Introduction

Chronic thromboembolic pulmonary hypertension (CTEPH) is defined as a mean arterial pulmonary pressure greater than 25 mm Hg and pulmonary capillary wedge pressure less than or equal to 15 mm Hg, which persists for more than 6 months following anticoagulation therapy in the setting of pulmonary emboli (PE).1

CTEPH is currently categorized as WHO group 4 pulmonary hypertension.2 CTEPH can be cured, unlike other types of pulmonary hypertension (PAH)

CTEPH develops more commonly in patients with prothrombotic states.3 In CTEPH lesions, thrombus organizes intraluminally and results in obliteration of pulmonary arteries which, in turn, leads to increased pulmonary vascular resistance (PVR) and pulmonary hypertension, resulting in decreased right ventricular (RV) function and in long-term leads to right heart failure.4

Pulmonary endarterectomy (PEA) is the gold standard treatment for patients with CTEPH with favorable long-term prognosis.

Balloon pulmonary angioplasty along with medical therapy is emerging as new therapeutic option for CTEPH patients with distal disease and those with contraindications to surgery.

Echocardiography (Echo) is the first available imaging modality for screening of pulmonary hypertension, but it is challenging due to the complex geometry of the RV.5 6

It can be used in measuring pulmonary artery pressure (PAP) and RV function by tricuspid annular plane systolic excursion (TAPSE).6 7 8

Common findings of Echo in patient with CTEPH includes RV and right atrial (RA) enlargement, hypertrophy of RV, decreased RV function, tricuspid valve regurgitation, and elevated PAP.

The most sensitive test for diagnosing CTEPH is ventilation/perfusion (V/Q) scan.9 It reveals burden of lung perfusion defect present and even helps in monitoring disease.

Computed tomography pulmonary angiogram (CTPA) helps in diagnosing lung parenchymal disease and has shown sensitivity for detecting CTEPH-related disease in main, lobar, and segmental vessels.10

Pulmonary angiography is the gold standard for confirming the diagnosis of CTEPH.

CTEPH lesions angiographically can be classified into five types, depending on lesion opacity and blood flow distal to the lesion, which are as follows: type A—ring-like stenosis, type B—web lesion, type C—subtotal occlusion, type D—total occlusion, and type E—torturous lesion.11 12

In CTEPH patients, right heart catheterization (RHC) should be done to measure PAP, RV systolic pressure and RA mean pressure and assess response to vasodilator medications.13

The 6-minute walk distance (6MWD) can be used in CTEPH patients, as it corelates well with functional and disease severity.

It can be used in monitoring disease progression and even to assess response to intervention.14 15 16 17

Treatment

Multidisciplinary approach should be used to treat CTEPH patients at experienced centers comprising cardiologists and cardiothoracic surgeons.11

Lifelong anticoagulation should be given to CTEPH patients; vitamin K antagonists should be used to maintain international normalized ratio (INR) around 2 to 3.

Pulmonary vasodilators like Riociguat have shown benefit in CTEPH patients by decreasing PAP and PVR and increasing 6MWD.1 18

Role of Surgical Therapy (PTE)

• PTE is the gold standard treatment option for CTEPH patients in whom lesions are accessible for surgery.

• Bilateral PTE is known to improve long-term outcomes in CTEPH patients (Fig. 1).19 20 21

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Fig. 1 CTEPH treatment algorithm.11

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Fig. 1 CTEPH treatment algorithm.11

Aims and Objectives

To know the efficacy of BPA in patients with distal CTEPH by monitoring 6MWD and New York Heart Association (NYHA) functional class.

To study reduction in PAP and improvement in RA and RV function by Echo.

Material and Method

Study area: Department of Cardiology.

Study population: CTEPH patients presenting to the hospital during the study interval of 16 months from January 2017 to April 2018, meeting the inclusion and exclusion criteria of the study.

Sample size and sample technique: We have expected the standard deviation (SD) of the variable 6MWD meters in CTEPH patients who underwent BPA as 80, and mean values of 6MWD before and after BPA as 403 m and 445 m, respectively, with 90% confidence interval (CI) and 90% power; the minimum required sample size was 22.

However, during our study, we got only 11 distal CTEPH patients who underwent BPA. As it is a very rare procedure performed, so we got a smaller sample size.

Results and Discussion

A total of 11 patients were included in the study; 6 were males and 5 were females.

Mean age of presentation was 39.81 ± 12 years in our study.

In this study, 40.5 months was mean duration of symptoms.

All patients complained of breathing difficulty, which is a common presentation in CTEPH. One patient had history of hemoptysis (Fig. 2).

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Fig. 2 Symptoms.

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Fig. 2 Symptoms.

At baseline, 8 patients were in NYHA class 3 and 3 patients were in NYHA class 4.

After BPA sessions, 8 patients were in NYHA class 3 and 3 were in NYHA class 2 (p-value < 0.001). There was significant increase in functional capacity (Fig. 3).

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Fig. 3 Associated medical conditions: In number of patients.

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Fig. 3 Associated medical conditions: In number of patients.

Past history of deep vein thrombosis (DVT) was noted in 27.27% patients. Hypothyroidism was noted in one patient. Hyperhomocysteinemia was noted in 18.18% patients.

Overall, thrombophilia conditions were noted in 36.36% patients.

Acute pulmonary embolism (PE) history was seen in 45.5% patients. Out of 5 patients of PE, 3 patients were thrombolysed with streptokinase and two were treated by low-molecular weight heparin (LMWH).

Mean hemoglobin (Hb) before BPA was 14.21 ± 2.26 g/Dl and packed-cell volume (PCV) was 42.18 ± 6.445.

Baseline Echo showed RA and RV dilatation and decreased RV function (TAPSE) and elevated PAP. Mean RA minor dimension was 48 ± 4.074 mm, RV basal diameter was 41.27 ± 5.60 mm, TAPSE was 15.37 ± 2.29 mm, and pulmonary artery systolic pressure (PASP) was 92 ± 31.4 mm Hg.

CTPA showed diagnostic features of CTEPH in all patients, and it correlated well with pulmonary angiography findings.

During cardiac catheterization, baseline peak PASP was 111.55 ± 40.31 mm Hg, which is significantly high as compared with PASP calculated by Echo, which was 92 ± 31.642 mm Hg.

Mean right atrial pressure (RAP) by cath was 15.91 ± 5.069 mm Hg, and mean RAP measured by ECHO was 13.09 ± 3.26 mm Hg.

All CTEPH patients had normal coronary arteries. Right coronary artery was dominant in 10 patients and codominance was noted in 1 patient.

Collaterals are noted in 100% of patients from different sources like bronchial arteries, aorta and coronary arteries, which is a hallmark of CTEPH. Pulmonary angiography in all our patients revealed segmental and subsegmental disease.

V/Q scan revealed mismatched perfusion defects in 90.90% patients, with high probability of pulmonary thromboembolism, and one patient with low probability, but in that patient, CTEPH confirmed by pulmonary angiography, which is the gold standard for diagnosing CTEPH.

A total of 30 BPA sessions were performed; 45.5% of patients underwent 2 BPA sessions.

One patient underwent 5 BPA procedures, which was maximum during our study, and only 1 BPA session was done in one patient.

Mean contrast (omnipaque) used was 123.93 mL.

Segmental arteries totally treated during the study period were 104.

A total of 32 segmental arteries were dilated in right lower lobe and 29 segmental arteries dilated in left lower lobe. Twelve segmental arteries were dilated in right middle lobe and 14 in left lingular lobe. Segmental artery dilated in lower lobe of lungs is more when compared with other lung lobes. Segmental vessels dilated before each session was 3.46 ± 0.86 (Table 1).

Only 2 patients developed reperfusion pulmonary edema during the BPA session.

Mild complication requiring only nasal oxygen was observed in one patient, and moderate complication requiring noninvasive ventilation was observed in one patient.

Moderate complication was observed in that patient in whom baseline PAP was of suprasystemic level.

There was no pulmonary artery dissection, major vascular complication at access site, or death seen in our patients during or after BPA.

Mean RA minor diameter decreased from 48 ± 4.074 mm to 40.36 ± 6.47 mm, which is statistically significant (p-value < 0.001). Inferior vena cava (IVC) dimension pre BPA 18.82 ± 3.601 mm decreased to 9.45 ± 1.036 mm post-BPA, which is statistically significant (p-value 0.001).

Mean RAP decreased from 13.09 ± 3.26 mm Hg to 7.90 ± 4.15 post-BPA, which is statistically significant (p-value < 0.001) (Table 2).

Resting basal oxygen saturation, pre-BPA SPO₂ was 88.91 ± 3.208%, which increased to SPO₂ 92.18 ± 1.662% post-BPA, which is statistically significant (p-value < 0.001).

Discussion

The 6MWD, even with its own limitations, may better reflect the functional exercise level for daily physical activities. In many centers, it is used to assess response to therapy and prognosis (Table 3).

The present study shows a statistically significant increase in 6MWD and can be compared with other studies.

This improvement in functional capacity is strongly associated with the improvement in RV function as with the reduction in PAP (Table 4).

Limitations of the Study

• We had only small sample size.

• We lacked the controlled comparison with patients who were treated with medical management or PEA alone.

• In our study, hemodynamic data (PAP) was assessed by Echo in post-BPA sessions.

• We do not have results of long-term follow-up.

• So, further studies at multiple centers are needed to evaluate efficacy of BPA.

Key Messages from the Study

• We recommend detailed thrombophilia workup of all patients diagnosed with CTEPH.

• We also recommend that all patients diagnosed with PE should be screened for CTEPH if they develop exercise intolerance.

• Transthoracic echocardiography should be done as an initial screening test. If RV dysfunction and elevated PAP are noted, it should be referred to a center which possesses expertise in treating CTEPH cases for further management.

• In CTEPH patients, multimodality imaging should be considered, and it is preferable to do V/Q scan, CTPA, RHC and pulmonary angiography and assess collateral blood supply to lungs before deciding on treatment.

• Balloon pulmonary angioplasty should be considered in patients with distal CTEPH at an expert center.

• It is preferable to keep all hardware ready (different balloon sizes) before performing BPA. It is recommended to dilate only minimal (3–4) number of segmental vessels per each BPA session in order to avoid reperfusion pulmonary edema.

• It is recommended to have an extracorporeal membrane oxygenation (ECMO) team and cardiac surgery team as backups while performing BPA in managing untoward complications.

• All CTEPH patients, even after BPA, should be on lifelong anticoagulants (vitamin K antagonists), and prothrombin time (PT) and INR should be monitored regularly.

• The 6MWD, can be used to assess prognosis and response to BPA.

• RV function and PAP should be monitored regularly by Echo after BPA to assess response to procedure and frequency, which will depend on the clinical circumstances.

Conclusion

For CTEPH patients who undergo BPA, there is improvement in 6MWD, and Echo shows RV reverse remodeling and improved function, which is achieved by reduction in PAP and PVR.

So, BPA is recommended in patients with distal CTEPH, which is inaccessible by PEA.

Echo helps in assessing hemodynamic changes and RV function in these patients.

Even after BPA, patients should be on long-term anticoagulants.