard CMR metrics. Moreover, establishing the diagnosis using the approach was less time-consuming, being achieved within 10 s. Learnt features were visualized in feature maps with correspondence to cardiac phases, confirming known and also identifying potentially new diagnostic features in PAH.

CONCLUSION

A tensor-based machine learning approach has been developed and applied to CMR. High diagnostic accuracy has been shown for PAH diagnosis and new learnt features were visualized with diagnostic potential.

Computed tomography appearances of the lung parenchyma in pulmonary hypertension

Computed tomography (CT) is a valuable tool in the workup of patients under investigation for pulmonary hypertension (PH) and may be the first test to suggest the diagnosis. CT parenchymal lung changes can help to differentiate the aetiology of PH. CT can demonstrate interstitial lung disease, emphysema associated with chronic obstructive pulmonary disease, features of left heart failure (including interstitial oedema), and changes secondary to miscellaneous conditions such as sarcoidosis. CT also demonstrates parenchymal changes secondary to chronic thromboembolic disease and venous diseases such as pulmonary venous occlusive disease (PVOD) and pulmonary capillary haemangiomatosis (PCH). It is important for the radiologist to be aware of the various manifestations of PH in the lung, to help facilitate an accurate and timely diagnosis. This pictorial review illustrates the parenchymal lung changes that can be seen in the various conditions causing PH.

Renal protective effect of sodium ferulate on pulmonary hypertension patients undergoing computed tomography pulmonary angiography

This study aimed to explore the correlation of sodium ferulate and the renal protective effect on computed tomography pulmonary angiography in patients suffering from pulmonary hypertension. This prospective study enrolled 92 consecutive patients with pulmonary hypertension diagnosed by echocardiography, and all included patients underwent computed tomography pulmonary angiography after admission. The participants were randomized, divided into sodium ferulate group (n = 49) and control group (n = 43), of which patients in the sodium ferulate group received intravenous sodium ferulate 3.0 g per day from 12 h before computed tomography pulmonary angiography examination to 72 h after that, and patients in the control group were provided with routine treatment. Renal function was assessed by measuring serum creatinine, estimated glomerular filtration rate, Cystatin-C as well as 24 h, 48 h, and 72 h after computed tomography pulmonary angiography, followed by the calculation of the incidence of contrast-induced nephropathy for contrast-induced nephropathy and non-contrast-induced nephropathy grouping. Besides, renal resistive index was determined via Doppler ultrasound examination before, after 1 h and 24 h after computed tomography pulmonary angiography. There were no significant differences between the two groups in serum creatinine at baseline and 24 h after computed tomography pulmonary angiography (P > 0.05, respectively), but at 48 h and 72 h, it was lower in the sodium ferulate group (P < 0.05). There were no significant differences of estimated glomerular filtration rate between the two groups (P > 0.05). The level of Cystatin-C at 48 h and 72 h after computed tomography pulmonary angiography was lower than in the sodium ferulate group (P < 0.05). Contrast-induced nephropathy was identified in nine patients (9.78%). Sodium ferulate was associated with a decline in the incidence of contrast-induced nephropathy (4.08 vs. 16.28 %, P < 0.05). Compared to patients with contrast-induced nephropathy, lower renal resistive index were observed at 1 h and 24 h after computed tomography pulmonary angiography in patients without contrast-induced nephropathy (P < 0.05). Infusion of sodium ferulate before and after computed tomography pulmonary angiography was associated with a decline in incidence of contrast-induced nephropathy.

Diagnostic accuracy of CT pulmonary angiography in suspected pulmonary hypertension

Objectives

Computed tomography (CT) pulmonary angiography is widely used in patients with suspected pulmonary hypertension (PH). However, the diagnostic and prognostic significance remains unclear. The aim of this study was to (a) build a diagnostic CT model and (b) test its prognostic significance.

Methods

Consecutive patients with suspected PH undergoing routine CT pulmonary angiography and right heart catheterisation (RHC) were identified. Axial and reconstructed images were used to derive CT metrics. Multivariate regression analysis was performed in the derivation cohort to identify a diagnostic CT model to predict mPAP ≥ 25 mmHg (the existing ESC guideline definition of PH) and > 20 mmHg (the new threshold proposed at the 6th World Symposium on PH). In the validation cohort, sensitivity, specificity and compromise CT thresholds were identified with receiver operating characteristic (ROC) analysis. The prognostic value of the CT model was assessed using Kaplan-Meier analysis.

Results

Between 2012 and 2016, 491 patients were identified. In the derivation cohort (n = 247), a CT model was identified including pulmonary artery diameter, right ventricular outflow tract thickness, septal angle and left ventricular area. In the validation cohort (n = 244), the model was diagnostic, with an area under the ROC curve of 0.94/0.91 for mPAP ≥ 25/> 20 mmHg respectively. In the validation cohort, 93 patients died; mean follow-up was 42 months. The diagnostic thresholds for the CT model were prognostic, log rank, all p < 0.01.

Discussion

In suspected PH, a diagnostic CT model had diagnostic and prognostic utility.

Key Points

• Diagnostic CT models have high diagnostic accuracy in a tertiary referral population of with suspected PH.

• Diagnostic CT models stratify patients by mortality in suspected PH.

Electronic supplementary material

The online version of this article (10.1007/s00330-020-06846-1) contains supplementary material, which is available to authorized users.

Novel imaging techniques in pulmonary hypertension

PURPOSE OF REVIEW

Pulmonary hypertension is a life-shortening condition, which may be idiopathic but is more frequently seen in association with other conditions. Current guidelines recommend cardiac catheterization to confirm the diagnosis of pulmonary hypertension. Evidence suggests an increasing role for noninvasive imaging modalities in the initial diagnostic and prognostic assessment and evaluation of treatment response.

RECENT FINDINGS

In this review we examine the evidence for current noninvasive imaging methodologies: echocardiography computed tomography and MRI in the diagnostic and prognostic assessment of suspected pulmonary hypertension and explore the potential utility of modeling and machine-learning approaches.

SUMMARY

Noninvasive imaging allows a comprehensive assessment of patients with suspected pulmonary hypertension. It plays a key part in the initial diagnostic and prognostic assessment and machine-learning approaches show promise in the diagnosis of pulmonary hypertension.

EXPRESS: Statement on imaging and pulmonary hypertension from the Pulmonary Vascular Research Institute (PVRI)

Pulmonary hypertension (PH) is highly heterogeneous and despite treatment advances it remains a life-shortening condition. There have been significant advances in imaging technologies, but despite evidence of their potential clinical utility, practice remains variable, dependent in part on imaging availability and expertise. This statement summarizes current and emerging imaging modalities and their potential role in the diagnosis and assessment of suspected PH. It also includes a review of commonly encountered clinical and radiological scenarios, and imaging and modeling-based biomarkers. An expert panel was formed including clinicians, radiologists, imaging scientists, and computational modelers. Section editors generated a series of summary statements based on a review of the literature and professional experience and, following consensus review, a diagnostic algorithm and 55 statements were agreed. The diagnostic algorithm and summary statements emphasize the key role and added value of imaging in the diagnosis and assessment of PH and highlight areas requiring further research.