Proximal Chronic Thromboembolic Pulmonary Hypertension Research Articles

Safety and efficacy of balloon pulmonary angioplasty for technically operable chronic thromboembolic pulmonary hypertension.

Balloon pulmonary angioplasty (BPA) has been proven effective for addressing technically inoperable chronic thromboembolic pulmonary hypertension (CTEPH). However, the effectiveness of BPA in technically operable CTEPH patients who, for various reasons, did not undergo the procedure remains an area requiring exploration. This study sought to assess the safety and efficacy of BPA in such cases. We collected and reviewed data from CTEPH patients who underwent BPA in a consecutive manner. Following multidisciplinary team (MDT) decisions, patients were classified into two groups: technically inoperable (group A) and operable (group B). Group B comprised patients deemed technically suitable for pulmonary endarterectomy (PEA) but who did not undergo the procedure for various reasons. All patients underwent a comprehensive diagnostic work-up, including right heart categorization at baseline and the last intervention. This study compared changes in hemodynamic parameters, functional capacity, and quality of life between the two groups. In total, 161 patients underwent 414 procedures at our center, with Group A comprising 112 patients who underwent 282 BPA sessions and group B comprising 49 patients who underwent 132 BPA sessions. Significantly, both groups exhibited improvements in hemodynamics, functional capacity, and quality of life. The occurrence rate of complications, including hemoptysis and lung injury, was similar [12 (63.2%) vs. 7 (36.8%), p = 0.68]. BPA demonstrated favorable outcomes in patients with proximal CTEPH who did not undergo pulmonary endarterectomy. However, the clinical impact of BPA in technically operable CTEPH was found to be less significant than in inoperable cases.

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

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. 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. 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±12mmHg) 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). 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.

Excess ventilation and exertional dyspnoea in heart failure and pulmonary hypertension.

Increased ventilation relative to metabolic demands, indicating alveolar hyperventilation and/or increased physiological dead space (excess ventilation), is a key cause of exertional dyspnoea. Excess ventilation has assumed a prominent role in the functional assessment of patients with heart failure (HF) with reduced (HFrEF) or preserved (HFpEF) ejection fraction, pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). We herein provide the key pieces of information to the caring physician to 1) gain unique insights into the seeds of patients' shortness of breath and 2) develop a rationale for therapeutically lessening excess ventilation to mitigate this distressing symptom. Reduced bulk oxygen transfer induced by cardiac output limitation and/or right ventricle-pulmonary arterial uncoupling increase neurochemical afferent stimulation and (largely chemo-) receptor sensitivity, leading to alveolar hyperventilation in HFrEF, PAH and small-vessel, distal CTEPH. As such, interventions geared to improve central haemodynamics and/or reduce chemosensitivity have been particularly effective in lessening their excess ventilation. In contrast, 1) high filling pressures in HFpEF and 2) impaired lung perfusion leading to ventilation/perfusion mismatch in proximal CTEPH conspire to increase physiological dead space. Accordingly, 1) decreasing pulmonary capillary pressures and 2) mechanically unclogging larger pulmonary vessels (pulmonary endarterectomy and balloon pulmonary angioplasty) have been associated with larger decrements in excess ventilation. Exercise training has a strong beneficial effect across diseases. Addressing some major unanswered questions on the link of excess ventilation with exertional dyspnoea under the modulating influence of pharmacological and nonpharmacological interventions might prove instrumental to alleviate the devastating consequences of these prevalent diseases.

Association of Electrocardiographic Signs of Right Ventricular Hypertrophy and Clot Localization in Chronic Thromboembolic Pulmonary Hypertension.

The role of electrocardiography (ECG) in chronic thromboembolic pulmonary hypertension (CTEPH) diagnosis and prognosticating has not been yet established. We aimed to assess the relationships of the recommended ECG criteria of right ventricular hypertrophy (RVH) with clot localization in CTEPH patients. ECG patterns of RVH according to the American College of Cardiology Foundation were assessed in patients with newly diagnosed CTEPH. We enrolled 58 (45.3%) patients with proximal and 70 (54.7%) with distal CTEPH. Receiver-operating characteristics curves analysis indicated that the following ECG abnormalities predicted proximal CTEPH localization: RV1 > 6 mm—AUC 0.75 (CI: 0.66–0.84, p < 0.00001); SV6 > 3 mm—AUC 0.70 (CI: 0.60–0.79, p < 0.00001); SI > RI wave—AUC 0.67 (CI: 0.58–0.77, p = 0.0004); RV1:SV1 > 1.0—AUC 0.66 (CI: 0.56–0.76, p = 0.0009); RV1 peak > 0.035 s (QRS < 120 ms)—AUC 0.66 (CI: 0.56–0.75, p = 0.0016); RV1:SV1 > RV3(V4):SV3(V4)—AUC-0.65 (CI: 0.54–0.75, p = 0.0081); RaVR > 4 mm—AUC 0.62 (CI: 0.52–0.71, p = 0.002) and PII > 2.5 mm—AUC 0.62 (CI: 0.52–0.72, p = 0.00162). Pulmonary vascular resistance significantly correlated with amplitudes of RV1 (r = 0.34, p = 0.008), SV6 (r = 0.53, p = 0.000027) and PII (r = 0.44, p = 0.00007). In patients with CTEPH, only 8 out of 23 ECG RVH criteria were useful for differentiating between proximal and distal CTEPH localization and we found that RV1 and SV6 may contribute as potential discriminators.

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

BackgroundHypodense 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 ResultsBlinded 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).ConclusionsPVS 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.

Balloon Pulmonary Angioplasty with Stent Implantation as a Treatment of Proximal Chronic Thromboembolic Pulmonary Hypertension

We present a case of a 67-year-old female with proximal chronic thromboembolic pulmonary hypertension (CTEPH), disqualified from pulmonary endarterectomy due to multiple comorbidities and high risk-to-benefit ratio as assessed by multidisciplinary CTEPH team. She was referred for balloon pulmonary angioplasty (BPA) and underwent three sessions with balloon catheters up to 8 mm diameter. During the second procedure, the elastic recoil phenomenon was observed in the treated post-thrombotic lesion of the right lower lobe artery, which made the balloon angioplasty ineffective. It was decided to implant a self-expanding stent for the prevention of restenosis. The procedure resulted in significant improvement of regional perfusion, as confirmed by control angiography. We feel that it contributed to the significant improvement of hemodynamic parameters and exercise capacity, as assessed three months after the last BPA procedure. In conclusion, pulmonary artery stenting may be an option in proximal CTEPH when elastic recoil phenomenon makes balloon angioplasty of a large vessel ineffective.

Balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension.

Chronic thromboembolic pulmonary hypertension (CTEPH) is classified as Group-4 pulmonary hypertension caused by organized thrombi in pulmonary arteries. Pulmonary endarterectomy (PEA) has been shown to improve the symptoms and prognoses of patients with proximal CTEPH. The soluble guanylate cyclase stimulator (riociguat) is the sole FDA-licensed drug for the treatment of CTEPH, and guidelines recommend its use for patients with inoperable CTEPH or residual or recurrent pulmonary hypertension following PEA. Balloon pulmonary angioplasty (BPA) is a new procedure, but it is a promising alternative to PEA, especially in patients with inoperable CTEPH. This review summarizes the history, indications, procedures and complications of BPA. Finally, we discuss the future perspective of BPA for better management of CTEPH.

Klippel-Trenaunay syndrome as a rare cause of chronic thromboemboembolic pulmonary hypertension

Klippel-Trenaunay syndrome (KTS) is a congenital disorder characterized by cutaneous capillary malformations, soft tissue and bone hypertrophy, and multiple capillary, venous or lymphatic malformations. KTS is associated with recurrent thromboembolic events. We reported herein five cases of chronic thromboembolic pulmonary hypertension (CTEPH) associated with KTS (age minimum–maximum 26–50 years old, 3 males/2 females). Hemodynamics showed severe pulmonary hypertension (PH) with pulmonary vascular resistance ranging from 5.6 to 18.3 Wood units (WU), associated with marked clinical impairment (NYHA functional class III or IV in 4 patients). Computed tomography (CT) of the chest and pulmonary angiography confirmed proximal CTEPH accessible to surgical intervention in one patient and distal forms of CTEPH in 4 patients. Evolution after pulmonary endarterectomy showed hemodynamic normalization, while the patients with distal CTEPH had severe outcomes with 2 early deaths after PH diagnosis (44 and 35 months respectively). One patient with distal CTEPH was still alive 16 years after diagnosis on specific PH therapy and one was transplanted after 15 years because of right heart failure (death after 12 months). Histological analysis of the lung explants showed typical chronic thromboembolic material specific for CTEPH. In conclusion, KTS may be complicated by severe CTEPH requiring careful anticoagulation and multidisciplinary follow-up in expert centers to screen for disease potentially accessible to endarterectomy. In the modern management era of CTEPH, balloon pulmonary angioplasty will certainly be an interesting option in patients with inoperable disease.

An insider view on the World Symposium on Pulmonary Hypertension

An insider view on the World Symposium on Pulmonary Hypertension

The role of computed tomography in the diagnosis of acute and chronic pulmonary embolism.

Pulmonary embolism (PE) is a potentially life threatening condition requiring adequate diagnosis and treatment. Computed tomography pulmonary angiography (CTPA) is excellent for including and excluding PE, therefore CT is the first-choice diagnostic imaging technique in patients suspected of having acute PE. Due to its wide availability and low invasiveness, CTPA tends to be overused. Correct implementation of clinical decision rules in diagnostic workup for PE improves adequate use of CT. Also, CT adds prognostic value by evaluating right ventricular (RV) function. CT-assessed RV dysfunction and to lesser extent central emboli location predicts PE-related mortality in normotensive and hypotensive patients, while PE embolic obstruction index has limited prognostic value. Simple RV/left ventricular (LV) diameter ratio measures >1.0 already predict risk for adverse outcome, whereas ratios <1.0 can safely exclude adverse outcome. Consequently, assessing the RV/LV diameter ratio may help identify patients who are potential candidates for treatment at home instead of treatment in the hospital. A minority of patients develop chronic thromboembolic pulmonary hypertension (CTEPH) following acute PE, which is a life-threatening condition that can be diagnosed by CT. In proximal CTEPH, involving the more central pulmonary arteries, thrombectomy usually results in good outcome in terms of both functional status and long-term survival rate. CT is becoming the imaging method of choice for diagnosing CTEPH as it can identify patients who may benefit from thrombectomy. New CT developments such as distensibility measurements and dual-energy or subtraction techniques may further refine diagnosis and prognosis for improved patient care.

Left ventricular diastolic dysfunction in pulmonary hypertension predicts functional capacity and clinical worsening: a tissue phase mapping study.

BackgroundThe function of the right and left ventricles is intimately related through a shared septum and pericardium. Therefore, right ventricular (RV) disease in pulmonary hypertension (PH) can result in abnormal left ventricular (LV) myocardial mechanics. To assess this, we implemented novel cardiovascular magnetic resonance (CMR) tissue phase mapping (TPM) to assess radial, longitudinal and tangential LV myocardial velocities in patients with PH.MethodsRespiratory self-gated TPM was performed using a rotating golden-angle spiral acquisition with retrospective cardiac gating. TPM of a mid ventricular slice was acquired in 40 PH patients and 20 age- and sex-matched healthy controls. Endocardial and epicardial LV borders were manually defined, and myocardial velocities calculated using in-house software. Patients without proximal CTEPH (chronic thromboembolic PH) and not receiving intravenous prostacyclin therapy (n = 34) were followed up until the primary outcome of disease progression (death, transplantation, or progression to intravenous therapy) or the end of the study. Physicians who determined disease progression were blinded to CMR data. Conventional ventricular volumetric indices and novel TPM metrics were analyzed for prediction of 6-min walk distance (6MWD) and disease progression.ResultsPeak longitudinal (p < 0.0001) and radial (p = 0.001) early diastolic (E) wave velocities were significantly lower in PH patients compared with healthy volunteers. Reversal of tangential E waves was observed in all patients and was highly discriminative for the presence of PH (p < 0.0001).The global radial E wave (β = 0.41, p = 0.017) and lateral wall radial systolic (S) wave velocities (β = 0.33, p = 0.028) were the only independent predictors of 6MWD in a model including RV ejection fraction (RVEF) and LV stroke volume.Over a median follow-up period of 20 months (IQR 7.9 months), 8 patients commenced intravenous therapy and 1 died. Global longitudinal E wave was the only independent predictor of clinical worsening (6.3× increased risk, p = 0.009) in a model including RVEF and septal curvature.ConclusionsTPM metrics of LV diastolic function are significantly abnormal in PH. More importantly, abnormal LV E wave velocities are the only independent predictors of functional capacity and clinical worsening in a model that includes conventional metrics of biventricular function.Electronic supplementary materialThe online version of this article (doi:10.1186/s12968-015-0220-3) contains supplementary material, which is available to authorized users.

Decreased time constant of the pulmonary circulation in chronic thromboembolic pulmonary hypertension

This study analyzed the relationship between pulmonary vascular resistance (PVR) and pulmonary arterial compliance (Ca) in patients with idiopathic pulmonary arterial hypertension (IPAH) and proximal chronic thromboembolic pulmonary hypertension (CTEPH). It has recently been shown that the time constant of the pulmonary circulation (RC time constant), or PVR × Ca, remains unaltered in various forms and severities of pulmonary hypertension, with the exception of left heart failure. We reasoned that increased wave reflection in proximal CTEPH would be another cause of the decreased RC time constant. We conducted a retrospective analysis of invasive pulmonary hemodynamic measurements in IPAH (n = 78), proximal CTEPH (n = 91) before (pre) and after (post) pulmonary endarterectomy (PEA), and distal CTEPH (n = 53). Proximal CTEPH was defined by a postoperative mean pulmonary artery pressure (PAP) of ≤25 mmHg. Outcome measures were the RC time constant, PVR, Ca, and relationship between systolic and mean PAPs. The RC time constant for pre-PEA CTEPH was 0.49 ± 0.11 s compared with post-PEA-CTEPH (0.37 ± 0.11 s, P < 0.0001), IPAH (0.63 ± 0.14 s, P < 0.001), and distal CTEPH (0.55 ± 0.12 s, P < 0.05). A shorter RC time constant was associated with a disproportionate decrease in systolic PAP with respect to mean PAP. We concluded that the pulmonary RC time constant is decreased in proximal CTEPH compared with IPAH, pre- and post-PEA, which may be explained by increased wave reflection but also, importantly, by persistent structural changes after the removal of proximal obstructions. A reduced RC time constant in CTEPH is in accord with a wider pulse pressure and hence greater right ventricular work for a given mean PAP.

Occlusion pressure analysis role in partitioning of pulmonary vascular resistance in CTEPH.

Flow-directed pulmonary artery occlusion is posited to enable partitioning of vascular resistance into small and large vessels. As such it may have a role in assessment for pulmonary endarterectomy. To test if the occlusion technique distinguished small from large vessel disease we studied 59 subjects with chronic thromboembolic pulmonary hypertension (CTEPH), idiopathic pulmonary arterial hypertension (IPAH), and connective tissue disease (CTD)-associated PAH. At right heart catheterisation, occlusion pressures were recorded. With fitting of the pressure decay curve, pulmonary vascular resistance was partitioned into downstream (small vessels) and upstream (large vessels, Rup). 47 patients completed the study; 14 operable CTEPH, 15 inoperable CTEPH, 13 idiopathic or CTD-PAH and five post-operative CTEPH. There was a significant difference in mean Rup in the proximal operable CTEPH group 87.3 (95% CI 84.1-90.5); inoperable CTEPH mean 75.8 (95% CI 66.76-84.73), p=0.048; and IPAH/CTD, mean 77.1 (95% CI 71.86-82.33), p=0.003. Receiver operating characteristic curves to distinguish operable from inoperable CTEPH demonstrated an area under the curve of 0.75, p=0.0001. A cut-off of 79.3 gave 100% sensitivity (95% CI 73.5-100%) but 57.1% specificity (95% CI 28.9-82.3%). In a subgroup analysis of multiple lobar sampling there was demonstrable heterogeneity. Rup is significantly increased in operable proximal CTEPH compared with non-operable distal CTEPH and IPAH/CTD-PAH. Rup variability in patients with CTEPH and PAH is suggestive of pathophysiological heterogeneity.

S25 Incidence of surgically treated patients with chronic thromboembolic pulmonary hypertension in the UK during the last decade

IntroductionPulmonary endarterectomy (PEA) is the treatment of choice for patients with proximal chronic thromboembolic pulmonary hypertension (CTEPH). The UK has a single centre performing this operation and the program became...

Bosentan as a bridge to pulmonary endarterectomy for chronic thromboembolic pulmonary hypertension

In proximal chronic thromboembolic pulmonary hypertension, pulmonary endarterectomy is the treatment of first choice. In general, medical treatment before pulmonary endarterectomy is not indicated. However, selected "high-risk" patients might benefit by optimization of pulmonary hemodynamics. Moreover, in patients whose surgery is delayed owing to limited medical resources, pretreatment may prevent clinical deterioration. The primary objective of this study was to determine whether the dual endothelin-1 antagonist bosentan improves pulmonary hemodynamics and functional capacity in patients with proximal chronic thromboembolic pulmonary hypertension waiting for pulmonary endarterectomy. We used an investigator-initiated, randomized, controlled single-blind study. Patients were randomized to receive bosentan (n = 13) or no bosentan (n = 12) for 16 weeks, next to "best standard of care." The primary end point was change in total pulmonary resistance. Secondary end points included changes in 6-minute walk distance, mean pulmonary artery pressure, and cardiac index. After 16 weeks, the mean differences in change from baseline between the groups were as follows: total pulmonary resistance 299 dynes x s x cm(-5) (P = .004), 6-minute walk distance 33 m (P = .014), mean pulmonary artery pressure 11 mm Hg (P = .005), and cardiac index 0.3 L x min(-1) x m(-2) (P = .08). Treatment with bosentan was safe. After pulmonary endarterectomy, 4 patients died (no-bosentan group: n = 3); the short-term in-hospital postoperative clinical course was similar in both groups of patients. Patients with proximal chronic thromboembolic pulmonary hypertension may benefit hemodynamically and clinically from treatment with bosentan before pulmonary endarterectomy. Individual factors predictive of a beneficial response and whether this influences either morbidity or mortality associated with pulmonary endarterectomy remain to be established.

Clinical analysis of 62 cases of chronic thromboembolic pulmonary hypertension treated with pulmonary thromboendarterectomy without early and late deaths

To retrospectively evaluate the effects of pulmonary thromboendarterectomy (PTE) on chronic thromboembolic pulmonary hypertension (CTEPH). Sixty-two cases of CTEPH operated with PTE from October 2002 to September 2008 at Anzhen Hospital were retrospectively reviewed and were assigned into either proximal CTEPH group (n = 46) or distal CTEPH group (n = 16). No early death was reported. 15 had residual pulmonary hypertension and 23 had pulmonary reperfusion injury postoperatively. And reperfusion injury was recovered with the support of ventilation or ECMO. Between pre and post-procedure, the pulmonary artery systolic pressure changed from 91 +/- 38 mm Hg to 53 +/- 21 mm Hg, the pulmonary vascular resistance from 916 +/- 548 dynxsxcm(-5) to 368 +/- 302 dynxsxcm(-5) (t = 6.896, P = 0.0001), and the arterial partial pressure of oxygen (PaO(2)) from 51 +/- 7 mm Hg to 90 +/- 7 mm Hg and the arterial oxygen saturation (SaO(2)) from 87.0% +/- 3.9% to 96.1% +/- 3.3%, P < 0.05. With the follow-up of (24.8 +/- 14.6) months (cumulative follow-up was 121.6 patient-years), there was no late death and 38 were in NYHA functional class I, 20 class II, 2 class III and 2 class IV. According to Kaplan-Meier actuarial curve, the freedom from reembolism at 3 years was 96.7% +/- 2.8%. The linear bleeding rate related to anticoagulation was 2.47% patient-years, and the linear thromboembolic rate related to anticoagulation is 1.64% patient-years. The early and mid-long term survival rate of PTE procedure on CTEPH is acceptable and the complication rate related to anticoagulation with warfarin is relatively low.

Demographic features, BMPR2 status and outcomes in distal chronic thromboembolic pulmonary hypertension

Although pulmonary endarterectomy (PEA) is potentially curative in chronic thromboembolic pulmonary hypertension (CTEPH), some patients have distally distributed disease that is not amenable to surgery. The aetiology and characteristics of this patient group are currently not well understood. This study compares the baseline demographic features and outcomes in subjects with distal CTEPH, those with proximal CTEPH and those with idiopathic pulmonary arterial hypertension (IPAH) to determine whether these conditions represent separate entities or whether they exist along the same spectrum of disease. The medical history, clinical characteristics, bone morphogenetic protein receptor type II (BMPR2) mutation status and outcomes of 96 subjects with IPAH, 35 with distal CTEPH and 68 with proximal CTEPH referred to a single specialist centre between 1994 and 2005 were reviewed. There were significant differences between the distal CTEPH, proximal CTEPH and IPAH groups in age (55.9 years vs 54.8 years vs 46.2 years, p<0.001), proportion who were male (43% vs 69% vs 29%, p<0.001), previous deep vein thrombosis (28.6% vs 30.9% vs 3.1%, p<0.001), positive BMPR2 status (0% vs 0% vs 15%, p = 0.018), mean pulmonary artery pressure (47.3 mm Hg vs 45.4 mm Hg vs 54.8 mm Hg, p<0.001) and total pulmonary resistance (12.9 WU vs 12.4 WU vs 18.1 WU, p<0.001). Patients with distal CTEPH and those with IPAH were managed similarly and had comparable survival characteristics (1 year survival 77% vs 86%; 3 year survival 53% vs 60%; p = 0.68). Patients with distal CTEPH share certain demographic features with patients with proximal CTEPH that not only indicate a common aetiology but also help to differentiate them from patients with IPAH. Despite more favourable haemodynamic parameters in those with distal CTEPH, patients in this group had a poor long-term outcome which was similar to that of patients with IPAH.