Diagnostic advances and opportunities in chronic thromboembolic pulmonary hypertension

Non-contrasted computed tomography (NCCT) based chronic thromboembolic pulmonary hypertension (CTEPH) automatic diagnosis using cascaded network with multiple instance learning

Objective.The diagnosis of chronic thromboembolic pulmonary hypertension (CTEPH) is challenging due to nonspecific early symptoms, complex diagnostic processes, and small lesion sizes. This study aims to develop an automatic diagnosis method for CTEPH using non-contrasted computed tomography (NCCT) scans, enabling automated diagnosis without precise lesion annotation.Approach.A novel cascade network (CN) with multiple instance learning (CNMIL) framework was developed to improve the diagnosis of CTEPH. This method uses a CN architecture combining two Resnet-18 CNN networks to progressively distinguish between normal and CTEPH cases. Multiple instance learning (MIL) is employed to treat each 3D CT case as a 'bag' of image slices, using attention scoring to identify the most important slices. An attention module helps the model focus on diagnostically relevant regions within each slice. The dataset comprised NCCT scans from 300 subjects, including 117 males and 183 females, with an average age of 52.5 ± 20.9 years, consisting of 132 normal cases and 168 cases of lung diseases, including 88 cases of CTEPH. The CNMIL framework was evaluated using sensitivity, specificity, and the area under the curve (AUC) metrics, and compared with common 3D supervised classification networks and existing CTEPH automatic diagnosis networks.Main results. The CNMIL framework demonstrated high diagnostic performance, achieving an AUC of 0.807, accuracy of 0.833, sensitivity of 0.795, and specificity of 0.849 in distinguishing CTEPH cases. Ablation studies revealed that integrating MIL and the CN significantly enhanced performance, with the model achieving an AUC of 0.978 and perfect sensitivity (1.000) in normal classification. Comparisons with other 3D network architectures confirmed that the integrated model outperformed others, achieving the highest AUC of 0.8419.Significance. The CNMIL network requires no additional scans or annotations, relying solely on NCCT. This approach can improve timely and accurate CTEPH detection, resulting in better patient outcomes.

State-of-the Art Cardiac Magnetic Resonance in Pulmonary Hypertension - An Update on Diagnosis, Risk Stratification and Treatment

Pulmonary hypertension (PH) is a globally under-recognized but life-shortening disease with a poor prognosis if untreated, delayed or inappropriately treated. One of the most important issues for PH is to improve patient quality of life and survival through timely and accurate diagnosis, precise risk stratification and prognosis prediction. Cardiac magnetic resonance (CMR), a non-radioactive, non-invasive image-based examination with excellent tissue characterization, provides a comprehensive assessment of not only the disease severity but also secondary changes in cardiac structure, function and tissue characteristics. The purpose of this review is to illustrate an updated status of CMR for PH assessment, focusing on the application of both conventional and emerging technologies as well as the latest clinical trials.

Pathogenesis, Diagnosis, and Management of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is thought to occur as a sequelae of thromboembolic processes in the pulmonary vasculature. The pathophysiology of CTEPH is multifactorial, including impaired fibrinolysis, endothelial dysregulation, and hypoxic adaptations. The diagnosis of CTEPH is typically delayed considering the nonspecific nature of the symptoms, lack of screening, and relatively low incidence. Diagnostic tools include ventilation-perfusion testing, echocardiography, cardiac catheterization, and pulmonary angiography. The only potentially curative treatment for CTEPH is pulmonary endarterectomy However, approximately 40% of patients are inoperable. Currently, only Riociguat is Food and Drug Administration approved specifically for CTEPH, with additional drug trials underway.

Central versus Peripheral CTEPH-Clinical and Hemodynamic Specifications

Background and Objectives: Chronic thromboembolic pulmonary hypertension (CTEPH) is a chronic progressive disease, resulting from persistent arterial obstruction combined with small-vessel remodeling. Central and peripheral CTEPH are distinguished, according to the dominant lesion's location. This is important for surgical or percutaneous interventional assessment or for medical treatment. Material and Methods: Eighty-one patients (51 male/30 female) with confirmed CTEPH were analyzed, while the CENTRAL type included 51 patients (63%) and the PERIPHERAL type 30 patients (37%). Results: A significant difference in CENTRAL type vs. PERIPHERAL type was determined in gender (male 72.5% vs. 46.7%; p = 0.0198). No difference was found in age, functional status, or echocardiographic parameters. Invasive hemodynamic parameters showed a significant difference in mean pulmonary arterial pressure (46 vs. 58 mmHg; p = 0.0002), transpulmonary gradient (34 vs. 47 mmHg; p = 0.0005), and cardiac index (2.04 vs. 2.5 L.min.m²; p = 0.02) but not in pulmonary vascular resistance. Risk factors showed a significant difference only in acute pulmonary embolism (93.8% vs. 60%; p = 0.0002) and malignancy (2% vs. 13.3%; p = 0.0426). Conclusions: Our study showed hemodynamic differences between CENTRAL type vs. PERIPHERAL type CTEPH with a worse hemodynamic picture in CENTRAL form. This may indicate a different pathophysiological response and/or possible additional influences contributing especially to the peripheral pulmonary bed affection.

Perfusion Scintigraphy in Diagnosis and Management of Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a life-threatening complication of acute pulmonary embolism (PE). Because the treatment of CTEPH is markedly different from that of other types of pulmonary hypertension, lung ventilation-perfusion (V/Q) scintigraphy is recommended for the workup of patients with unexplained pulmonary hypertension. Lung V/Q scintigraphy is superior to CT pulmonary angiography for detecting CTEPH. Perfusion defect findings of CTEPH can be different from those of acute PE. Familiarity with the patterns of perfusion defects seen during the initial workup of CTEPH and the expected posttreatment changes seen at follow-up imaging is essential for accurate interpretation of V/Q scintigraphy findings. ^©RSNA, 2019.

Pulmonary vasculitis mimicking chronic thromboembolic disease

A 29-year-old female patient presented with chest pain, breathlessness and syncope on the background of constitutional symptoms, oral ulceration and a rash. Multiple investigations were performed, including a CT pulmonary angiogram (CTPA) that was initially felt to show imaging features consistent with a diagnosis of chronic thromboembolic disease (CTED). The patient was referred to a tertiary pulmonary hypertension centre and the possibility of pulmonary vasculitis was raised. Subsequent positron emission tomography (PET)-CT revealed imaging features supporting this diagnosis. The patient was treated with intravenous cyclophosphamide infusions, following which her symptoms improved. A repeat PET-CT 6 months after treatment showed resolution in pulmonary artery and mediastinal uptake, but persistence of pulmonary artery occlusions on a repeat CTPA. A final diagnosis of pulmonary vasculitis secondary to Behçet's disease was made. This case report aims to raise awareness of the imaging features of CTED and its mimics.

Non-invasive Multimodality Cardiovascular Imaging of the Right Heart and Pulmonary Circulation in Pulmonary Hypertension

Pulmonary hypertension (PH) is defined as resting mean pulmonary arterial pressure (mPAP) ≥25 millimeters of mercury (mmHg) via right heart (RH) catheterization (RHC), where increased afterload in the pulmonary arterial vasculature leads to alterations in RH structure and function. Mortality rates have remained high despite therapy, however non-invasive imaging holds the potential to expedite diagnosis and lead to earlier initiation of treatment, with the hope of improving prognosis. While historically the right ventricle (RV) had been considered a passive chamber with minimal role in the overall function of the heart, in recent years in the evaluation of PH and RH failure the anatomical and functional assessment of the RV has received increased attention regarding its performance and its relationship to other structures in the RH-pulmonary circulation. Today, the RV is the key determinant of patient survival. This review provides an overview and summary of non-invasive imaging methods to assess RV structure, function, flow, and tissue characterization in the setting of imaging's contribution to the diagnostic, severity stratification, prognostic risk, response of treatment management, and disease surveillance implications of PH's impact on RH dysfunction and clinical RH failure.

Chronic thromboembolic pulmonary hypertension: an enigma

Chronic thromboembolic pulmonary hypertension (CTEPH) is a form of pulmonary arterial hypertension (PAH) in which the pulmonary thrombus fails to resolve, resulting in occlusion and remodelling of pulmonary arteries.¹ Timely diagnosis is critical since it is potentially curable by pulmonary thromboendarterectomy. Twenty five per cent of cases do not have a history of thromboembolic event. The diagnosis should be considered in the diagnostic work-up of PAH despite lack of history of episodes of thromboembolism. Here we are reporting a case of CTEPH with multiple systemic to pulmonary collaterals delineated by angiogram and CT.

Abnormal Ventilation-Perfusion Scan Is Associated with Pulmonary Hypertension in Sickle Cell Adults

Pulmonary hypertension (PH) in adults with sickle cell disease (SCD) is associated with early mortality. Chronic thromboembolic PH (CTEPH) is an important complication and contributor to PH in SCD but is likely underappreciated. Guidelines recommend ventilation-perfusion (V/Q) scintigraphy as the imaging modality of choice to exclude CTEPH. Data on V/Q scanning are limited in SCD. Our objective was to compare the performance of V/Q scanning with that of CT pulmonary angiography (CTPA) and to report clinical outcomes associated with abnormal V/Q findings. Methods: Laboratory data, echocardiography, 6-min-walk testing, V/Q scanning, CTPA, and right heart catheterization (RHC) were prospectively obtained. High-probability and intermediate-probability V/Q findings were considered to be abnormal. Included for analysis were 142 SCD adults (aged 40.1 ± 13.7 y, 83 women, 87% hemoglobin SS) in a stable state enrolled consecutively between March 13, 2002, and June 8, 2017. Results: V/Q results were abnormal in 65 of 142 patients (45.8%). CTPA was positive for pulmonary embolism in 16 of 60 (26.7%). RHC confirmed PH (mean pulmonary artery pressure ≥ 25 mmHg) in 46 of 64 (71.9%), of whom 34 (73.9%) had abnormal V/Q findings. Among those without PH by RHC (n = 18), 2 of 18 patients had abnormal V/Q findings. Thirty-three patients had a complete dataset (V/Q scanning, CTPA, and RHC); 29 of 33 had abnormal RHC findings, of whom 26 had abnormal V/Q findings, compared with 11 who had abnormal CTPA findings. There was greater concordance between V/Q findings and RHC (κ-value = 0.53; P < 0.001) than between CTPA and RHC (κ-value = 0.13; P = 0.065). The sensitivity and specificity for V/Q scanning was 89.7% and 75.0%, respectively, whereas CTPA had sensitivity of 37.3% and specificity of 100%. Abnormal V/Q finding swere associated with hemodynamic severity (mean pulmonary artery pressure, 35.2 ± 9.6 vs. 26.9 ± 10.5 mm Hg, P = 0.002; transpulmonary gradient, 21.5 ± 9.7 vs. 12.16 ± 11 mmHg, P = 0.005; and pulmonary vascular resistance, 226.5 ± 135 vs. 140.7 ± 123.7 dynes⋅s⋅cm^-5, P = 0.013) and exercise capacity (6-min-walk distance, 382.8 ± 122.3 vs. 442.3 ± 110.6 m, P < 0.010). Thirty-four deaths were observed over 15 y. All-cause mortality was higher in the abnormal-V/Q group (21 [61.8%]) than in the normal-V/Q group (13 [38.2%]) (log-rank test, P = 0.006; hazard ratio, 2.54). Conclusion: V/Q scanning is superior to CTPA in detecting thrombotic events in SCD. Abnormal V/Q findings are associated with PH, worse hemodynamics, lower functional capacity, and higher mortality. Despite high sensitivity in detecting CTEPH, V/Q scanning is underutilized. We recommend the use of V/Q scanning in the evaluation of dyspnea in adult SCD patients given the important implications toward management.

Interventional Therapies in Pulmonary Hypertension

Despite advances in drug therapy, pulmonary hypertension-particularly arterial hypertension (PAH)-remains a fatal disease. Untreatable right heart failure (RHF) from PAH eventually ensues and remains a significant cause of death in these patients. Lowering pulmonary input impedance with different PAH-specific drugs is the obvious therapeutic target in RHF due to chronically increased afterload. However, potential clinical gain can also be expected from attempts to unload the right heart and increase systemic output. Atrial septostomy, Potts anastomosis, and pulmonary artery denervation are interventional procedures serving this purpose. Percutaneous balloon pulmonary angioplasty, another interventional therapy, has re-emerged in the last few years as a clear alternative for the management of patients with distal, inoperable, chronic thromboembolic pulmonary hypertension. The current review discusses the physiological background, experimental evidence, and potential clinical and hemodynamic benefits of all these interventional therapies regarding their use in the setting of RHF due to severe pulmonary hypertension.

The changing landscape of chronic thromboembolic pulmonary hypertension management

For patients with chronic thromboembolic pulmonary hypertension (CTEPH), the current standard of care involves surgical removal of fibro-thrombotic obstructions by pulmonary endarterectomy. While this approach has excellent outcomes, significant proportions of patients are not eligible for surgery or suffer from persistent/recurrent pulmonary hypertension after the procedure. The availability of balloon pulmonary angioplasty and the approval of the first medical therapy for use in CTEPH have significantly improved the outlook for patients ineligible for pulmonary endarterectomy. In this comprehensive review, we discuss the latest developments in the rapidly evolving field of CTEPH. These include improvements in imaging modalities and advances in surgical and interventional techniques, which have broadened the range of patients who may benefit from such procedures. The efficacy and safety of targeted medical therapies in CTEPH patients are also discussed, particularly the encouraging data from the recent MERIT-1 trial, which demonstrated the beneficial impact of using macitentan to treat patients with inoperable CTEPH, including those on background therapy. As the treatment options for CTEPH improve, hybrid management involving more than one intervention in the same patient may become a viable option in the near future.

Management of CTEPH is evolving rapidly, leading to improved patient outcomeshttp://ow.ly/rHrt30gUQWX

Long-term outcomes of surgery for chronic thromboembolic pulmonary hypertension compared with medical therapy at a single Korean center

BACKGROUND/AIMS

Pulmonary endarterectomy (PEA) is the gold standard for treating chronic thromboembolic pulmonary hypertension (CTEPH) in Western countries. The aim of this study was to investigate the long-term outcomes of performing PEA on CTEPH patients in comparison with medical therapy at a single Korean center.

METHODS

This retrospective study included 88 CTEPH patients. These patients were classified into the PEA group (n = 37) or non-PEA group (i.e., medical therapy; n = 51). The clinical characteristics, hemodynamic data, and long-term survival rates were compared. Independent prognostic factors for CTEPH were also investigated.

RESULTS

CTEPH was not associated with either gender, and the mean age at diagnosis was 53.3 ± 13.7 years. Echocardiography revealed that the mean peak velocity of the tricuspid regurgitation jet was 4.2 ± 0.7 m/sec and the mean pulmonary arterial pressure was 51.7 ± 15.1 mmHg. The PEA and non-PEA groups demonstrated no significant differences, except in terms of the right ventricular end-diastolic diameter. The survival rates of the PEA group were significantly higher than the non-PEA group at 1, 3, 5, and 10 years (p = 0.032). Multivariate analyses indicated that World Health Organization class IV and PEA were significant predictors of poorer and better outcomes, respectively.

CONCLUSIONS

PEA demonstrates more favorable effects on long-term survival than medical therapy in Korean CTEPH patients who were considered operable.

Balloon pulmonary angioplasty in chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is thought to result from incomplete resolution of pulmonary thromboemboli that undergo organisation into fibrous tissue within pulmonary arterial branches, filling pulmonary arterial lumina with collagenous obstructions. The treatment of choice is pulmonary endarterectomy (PEA) in CTEPH centres, which has low post-operative mortality and good long-term survival. For patients ineligible for PEA or who have recurrent or persistent pulmonary hypertension after surgery, medical treatment with riociguat is beneficial. In addition, percutaneous balloon pulmonary angioplasty (BPA) is an emerging option, and promises haemodynamic and functional benefits for inoperable patients. In contrast to conventional angioplasty, BPA with undersized balloons over guide wires exclusively breaks intraluminal webs and bands, without dissecting medial vessel layers, and repeat sessions are generally required. Observational studies report that BPA improves haemodynamics, symptoms and functional capacity in patients with CTEPH, but controlled trials with long-term follow-up are needed. Complications include haemoptysis, wire injury, vessel dissection, vessel rupture, reperfusion pulmonary oedema, pulmonary parenchymal bleeding and haemorrhagic pleural effusions. This review summarises the available evidence for BPA, patient selection, recent technical refinements and periprocedural imaging, and discusses the potential future role of BPA in the management of CTEPH.

Balloon pulmonary angioplasty is an emerging percutaneous vascular intervention for non-operable CTEPHhttp://ow.ly/tIN3309hys3

Clinical Study of Acute Vasoreactivity Testing in Patients with Chronic Thromboembolic Pulmonary Hypertension

BACKGROUND

The clinical significance of acute vasoreactivity testing (AVT) in patients with chronic thromboembolic pulmonary hypertension (CTEPH) remains unclear. We analyzed changes in hemodynamics and oxygenation dynamics indices after AVT in patients with CTEPH using patients with pulmonary arterial hypertension (PAH) as controls.

METHODS

We analyzed retrospectively the results of AVT in 80 patients with PAH and 175 patients with CTEPH registered in the research database of Beijing Chao-Yang Hospital between October 2005 and August 2014. Demographic variables, cardiopulmonary indicators, and laboratory findings were compared in these two subgroups. A long-term follow-up was conducted in patients with CTEPH. Between-group comparisons were performed using the independent-sample t-test or the rank sum test, within-group comparisons were conducted using the paired t-test or the Wilcoxon signed-rank test, and count data were analyzed using the Chi-squared test. Survival was estimated using the Kaplan-Meier method and log-rank test.

RESULTS

The rates of positive response to AVT were similar in the CTEPH (25/175, 14.3%) and PAH (9/80, 11.3%) groups (P > 0.05). Factors significantly associated a positive response to AVT in the CTEPH group were level of N-terminal pro-brain natriuretic peptide (≤1131.000 ng/L), mean pulmonary arterial pressure (mPAP, ≤44.500 mmHg), pulmonary vascular resistance (PVR, ≤846.500 dyn·s-1·m-5), cardiac output (CO, ≥3.475 L/min), and mixed venous oxygen partial pressure (PvO2, ≥35.150 mmHg). Inhalation of iloprost resulted in similar changes in mean blood pressure, mPAP, PVR, systemic vascular resistance, CO, arterial oxygen saturation (SaO2), mixed venous oxygen saturation, partial pressure of oxygen in arterial blood (PaO2), PvO2, and intrapulmonary shunt (Qs/Qt) in the PAH and CTEPH groups (all P > 0.05). The survival time in patients with CTEPH with a negative response to AVT was somewhat shorter than that in AVT-responders although the difference was not statistically significant (χ2 =3.613, P = 0.057). The survival time of patients with CTEPH who received calcium channel blockers (CCBs) was longer than that in the group with only basic treatment and not shorter than that of patients who receiving targeted drugs or underwent pulmonary endarterectomy (PEA) although there was no significant difference between the four different treatment regimens (χ2 =3.069, P = 0.381).

CONCLUSIONS

The rates of positive response to AVT were similar in the CTEPH and PAH groups, and iloprost inhalation induced similar changes in hemodynamics and oxygenation dynamics indices. A positive response to AVT in the CTEPH group was significantly correlated with milder disease and better survival. Patients with CTEPH who cannot undergo PEA or receive targeted therapy but have a positive response to AVT might benefit from CCB treatment.

An international physician survey of chronic thromboembolic pulmonary hypertension management

We conducted an international study to evaluate practices in the diagnosis and management of patients with chronic thromboembolic pulmonary hypertension (CTEPH) globally across different regions. Between August and October 2012, CTEPH-treating physicians completed a 15-minute online questionnaire and provided patient record data for their 2-5 most recent patients with CTEPH. Overall, 496 physicians (Europe: 260; United States: 152; Argentina: 52; Japan: 32) completed the questionnaire and provided patient record data for 1,748 patients. The proportion of physicians who described themselves as working in or affiliated with a specialized pulmonary hypertension (PH) center ranged from 38% in France and Italy to 83% in the United States. A large proportion of patients did not undergo ventilation/perfusion scanning (46%-67%) or right heart catheterization (24%-57%) for the diagnosis of CTEPH. Referral rates for pulmonary endarterectomy evaluation ranged from 25% in Japan to 44% in Europe, with higher referral rates in PH centers; the main reasons for lack of referral were that surgery was not considered unless medical treatment was failing and patient refusal. Other variations in management included greater use of phosphodiesterase 5 inhibitors in the United States than in Europe and Japan and greater use of combination treatment in the United States than in Europe. Physicians' perceptions of their treatment strategy were generally consistent with patient record data. Results from this study, which includes a global aspect of CTEPH care, demonstrate not only regional differences in CTEPH management but, more importantly, considerable nonadherence to the diagnosis and treatment guidelines for CTEPH, even in PH centers.

A review of imaging modalities in pulmonary hypertension

Pulmonary hypertension (PH) is defined as resting mean pulmonary artery pressure ≥25 mmHg measured by right heart catheterization. PH is a progressive, life-threatening disease with a variety of etiologies. Swift and accurate diagnosis of PH and appropriate classification in etiologic group will allow for earlier treatment and improved outcomes. A number of imaging tools are utilized in the evaluation of PH, such as chest X-ray, computed tomography (CT), ventilation/perfusion (V/Q) scan, and cardiac magnetic resonance imaging. Newer imaging tools such as dual-energy CT and single-photon emission computed tomography/computed tomography V/Q scanning have also emerged; however, their place in the diagnostic evaluation of PH remains to be determined. In general, each imaging technique provides incremental information, with varying degrees of sensitivity and specificity, which helps suspect the presence and identify the etiology of PH. The present study aims to provide a comprehensive review of the utility, advantages, and shortcomings of the imaging modalities that may be used to evaluate patients with PH.

Balloon Pulmonary Angioplasty Improves Biventricular Functions and Pulmonary Flow in Chronic Thromboembolic Pulmonary Hypertension

BACKGROUND

It remains to be determined whether balloon pulmonary angioplasty (BPA) improves biventricular cardiac functions and pulmonary flow in patients with chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS AND RESULTS

We enrolled 30 consecutive patients with inoperable CTEPH who underwent BPA, and carried out serial cardiac magnetic resonance imaging (CMR; M/F, 9/21; median age, 65.2 years). No patient died during the treatment or follow-up period. BPA significantly improved WHO functional class (III/IV, 83.0 to 4.0%), 6-min walking distance (330.2±168.7 to 467.3±114.4 m), mean pulmonary artery pressure (40.8±10.7 to 23.2±4.94 mmHg), pulmonary vascular resistance (9.26±4.19 to 3.35±1.40 WU) and cardiac index (2.19±0.64 to 2.50±0.57 L·min·m(2); all P<0.01). CMR also showed improvement of right ventricular (RV) ejection fraction (EF; 41.3±12.4 to 50.7±8.64%), left ventricular (LV) end-diastolic volume index (72.1±14.0 to 81.6±18.6 ml/m(2)) and LV stroke volume index (41.0±9.25 to 47.8±12.3 ml/m(2); all P<0.01). There was a significant correlation between change in RVEF and LVEF (Pearson's r=0.45, P=0.01). Average velocity in the main pulmonary artery was also significantly improved (7.50±2.43 to 9.79±2.92 cm/s, P<0.01).

CONCLUSIONS

BPA improves biventricular functions and pulmonary flow in patients with inoperable CTEPH. (Circ J 2016; 80: 1470-1477).

Chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a form of pulmonary hypertension (PH) characterized by the persistence of thromboembolic obstructing the pulmonary arteries as an organized tissue and the presence of a variable small vessel arteriopathy. The consequence is an increase in pulmonary vascular resistance resulting in progressive right heart failure. CTEPH is classified as group IV pulmonary hypertension according to the WHO classification of pulmonary hypertension. CTEPH is defined as precapillary pulmonary hypertension (mean pulmonary artery pressure ≥ 25 mmHg with a pulmonary capillary wedge pressure ≤ 15 mmHg) associated with mismatched perfusion defects on ventilation-perfusion lung scan and signs of chronic thromboembolic disease on computed tomography pulmonary angiogram and/or conventional pulmonary angiography, in a patient who received at least 3 months of therapeutic anticoagulation. CTEPH as a direct consequence of symptomatic pulmonary embolism (PE) is rare, and a significant number of CTEPH cases develop in the absence of history of PE. Thus, CTEPH should be considered in any patient with unexplained PH. Splenectomy, chronic inflammatory conditions such as inflammatory bowel disease, indwelling catheters and cardiac pacemakers have been identified as associated conditions increasing the risk of CTEPH. Ventilation-perfusion scan (V/Q) is the best test available for establishing the thromboembolic nature of PH. When CTEPH is suspected, patients should be referred to expert centres where pulmonary angiography, right heart catheterization and high-resolution CT scan will be performed to confirm the diagnosis and to assess the operability. Pulmonary endarterectomy (PEA) remains the gold standard treatment for CTEPH when organized thrombi involve the main, lobar or segmental arteries. This operation should only be performed by experienced surgeons in specialized centres. For inoperable patients, current ESC/ERS guidelines for the diagnosis and treatment of pulmonary hypertension recommend the use of riociguat and say that off-label use of drugs approved for PAH and pulmonary angioplasty may be considered in expert centres.