Pulmonary microvascular remodeling after balloon pulmonary angioplasty in a patient with chronic thromboembolic pulmonary hypertension

Balloon Pulmonary Angioplasty for Chronic Thromboembolic Pulmonary Hypertension: A Systematic Review and Meta-analysis

PURPOSE

To perform a systematic review and meta-analysis assessing the safety and efficacy of balloon pulmonary angioplasty (BPA) in the treatment of chronic thromboembolic pulmonary hypertension (CTEPH).

MATERIALS AND METHODS

Systematic literature searches were performed from inception to June 2022 to identify studies assessing BPA for CTEPH. Outcomes of interest included the following functional and hemodynamic measures: (a) six-minute walk distance (6MWD), (b) New York Heart Association (NYHA) status, (c) World Health Organization (WHO)-Functional Class status, (d) cardiac index (CI), (e) mean pulmonary artery pressure (mPAP), (f) mean right atrial pressure (mRAP), and (g) pulmonary vascular resistance (PVR). Subgroup analysis was also performed for BPA in post-pulmonary endarterectomy (PEA) patients. All reported BPA-related complications were also recorded. Forty unique studies with a total of 1763 patients were identified for meta-analysis.

RESULTS

All functional and hemodynamic parameters improved significantly following BPA; 6MWD increased 70 m (95% CI 58-82; P < 0.001), NYHA class improved by - 0.9 classes (95% CI - 1.0 to - 0.8; P < 0.001), WHO-FC class improved by - 1 classes ((95% CI - 1.2 to - 0.9; P < 0.001), CI increased 0.26 L/min/m² (95% CI 0.17-0.35; P < 0.001), mPAP decreased - 13.2 mmHg (95% CI - 14.7 to - 11.8; P < 0.001), mRAP decreased - 2.2 mmHg (95% CI - 2.8 to - 1.6; P < 0.001), and PVR decreased - 311 dyne/cm/s^-5 (95% CI - 350 to - 271; P < 0.001). Meta-analysis of patients who underwent BPA for persistent pulmonary hypertension post-PEA demonstrated significant improvements in 6MWD, WHO-FC, PVR and mPAP. Most common complications included lung injury (8.16%), hemoptysis (7.07%) and vessel injury (5.05%).

CONCLUSION

BPA represents a safe and effective treatment option for select individuals with CTEPH with significant improvements in hemodynamic parameters, improved exercise tolerance and a relatively low risk of major complications.

Interventional Management of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension is a distinct form of pulmonary hypertension characterized by the nonresolution of thrombotic material in the pulmonary tree; whenever feasible and safe, first-line treatment should be pulmonary thromboendarterectomy. In patients who are not operative candidates, balloon pulmonary angioplasty (BPA) has emerged as an effective treatment modality that results in improvements in functional class, symptoms, hemodynamics, 6-minute walk distance, and right ventricular and pulmonary artery mechanics. Careful attention to procedural technique and rapid identification and treatment of complications are critical for a successful BPA program.

Continual Improvement in Pressure Gradient at the Lesion After Balloon Pulmonary Angioplasty for Chronic Thromboembolic Pulmonary Hypertension

BACKGROUND

Lung injury is a serious complication of balloon pulmonary angioplasty (BPA) for chronic thromboembolic pulmonary hypertension (CTEPH). Selecting a smaller balloon might minimize the occurrence of lung injury; however, it could also increase the risk of restenosis.

METHODS

We analyzed the first target lesions in the initial BPA procedure in 34 consecutive patients with CTEPH. We measured proximal pressure with a guiding catheter and distal pressure with a pressure wire. We retrospectively investigated pressure gradients at the lesions before and immediately after the initial dilation with a smaller balloon and before the second procedure.

RESULTS

The proximal pressure decreased, and the distal pressure increased immediately after the initial balloon dilation. The pressure gradient at the lesion diminished significantly by the second procedure (from 26.4 ± 10.7 to 18.2 ± 9.9 mm Hg, P < 0.001) without serious complications. The residual pressure gradient had further diminished (to 9.8 ± 6.5 mm Hg, P = 0.02) until the second procedure. The reduction in pressure gradient at the lesion from immediately after the initial balloon dilation to the second procedure was positively correlated with both the baseline mean pulmonary arterial pressure (r² = 0.23, P = 0.004) and residual pressure gradient immediately after the initial balloon dilation (r² = 0.58, P < 0.001).

CONCLUSIONS

The residual pressure gradient at the lesion diminished continually after dilation with a smaller balloon. This strategy could decrease pulmonary arterial pressure safely. It would be reasonable to dilate the lesions sequentially in 2 procedures.

Assessment of oxygenation after balloon pulmonary angioplasty for patients with inoperable chronic thromboembolic pulmonary hypertension

BACKGROUND

The efficacy of balloon pulmonary angioplasty (BPA) in patients with inoperable chronic thromboembolic pulmonary hypertension would be promising. However, some patients showed residual dyspnea or symptoms, despite normalized hemodynamics. We aimed to clarify the clinical impact of oxygenation parameters on BPA outcome.

METHOD

Ninety-nine consecutive patients who underwent BPA from September 2011 to December 2019 were enrolled. We evaluated hemodynamics with right heart catheterization, arterial blood gas examination, New York Heart Association functional class (NYHA-FC), respiratory function tests, nocturnal oximetry, and exercise capacity (6-min walk test and cardiopulmonary exercise testing) at baseline and after BPA.

RESULT

Nearly normal hemodynamics was achieved after BPA (mean pulmonary artery pressure (PAP): 37.5 ± 10.0 to 20.6 ± 4.9 mmHg, p < 0.01). Oxygenation slightly improved (partial pressure of arterial oxygen; 61.5 ± 12.3 to 67.7 ± 12.7 mmHg, p < 0.01). Exertional desaturation remained unchanged (-8.1 ± 4.8 to -7.8 ± 5.1, p = 0.59), and this was associated with residual symptom (NYHA-FC ≥ 2) after BPA (OR 0.591, 95% CI 0.416-0.840, p = 0.003) in multivariate regression analyses. Lower vital capacity (r² = 0.03, p = 0.01), higher mean PAP (r² = 0.08, p = 0.02), and higher minute ventilation/carbon dioxide production (VE/VCO₂) slope (r² = 0.18, p < 0.01), the marker of ventilatory inefficiency, were correlated with exertional desaturation after BPA in multivariate linear analyses.

CONCLUSION

Although hemodynamics nearly normalized, oxygenation did not. Moreover, exertional desaturation remained unchanged. This might cause residual symptom after BPA. Residual pulmonary hypertension suggesting incurable arteriopathy, and higher VE/VCO₂ slope suggesting ventilation-perfusion mismatch might be related to exertional desaturation. Domiciliary oxygen therapy should be continued, if necessary.

Pulmonary angioplasty: A step further in the continuously changing landscape of chronic thromboembolic pulmonary hypertension management

Chronic thromboembolic pulmonary hypertension (CTEPH) is a potentially fatal and frequently undiagnosed form of pulmonary hypertension (PH), classified within group 4 by the World Health Organization (WHO). It is a type of precapillary PH, which uncommonly develops as a peculiar sequel of acute pulmonary embolism due to the partial resolution of the mechanically obstructing thrombus with a coexisting inflammatory response from pulmonary vessels. CTEPH is one of the potentially treatable forms of PH whose current standard of care is surgical pulmonary endarterectomy. Medical therapy with few drugs in non-operable disease is approved and has shown improvement in patients' hemodynamic condition and functional ability. Recently, balloon pulmonary angioplasty (BPA) has shown promising results as a treatment option for technically inoperable patients, those with unacceptable risk-to-benefit ratio and in a case of residual PH after endarterectomy. Lack of meticulous CTEPH screening programs in post-pulmonary embolism patients leading to underdiagnosis of this condition, complex operability assessment, and diversity in BPA techniques among different institutions are still the issues that need to be addressed. In this paper, we review the recent achievements in the management of non-operable CTEPH, their outcome and safety, based on available data.

Balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension: State of the art

Chronic thromboembolic pulmonary hypertension (CTEPH) is a complex chronic disease in which pulmonary artery stenosis or obstruction caused by organized thrombus can lead to increased pulmonary artery pressure and pulmonary vascular resistance, ultimately triggering progressive right heart failure and death. Currently, its exact mechanism is not fully understood. Pulmonary endarterectomy (PEA) has immediate effects with low perioperative mortality and satisfactory prognosis in experienced expert centers for CTEPH patients with proximal lesions. Nevertheless, 37% of patients are deemed unsuitable for PEA surgery due to comorbidities and other factors, and nearly half of the operated patients have residual or recurrent pulmonary hypertension. Riociguat is the only approved drug for CTEPH, although its effect is limited. Balloon pulmonary angioplasty (BPA) is a promising alternative treatment for patients with CTEPH. After more than 30 years of development and refinements, emerging evidence has confirmed its role in patients with inoperable CTEPH or residual/recurrent pulmonary hypertension, with acceptable complications and comparable long-term prognosis to PEA. This review summarizes the pathophysiology of CTEPH, BPA history and development, therapeutic principles, indications and contraindications, interventional procedures, imaging modalities, efficacy and prognosis, complications and management, bridging and hybrid therapies, ongoing clinical trials and future prospects.

Vessel Stretching Is a Cause of Lumen Enlargement Immediately After Balloon Pulmonary Angioplasty: Intravascular Ultrasound Analysis in Patients With Chronic Thromboembolic Pulmonary Hypertension

BACKGROUND

Balloon pulmonary angioplasty (BPA) has become an alternative therapy for patients with chronic thromboembolic pulmonary hypertension who are ineligible for pulmonary endarterectomy. We retrospectively investigated intravascular ultrasound measurements to elucidate how the lumen enlarges immediately after BPA.

METHODS AND RESULTS

A total of 326 lesions in 71 patients with chronic thromboembolic pulmonary hypertension were analyzed. The cross-sectional areas (CSAs) of the external elastic membrane and lumen measured by intravascular ultrasound before and after BPA were assessed for each lesion type (type A, ring-like stenosis lesions; type B, web lesions; type C, subtotal occlusion lesions). Comparing the lesion types, the proportion of the area occupied by fibrous tissue was smallest in the type A lesions and largest in the type C lesions. The mean lesion lumen CSA was increased after BPA because of an increase in external elastic membrane CSA (from 23.2±12.9 to 27.2±14.3 mm²; P<0.001) with a slight decrease in fibrous tissue plus media CSA (from 17.7±11.7 to 17.3±11.1 mm²; P<0.001). The change in lumen CSA correlated strongly with the change in external elastic membrane CSA (r²=0.762; P<0.001).

CONCLUSIONS

Lumen enlargement immediately after BPA was obtained by the overall vessel expansion induced by a stretch of the arterial wall. In addition, the amount of fibrous tissue depended on each lesion type. Thus, it might be beneficial to change the balloon size to correspond with the lesion type.

Chronic Thromboembolic Pulmonary Hypertension: Endovascular Treatment

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare cause of pulmonary hypertension; less than 5% of pulmonary hypertension is caused by recurrent pulmonary thromboembolism (PTE). By definition, CTEPH happens within the first two years after symptomatic PTE; however, cases are often diagnosed without a history of acute PTE. Because of the poor functional status and chronicity of this disease, the classic and curative strategy of open pulmonary endarterectomy cannot be applied in some patients with lesions that involve the distal subsegmental pulmonary artery. Bridging therapy is needed for cases that are technically operable but have an unacceptable risk-benefit assessment or residual symptomatic pulmonary hypertension following surgical removal. Groups in Europe and Japan recently introduced balloon pulmonary angioplasty or percutaneous transluminal pulmonary angioplasty, which has led to significant improvement in functional and hemodynamic parameters in patients with CTEPH. This article introduces recent updates in patient selection and interventional procedures for this chronic and devastating disease.

After the Dawn - Balloon Pulmonary Angioplasty for Patients With Chronic Thromboembolic Pulmonary Hypertension

In the past 5 years, balloon pulmonary angioplasty (BPA) for patients with chronic thromboembolic pulmonary hypertension (CTEPH) who are deemed inoperable has undergone significant refinement. As a result, the procedure is now used worldwide and has become a promising therapeutic option for those patients. However, pulmonary endarterectomy remains the gold standard treatment for patients with CTEPH because the techniques and strategies for BPA are not yet unified. The best therapeutic option for each patient should be determined based on discussion among a multidisciplinary team of experts. For BPA to become an established treatment for CTEPH, further data are needed. This review summarizes the techniques and strategies of BPA at present and discusses the future development of the procedure.

Severe Pulmonary Arteriopathy Is Associated with Persistent Hypoxemia after Pulmonary Endarterectomy in Chronic Thromboembolic Pulmonary Hypertension

BACKGROUND

Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by occlusion of pulmonary arteries by organized chronic thrombi. Persistent hypoxemia and residual pulmonary hypertension (PH) following successful pulmonary endarterectomy (PEA) are clinically important problems; however, the underlying mechanisms remain unclear. We have previously reported that residual PH is closely related to severe pulmonary vascular remodeling and hypothesize that this arteriopathy might also be involved in impaired gas exchange. The purpose of this study was to evaluate the association between hypoxemia and pulmonary arteriopathy after PEA.

METHODS AND RESULTS

Between December 2011 and November 2014, 23 CTEPH patients underwent PEA and lung biopsy. The extent of pulmonary arteriopathy was quantified pathologically in lung biopsy specimens. We then analyzed the relationship between the severity of pulmonary arteriopathy and gas exchange after PEA. We observed that the severity of pulmonary arteriopathy was negatively correlated with postoperative and follow-up PaO2 (postoperative PaO2: r = -0.73, p = 0.0004; follow-up PaO2: r = -0.66, p = 0.001), but not with preoperative PaO2 (r = -0.373, p = 0.08). Multivariate analysis revealed that the obstruction ratio and patient age were determinants of PaO2 one month after PEA (R2 = 0.651, p = 0.00009). Furthermore, the obstruction ratio and improvement of pulmonary vascular resistance were determinants of PaO2 at follow-up (R2 = 0.545, p = 0.0002). Severe pulmonary arteriopathy might increase the alveolar-arterial oxygen difference and impair diffusion capacity, resulting in hypoxemia following PEA.

CONCLUSION

The severity of pulmonary arteriopathy was closely associated with postoperative and follow-up hypoxemia.

Pulmonary endarterectomy for the treatment of chronic thromboembolic pulmonary hypertension

Pulmonary endarterectomy is a curative treatment option for patients with chronic thromboembolic pulmonary hypertension (CTEPH). There is a growing body of evidence suggesting that not only patients with CTEPH but also patients with pulmonary arterial obstructions and mean pulmonary artery pressures < 25 mmHg should be offered surgery. In this review, the recent literature regarding pathophysiology, diagnostic methods, decision making by an expert CTEPH team, and surgical techniques will be summarized. Novel alternative treatment options for inoperable CTEPH patients will be discussed, i.e. targeted medical therapy and balloon pulmonary angioplasty. For the future the major task will be to define a clear selection process for the optimal treatment of the individual CTEPH patient.

Balloon Pulmonary Angioplasty: A Treatment Option for Inoperable Patients with Chronic Thromboembolic Pulmonary Hypertension

In chronic thromboembolic pulmonary hypertension (CTEPH), stenoses or obstructions of the pulmonary arteries due to organized thrombi can cause an elevation in pulmonary artery resistance, which in turn can result in pulmonary hypertension. CTEPH can be cured surgically by pulmonary endarterectomy (PEA); however, patients deemed unsuitable for PEA due to lesion, advanced age, or comorbidities have a poor prognosis and limited treatment options. Recently, advances have been made in balloon pulmonary angioplasty for these patients, and this review highlights this recent progress.