A simple non-invasive diagnostic algorithm for ruling out chronic thromboembolic pulmonary hypertension in patients after acute pulmonary embolism

Open AccessPublished:March 31, 2011DOI:https://doi.org/10.1016/j.thromres.2011.03.004

      Abstract

      Background

      Our aim was to construct a diagnostic model for ruling out chronic thromboembolic pulmonary hypertension (CTEPH) in symptomatic patients after acute pulmonary embolism (PE) that is based on simple, non-invasive tests.

      Methods

      Plasma levels of various CTEPH associated biomarkers and conventional ECG criteria for right ventricular pressure overload were assessed in 82 consecutive patients with confirmed CTEPH and 160 consecutive patients with a history of PE who were suspected to have CTEPH, but in whom this disease was ruled out.

      Results

      ECG criteria of right ventricular hypertrophy were detected more frequently in patients with CTEPH (77%) than in the patients without CTEPH (11%, Odds ratio 26, 95% confidence interval [CI] 13–53). Also, clotting factor FVIII activity and the levels of N-terminal-pro-brain-type natriuretic peptide (NT-pro-BNP), Growth Differentiation Factor-15, C-reactive protein and urate, but not D-dimer level, were higher in patients with CTEPH. A diagnostic model including ECG criteria and NT-pro-BNP levels had a sensitivity of 94% (95% CI 86-98%) and a specificity of 65% (95% CI 56-72%). The area under the receiver-operator-characteristic curve was 0.80 (95% CI 0.74-0.85) for the diagnosis of CTEPH. Even with high disease prevalences of up to 10%, the negative predictive value of this model proved to be very high (99%, 95% CI 97-100%).

      Conclusions

      Ruling out CTEPH in patients after acute PE seems to be safe without additional diagnostic testing in absence of ECG criteria indicative of right ventricular hypertrophy and a normal NT-pro-BNP level.

      Introduction

      Chronic thromboembolic pulmonary hypertension (CTEPH) results from chronic obstruction of the pulmonary vascular bed by organized thrombi [
      • Hoeper M.M.
      • Mayer E.
      • Simonneau G.
      • Rubin L.J.
      Chronic thromboembolic pulmonary hypertension.
      ]. The incidence of CTEPH in patients who suffered from acute pulmonary embolism (PE) has been reported to be in the range of 0.5-3.8%, depending on the selection criteria applied in the individual studies [
      • Hoeper M.M.
      • Mayer E.
      • Simonneau G.
      • Rubin L.J.
      Chronic thromboembolic pulmonary hypertension.
      ,
      • Pengo V.
      • Lensing A.W.
      • Prins M.H.
      • et al.
      Incidence of chronic thromboembolic pulmonary hypertension after pulmonary embolism.
      ,
      • Klok F.A.
      • van Kralingen K.W.
      • van Dijk A.P.J.
      • et al.
      Prospective cardiopulmonary screening program to detect chronic thromboembolic pulmonary hypertension in patients after acute pulmonary embolism.
      ,
      • Becattini C.
      • Agnelli G.
      • Pesavento R.
      • Silingardi M.
      • Poggio R.
      • Taliani M.R.
      • et al.
      Incidence of chronic thromboembolic pulmonary hypertension after a first episode of pulmonary embolism.
      ,
      • Miniati M.
      • Monti S.
      • Bottai M.
      • Scoscia E.
      • Bauleo C.
      • Tonelli L.
      • et al.
      Survival and restoration of pulmonary perfusion in a long-term follow-up of patients after acute pulmonary embolism.
      ,
      • Poli D.
      • Grifoni E.
      • Antonucci E.
      • Arcangeli C.
      • Prisco D.
      • Abbate R.
      • et al.
      Incidence of recurrent venous thromboembolism and of chronic thromboembolic pulmonary hypertension in patients after a first episode of pulmonary embolism.
      ]. The prognosis of patients with CTEPH is poor, unless a successful pulmonary endarterectomy is possible [
      • Hoeper M.M.
      • Mayer E.
      • Simonneau G.
      • Rubin L.J.
      Chronic thromboembolic pulmonary hypertension.
      ,
      • Corsico A.G.
      • D'Armini A.M.
      • Cerveri I.
      • et al.
      Long-term outcome after pulmonary endarterectomy.
      ]. Therefore, early recognition of this disease is crucial for timely referral to a center specialized in the management of pulmonary hypertension, allowing swift and adequate therapeutical intervention.
      The clinical presentation of CTEPH is characterized by non-specific symptoms and include exercise intolerance and dyspnea, fatigue, chest pain, and syncope (at exercise). These symptoms are also consistent with other, more common cardiopulmonary conditions such as asthma, chronic obstructive pulmonary disease (COPD), interstitial lung disease, coronary artery disease, cardiac arrhythmia or heart failure not caused by chronic pulmonary thrombi [
      • Hoeper M.M.
      • Mayer E.
      • Simonneau G.
      • Rubin L.J.
      Chronic thromboembolic pulmonary hypertension.
      ,
      Dyspnea
      Mechanisms, assessment, and management: a consensus statement. American Thoracic Society.
      ,
      • Pratter M.R.
      • Curley F.J.
      • Dubois J.
      • Irwin R.S.
      Cause and evaluation of chronic dyspnea in a pulmonary disease clinic.
      ]. These non-specific symptoms are commonly reported by patients who suffered from an acute PE and therefore, the possibility of CTEPH can be frequently considered [
      • Klok F.A.
      • Tijmensen J.E.
      • Haeck M.L.
      • et al.
      Persistent dyspnea complaints at long-term follow-up after an episode of acute pulmonary embolism: results of a questionnaire.
      ]. The diagnostic management of CTEPH is complex. In many patients pulmonary perfusion scintigraphy, transthoracic echocardiography and conventional pulmonary angiography with determination of pulmonary hemodynamics need to be performed before the diagnosis of CTEPH can be refuted. There is great need for more simple, easily available, less invasive and less expensive tests to safely rule out CTEPH [
      • Hoeper M.M.
      • Mayer E.
      • Simonneau G.
      • Rubin L.J.
      Chronic thromboembolic pulmonary hypertension.
      ]. These tests may include conventional 12-lead electrocardiography (ECG) and biomarkers of heart failure, inflammation or thrombosis that are associated with pathogenesis or prognosis of CTEPH, and which are widely available for and applicable to outpatient medical care [
      • Nickel N.
      • Kempf T.
      • Tapken H.
      • et al.
      Growth differentiation factor-15 in idiopathic pulmonary arterial hypertension.
      ,
      • Quarck R.
      • Nawrot T.
      • Meyns B.
      • Delcroix M.
      C-reactive protein: a new predictor of adverse outcome in pulmonary arterial hypertension.
      ,
      • Shimizu Y.
      • Nagaya N.
      • Satoh T.
      • et al.
      Serum uric acid level increases in proportion to the severity of pulmonary thromboembolism.
      ,
      • Bonderman D.
      • Turecek P.L.
      • Jakowitsch J.
      • et al.
      High prevalence of elevated clotting factor VIII in chronic thromboembolic pulmonary hypertension.
      ,
      • Kaczyńska A.
      • Kostrubiec M.
      • Pacho R.
      • et al.
      Elevated D-dimer concentration identifies patients with incomplete recanalization of pulmonary artery thromboemboli despite 6 months anticoagulation after the first episode of acute pulmonary embolism.
      ,
      • Andreassen A.K.
      • Wergeland R.
      • Simonsen S.
      • et al.
      N-terminal pro-B-type natriuretic peptide as an indicator of disease severity in a heterogeneous group of patients with chronic precapillary pulmonary hypertension.
      ]. Although the prognostic value of these biomarker levels for CTEPH or other entities of pulmonary hypertension are well described, their diagnostic potential has not been systematically studied [
      • Nickel N.
      • Kempf T.
      • Tapken H.
      • et al.
      Growth differentiation factor-15 in idiopathic pulmonary arterial hypertension.
      ,
      • Quarck R.
      • Nawrot T.
      • Meyns B.
      • Delcroix M.
      C-reactive protein: a new predictor of adverse outcome in pulmonary arterial hypertension.
      ,
      • Shimizu Y.
      • Nagaya N.
      • Satoh T.
      • et al.
      Serum uric acid level increases in proportion to the severity of pulmonary thromboembolism.
      ,
      • Bonderman D.
      • Turecek P.L.
      • Jakowitsch J.
      • et al.
      High prevalence of elevated clotting factor VIII in chronic thromboembolic pulmonary hypertension.
      ,
      • Kaczyńska A.
      • Kostrubiec M.
      • Pacho R.
      • et al.
      Elevated D-dimer concentration identifies patients with incomplete recanalization of pulmonary artery thromboemboli despite 6 months anticoagulation after the first episode of acute pulmonary embolism.
      ,
      • Andreassen A.K.
      • Wergeland R.
      • Simonsen S.
      • et al.
      N-terminal pro-B-type natriuretic peptide as an indicator of disease severity in a heterogeneous group of patients with chronic precapillary pulmonary hypertension.
      ].
      In the present study, we examined whether CTEPH can be ruled out in symptomatic patients with a documented history of acute PE by using ECG assessment and measurement of several biomarkers, i.e. N-terminal-pro-B-type natriuretic peptide (NT-pro-BNP), Growth Differentiation Factor-15 (GDF-15), C-reactive protein (CRP), urate, plasma factor VIII coagulant activity (FVIII:C) and D-dimer, or a combination of these tests.

      Materials and methods

       Patients

      We studied patients from a large follow-up study of patients with acute PE in an academic (Leiden University Medical Center, Leiden, the Netherlands) and affiliated teaching hospital (Medical Center Haaglanden, The Hague, the Netherlands) [
      • Klok F.A.
      • van Kralingen K.W.
      • van Dijk A.P.J.
      • et al.
      Prospective cardiopulmonary screening program to detect chronic thromboembolic pulmonary hypertension in patients after acute pulmonary embolism.
      ]. This study included all patients who were diagnosed with acute PE between January 2001 and July 2007. The diagnosis of acute PE was based on intraluminal filling defects on pulmonary angiography or computed-tomography pulmonary-angiography (CTPA), high probability ventilation perfusion scintigraphy (VQ-scan) or intermediate probability VQ-scan in combination with objectively diagnosed deep vein thrombosis (DVT) [
      • Huisman M.V.
      • Klok F.A.
      Diagnostic management of clinically suspected acute pulmonary embolism.
      ]. All patients were treated with at least 5 days of either unfractionated heparin or weight based therapeutic doses of low molecular weight heparin, followed by vitamin-K antagonists for a period of at least 6 months. The goal of this study was to determine the incidence of CTEPH in an large and unselected cohort and in addition, study the yield of an echocardiography based screening program for CTEPH. Therefore, we invited all surviving patients who were no yet diagnosed with pulmonary hypertension at the start of our study (July 2007) for a single visit to our outpatient clinic for cardiopulmonary work-up including echocardiography [
      • Klok F.A.
      • van Kralingen K.W.
      • van Dijk A.P.J.
      • et al.
      Prospective cardiopulmonary screening program to detect chronic thromboembolic pulmonary hypertension in patients after acute pulmonary embolism.
      ]. From the 877 consecutive patients in the original study cohort, 259 had died before the start of the study, 11 were living abroad and therefore lost to follow-up, 19 were previously diagnosed with pulmonary hypertension and 186 declined participation. For the present analysis, we only studied the remaining patients who were clinically suspected of having CTEPH because they reported exertional dyspnea and/or decreased exercise capacity.
      We additionally included 82 consecutive patients from a CTEPH referral centre (Academic Medical Center, Amsterdam, the Netherlands), who were previously diagnosed with CTEPH by regular clinical care. This study was approved by the institutional review board of all participating hospitals and all patients provided written informed consent.

       Procedures

      In all three participating centers, the routine diagnostic workup of patients with suspected CTEPH started with echocardiography. We used very sensitive echocardiographic criteria for establishing the suspicion of pulmonary hypertension: 1) estimated systolic pulmonary artery pressure ≥35 mmHg (maximal pressure gradient across the tricuspid valve calculated by the modified Bernoulli equation plus the estimated right atrium pressure, 2) maximal tricuspid regurgitation velocity >2.8 m/s, 3) borderline value of criterion 1 or 2 in combination with a right ventricular TEI index >0.36 (isovolumic contraction time plus isovolumic relaxation time divided by ejection time), 4) estimated mean pulmonary artery pressure ≥25 mmHg (estimated systolic pressure plus 2 times enddiastolic pressure as estimated by pulmonary regurgitation enddiastolic velocity divided by 3, 5) AcT (acceleration time ) <120 or AcT/RVET (right ventricular ejection time) <0.40, 6) secondary changes associated with pulmonary hypertension, e.g. systolic septal flattening, right ventricular hypertrophy or W-pattern in the right ventricular outflow curve [
      • Klok F.A.
      • van Kralingen K.W.
      • van Dijk A.P.J.
      • et al.
      Prospective cardiopulmonary screening program to detect chronic thromboembolic pulmonary hypertension in patients after acute pulmonary embolism.
      ]. All patients who met one or more of these 6 criteria were suspected of having pulmonary hypertension and underwent further standardized work-up including perfusion lung scintigraphy and right heart catheterization for pressure measurements. Criteria for the diagnosis of CTEPH were a mean pulmonary artery pressure (mPAP) assessed by right heart catheterization exceeding 25 mmHg and a normal pulmonary capillary wedge pressure in combination with segmental of subsegmental perfusion defects on perfusion scintigram and signs of CTEPH on conventional pulmonary angiography [
      • Hoeper M.M.
      • Mayer E.
      • Simonneau G.
      • Rubin L.J.
      Chronic thromboembolic pulmonary hypertension.
      ,
      • McLaughlin V.V.
      • Archer S.L.
      • Badesch D.B.
      • et al.
      ACCF/AHA. ACCF/AHA 2009 expert consensus document on pulmonary hypertension: a report of the American College of Cardiology Foundation Task Force on Expert Consensus Documents and the American Heart Association: developed in collaboration with the American College of Chest Physicians, American Thoracic Society, Inc., and the Pulmonary Hypertension Association.
      ].
      All patients were classified according to the modified New York Heart Association (NYHA) classification of the World Health Organization. Conventional 12-lead ECGs were obtained and blood samples were drawn and stored on the day that the participants of the follow-up study were screened for pulmonary hypertension, or before pulmonary endarterectomy was performed or medical treatment was initiated in the patients with established CTEPH. The ECGs were recorded with the patient in supine position for a 10-second period using the standard 12-lead electrode configuration at a conventional speed (25 mm/s) and sensitivity (1 mV/10 mm). All ECGs were evaluated for the presence of one or more of the following three criteria of right ventricular hypertrophy that have been demonstrated by multivariate logistic regression to predict the presence of pulmonary hypertension optimally: 1) rSR’ or RSr’ pattern in lead V1, 2) R:S >1 in lead V1 with R >0.5 mV and 3) QRS axis >90° [
      • Henkens I.R.
      • Mouchaers K.T.
      • Vonk-Noordegraaf A.
      • et al.
      Improved ECG detection of presence and severity of right ventricular pressure load validated with cardiac magnetic resonance imaging.
      ].
      All blood samples were analyzed in batches after a single thaw. Levels of NT-pro-BNP were measured with the use of quantitative immunoassays (Hitachi Modular E 170 unit, Roche Diagnostics, Mannheim, Germany). GDF-15 serum concentrations were assessed by immunoradiometric assays using a polyclonal GDF-15 affinity-chromatography-purified, goat anti-human GDF-15 IgG antibody (AF957) from R&D Systems (Minneapolis, MN) [
      • Kempf T.
      • Horn-Wichmann R.
      • Brabant G.
      • et al.
      Circulating concentrations of growth-differentiation factor 15 in apparently healthy elderly individuals and patients with chronic heart failure as assessed by a new immunoradiometric sandwich assay.
      ]. CRP and urate measurements were performed using A Hitachi Modular system according the recommendations of the reagent manufacture (Roche, Diagnostics, Mannheim, Germany). FVIII:C was measured in a one-stage APTT-based clotting assay using immunodepleted FVIII-deficient plasma and Automated APTT (BioMerieux, Boxtel, the Netherlands) on an automated coagulation analyzer (STA-R Evolution, Diagnostica Stago, Roche Diagnostics). Results for FVIII:C are expressed as international units (IU) per dL with reference to a normal pooled plasma calibrated against the 4th WHO international standard FVIII/VWF plasma (97/586) (NIBSC, Potters Bar, UK). The D-dimers were measured on the same analyzer using the STA-Liatest D-dimer assay (Diagnostica Stago). The detection range ≥50 pg/mL for NT-pro-BNP, ≥20 ng/L for GDF-15, ≥1.0 mg/mL for CRP and ≥25020000 ng/mL for D-dimer. All biomarker measurements were performed by investigators who were blinded to the patients' diagnosis. We used predefined reference values for the biomarkers under study to predict the presence of CTEPH: NT-pro-BNP dependent on age and sex as suggested by the manufacturer, GDF-151200 ng/L, CRP3.0 mg/L, uric acid >0.34 mmol/L for female and >0.42 mmol/L for male patients as suggested by the manufacturer, FVIII:C150 IU/dL, and D-dimer >500 ng/mL FEU being the optimal predictor of thrombosis [
      • Kempf T.
      • Horn-Wichmann R.
      • Brabant G.
      • et al.
      Circulating concentrations of growth-differentiation factor 15 in apparently healthy elderly individuals and patients with chronic heart failure as assessed by a new immunoradiometric sandwich assay.
      ,
      • Koster T.
      • Blann A.D.
      • Briët E.
      • et al.
      Role of clotting factor VIII in effect of von Willebrand factor on occurrence of deep-vein thrombosis.
      ,
      • Bounameaux H.
      • Cirafici P.
      • de Moerloose P.
      • et al.
      Measurement of D-dimer in plasma as diagnostic aid in suspected pulmonary embolism.
      ].

       Statistics

      We calculated the sensitivity and specificity of the conventional ECG criteria of right ventricular hypertrophy and the biomarkers under study for the presence of CTEPH in all patients. Patients from the screening study who were identified as having pulmonary hypertension of other etiology than CTEPH were excluded from further analysis. Differences between the study groups were analyzed using student T-tests for normally distributed continuous variables, Mann-Whitney-U tests for skewed distributed continuous variables and chi-square tests for categorical variables. Further, starting with the clinical test with the highest area under the receiver operator characteristic (AUC of ROC) curve and thus with the highest predictive accuracy, we derived 7 additional clinical models by including consecutive diagnostic tests with decreasing AUC in a model to identify the most favorable combination of clinical tests for this purpose. AUC of ROC analyses were compared by the method described by Hanley and McNeil [
      • Hanley J.A.
      • McNeil B.J.
      The meaning and use of the area under a receiver operating (ROC) curve.
      ]. Our final diagnostic model was based on the combination of diagnostic tests with the optimal combination of sensitivity and thus negative predictive value, and specificity for efficacy reasons. Finally, we used the following formula to calculate the negative predictive value of the newly constructed optimal model according to increasing assumed prevalences of CTEPH: (specificity*(1-prevelence))/{((1-sensitivity)*prevalence)+(specificity*(1-prevalence))}. SPSS version 14.02 (SPSS Inc, Chicago, IL) was used for all analysis. A p-value of 0.05 or less was considered to indicate a significant difference.

      Results

       Study patients

      We included 170 patients with a history of acute PE (mean follow-up period after PE diagnosis 4.5±0.7 years) and clinically suspected CTEPH. After extensive diagnostic testing including right heart catheterization and pulmonary scintigraphy, 10 of these 170 patients were diagnosed with pulmonary hypertension: 5 with COPD associated pulmonary hypertension and 5 with left heart disease associated pulmonary hypertension, but none with CTEPH. Therefore, these 10 patients were excluded from further analysis. Pulmonary hypertension was ruled out in the remaining 160 patients by either echocardiography without any signs of pulmonary hypertension or else right heart catheterization indicating normal pulmonary artery pressure. An alternative explanation for the dyspnea was found in the majority of the patients, including previously established or newly diagnosed heart or lung disease, anemia, morbid obesity or a combination of these conditions [
      • Klok F.A.
      • van Kralingen K.W.
      • van Dijk A.P.
      • Heyning F.H.
      • Vliegen H.W.
      • Huisman M.V.
      Prevalence and potential determinants of exertional dyspnea after acute pulmonary embolism.
      ]. The study population was completed by 82 consecutive patients with established CTEPH. The baseline characteristics of the study patients are presented in Table 1.
      Table 1Patient characteristics.
      Patients with CTEPH (n=82)Patients in whom CTEPH was ruled out (n=160)p-value
      Age (years±SD)57±1457±16NS
      Male sex (n, %)32 (39)73 (46)NS
      Active malignancy (n, %)8 (9.8)22 (14)NS
      COPD (n, %)6 (7.3)35 (22)0.04
      Left sided heart disease (n, %)6 (7.3)22 (14)<0.001
      BMI, kg/m2 (mean, ±SD)28±6.029±5.2NS
      mPAP, mmHg (mean, ±SD)44±11-NA
      CTEPH=chronic thromboembolic pulmonary hypertension, n=number, SD=standard deviation, COPD=chronic obstructive pulmonary disease, BMI=body mass index, NS=no statistical significance, NA=not applicable, mPAP=mean pulmonary artery pressure.

       ECG characteristics and biomarker levels

      The typical predefined electrocardiographic signs of pulmonary hypertension were detected significantly more often in patients with CTEPH (77%) than in the symptomatic patients without pulmonary hypertension (11%; Odds ratio 26, 95% confidence interval (CI) 13–53). A closer look at the distribution of the 3 ECG characteristics revealed that right axis was observed most frequently in patients with CTEPH (55%), followed by rSR’ or RSr’ pattern in lead V1 (45%) and R:S >1 in lead V1 with R >0.5 mV (28%); 31 (38%) patients with CTEPH had more than one of the three prespecified ECG characteristics. Circulating levels of NT-pro-BNP, GDF-15, CRP and Urate were significantly higher in patients with CTEPH than in the other study group (Table 2 and Fig. 1). On the other hand, D-dimer levels were not different between the two study groups, with over 50% of the values beneath the detection level of the used assays (Table 2 and Fig. 1).
      Table 2Biomarker levels in the study population.
      Patients with CTEPH (n=82)Patients in whom CTEPH was ruled out (n=160)p-value
      NT-pro-BNP (pg/mL)756 (161–2563)103 (53–214)<0.001
      GDF-15 (ng/L)1580 (1058–2741)1200 (813–1789)<0.001
      CRP (mg/L)4.5 (1.7-8.3)2.5 (1.3-4.6)<0.001
      Urate (mmol/L)0.34 (0.24-0.45)0.31 (0.27-0.38)<0.001
      FVIII:C (IU/dL)2.0 (1.7-2.5)1.7 (1.4-2.0)<0.001
      D-dimer (ng/mL FEU)<250 (<250–432)<250 (<250–457)NS
      Medians and interquartile range are presented. NS=no statistical significance.
      Figure thumbnail gr1
      Fig. 1Biomarker levels in the 2 study groups. Horizontal bars represent medians. FVIII:C levels were missing for 29 patients with CTEPH. Circles represent patients with CTEPH, triangles patients without pulmonary hypertension; *p<0.001.

       Derivation of a diagnostic model

      Clear differences between the sensitivity and specificity and AUC of the ROC curves were observed between the ECG-characteristics and the biomarkers under study using these cut-off points (Table 3). The sensitivity of the ECG criteria (77%, 95% CI 67–86), elevated NT-pro-BNP levels (82%, 95% CI 72–89) and high FVIII:C (83%, 95% CI 70–92) were higher than those of elevated GDF-15 (63%, 95% CI 52–74), CRP (64%, 95% CI 53–75), urate (46%, 95% CI 35–57) and D-dimer levels (24%, 95% CI 16–35). On the other hand, specificity was best for the ECG-criteria (89%, 95% CI 83–93) and elevated urate levels (80%, 95% CI 73–86). The area under the ROC curve (AUC) was slightly higher for the ECG-criteria (0.83, 95% CI 0.77-0.89) than for NT-pro-BNP (difference 0.09, 95% CI −0.04-0.17), and significantly higher than GDF-15 (difference 0.21, 95% CI 0.09-0.30), CRP (difference 0.21, 95% CI 0.08-0.32), Urate (difference 0.21, 95% CI 0.11-0.21), FVIII:C (difference 0.26, 95% CI 0.12-0.35) and D-dimer levels (0.48, difference 0.35, 95% CI 0.18-0.41; Table 3).
      Table 3Test characteristics of ECG and biomarkers for the diagnosis of CTEPH in symptomatic patients after acute pulmonary embolism.
      Sensitivity (%, 95% CI)Specificity (%, 95% CI)AUC (95% CI)
      ECG criteria77 (67–86)89 (83–93)0.83 (0.77-0.89)
      NT-pro-BNP82 (72–89)70 (62–77)0.74 (0.66-0.82)
      GDF-1563 (52–74)50 (42–58)0.62 (0.49-0.64)
      CRP¥64 (53–75)61 (52–68)0.62 (0.53-0.71)
      Urate46 (35–57)80 (73–86)0.62 (0.52-0.71)
      FVIII:CΔ83 (70–92)32 (25–40)0.57 (0.48-0.66)
      D-dimer§24 (16–35)78 (70–84)0.48 (0.39-0.57)
      Presence of at least 1 of the following criteria: rSR’ or rSr’ pattern in lead V1, R:S >1 in lead V1 with R >0.5 mV and QRS axis >90°; sex and age dependent threshold; threshold 1200 ng/L; ¥threshold 3.0 mg/L; Δthreshold 150 IU/dL; §threshold 500 ng/mL FEU. CI=confidence interval, ECG=electrocardiography, AUC=area under the receiver operator characteristic curve.
      We calculated the additional diagnostic value of the biomarkers to ECG assessment, which proved to be the most discriminative test for CTEPH (Table 4). After including NT-pro-BNP to the model (i.e., either one of the 3 ECG criteria positive or NT-pro-BNP levels elevated), the sensitivity increased significantly (+17%, 95% CI 5.4-29), at the cost of specificity (−24%, 95% CI −15 to −33). The AUC of the ROC curve did not change significantly. By including the remaining tests one after the other to the model, the specificity decreased considerably to 39% and even lower, whereas the sensitivity increased only marginally leading to significantly decreased AUC in model C which consists of ECG assessment, NT-pro-BNP and CRP level measurements (difference 0.17, 95% CI 0.06-0.30), and in all further models. Therefore, we determined that model B, which includes ECG-assessment as well as NT-pro-BNP testing, was the most optimal diagnostic model for ruling out CTEPH. This model identified all patients with mPAP greater than 30 mmHg. False negative test result only occurred in a small number of the patients with relatively mild disease (mPAP between 26 and 30 mmHg). Interestingly, one of these latter patients even had normal results from all tests.
      Table 4Additional value of biomarkers to ECG assessment for diagnosing CTPEH.
      ModelSensitivity (%, 95% CI)Specificity (%, 95% CI)AUC (95% CI)
      AECG criteria77 (67–86)89 (83–93)0.83 (0.77-0.89)
      BNT-pro-BNP+model A94 (86–98)65 (56–72)0.80 (0.74-0.85)
      CCRP+model B94 (86–98)39 (31–47)0.66 (0.60-0.73)
      DUrate+model C94 (86–98)33 (26–41)0.64 (0.56-0.71)
      EGDF-15+model D96 (90–99)23 (17–30)0.60 (0.53-0.67)
      FFVIII:C+model E98 (91–99.7)13 (7.8-19)0.55 (0.48-0.63)
      GD-dimer+model F99 (93->99.9)12 (7.3-18)0.55 (0.48-0.63)
      ECG=electrocardiography, AUC=area under the receiver operator characteristic curve, CI=confidence interval.

       Effectiveness of the diagnostic model

      To test the effectiveness of our diagnostic model, we calculated its negative predictive value for hypothetically increasing disease prevalences (Table 5). In case of a normal NT-pro-BNP level and in the absence of typical ECG characteristics of pulmonary hypertension, it is very unlikely that a dyspnoeic patient with a history of acute PE suffers from CTEPH with negative predictive values of 99% or higher, even in the presence of very high incidences of CTEPH (up to 10%).
      Table 5Negative predictive value of our final algorithm (model B) for increasing assumed prevalences of CTEPH.
      Hypothetical incidence of CTEPHNegative predictive value (95% CI)
      0.5%99.9 (99.9- >99.9)
      1.0%99.9 (99.7- >99.9)
      2.0%99.8 (99.5-99.9)
      3.0%99.7 (99.2-99.9)
      4.0%99.6 (99.0-99.9)
      5.0%99.5 (98.7-99.9)
      7.5%99.3 (98.0-99.8)
      10%99.0 (97.3-99.7)
      15%98.4 (95.8-99.5)
      CI=confidence interval.

      Discussion

      Our results demonstrate that a simple diagnostic model based on ECG-evaluation and NT-pro-BNP measurements can rule out CTEPH with a high level of confidence in patients with a documented history of acute PE and clinically suspected CTEPH. Additional more expensive and invasive testing in these patients to rule out CTEPH seems therefore not necessary.
      The sensitivity of the ECG criteria alone was 77%, which confirms earlier studies describing the insufficient diagnostic potential of these ECG criteria for pulmonary hypertension screening purposes [
      • Henkens I.R.
      • Mouchaers K.T.
      • Vonk-Noordegraaf A.
      • et al.
      Improved ECG detection of presence and severity of right ventricular pressure load validated with cardiac magnetic resonance imaging.
      ,
      • McGoon M.
      • Gutterman D.
      • Steen V.
      • et al.
      Screening, early detection, and diagnosis of pulmonary arterial hypertension: ACCP evidence-based clinical practice guidelines.
      ]. The sensitivity, specificity and AUC of the 3 ECG parameters in our cohort were even lower than previously reported [
      • Henkens I.R.
      • Mouchaers K.T.
      • Vonk-Noordegraaf A.
      • et al.
      Improved ECG detection of presence and severity of right ventricular pressure load validated with cardiac magnetic resonance imaging.
      ]. This is likely due to the higher fraction of patients with only mildly elevated mPAP in our study cohort. NT-pro-BNP levels alone showed slightly higher, but still insufficient sensitivity for CTEPH. Combining the 3 ECG criteria with NT-pro-BNP levels, we obtained a higher sensitivity (94%) with an acceptable specificity.
      Although the overall prevalence of CTEPH after acute PE - irrespective of complaints - ranges from 0.5% to 3.8%, this number likely increases 2 or 3 fold in selected patients with prior acute PE who present with clinically suspected CTEPH [
      • Hoeper M.M.
      • Mayer E.
      • Simonneau G.
      • Rubin L.J.
      Chronic thromboembolic pulmonary hypertension.
      ,
      • Pengo V.
      • Lensing A.W.
      • Prins M.H.
      • et al.
      Incidence of chronic thromboembolic pulmonary hypertension after pulmonary embolism.
      ,
      • Klok F.A.
      • van Kralingen K.W.
      • van Dijk A.P.J.
      • et al.
      Prospective cardiopulmonary screening program to detect chronic thromboembolic pulmonary hypertension in patients after acute pulmonary embolism.
      ,
      • Becattini C.
      • Agnelli G.
      • Pesavento R.
      • Silingardi M.
      • Poggio R.
      • Taliani M.R.
      • et al.
      Incidence of chronic thromboembolic pulmonary hypertension after a first episode of pulmonary embolism.
      ,
      • Miniati M.
      • Monti S.
      • Bottai M.
      • Scoscia E.
      • Bauleo C.
      • Tonelli L.
      • et al.
      Survival and restoration of pulmonary perfusion in a long-term follow-up of patients after acute pulmonary embolism.
      ,
      • Poli D.
      • Grifoni E.
      • Antonucci E.
      • Arcangeli C.
      • Prisco D.
      • Abbate R.
      • et al.
      Incidence of recurrent venous thromboembolism and of chronic thromboembolic pulmonary hypertension in patients after a first episode of pulmonary embolism.
      ]. To facilitate correct interpretation and use of our study results for different clinical settings and patient cohorts, we observed high negative predictive value of our diagnostic model for different hypothetical incidences ranging from 0.5 to 15%, thereby enabling physicians to distinguish the negative predictive value applicable to their specific practice. Importantly, the specificity of our model was not sufficiently high to confirm CTEPH: patients with suspected CTEPH and one or more ECG characteristics of pulmonary hypertension or elevated blood levels of NT-pro-BNP should be subjected to further diagnostic tests, including echocardiography and right heart catheterization.
      Although all biochemical tests under study have been shown to be correlated to the presence and/or prognosis of pulmonary hypertension [
      • Nickel N.
      • Kempf T.
      • Tapken H.
      • et al.
      Growth differentiation factor-15 in idiopathic pulmonary arterial hypertension.
      ,
      • Quarck R.
      • Nawrot T.
      • Meyns B.
      • Delcroix M.
      C-reactive protein: a new predictor of adverse outcome in pulmonary arterial hypertension.
      ,
      • Shimizu Y.
      • Nagaya N.
      • Satoh T.
      • et al.
      Serum uric acid level increases in proportion to the severity of pulmonary thromboembolism.
      ,
      • Bonderman D.
      • Turecek P.L.
      • Jakowitsch J.
      • et al.
      High prevalence of elevated clotting factor VIII in chronic thromboembolic pulmonary hypertension.
      ,
      • Kaczyńska A.
      • Kostrubiec M.
      • Pacho R.
      • et al.
      Elevated D-dimer concentration identifies patients with incomplete recanalization of pulmonary artery thromboemboli despite 6 months anticoagulation after the first episode of acute pulmonary embolism.
      ,
      • Andreassen A.K.
      • Wergeland R.
      • Simonsen S.
      • et al.
      N-terminal pro-B-type natriuretic peptide as an indicator of disease severity in a heterogeneous group of patients with chronic precapillary pulmonary hypertension.
      ], and almost all tests were more increased in patients with CTEPH than in the patients without this disease, their diagnostic value for CTEPH proved to be limited, with the exception of NT-pro-BNP. There are 3 plausible explanations for this observation: 1) the studied biomarkers are especially elevated during acute thrombotic states (D-dimer, FVIII:C, CRP) or during acute heart failure (NT-pro-BNP, urate, GDF-15) while CTEPH is a chronic disease characterized by relatively slow progression, 2) all studied biomarkers are established prognostic factors for CTEPH and therefore, mostly present in the patients with severe or worsening disease and 3) a considerable proportion of our patient population without CTEPH had co-existing cardiopulmonary and malignant diseases, which are associated with elevation of one or more of the studied biomarkers as well. For instance, GDF-15, a stress-responsive, transforming growth factor-β-related cytokine, is weakly produced under baseline conditions in most tissues but its production increases sharply in response to hemodynamic stress, inflammation, and tissue injury [
      • Kempf T.
      • Wollert K.C.
      Growth-differentiation factor-15 in heart failure.
      ]. Elevated circulating levels of GDF-15 have been reported in patients with acute PE and idiopathic pulmonary arterial hypertension and have been shown to provide strong and independent prognostic information in these conditions [
      • Nickel N.
      • Kempf T.
      • Tapken H.
      • et al.
      Growth differentiation factor-15 in idiopathic pulmonary arterial hypertension.
      ]. However, elevated levels of GDF-15 can also be detected in other cardiovascular disease states and in patients with malignant tumors. Therefore, and possibly due to the relatively mildly elevated mPAP in some of our patients, GDF-15 proved to be a poor diagnostic test for CTEPH in our population. CRP is a well-known marker of inflammation and tissue damage that recently has been shown to predict the severity and the outcome in patients with pulmonary hypertension [
      • Quarck R.
      • Nawrot T.
      • Meyns B.
      • Delcroix M.
      C-reactive protein: a new predictor of adverse outcome in pulmonary arterial hypertension.
      ]. Also, serum urate or uric acid, the final product of purine degradation, has been proposed to be a prognostic marker for hypoxic states such as chronic heart failure and pulmonary hypertension [
      • Shimizu Y.
      • Nagaya N.
      • Satoh T.
      • et al.
      Serum uric acid level increases in proportion to the severity of pulmonary thromboembolism.
      ]. Nonetheless, the arguments raised to explain the limited diagnostic accuracy of GDF-15 can also explain the lack of discriminative power of urate and CRP levels for CTEPH. Finally, D-Dimer is a global indicator of coagulation activation and fibrinolysis. D-dimers and FVIII:C are known to be increased during and after acute PE, but also in a wide variety of other diseases as infection or inflammatory and malignant conditions [
      • Kyrle P.A.
      • Minar E.
      • Hirschl M.
      • et al.
      High plasma levels of factor VIII and the risk of recurrent venous thromboembolism.
      ,
      • Eichinger S.
      • Minar E.
      • Bialonczyk C.
      • et al.
      D-dimer levels and risk of recurrent venous thromboembolism.
      ]. Both D-dimer and FVIII:C were shown to have very limited diagnostic value for CTEPH in our patient cohort. Altering our pre-defined thresholds for GDF-15, CRP, urate, FVIII:C or D-dimer did not significantly change our observations (data not shown).
      Strengths of this study include the analysis of a large patient cohort with and without CTEPH and the standardized and blinded assessment of ECG characteristics and biomarker levels, thereby increasing the likelihood of generalizability of our results and precluding important biases. Notably, none of the patients with suspected CTEPH from the screening study was diagnosed with CTEPH. One important explanation for this low prevalence is that all patients who were diagnosed with CTEPH prior to the start of our study were included in the CTEPH cohort and consequently, not in the screening study. Our study also had limitations. In spite of the narrow confidence intervals, our conclusions should be confirmed in a future prospective trial since ours was an exploratory but not an outcome study, and therefore, the sensitivity and specificity of the diagnostic tests were calculated retrospectively.
      In conclusion, the present study shows that a diagnostic model based on ECG assessment and NT-pro-BNP measurements can be used to rule out CTEPH in patients with a history of acute PE and clinically suspected CTEPH. Therefore, more invasive tests to rule out this disease do not seem necessary in patients without 3 specific ECG criteria of right ventricular pressure overload and a normal NT-pro-BNP level.

      Disclosures

      Drs. Wollert and Kempf have filed a patent and have a contract with Roche Diagnostics to develop a GDF-15 assay for cardiovascular applications.

      Author contribution

      F.A.K. was responsible for study concept and design, acquired, analyzed, and interpreted the data, and drafted the manuscript, he takes responsibility for the integrity of the work; K.W.v.K., P.B., K.C.W and M.V.H. were responsible for study concept and design, interpreted the data and critically revised the manuscript for important intellectual content, A.P.J.v.D. and H.W.V. were responsible for study concept and design and critically revised the manuscript for important intellectual content and S.S., T.K, J.P.v.S and J.E analysed data and critically revised the manuscript for important intellectual content.

      Conflict of interest

      None.

      Acknowledgments

      The study was supported by an unrestricted research grant from Actelion Pharmaceuticals Ltd.

      References

        • Hoeper M.M.
        • Mayer E.
        • Simonneau G.
        • Rubin L.J.
        Chronic thromboembolic pulmonary hypertension.
        Circulation. 2006; 113: 2011-2020
        • Pengo V.
        • Lensing A.W.
        • Prins M.H.
        • et al.
        Incidence of chronic thromboembolic pulmonary hypertension after pulmonary embolism.
        N Engl J Med. 2004; 350: 2257-2264
        • Klok F.A.
        • van Kralingen K.W.
        • van Dijk A.P.J.
        • et al.
        Prospective cardiopulmonary screening program to detect chronic thromboembolic pulmonary hypertension in patients after acute pulmonary embolism.
        Haematologica. 2010; 95: 970-975
        • Becattini C.
        • Agnelli G.
        • Pesavento R.
        • Silingardi M.
        • Poggio R.
        • Taliani M.R.
        • et al.
        Incidence of chronic thromboembolic pulmonary hypertension after a first episode of pulmonary embolism.
        Chest. 2006; 130: 172-175
        • Miniati M.
        • Monti S.
        • Bottai M.
        • Scoscia E.
        • Bauleo C.
        • Tonelli L.
        • et al.
        Survival and restoration of pulmonary perfusion in a long-term follow-up of patients after acute pulmonary embolism.
        Medicine (Baltimore). 2006; 85: 253-262
        • Poli D.
        • Grifoni E.
        • Antonucci E.
        • Arcangeli C.
        • Prisco D.
        • Abbate R.
        • et al.
        Incidence of recurrent venous thromboembolism and of chronic thromboembolic pulmonary hypertension in patients after a first episode of pulmonary embolism.
        J Thromb Thrombolysis. 2010; 30: 294-299
        • Corsico A.G.
        • D'Armini A.M.
        • Cerveri I.
        • et al.
        Long-term outcome after pulmonary endarterectomy.
        Am J Respir Crit Care Med. 2008; 178: 419-424
        • Dyspnea
        Mechanisms, assessment, and management: a consensus statement. American Thoracic Society.
        Am J Respir Crit Care Med. 1999; 159: 321-340
        • Pratter M.R.
        • Curley F.J.
        • Dubois J.
        • Irwin R.S.
        Cause and evaluation of chronic dyspnea in a pulmonary disease clinic.
        Arch Intern Med. 1989; 149: 2277-2282
        • Klok F.A.
        • Tijmensen J.E.
        • Haeck M.L.
        • et al.
        Persistent dyspnea complaints at long-term follow-up after an episode of acute pulmonary embolism: results of a questionnaire.
        Eur J Intern Med. 2008; 19: 625-629
        • Nickel N.
        • Kempf T.
        • Tapken H.
        • et al.
        Growth differentiation factor-15 in idiopathic pulmonary arterial hypertension.
        Am J Respir Crit Care Med. 2008; 178: 534-541
        • Quarck R.
        • Nawrot T.
        • Meyns B.
        • Delcroix M.
        C-reactive protein: a new predictor of adverse outcome in pulmonary arterial hypertension.
        J Am Coll Cardiol. 2009; 53: 1211-1218
        • Shimizu Y.
        • Nagaya N.
        • Satoh T.
        • et al.
        Serum uric acid level increases in proportion to the severity of pulmonary thromboembolism.
        Circ J. 2002; 66: 571-575
        • Bonderman D.
        • Turecek P.L.
        • Jakowitsch J.
        • et al.
        High prevalence of elevated clotting factor VIII in chronic thromboembolic pulmonary hypertension.
        Thromb Haemost. 2003; 90: 372-376
        • Kaczyńska A.
        • Kostrubiec M.
        • Pacho R.
        • et al.
        Elevated D-dimer concentration identifies patients with incomplete recanalization of pulmonary artery thromboemboli despite 6 months anticoagulation after the first episode of acute pulmonary embolism.
        Thromb Res. 2008; 122: 21-25
        • Andreassen A.K.
        • Wergeland R.
        • Simonsen S.
        • et al.
        N-terminal pro-B-type natriuretic peptide as an indicator of disease severity in a heterogeneous group of patients with chronic precapillary pulmonary hypertension.
        Am J Cardiol. 2006; 98: 525-529
        • Huisman M.V.
        • Klok F.A.
        Diagnostic management of clinically suspected acute pulmonary embolism.
        J Thromb Haemost. 2009; 7: 312-317
        • McLaughlin V.V.
        • Archer S.L.
        • Badesch D.B.
        • et al.
        ACCF/AHA. ACCF/AHA 2009 expert consensus document on pulmonary hypertension: a report of the American College of Cardiology Foundation Task Force on Expert Consensus Documents and the American Heart Association: developed in collaboration with the American College of Chest Physicians, American Thoracic Society, Inc., and the Pulmonary Hypertension Association.
        J Am Coll Cardiol. 2009; 53: 1573-1619
        • Henkens I.R.
        • Mouchaers K.T.
        • Vonk-Noordegraaf A.
        • et al.
        Improved ECG detection of presence and severity of right ventricular pressure load validated with cardiac magnetic resonance imaging.
        Am J Physiol Heart Circ Physiol. 2008; 294: H2150-H2157
        • Kempf T.
        • Horn-Wichmann R.
        • Brabant G.
        • et al.
        Circulating concentrations of growth-differentiation factor 15 in apparently healthy elderly individuals and patients with chronic heart failure as assessed by a new immunoradiometric sandwich assay.
        Clin Chem. 2007; 53: 284-291
        • Koster T.
        • Blann A.D.
        • Briët E.
        • et al.
        Role of clotting factor VIII in effect of von Willebrand factor on occurrence of deep-vein thrombosis.
        Lancet. 1995; 345: 152-155
        • Bounameaux H.
        • Cirafici P.
        • de Moerloose P.
        • et al.
        Measurement of D-dimer in plasma as diagnostic aid in suspected pulmonary embolism.
        Lancet. 1991; 337: 196-200
        • Hanley J.A.
        • McNeil B.J.
        The meaning and use of the area under a receiver operating (ROC) curve.
        Radiology. 1982; 143: 29-36
        • Klok F.A.
        • van Kralingen K.W.
        • van Dijk A.P.
        • Heyning F.H.
        • Vliegen H.W.
        • Huisman M.V.
        Prevalence and potential determinants of exertional dyspnea after acute pulmonary embolism.
        Respir Med. 2010; 104: 1744-1749
        • McGoon M.
        • Gutterman D.
        • Steen V.
        • et al.
        Screening, early detection, and diagnosis of pulmonary arterial hypertension: ACCP evidence-based clinical practice guidelines.
        Chest. 2004; 126: 14S-34S
        • Kempf T.
        • Wollert K.C.
        Growth-differentiation factor-15 in heart failure.
        Heart Fail Clin. 2009; 5: 537-547
        • Kyrle P.A.
        • Minar E.
        • Hirschl M.
        • et al.
        High plasma levels of factor VIII and the risk of recurrent venous thromboembolism.
        N Engl J Med. 2000; 343: 457-462
        • Eichinger S.
        • Minar E.
        • Bialonczyk C.
        • et al.
        D-dimer levels and risk of recurrent venous thromboembolism.
        JAMA. 2003; 290: 1071-1074