Diagnostic accuracy of computed tomography for chronic thromboembolic pulmonary hypertension: a systematic review and meta-analysis

Haemolytic Anaemia-Related Pulmonary Hypertension

Haemolytic anaemia represents a risk factor for the development of pulmonary hypertension (PH), currently classified as World Health Organization group 5 PH, and data regarding appropriate therapeutic strategy are limited. A total of 28 patients, 85.7% with thalassaemia and 14.3% with sickle cell disease, with a diagnosis of PH confirmed by right heart catheterization were included in the study. The patients were divided into three groups according to the PH haemodynamic definition and overall diagnostic approach: 42.9% had precapillary PH (pulmonary arterial hypertension-PAH group), 25% had post-capillary PH, and 32.1% had chronic thromboembolic PH (CTEPH) (29% of b-thalassemia and 50% of SCD patients). The therapeutic approach in each group and its impact on the outcome and haemodynamics were recorded. PAH-specific drug therapy received 82.1% of patients, and balloon pulmonary angioplasty (BPA) was performed in six patients with CTEPH. There were statistically significant differences in baseline mPAP and PVR values between the CTEPH-haemolytic anaemia group and other groups. PAH-specific drug therapy resulted in haemodynamic improvement for the PAH group. Patients who underwent BPA had improved pulmonary haemodynamics. The median survival time was 162 months, and the survival rate was 1 year-100%; 2, 3, 4, 5, and 6 years-96%; 9 years-90%; and 13 years-78%. In patients with haemolytic anaemia, the wide spectrum of induced PH highlighted the importance of a correct predominant diagnosis. BPA in CTEPH patients and specific-PAH drug therapy for PAH patients represent potential therapeutic strategies; however, the management should be offered in expert PH centres under individualized approaches for patients.

Chronic Thromboembolic Pulmonary Hypertension: Clinical and Imaging Evaluation

Chronic thromboembolic pulmonary hypertension (CTEPH) is a complication of pulmonary embolism and is an important cause of pulmonary hypertension. As a clinical entity, it is frequently underdiagnosed with prolonged diagnostic delays. This study reviews the clinical and radiographic findings associated with CTEPH to improve awareness and recognition. Strengths and limitations of multiple imaging modalities are reviewed. Accompanying images are provided to supplement the text and provide examples of important findings for the reader.

Machine learning assisted feature identification and prediction of hemodynamic endpoints using computed tomography in patients with CTEPH

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare but potentially curable cause of pulmonary hypertension (PH). Currently PH is diagnosed by right heart catheterisation. Computed tomography (CT) is used for ruling out other causes and operative planning. This study aims to evaluate importance of different quantitative/qualitative imaging features and develop a supervised machine learning (ML) model to predict hemodynamic risk groups. 127 Patients with diagnosed CTEPH who received preoperative right heart catheterization and thoracic CTA examinations (39 ECG-gated; 88 non-ECG gated) were included. 19 qualitative/quantitative imaging features and 3 hemodynamic parameters [mean pulmonary artery pressure, right atrial pressure (RAP), pulmonary artery oxygen saturation (PA SaO2)] were gathered. Diameter-based CT features were measured in axial and adjusted multiplane reconstructions (MPR). Univariate analysis was performed for qualitative and quantitative features. A random forest algorithm was trained on imaging features to predict hemodynamic risk groups. Feature importance was calculated for all models. Qualitative and quantitative parameters showed no significant differences between ECG and non-ECG gated CTs. Depending on reconstruction plane, five quantitative features were significantly different, but mean absolute difference between parameters (MPR vs. axial) was 0.3 mm with no difference in correlation with hemodynamic parameters. Univariate analysis showed moderate to strong correlation for multiple imaging features with hemodynamic parameters. The model achieved an AUC score of 0.82 for the mPAP based risk stratification and 0.74 for the PA SaO2 risk stratification. Contrast agent retention in hepatic vein, mosaic attenuation pattern and the ratio right atrium/left ventricle were the most important features among other parameters. Quantitative and qualitative imaging features of reconstructions correlate with hemodynamic parameters in preoperative CTEPH patients-regardless of MPR adaption. Machine learning based analysis of preoperative imaging features can be used for non-invasive risk stratification. Qualitative features seem to be more important than previously anticipated.

Even non-expert radiologists report chronic thromboembolic pulmonary hypertension (CTEPH) on CT pulmonary angiography with high sensitivity and almost perfect agreement

OBJECTIVES

To assess the diagnostic performance and interobserver agreement of CT pulmonary angiography (CTPA) in the detection of chronic thromboembolic pulmonary hypertension (CTEPH) and its features among radiologists of different levels of experience.

MATERIALS AND METHODS

In this retrospective, single-center, single-blinded study, three radiologists with different levels of experience in CT imaging (R1:15 years, R2:6 years, and R3:3 years) evaluated CTPA of 51 patients ultimately diagnosed with CTEPH (European Society of Cardiology guidelines) and 49 patients without CTEPH in random order to assess the presence of CTEPH, its features in the pulmonary artery tree, proximal level of involvement, bronchial artery hypertrophy, mosaic perfusion, and right heart overload.

RESULTS

CTPAs of 51 patients with CTEPH (median age, 66 years (IQR 56-72), 28 men) and 49 patients without CTEPH (median age, 65 years (IQR 50-74), 25 men) were evaluated. The sensitivity and specificity for the detection of CTEPH was 100% (all radiologists) and 100% (R1), 96% (R2), and 96% (R3) with almost perfect agreement (κ = 0.95). The sensitivity and specificity for detecting CTEPH by mosaic perfusion would be 89% (95%CI 83-93%) and 81% (74-87%). The level of pulmonary artery involvement was reported with moderate agreement (κ = 0.54, 95%CI 0.40-0.65). Substantial agreement was found in the evaluation of mosaic attenuation (κ = 0.75, 95%CI 0.64-0.84), right heart overload (κ = 0.68, 95%CI 0.56-0.79), and bronchial artery hypertrophy (0.71, 95%CI 0.59-0.82) which were the best predictors of CTEPH (p < 0.0001).

CONCLUSIONS

CTPA has high sensitivity and specificity in detecting CTEPH and almost perfect agreement among radiologists of different levels of expertise.

CLINICAL RELEVANCE

CT pulmonary angiography can be used as a first-line imaging modality in patients with suspected chronic thromboembolic pulmonary hypertension (CTEPH) even when interpreted by non-CTEPH experts.

KEY POINTS

• CT pulmonary angiography has high sensitivity and specificity in detecting chronic thromboembolic pulmonary hypertension (CTEPH) and almost perfect interobserver agreement among radiologists of different levels of expertise. • Substantial agreement exists in the assessment of mosaic attenuation, right heart overload, and bronchial artery hypertrophy, which are the best predictors of CTEPH.

Role of Surgical and Medical Management of Chronic Thromboembolic Pulmonary Hypertension: A Systematic Review

Chronic thromboembolic pulmonary hypertension (CTEPH) is underdiagnosed and has recently surfaced as one of the leading triggers of severe pulmonary hypertension. This disease process is described by structural changes of pulmonary arteries such as fibrous stenosis, complete obliteration, or the presence of a resistant intraluminal thrombus, resulting in increased pulmonary resistance and eventually progressing to right-sided heart failure. Hence, this study aims to describe the current treatments for CTEPH and their efficacy in hemodynamic improvement and prevention of recurring thromboembolic episodes in patients. This systematic review promptly follows the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. On February 13, 2022, our team searched through the following databases: PubMed, ProQuest, and ScienceDirect. The following keywords were used across all databases: CTEPH AND Pulmonary Endarterectomy (PEA), CTEPH AND Balloon Pulmonary Angioplasty (BPA), and CTEPH AND Medical Therapy OR Anticoagulation therapy. Twenty-nine thousand eighty-nine articles on current management techniques (PEA, Balloon angioplasty, anticoagulants) were selected, analyzed, and reviewed with each other. We found 19 articles concerning PEA, 15 concerning BPA, and six regarding anticoagulants. Most papers showed high success rates and promising evidence of PEA and anticoagulants as a post-operative regimen. BPA was the least preferred but is still reputable in patients unfit for invasive techniques. CTEPH is a condition presenting with either fibrous stenosis, complete obliteration of the artery, or a clogged thrombus. Recent studies have shown three techniques that physicians have used to treat CTEPH: balloon-pulmonary angioplasty, PEA, and medical management with anticoagulants. PEA followed by anticoagulants is preferred to balloon pulmonary angioplasties. CTEPH is an ongoing topic in research; as it continues to be researched, we hope to see more management techniques available.

Clinical-radiological-pathological correlation in chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare and potentially life-threatening complication of acute pulmonary embolism. It is characterised by persistent fibro-thrombotic pulmonary vascular obstructions and elevated pulmonary artery pressure leading to right heart failure. The diagnosis is based on two steps, as follows: 1) suspicion based on symptoms, echocardiography and ventilation/perfusion scan and 2) confirmation with right heart catheterisation, computed tomography pulmonary angiography and, in most cases, digital subtraction angiography. The management of CTEPH requires a multimodal approach, involving medical therapy, interventional procedures and surgical intervention. This clinical-radiological-pathological correlation paper illustrates the diagnostic and therapeutic management of two patients. The first had chronic thromboembolic pulmonary disease without pulmonary hypertension at rest but with significant physical limitation and was successfully treated with pulmonary endarterectomy. The second patient had CTEPH associated with splenectomy and was considered unsuitable for surgery because of exclusive subsegmental lesions combined with severe pulmonary hypertension. The patient benefited from multimodal treatment involving medical therapy followed by multiple sessions of balloon pulmonary angioplasty. Both patients had normalised functional capacity and pulmonary haemodynamics 3-6 months after the interventional treatment. These two examples show that chronic thromboembolic pulmonary diseases are curable if diagnosed promptly and referred to CTEPH centres for specialist treatment.

[Diagnostic Algorithm and Screening of Pulmonary Hypertension]

The new guidelines for the diagnosis and treatment of pulmonary hypertension include a new diagnostic algorithm and provide specific recommendations for the required diagnostic procedures, including screening methods. These recommendations are commented on by national experts under the auspices of the DACH. These comments provide additional decision support and background information, serving as a further guide for the complex diagnosis of pulmonary hypertension.

Enhancing preoperative assessment in chronic thromboembolic pulmonary hypertension: A comprehensive analysis of interobserver agreement and proximity-based CT pulmonary angiography scoring

Background

Surgical risk in chronic thromboembolic pulmonary hypertension (CTEPH) depends on the proximity of thromboembolism on CT pulmonary angiography (CTPA). We assessed interobserver agreement for the quantification of thromboembolic lesions in CTEPH using a novel CTPA scoring index.

Methods

Forty CTEPH patients (mean age, 58 ± 16 years; 19 men) with preoperative CTPA who underwent pulmonary endarterectomy (PEA) (08/2020-09/2021) were retrospectively included. Three radiologists scored each CTPA for chronic thromboembolism (occlusions, eccentric thickening, webs) using a 32-vessel model of the pulmonary vasculature, with interobserver agreement evaluated using Fleiss' kappa. CT level of disease was determined by the most proximal chronic thromboembolism: level 1 (main pulmonary artery), 2 (lobar), 3 (segmental) and 4 (subsegmental), and compared to surgical level at PEA.

Results

Interobserver agreement for CT level of disease was moderate overall (κ = 0.52). Agreement was substantial overall at the main/lobar level (κ, mean = 0.71) when excluding the left upper lobe (κ = 0.17). Though segmental and subsegmental agreement suffered (κ = 0.31), we found substantial agreement for occlusions (κ = 0.72) compared to eccentric thickening (κ = 0.45) and webs (κ = 0.14). Correlation between CT level and surgical level was strong overall (τb = 0.73) and in the right lung (τb = 0.68), but weak in the left lung (τb = 0.42) (p < 0.05). Radiologists often over- and underestimated the proximal extent of disease in right and left lung, respectively.

Conclusions

CT level of disease demonstrated good agreement between radiologists and was highly predictive of the surgical level in CTEPH. Occlusions were the most reliable sign of chronic thromboembolism and are important in assessing the segmental vasculature.

Comparison of echocardiographic pulmonary flow Doppler markers in patients with massive or submassive acute pulmonary embolism and control group: A cross-sectional study

Background and Aims

Computed tomography angiography (CTA) is the gold standard for the diagnosis of massive (MPE) and submassive pulmonary embolism (SMPE). Ultrasound has not been accepted as a diagnostic tool. We aim to evaluate the pattern of pulmonary Doppler echocardiography in patients with pulmonary embolism (PE).

Methods

From 2020 to 2022, 30 patients with acute MPE or SMPE confirmed by CTA and normal pulmonary pressures were selected. A control group was created with 30 individuals without PE. All patients had an echocardiography Doppler study of the pulmonary flow with a focus on early systolic notching (ESN), McConnell's (MC) sign, Right ventricular outflow tract velocity time integral (RVOT VTI), segmental thickness variability (STV), right ventricular end-diastolic diameter (RVEDD), tricuspid regurgitation (TR) gradient, pulmonary artery pressure (PAP), and acceleration (AT) or ejection time (ET).

Results

ESN was identified in 96.6% of PE patients and 0% of the control group (p < 0.001). In comparison with the control group, STV (p < 0.001), RVOT VTI (p < 0.001), ET (p = 0.04), and AT (p < 0.001) values were lower in patients with PE while RVEDD, TR gradient, PAP, ESN, MC sign, and d-shape were higher (p < 0.001). Identification of the ESN pattern and AT/ET < 0.4 showed excellent predictive ability for MPE and SMPE with a sensitivity of 97.0% and 100%, specificity of 99.0% and 97%, and an area under the ROC curve of 0.967 (95% CI 0.914-1.00) and 0.933 (95% CI 0.844-1.00), respectively.

Conclusion

Doppler echocardiography with particular attention to ESN, may be a suitable noninvasive method for the diagnosis of MPE and SMPE. Further studies with more sample sizes are needed to confirm its diagnostic benefit.

Pathophysiology and Treatment of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a condition in which an organic thrombus remains in the pulmonary artery (PA) even after receiving anticoagulation therapy for more than 3 months and is complicated by pulmonary hypertension (PH), leading to right-sided heart failure and death. CTEPH is a progressive pulmonary vascular disease with a poor prognosis if left untreated. The standard treatment for CTEPH is pulmonary endarterectomy (PEA), which is usually performed only in specialized centers. In recent years, balloon pulmonary angioplasty (BPA) and drug therapy for CTEPH have also shown good results. This review discusses the complex pathogenesis of CTEPH and presents the standard of care, PEA, as well as a new device called BPA, which is showing remarkable progress in efficacy and safety. Additionally, several drugs are now demonstrating established evidence of efficacy in treating CTEPH.

Highlights from the International Chronic Thromboembolic Pulmonary Hypertension Congress 2021

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare complication of acute pulmonary embolism. It is caused by persistent obstruction of pulmonary arteries by chronic organised fibrotic clots, despite adequate anticoagulation. The pulmonary hypertension is also caused by concomitant microvasculopathy which may progress without timely treatment. Timely and accurate diagnosis requires the combination of imaging and haemodynamic assessment. Optimal therapy should be individualised to each case and determined by an experienced multidisciplinary CTEPH team with the ability to offer all current treatment modalities. This report summarises current knowledge and presents key messages from the International CTEPH Conference, Bad Nauheim, Germany, 2021. Sessions were dedicated to 1) disease definition; 2) pathophysiology, including the impact of the hypertrophied bronchial circulation, right ventricle (dys)function, genetics and inflammation; 3) diagnosis, early after acute pulmonary embolism, using computed tomography and perfusion techniques, and supporting the selection of appropriate therapies; 4) surgical treatment, pulmonary endarterectomy for proximal and distal disease, and peri-operative management; 5) percutaneous approach or balloon pulmonary angioplasty, techniques and complications; and 6) medical treatment, including anticoagulation and pulmonary hypertension drugs, and in combination with interventional treatments. Chronic thromboembolic pulmonary disease without pulmonary hypertension is also discussed in terms of its diagnostic and therapeutic aspects.

Chronic Thromboembolic Pulmonary Disease and Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) and chronic thromboembolic pulmonary disease (CTEPD) are two terms characterizing symptomatic patients with chronic thromboembolic occlusions of pulmonary arteries with or without pulmonary hypertension at rest. Their diagnosis follows evolving schemas that integrate technological advances of pivotal imaging modalities among which computed tomography angiography plays a major role. This review article summarizes the current knowledge on the natural history of acute pulmonary embolism and its evolution toward chronic pulmonary embolism, as well as the imaging clues, for the identification of chronically obstructed pulmonary arteries. The requirements for imaging at the time of therapeutic decisions are also described in the light of recent updates in the literature from multidisciplinary groups of experts. Because an early diagnosis of CTEPH remains a challenge for the medical community, several practical issues are included in this article with the objective of improving the knowledge and collaboration between radiologists and clinicians in service to the patient.

Clinical Presentations and Multimodal Imaging Diagnosis in Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare but life-threatening pulmonary vascular disease caused by the presence of a prolonged thrombus in the pulmonary artery. CTEPH is a distinct disease entity classified as group 4 pulmonary hypertension according to the World Symposium on Pulmonary Hypertension. It is the only potentially curable cause of pulmonary hypertension. However, timely diagnosis and treatment are often hampered by nonspecific symptoms and signs and a lack of physician awareness regarding the condition. Thus, it is important to be familiar with the clinical features of CTEPH and the associated diagnostic processes. Herein, we cover the diagnostic approach for CTEPH using multimodal imaging tools in a clinical setting.

The diagnostic performance of CT pulmonary angiography in the detection of chronic thromboembolic pulmonary hypertension-systematic review and meta-analysis

OBJECTIVES

To examine the diagnostic performance of CT of the pulmonary artery (CTPA) as a potential first-choice imaging modality in patients with pulmonary arterial hypertension and suspected chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

A systematic review and meta-analysis were conducted in accordance with the PRISMA reporting checklist. Six scientific databases and registers (PubMed, EMBASE, Scopus, Web of Science, Cochrane, ClinicalTrials.gov ) were searched for studies evaluating the diagnostic performance of CTPA in suspected CTEPH in adult patients. Results were pooled separately for studies based on the evaluation of the pulmonary artery and those that relied solely on changes in parenchymal perfusion.

RESULTS

Ten single-center studies with 734 patients were eligible for pooling of the diagnostic performance of CTPA by evaluation of the pulmonary artery. The pooled sensitivity, specificity, PPV, NPV, accuracy, and diagnostic odds ratio (DOR) estimates for CTPA in the detection of CTEPH were 0.98, 0.99, 0.94, 1.00, 0.96, 0.96, and 292. Evaluation of perfusion changes yielded pooled estimates for sensitivity, specificity, PPV, NPV, accuracy, and DOR of 0.99, 0.84, 0.79, 0.98, 0.89, 0.89, and 98 across four studies with 278 patients. Scintigraphy, SPECT, digital subtraction angiography, right heart catheterization, pulmonary endarterectomy, and international guidelines were used to establish the diagnosis.

CONCLUSION

CTPA has high sensitivity and specificity in the detection of CTEPH when the examination is evaluated by expert radiologists. Evaluation of parenchymal perfusion alone is associated with slightly lower specificity. Further research is needed to determine the diagnostic performance of CTPA in excluding CTEPH in general radiology departments.

KEY POINTS

• CT pulmonary angiography (CTPA) is recommended in the diagnostic workup of chronic thromboembolic pulmonary hypertension (CTEPH). • CTPA has high sensitivity and specificity in the detection of CTEPH when evaluated by an expert radiologist. • Evaluation of changes in parenchymal perfusion alone is associated with slightly lower specificity. • Little is known about the diagnostic performance of CTPA in the detection of CTEPH in general radiology departments.

Interventional Imaging Roadmap to Successful Balloon Pulmonary Angioplasty for Chronic Thromboembolic Pulmonary Hypertension

Balloon pulmonary angioplasty (BPA) is an evolving treatment modality for patients with chronic thromboembolic pulmonary hypertension (CTEPH) who are not candidates for pulmonary endarterectomy. Although several imaging modalities currently exist for evaluating CTEPH, their individual use, specifically in the clinical practice of BPA, has not been well described. In this article, we provide a preprocedural, intraprocedural, and postprocedural interventional imaging roadmap for safe and effective BPA performance in routine clinical practice. Preprocedural assessment includes transthoracic echocardiography for right ventricular assessment, ventilation/perfusion scan to identify pulmonary segments with the highest degree of hypoperfusion, cross-sectional chest imaging excluding alternative causes of mismatched defects and providing anatomic and perfusion imaging concurrently, and nonselective invasive pulmonary angiography for risk stratification of individual lesion subtypes. Intraprocedural assessment includes subselective segmental angiography (SSA) for delineating segmental and subsegmental branch anatomy, lesion identification, and vessel sizing. Intravascular ultrasound and optical coherence tomography serve as adjunctive intraprocedural tools for more accurate vessel sizing and lesion characterization when SSA alone is insufficient. Postprocedural considerations include chest radiography to monitor for immediate postprocedure complications and echocardiography for the interval assessment of the right ventricle on longer-term follow-up.

Microvasculopathy Evaluated by Dual-Energy Computed Tomography in Patients with Chronic Thromboembolic Pulmonary Hypertension and Pulmonary Arterial Hypertension

Background: Poor subpleural perfusion (PSP) on dual-energy computed tomography (DE-CT) suggests microvasculopathy in chronic thromboembolic pulmonary hypertension (CTEPH). However, whether the microvasculopathy findings are equivalent to those in pulmonary arterial hypertension (PAH) remains unclear. The aim of this study was to elucidate the characteristics of microvasculopathy in CTEPH compared to those of that in PAH. Methods: We retrospectively reviewed subpleural perfusion on DE-CT and the hemodynamics of 23 patients with PAH and 113 with inoperable CTEPH. Subpleural perfusion on DE-CT was classified as poor (subpleural spaces in all segments with little or no perfusion) or normal. Results: PSP was observed in 51% of patients with CTEPH and in 4% of those with PAH (p < 0.01). CTEPH patients with PSP had poorer baseline hemodynamics and lower diffusing capacity for carbon monoxide divided by the alveolar volume (DLCO/VA) than those with CTEPH with normal perfusion (pulmonary vascular resistance [PVR]: 768 ± 445 dynes-sec/cm5 vs. 463 ± 284 dynes-sec/cm5, p < 0.01; DLCO/VA, 60.4 ± 16.8% vs. 75.9 ± 15.7%, p < 0.001). Despite the existence of PSP, hemodynamics improved to nearly normal in both groups after balloon pulmonary angioplasty. Conclusions: PSP on DE-CT, which is one of the specific imaging findings in CTEPH, might suggest a different mechanism of microvasculopathy from that in PAH.

Imaging in Pulmonary Vascular Disease-Understanding Right Ventricle-Pulmonary Artery Coupling

The right ventricle (RV) and pulmonary arterial (PA) tree are inextricably linked, continually transferring energy back and forth in a process known as RV-PA coupling. Healthy organisms maintain this relationship in optimal balance by modulating RV contractility, pulmonary vascular resistance, and compliance to sustain RV-PA coupling through life's many physiologic challenges. Early in states of adaptation to cardiovascular disease-for example, in diastolic heart failure-RV-PA coupling is maintained via a multitude of cellular and mechanical transformations. However, with disease progression, these compensatory mechanisms fail and become maladaptive, leading to the often-fatal state of "uncoupling." Noninvasive imaging modalities, including echocardiography, magnetic resonance imaging, and computed tomography, allow us deeper insight into the state of coupling for an individual patient, providing for prognostication and potential intervention before uncoupling occurs. In this review, we discuss the physiologic foundations of RV-PA coupling, elaborate on the imaging techniques to qualify and quantify it, and correlate these fundamental principles with clinical scenarios in health and disease. © 2022 American Physiological Society. Compr Physiol 12: 1-26, 2022.

Chronic thromboembolic pulmonary hypertension: diagnosis, operability assessment and patient selection for pulmonary endarterectomy

Healthcare providers outside pulmonary hypertension (PH) centers having misinformation or insufficient education, and a general lack of treatment awareness contribute to a massive underdiagnosis of chronic thromboembolic pulmonary hypertension (CTEPH), diagnostic delay and refusal of surgery by patients. Together with the subjective operability assessment, this leads to too few patients undergoing pulmonary endarterectomy (PEA); even though this surgery results in improved survival and exercise capacity. Acute pulmonary embolism (PE) survivors should undergo a CTEPH screening strategy. Patients screened positive and those with CTEPH symptoms (with or without history of PE), should undergo transthoracic echocardiography (TTE) to determine the probability of PH. High PH probability patients should undergo a ventilation/perfusion (V/Q) scan. A negative scan rules out CTEPH. Patients with a positive V/Q scan, but also patients with findings suggestive for CTEPH on computed tomography pulmonary angiography (CTPA) to diagnose acute PE, should be referred to a CTEPH center. Further diagnostic work-up currently consists of catheter based pulmonary angiography, CTPA and right heart catheterization. However, new imaging technologies might replace them in the near future, with one single imaging tool to screen, diagnose and assess operability as the ultimate goal. Operability assessment should be performed by a multidisciplinary CTEPH team. PEA surgery should be organized in a single center per country or for each forty to fifty million inhabitants in order to offer the highest level of expertise. Informing patients about PEA should preferably be done by the treating surgeon. Based on the estimated incidence of CTEPH and with a better education of patients and healthcare providers, despite the advent of new interventional and medical therapies for CTEPH, the number of PEA surgeries performed should still have the potential to grow significantly.

Detection of patients with chronic thromboembolic pulmonary hypertension by volumetric iodine quantification in the lung-a case control study

Background

To evaluate whether volumetric iodine quantification of the lung allows for the automatic identification of patients with chronic thromboembolic pulmonary hypertension (CTEPH) and whether the extent of pulmonary malperfusion correlates with invasive hemodynamic parameters.

Methods

Retrospective data base search identified 30 consecutive patients with CTEPH who underwent CT pulmonary angiography (CTPA) on a spectral-detector CT scanner. Thirty consecutive patients who underwent an identical CT examination for evaluation of suspected acute pulmonary embolism and had no signs of pulmonary embolism or PH, served as control cohort. Lungs were automatically segmented for all patients and normal and malperfused volumes were segmented based on iodine density thresholds. Results were compared between groups. For correlation analysis between the extent of malperfused volume and mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) 3 patients were excluded because of a time span of more than 30 days between CTPA and right heart catheterization.

Results

Patients with CTEPH had a higher percentage of malperfused lung compared to controls (43.25%±24.72% vs. 21.82%±20.72%; P=0.001) and showed reduced mean iodine density in malperfused and normal-perfused lung areas, as well as in the vessel volume. Controls showed a left-tailed distribution of iodine density in malperfused lung areas while patients with CTEPH had a more symmetrical distribution (Skew: -0.382±0.435 vs. -0.010±0.396; P=0.004). Patients with CTEPH showed a significant correlation between the percentage of malperfused lung volume and the PVR (r=0.57, P=0.001).

Conclusions

Volumetric iodine quantification helps to identify patients with CTEPH by showing increased areas of malperfusion. The extent of malperfusion might provide a measurement for disease severity in patients with CTEPH.

Dual-Energy CT Pulmonary Angiography for the Assessment of Surgical Accessibility in Patients with Chronic Thromboembolic Pulmonary Hypertension

We assessed the value of dual-energy CT pulmonary angiography (CTPA) for classification of the level of disease in chronic thromboembolic pulmonary hypertension (CTEPH) patients compared to the surgical Jamieson classification and prediction of hemodynamic changes after pulmonary endarterectomy. Forty-three CTEPH patients (mean age, 57 ± 16 years; 18 females) undergoing CTPA prior to surgery were retrospectively included. “Proximal” and “distal disease” were defined as L1 and 2a (main and lobar pulmonary artery [PA]) and L2b-4 (lower lobe basal trunk to subsegmental PA), respectively. Three radiologists had a moderate interobserver agreement for the radiological classification of disease (k = 0.55). Sensitivity was 92–100% and specificity was 24–53% to predict proximal disease according to the Jamieson classification. A median of 9 segments/patient had CTPA perfusion defects (range, 2–18 segments). L1 disease had a greater decrease in the mean pulmonary artery pressure (p = 0.029) and pulmonary vascular resistance (p = 0.011) after surgery compared to patients with L2a to L3 disease. The extent of perfusion defects was not associated with the level of disease or hemodynamic changes after surgery (p > 0.05 for all). CTPA is highly sensitive for predicting the level of disease in CTEPH patients with a moderate interobserver agreement. The radiological level of disease is associated with hemodynamic improvement after surgery.

ERS statement on chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare complication of acute pulmonary embolism, either symptomatic or not. The occlusion of proximal pulmonary arteries by fibrotic intravascular material, in combination with a secondary microvasculopathy of vessels <500 µm, leads to increased pulmonary vascular resistance and progressive right heart failure. The mechanism responsible for the transformation of red clots into fibrotic material remnants has not yet been elucidated. In patients with pulmonary hypertension, the diagnosis is suspected when a ventilation/perfusion lung scan shows mismatched perfusion defects, and confirmed by right heart catheterisation and vascular imaging. Today, in addition to lifelong anticoagulation, treatment modalities include surgery, angioplasty and medical treatment according to the localisation and characteristics of the lesions.This statement outlines a review of the literature and current practice concerning diagnosis and management of CTEPH. It covers the definitions, diagnosis, epidemiology, follow-up after acute pulmonary embolism, pathophysiology, treatment by pulmonary endarterectomy, balloon pulmonary angioplasty, drugs and their combination, rehabilitation and new lines of research in CTEPH.It represents the first collaboration of the European Respiratory Society, the International CTEPH Association and the European Reference Network-Lung in the pulmonary hypertension domain. The statement summarises current knowledge, but does not make formal recommendations for clinical practice.

Optimizing the diagnosis and assessment of chronic thromboembolic pulmonary hypertension with advancing imaging modalities

Imaging is key to nearly all aspects of chronic thromboembolic pulmonary hypertension including management for screening, assessing eligibility for pulmonary endarterectomy, and post-operative follow-up. While ventilation/perfusion scintigraphy, the gold standard technique for chronic thromboembolic pulmonary hypertension screening, can have excellent sensitivity, it can be confounded by other etiologies of pulmonary malperfusion, and does not provide structural information to guide operability assessment. Conventional computed tomography pulmonary angiography has high specificity, though findings of chronic thromboembolic pulmonary hypertension can be visually subtle and unrecognized. In addition, computed tomography pulmonary angiography can provide morphologic information to aid in pre-operative workup and assessment of other structural abnormalities. Advances in computed tomography imaging techniques, including dual-energy computed tomography and spectral-detector computed tomography, allow for improved sensitivity and specificity in detecting chronic thromboembolic pulmonary hypertension, comparable to that of ventilation/perfusion scans. Furthermore, these advanced computed tomography techniques, compared with conventional computed tomography, provide additional physiologic data from perfused blood volume maps and improved resolution to better visualize distal chronic thromboembolic pulmonary hypertension, an important consideration for balloon pulmonary angioplasty for inoperable patients. Electrocardiogram-synchronized techniques in electrocardiogram-gated computed tomography can also show further information regarding right ventricular function and structure. While the standard of care in the workup of chronic thromboembolic pulmonary hypertension includes a ventilation/perfusion scan, computed tomography pulmonary angiography, direct catheter angiography, echocardiogram, and coronary angiogram, in the future an electrocardiogram-gated dual-energy computed tomography angiography scan may enable a "one-stop" imaging study to guide diagnosis, operability assessment, and treatment decisions with less radiation exposure and cost than traditional chronic thromboembolic pulmonary hypertension imaging modalities.

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.

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.

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.

Imaging of Chronic Thromboembolic Disease

Acute pulmonary embolism (PE) is a leading cause of cardiovascular morbidity. The most common long-term complication of acute PE is chronic thromboembolic disease, a heterogenous entity which ranges from asymptomatic imaging sequelae to persistent symptoms. Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare disease that can develop in this population and represents the only treatable type of pulmonary hypertension. Recognition of the characteristic findings of chronic pulmonary embolism and CTEPH provides not only diagnostic information, but is also crucial for guiding therapy. The present state-of-the-art review focuses on the multimodality imaging features of chronic pulmonary embolism. Detailed description and illustrations of relevant imaging findings will be demonstrated for ventilation/perfusion (V/Q) scan, CT scan and Dual-Energy CT and MRI and features that distinguish chronic PE from common imaging mimics.

A systematic literature review and meta-analysis of spectral CT compared to scintigraphy in the diagnosis of acute and chronic pulmonary embolisms

PURPOSE

To examine the diagnostic accuracy of spectral CT pulmonary angiography (S-CTPA) using ventilation-perfusions lung scintigraphy (V/Q-scan) as a reference standard in the diagnosis of acute or chronic pulmonary embolism (APE/CPE) and chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

PubMed, Embase, Scopus, and Web of Science were searched for the period from 1 Jan 2006 to 7 Feb 2019; eligible studies had > 10 patients over 18 years old, a diagnostic outcome of PE or CTEPH, and used V/Q scan as a reference standard. Bias and applicability were assessed using QUADAS-2 tools. Sensitivities, specificities, and predictive values were noted or calculated from available information. Meta-analysis employed a fixed-effects model of Mantel and Haenszel. Heterogeneity was assessed with I-squared statistics.

RESULTS

Four hundred ninety-three unique records were identified. Following screening by title, 53 studies were included in the abstract and full-text assessment. A total of six articles were included; four were suitable for a meta-analysis. Pooled sensitivity was 94.2% (95% CI, 88.3-100%), pooled specificity was 88.5% (95% CI, 81.3-95.6%), and positive and negative predictive values were 87.8% (95% CI, 80.3-95.4%) and 94.5% (95% CI, 89.3-99.7%), respectively.

CONCLUSION

Data on S-CTPA for PE/CTEPH remains promising, but limited; only small studies with methodological issues are available. Evidence is best for CPE/CTEPH whereas no firm conclusions are possible for APE. There is a need for larger, prospective studies with a robust composite reference standard including state-of-the-art CTPA and V/Q-scans.

KEY POINTS

• S-CTPA has high sensitivity and specificity for perfusion defects in patients with PE or CPETH. • Methodological issues and diversity of reference standards were found in the small number of included studies. • There is a need for larger prospective studies with more robust composite reference standards.

Evaluation of the CT imaging findings in the diagnosis of pulmonary hypertension due to chronic thromboembolism

PURPOSE

Chronic thromboembolic pulmonary hypertension (CTEPH) is the only pulmonary hypertension that can be treated surgically. Multidedector computerized tomography angiography (MDCTA) is considered as an important tool. In this study, the important CT findings of CTEPH and the vascular MDCTA findings of CTEPH were classified as central, peripheral, central and peripheral. The aim of this study was to investigate the relationship between these groups with parenchymal and hemodynamic findings.

MATERIALS AND METHODS

MDCTA examinations of 26 patients who had been diagnosed with CTEPH were retrospectively reviewed. Vascular, cardiac and parenchymal findings were examined in MDCTA. Patients were divided into three groups as peripheral, central and peripheral and central chronic thromboembolism. The relationship between these groups with demographic, vascular, parenchymal and hemodynamic findings was investigated.

RESULTS

The most common vascular finding was the wall filling defects attached to the lobar and/or segmental arterial walls, while the parenchymal finding was the fibrotic shrinkage. There were no statistically significant differences between the three groups compared to parenchymal findings which are mosaic pattern, brochiectasis, fibrotic changes and atelectasis, pulmonary artery diameter, right atrial diameter and RV/LV ratio. Age and sex were not different in patients between the three groups.

CONCLUSION

The results of the this study confirm the important role of MDCTA in the evaluation of vascular, cardiac and parenchymal findings in the patients with CTEPH and identifying patients that would most benefit from surgical treatment by visualization of the segmental and subsegmental branches of the pulmonary arteries.

CTPA, DECT, MRI, V/Q Scan, and SPECT/CT V/Q for the noninvasive diagnosis of chronic thromboembolic pulmonary hypertension: A protocol for systemic review and network meta-analysis of diagnostic test accuracy

BACKGROUND

To determine the diagnostic accuracy of techniques with chronic thromboembolic pulmonary hypertension (CTEPH) patients via a protocol for systemic review and network meta-analysis.

METHODS

We will search PubMed, EMBASE, Web of Science, and Google Scholar from inception to October 1, 2018. The reference lists of the retrieved articles are also consulted. Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) will be used to assess the risk of bias in each study. The direct meta-analyses, network meta-analyses, and ranking of competing diagnostic tests will be used by STATA 12.0 and WINBUGS 1.4. Heterogeneity and inconsistency are assessed.

RESULTS

This study is ongoing, will be submitted to a peer-reviewed journal publication once completed.

CONCLUSION

This study will provide a comprehensive evidence summary of diagnostic test accuracy in detecting the CTEPH, and can help patients and clinicians to select appropriate or best diagnostic test.

ETHICS AND COMMUNICATION

No ethical approval and patient consent are required, because it is based on published researches.

PROSPERO REGISTRATION NUMBER

CRD42019121279.

IodiNe Subtraction mapping in the diagnosis of Pulmonary chronIc thRomboEmbolic disease (INSPIRE): Rationale and methodology of a cross-sectional observational diagnostic study

Chronic thromboembolic pulmonary hypertension (CTEPH) is a severe but treatable disease that is commonly underdiagnosed. Computed tomography lung subtraction iodine mapping (CT-LSIM) in addition to standard CT pulmonary angiography (CTPA) may improve the evaluation of suspected chronic pulmonary embolism and improve the diagnostic pick up rate. We aim to recruit 100 patients suspected of having CTEPH and perform CT-LSIM scans in addition to the current gold standard test of nuclear medicine test (lung single photon emission computed tomography (SPECT) imaging) as a pilot study which will contribute to and inform the definitive trial. The diagnostic accuracy of CT-LSIM and lung SPECT will be compared. The primary outcome of the full definitive study is non-inferiority of CT-LSIM versus lung SPECT imaging.

State of the art: utility of multi-energy CT in the evaluation of pulmonary vasculature

Multi-energy computed tomography (MECT) refers to acquisition of CT data at multiple energy levels (typically two levels) using different technologies such as dual-source, dual-layer and rapid tube voltage switching. In addition to conventional/routine diagnostic images, MECT provides additional image sets including iodine maps, virtual non-contrast images, and virtual monoenergetic images. These image sets provide tissue/material characterization beyond what is possible with conventional CT. MECT provides invaluable additional information in the evaluation of pulmonary vasculature, primarily by the assessment of pulmonary perfusion. This functional information provided by the MECT is complementary to the morphological information from a conventional CT angiography. In this article, we review the technique and applications of MECT in the evaluation of pulmonary vasculature.

Pulmonary Hypertension in Intensive Care Units: An Updated Review

Pulmonary hypertension (PH) is a condition associated with high morbidity and mortality. Patients with PH who require critical care usually have severe right ventricular (RV) dysfunction. Although different groups of PH have different etiologies, pulmonary vascular dysfunction is common in these groups. PH can lead to increased pulmonary artery pressure, which can ultimately cause RV failure. Clinicians should be familiar with the presentations of this disease and diagnostic tools. The contributing factors, if present (e.g., sepsis), and coexisting conditions (e.g., arrhythmias) should be identified and addressed accordingly. The preload should be optimized by fluid administration, diuretics, and dialysis, if necessary. On the other hand, the RV afterload should be reduced to improve the RV function with pulmonary vasodilators, such as prostacyclins, inhaled nitric oxide, and phosphodiesterase type 5 inhibitors, especially in group 1 PH. Inotropes are also used to improve RV contractility, and if inadequate, use of ventricular assist devices and extracorporeal life support should be considered in suitable candidates. Moreover, vasopressors should be used to maintain systemic blood pressure, albeit cautiously, as they increase the RV afterload. Measures should be also taken to ensure adequate oxygenation. However, mechanical ventilation is avoided in RV failure. In this study, we reviewed the pathophysiology, manifestations, diagnosis, monitoring, and management strategies of PH, especially in intensive care units.

Current and emerging imaging techniques in the diagnosis and assessment of pulmonary hypertension

INTRODUCTION

Pulmonary hypertension (PH) is a challenging condition to diagnose and treat. Over the last two decades, there have been significant advances in therapeutic approaches and imaging technologies. Current guidelines emphasize the importance of cardiac catheterization; however, the increasing availability of non-invasive imaging has the potential to improve diagnostic rates, whilst providing additional information on patient phenotypes. Areas covered: This review discusses the role of imaging in the diagnosis, prognostic assessment and follow-up of patients with PH. Imaging methods, ranging from established investigations (chest radiography, echocardiography, nuclear medicine and computerized tomography (CT)), to emerging modalities (dual energy CT, magnetic resonance imaging (MRI), optical coherence tomography and positron emission tomography (PET)) are reviewed. The value and limitations of the clinical utility of these imaging modalities and their potential clinical application are reviewed. Expert commentary: Imaging plays a key role in the diagnosis and classification of pulmonary hypertension. It also provides valuable prognostic information and emerging evidence supports a role for serial assessments. The authors anticipate an increasing role for imaging in the pulmonary hypertension clinic. This will reduce the need for invasive investigations, whilst providing valuable insights that will improve our understanding of disease facilitate a more targeted approach to treatment.

Dual-energy CT (DECT) lung perfusion in pulmonary hypertension: concordance rate with V/Q scintigraphy in diagnosing chronic thromboembolic pulmonary hypertension (CTEPH)

OBJECTIVES

To evaluate the concordance between DECT perfusion and ventilation/perfusion (V/Q) scintigraphy in diagnosing chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

Eighty patients underwent V/Q scintigraphy and DECT perfusion on a 2nd- and 3rd-generation dual-source CT system. The imaging criteria for diagnosing CTEPH relied on at least one segmental triangular perfusion defect on DECT perfusion studies and V/Q mismatch on scintigraphy examinations.

RESULTS

Based on multidisciplinary expert decisions that did not include DECT perfusion, 36 patients were diagnosed with CTEPH and 44 patients with other aetiologies of PH. On DECT perfusion studies, there were 35 true positives, 6 false positives and 1 false negative (sensitivity 0.97, specificity 0.86, PPV 0.85, NPV 0.97). On V/Q scans, there were 35 true positives and 1 false negative (sensitivity 0.97, specificity 1, PPV 1, NPV 0.98). There was excellent agreement between CT perfusion and scintigraphy in diagnosing CTEPH (kappa value 0.80). Combined information from DECT perfusion and CT angiographic images enabled correct reclassification of the 6 false positives and the unique false negative case of DECT perfusion.

CONCLUSION

There is excellent agreement between DECT perfusion and V/Q scintigraphy in diagnosing CTEPH. The diagnostic accuracy of DECT perfusion is reinforced by the morpho-functional analysis of data sets.

KEY POINTS

• Chronic thromboembolic pulmonary hypertension (CTEPH) is potentially curable by surgery. • The triage of patients with pulmonary hypertension currently relies on scintigraphy. • Dual-energy CT (DECT) can provide standard diagnostic information and lung perfusion from a single acquisition. • There is excellent agreement between DECT perfusion and scintigraphy in separating CTEPH and non-CTEPH patients.

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

Chronic Thromboembolic Pulmonary Hypertension: Pearls and Pitfalls of Diagnosis

Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by chronic obstruction of major pulmonary arteries by organized thromboembolic material. Untreated CTEPH can result in pulmonary hypertension and eventually right heart failure, yet it is the only form of pulmonary hypertension that is potentially curable with surgical or catheter-based intervention. While early diagnosis is key to increasing the likelihood of successful treatment, CTEPH remains largely underdiagnosed. This article reviews the role of echocardiogram, ventilation/perfusion scan, and other available modalities in the diagnosis of CTEPH.

Contrast-enhanced CT- and MRI-based perfusion assessment for pulmonary diseases: basics and clinical applications

Assessment of regional pulmonary perfusion as well as nodule and tumor perfusions in various pulmonary diseases are currently performed by means of nuclear medicine studies requiring radioactive macroaggregates, dual-energy computed tomography (CT), and dynamic first-pass contrast-enhanced perfusion CT techniques and unenhanced and dynamic first-pass contrast enhanced perfusion magnetic resonance imaging (MRI), as well as time-resolved three-dimensional or four-dimensional contrast-enhanced magnetic resonance angiography (MRA). Perfusion scintigraphy, single-photon emission tomography (SPECT) and SPECT fused with CT have been established as clinically available scintigraphic methods; however, they are limited by perfusion information with poor spatial resolution and other shortcomings. Although positron emission tomography with 15O water can measure absolute pulmonary perfusion, it requires a cyclotron for generation of a tracer with an extremely short half-life (2 min), and can only be performed for academic purposes. Therefore, clinicians are concentrating their efforts on the application of CT-based and MRI-based quantitative and qualitative perfusion assessment to various pulmonary diseases. This review article covers 1) the basics of dual-energy CT and dynamic first-pass contrast-enhanced perfusion CT techniques, 2) the basics of time-resolved contrast-enhanced MRA and dynamic first-pass contrast-enhanced perfusion MRI, and 3) clinical applications of contrast-enhanced CT- and MRI-based perfusion assessment for patients with pulmonary nodule, lung cancer, and pulmonary vascular diseases. We believe that these new techniques can be useful in routine clinical practice for not only thoracic oncology patients, but also patients with different pulmonary vascular diseases.

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.

Chronic Embolic Pulmonary Hypertension Caused by Pulmonary Embolism and Vascular Endothelial Growth Factor Inhibition

Our understanding of the pathophysiological basis of chronic thromboembolic pulmonary hypertension (CTEPH) will be accelerated by an animal model that replicates the phenotype of human CTEPH. Sprague-Dawley rats were administered a combination of a single dose each of plastic microspheres and vascular endothelial growth factor receptor antagonist in polystyrene microspheres (PE) + tyrosine kinase inhibitor SU5416 (SU) group. Shams received volume-matched saline; PE and SU groups received only microspheres or SU5416, respectively. PE + SU rats exhibited sustained pulmonary hypertension (62 ± 13 and 53 ± 14 mmHg at 3 and 6 weeks, respectively) with reduction of the ventriculoarterial coupling in vivo coincident with a large decrement in peak rate of oxygen consumption during aerobic exercise, respectively. PE + SU produced right ventricular hypokinesis, dilation, and hypertrophy observed on echocardiography, and 40% reduction in right ventricular contractile function in isolated perfused hearts. High-resolution computed tomographic pulmonary angiography and Ki-67 immunohistochemistry revealed abundant lung neovascularization and cellular proliferation in PE that was distinctly absent in the PE + SU group. We present a novel rodent model to reproduce much of the known phenotype of CTEPH, including the pivotal pathophysiological role of impaired vascular endothelial growth factor-dependent vascular remodeling. This model may reveal a better pathophysiological understanding of how PE transitions to CTEPH in human treatments.