Correlation between Pulmonary Artery Pressure and Vortex Duration Determined by 4D Flow MRI in Main Pulmonary Artery in Patients with Suspicion of Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

Chronic thromboembolic pulmonary hypertension (CTEPH) is one of the causes of pulmonary hypertension (PH) and requires invasive measurement of the mean pulmonary artery pressure (mPAP) during right heart catheterisation (RHC) for the diagnosis. 4D flow MRI could provide non-invasive parameters to estimate the mPAP. Twenty-five patients with suspected CTEPH underwent cardiac MRI. Mean vortex duration (%), pulmonary distensibility, right ventricular volumes and function were measured using 4D flow MRI and cine sequences, and compared with the mPAP measured by RHC. The mPAP measured during RHC was 33 ± 16 mmHg (10−66 mmHg). PH (defined as mPAP > 20 mmHg) was present in 19 of 25 patients (76%). A vortical flow was observed in all but two patients (92%) on 4D flow images, and vortex duration showed good correlation with the mPAP (r = 0.805; p < 0.0001). Youden index analysis showed that a vortex duration of 8.6% of the cardiac cycle provided a 95% sensitivity and an 83% specificity to detect PH. Reliability for the measurement of vortex duration was excellent for both intra-observer ICC = 0.823 and inter-observer ICC = 0.788. Vortex duration could be a useful parameter to non-invasively estimate mPAP in patients with suspected CTEPH.

Role of extracorporeal membrane oxygenation and surgical embolectomy in acute pulmonary embolism

PURPOSE OF REVIEW

Surgery is an important option to consider in patients with massive and submassive pulmonary emboli. Earlier intervention, better patient selection, improved surgical techniques and the use of veno-arterial extracorporeal membrane oxygenation (VA ECMO) have contributed to improve the safety of surgery for pulmonary emboli.

RECENT FINDINGS

VA ECMO is rapidly changing the initial management of patients with massive pulmonary emboli, providing an opportunity for stabilization and optimization before intervention. The early and long-term consequences of acute pulmonary emboli are better understood, in particular with regard to the risks of chronic thromboembolic pulmonary hypertension (CTEPH), an entity that should be identified in the acute setting as much as possible. The presence of chronic thromboembolic pulmonary disease can be associated with persistent haemodynamic instability despite removal of the acute thrombi, particularly if pulmonary hypertension is established. The pulmonary embolism response team (PERT) is an important component in the management of massive and submassive acute pulmonary emboli to determine the best treatment options for each patient depending on their clinical presentation.

SUMMARY

Three types of surgery can be performed for pulmonary emboli depending on the extent and degree of organization of the thrombi (pulmonary embolectomy, pulmonary thrombo-embolectomy and pulmonary thrombo-endarterectomy). Other treatment options in the context of acute pulmonary emboli include thrombolysis and catheter-directed embolectomy. Future research should determine how best to integrate VA ECMO as a bridging strategy to recovery or intervention in the treatment algorithm of patients with acute massive pulmonary emboli.

Congenital Anomalous Azygos Vein Drainage Causing Pulmonary Embolus in a 91-Year-Old Patient

Background

Retroaortic course and azygos continuation of aberrant left brachiocephalic vein is a rare venous anomaly, which is usually associated with congenital heart disease and pulmonary artery anomalies. Venous stasis is a cause of pulmonary arterial thromboembolism, which can result from venous anomalies.

Case presentation

We describe the case of a 91-year-old female admitted to our hospital with shortness of breath diagnosed with pulmonary embolism and infarctions by a CT pulmonary angiogram. CT also showed aberrant left brachiocephalic vein with vascular webs at its retroaortic course and azygos continuation, suggesting chronic venous thrombosis, which was considered to be the suspected source of emboli.

Conclusion

To our knowledge, this is the first report presenting this vascular anomaly manifesting with chronic venous thrombosis and pulmonary embolism. Although rare, awareness and identification of this entity is important, especially in the absence of obvious embolic sources or in patients with recurrent embolus/consolidation.

LEARNING POINTS

Abnormal Pulmonary Venous Filling: An Adjunct Feature in the Computed Tomography Pulmonary Angiogram Assessment of Chronic Thromboembolic Pulmonary Hypertension

Background

Hypodense filling defects within the pulmonary veins on computed tomography described as pulmonary vein sign (PVS) have been noted in acute pulmonary embolism and shown to be associated with poor prognosis. We evaluated venous flow abnormalities in chronic thromboembolic pulmonary hypertension (CTEPH) to determine its usefulness in the computed tomography assessment of CTEPH.

Methods and Results

Blinded retrospective computed tomography analysis of 50 proximal CTEPH cases and 3 control groups—50 acute pulmonary embolism, 50 nonthromboembolic cohort, and 50 pulmonary arterial hypertension. Venous flow reduction was assessed by the following: (1) presence of a filling defect of at least 2 cm in a pulmonary vein draining into the left atrium, and (2) left atrium attenuation (>160 Hounsfield units). PVS was most prevalent in CTEPH. Compared with all controls, sensitivity and specificity of PVS for CTEPH is 78.0% and 85.3% (95% CI, 64.0–88.5 and 78.6–90.6, respectively) versus 34.0% and 70.7% (95% CI, 21.2−48.8 and 62.7–77.8) in acute pulmonary embolism, 8.0% and 62% (95% CI, 2.2–19.2 and 53.7–69.8) in nonthromboembolic and 2.0% and 60% (95% CI, 0.1−10.7 and 51.7−67.9) in pulmonary arterial hypertension. In CTEPH, lobar and segmental arterial occlusive disease was most commonly associated with corresponding absent venous flow. PVS detection was highly reproducible (Kappa=0.96, 95% CI, 0.90–1.01, P<0.001).

Conclusions

PVS is easy to detect with higher sensitivity and specificity in CTEPH compared with acute pulmonary embolism and is not a feature of pulmonary arterial hypertension. Asymmetric enhancement of pulmonary veins may serve as an additional parameter in the computed tomography assessment of CTEPH and can be used to differentiate CTEPH from pulmonary arterial hypertension.

Dyspnea Postpulmonary Embolism From Physiological Dead Space Proportion and Stroke Volume Defects During Exercise

BACKGROUND

Many patients with pulmonary embolism (PE) report dyspnea on exertion following long-term treatment. Increased physiological dead space proportion (V_D/V_T) and decreased cardiac stroke volume reserve may distinguish persistent effects of PE itself from symptoms reflecting comorbid conditions or deconditioning.

METHODS

This retrospective study analyzed a consecutive series of incremental symptom-limited cardiopulmonary exercise tests that had been ordered to evaluate persistent dyspnea on exertion following long-term treatment for acute PE. Physiological V_D/V_T was determined at anaerobic threshold from exhaled CO₂ and transcutaneous Pco₂ (validated against Paco₂ measurements). Cardiac stroke volume reserve was estimated at rest and at anaerobic threshold by using oxygen consumption/pulse and previously validated estimates of the arteriovenous oxygen content difference.

RESULTS

Cardiopulmonary exercise tests were performed on 40 patients with post-PE dyspnea. In 65.0% (95% CI, 50.2-79.8), V_D/V_T at anaerobic threshold was abnormally elevated, stroke volume reserve was decreased, or both defects occurred. V_D/V_T at anaerobic threshold was abnormally elevated (≥ 0.27) in 35.0% (95% CI, 20.2-49.8). V_D/V_T at anaerobic threshold significantly correlated with the extent of unmatched perfusion defects on subsequent ventilation-perfusion scans (P = .0085). In 55.0% (95% CI, 39.6-70.4), stroke volume reserve at anaerobic threshold was abnormally decreased (≤ 128% of the resting value). Both defects were present in 25.0% (95% CI, 11.6-38.4).

CONCLUSIONS

Increased V_D/V_T at anaerobic threshold and decreased stroke volume reserve during exercise are common among patients with dyspnea on exertion after long-term treatment of PE. The defects can be disclosed noninvasively by using cardiopulmonary exercise testing.

Diagnostic Evaluation of Chronic Thromboembolic Pulmonary Hypertension

Pulmonary hypertension is defined by a mean pulmonary artery pressure greater than 25 mm Hg. Chronic thromboembolic pulmonary hypertension (CTEPH) is defined as pulmonary hypertension in the presence of an organized thrombus within the pulmonary vascular bed that persists at least 3 months after the onset of anticoagulant therapy. Because CTEPH is potentially curable by surgical endarterectomy, correct identification of patients with this form of pulmonary hypertension and an accurate assessment of surgical candidacy are essential to provide optimal care. Patients most commonly present with symptoms of exertional dyspnea and otherwise unexplained decline in exercise capacity. Atypical chest pain, a nonproductive cough, and episodic hemoptysis are observed less frequently. With more advanced disease, patients often develop symptoms suggestive of right ventricular compromise. Physical examination findings are minimal early in the course of this disease, but as pulmonary hypertension progresses, may include nonspecific finding of right ventricular failure, such as a tricuspid regurgitation murmur, pedal edema, and jugular venous distention. Chest radiographs may suggest pulmonary hypertension, but are neither sensitive nor specific for the diagnosis. Radioisotopic ventilation-perfusion scanning is sensitive for detecting CTEPH, making it a valuable screening study. Conventional catheter-based pulmonary angiography retains an important role in establishing the presence and extent of chronic thromboembolic disease. However, computed tomographic and magnetic resonance imaging are playing a growing diagnostic role. Innovative technologies such as dual-energy computed tomography, dynamic contrast-enhanced magnetic resonance imaging, and optical coherence tomography show promise for contributing diagnostic information and assisting in the preoperative characterization of patients with CTEPH.

Balloon pulmonary angioplasty for inoperable patients with chronic thromboembolic disease

Symptomatic patients with residual pulmonary perfusion defects or vascular lesions but no pulmonary hypertension at rest are diagnosed with chronic thromboembolic disease (CTED). Balloon pulmonary angioplasty (BPA) is an emerging treatment for patients with inoperable chronic thromboembolic pulmonary hypertension (CTEPH), but data regarding the safety and efficacy of BPA in patients with CTED are lacking. We report a prospective series of ten consecutive patients with CTED who underwent 35 BPA interventions (median of four per patient) at two German institutions. All patients underwent a comprehensive diagnostic workup at baseline and 24 weeks after their last intervention. BPA was safe, with one pulmonary vascular injury and subsequent self-limiting pulmonary bleeding as the only complication (2.9% of the interventions, 10% of the patients). After the procedures, World Health Organization functional class, 6-min walking distance, pulmonary vascular resistance, and pulmonary arterial compliance improved, and NT-proBNP concentrations declined in 9/10 patients. BPA may be a new treatment option for carefully selected patients with CTED. A larger, prospective, international registry is required to confirm these results.

Severity of pulmonary hypertension and obesity are not associated with worse functional outcomes after pulmonary thromboendarterectomy

Predictors of functional outcomes in patients with chronic thromboembolic pulmonary hypertension (CTEPH) undergoing pulmonary thromboendarterectomy (PTE) are important to identify preoperatively. We hypothesized that baseline severity of pulmonary hypertension and obesity would not be associated with 6-month functional outcomes after PTE. Clinical and hemodynamic data were collected on consecutive patients undergoing PTE from 2008 to 2014. Patients were stratified according to baseline pulmonary vascular resistance (PVR) and body mass index (BMI). Six-minute walk distance (6MWD), New York Heart Association functional class (FC), and echocardiography were assessed in each group at baseline and 6 months after PTE. Regression analyses were performed to evaluate for associations between functional outcomes and baseline PVR and BMI. Forty-two patients underwent PTE and had 6-month follow up data. In comparisons of patients with high and low baseline PVR, the baseline characteristics, distribution of disease, 6MWD, and FC were similar. Postoperative hemodynamics for both groups were similar. At 6 months, both groups achieved improvements in FC, and there were no between-group differences in the change in 6MWD or FC. In comparisons of obese and nonobese patients, perioperative and FC improvement were similar; however, obese patients achieved a greater improvement in 6MWD than nonobese patients (P = 0.04). In conclusion, our data suggest that baseline severity of CTEPH and obesity were not associated with worse functional outcome. Further studies are needed to confirm these results, as these findings could have implications for patient selection for PTE.

Evaluation of patients with chronic thromboembolic pulmonary hypertension for pulmonary endarterectomy

Pulmonary hypertension as a result of chronic thromboembolic disease (CTEPH) is potentially curable with pulmonary endarterectomy surgery. Consequently, correctly diagnosing patients with this type of pulmonary hypertension and evaluating these patients with the goal of establishing their candidacy for surgical intervention is of utmost importance. And as advancements in surgical techniques have allowed successful resection of segmental-level chronic thromboembolic disease, the number of CTEPH patients that are deemed suitable surgical candidates has expanded, making it even more important that the evaluation be conducted with greater precision. This article will review a diagnostic approach to patients with suspected chronic thromboembolic disease with an emphasis on the criteria considered in selecting patients for pulmonary endarterectomy surgery.