Importance of computed tomography in defining segmental disease in chronic thromboembolic pulmonary hypertension

Characterization of pulmonary arterial stiffness using cardiac MRI

Pulmonary arterial stiffness (PAS) is a pathologic hallmark of all types of pulmonary hypertension (PH). Cardiac MRI (CMR), a gold-standard imaging modality for the evaluation of pulmonary flow, biventricular morphology and function has been historically reserved for the longitudinal clinical follow-up, PH phenotyping purposes, right ventricular evaluation, and research purposes. Over the last two decades, numerous indices combining invasive catheterization and non-invasive CMR have been utilized to phenotype the character and severity of PAS in different types of PH and to assess its clinically prognostic potential with encouraging results. Many recent studies have demonstrated a strong role of CMR derived PAS markers in predicting long-term clinical outcomes and improving currently gold standard risk assessment provided by the REVEAL calculator. With the utilization of a machine learning strategies, strong diagnostic and prognostic performance of CMR reported in multicenter studies, and ability to detect PH at early stages, the non-invasive assessment of PAS is on verge of routine clinical utilization. In this review, we focus on appraising important CMR studies interrogating PAS over the last 20 years, describing the benefits and limitations of different PAS indices, and their pathophysiologic relevance to pulmonary vascular remodeling. We also discuss the role of CMR and PAS in clinical surveillance and phenotyping of PH, and the long-term future goal to utilize PAS as a biomarker to aid with more targeted therapeutic management.

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.

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.

Pulmonary Vein Sign on Computed Tomography Pulmonary Angiography in Proximal and Distal Chronic Thromboembolic Pulmonary Hypertension With Hemodynamic Correlation

BACKGROUND

Pulmonary vein sign (PVS) indicates abnormal pulmonary venous flow on computed tomography pulmonary angiography (CTPA) is a frequent finding in proximal chronic thromboembolic pulmonary hypertension (CTEPH). PVS's occurrence in distal CTEPH and correlation to disease severity is unknown. Using right heart catheterization data, we evaluated the relationship between PVS and CTEPH disease distribution and severity.

MATERIALS AND METHOD

A total of 93 consecutive CTEPH cases with both CTPA and right heart catheterization were identified in this retrospective multi-institutional study. After excluding 17 cases with suboptimal CTPA, there were 52 proximal and 24 distal CTEPH cases. Blood flow in the major pulmonary veins was graded qualitatively. Subgroup analysis of PVS was performed in 38 proximal CTEPH cases before and after pulmonary endarterectomy.

RESULTS

PVS was more frequent in proximal (79%) than distal CTEPH (29%) ( P <0.001). No significant difference was noted in invasive mean pulmonary artery pressure (46±11 and 41±12 mm Hg) or pulmonary vascular resistance (9.4±4.5 and 8.4±4.8 WU) between the 2 groups. In the subgroup analysis, PVS was present in 29/38 patients (76%) before surgery. Postoperatively, 33/38 cases (87%, P <0.001) had normal venous flow (mean pulmonary artery pressure 46±11 and 25; pulmonary vascular resistance 9.2±4.3 and 2.6 WU preop and postop, respectively).

CONCLUSION

PVS is a common feature in proximal but infrequent findings in distal CTEPH. PVS does not correlate with hemodynamic severity. PVS resolution was seen in the majority of patients following successful endarterectomy.

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.

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.