The role of cardiopulmonary exercise test in identifying pulmonary veno-occlusive disease

Pulmonary veno-occlusive disease: a clinical review

Pulmonary vasculopathy presents as a spectrum of diseases affecting the precapillary pulmonary arterioles, the capillaries and the venules. Pulmonary veno-occlusive disease (PVOD) is classified under group 1 pulmonary arterial hypertension (PAH) as subgroup 1.5 (PAH with features of capillary/venous involvement), and represents a progressive and fatal spectrum of pulmonary vascular disorders. PVOD and pulmonary capillary haemangiomatosis (PCH) can be clinically indistinguishable and often coexist, along with the same risk factors and genetic alterations; they are referred to together as PVOD/PCH in the literature. For brevity, we use the clinical term PVOD in this article. PVOD cannot be distinguished from other forms of PAH based on symptoms and haemodynamics. Risk factors include exposure to toxins/chemotherapeutic drugs and genetic mutation in the EIF2AK4 gene. Radiographic features such as mediastinal adenopathy, centrilobular ground-glass opacities, and interlobular septal thickening, along with the presence of hypoxia and reduced diffusion capacity of the lung may be required for a clinical diagnosis of PVOD, as lung biopsy carries a high risk for bleeding. Characteristic histological findings include narrowing/occlusion of small pulmonary veins. The development of pulmonary oedema with pulmonary vasodilator therapy limits therapeutic options for PVOD. With limited treatment options, lung transplantation remains the only curative treatment.

The Current Role of Cardiopulmonary Exercise Test in the Diagnosis and Management of Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a poor prognosis if left untreated. Despite remarkable achievements in understanding disease pathophysiology, specific treatments, and therapeutic strategies, we are still far from a definitive cure for the disease, and numerous evidences have underlined the importance of early diagnosis and treatment to improve the prognosis. Cardiopulmonary exercise testing (CPET) is the gold standard for assessing functional capacity and evaluating the pathophysiological mechanisms underlying exercise limitation. As effort dyspnea is the earliest and one of the main clinical manifestations of PAH, CPET has been shown to provide valid support in early detection, differential diagnosis, and prognostic stratification of PAH patients, being a useful tool in both the first approach to patients and follow-up. The purpose of this review is to present the current applications of CPET in pulmonary hypertension and to propose possible future utilization to be further investigated.

Diagnosis and management of pulmonary veno-occlusive disease

INTRODUCTION

Pulmonary veno-occlusive disease (PVOD) is an orphan disease and uncommon etiology of pulmonary arterial hypertension (PAH) characterized by substantial small pulmonary vein and capillary involvement.

AREAS COVERED

PVOD, also known as 'PAH with features of venous/capillary involvement' in the current ESC/ERS classification.

EXPERT OPINION

In recent years, particular risk factors for PVOD have been recognized, including genetic susceptibilities and environmental factors (such as exposure to occupational organic solvents, chemotherapy, and potentially tobacco). The discovery of biallelic mutations in the EIF2AK4 gene as the cause of heritable PVOD has been a breakthrough in understanding the molecular basis of PVOD. Venous and capillary involvement (PVOD-like) has also been reported to be relatively common in connective tissue disease-associated PAH (especially systemic sclerosis), and in rare pulmonary diseases like sarcoidosis and pulmonary Langerhans cell granulomatosis. Although PVOD and pulmonary arterial hypertension (PAH) exhibit similarities, including severe precapillary PH, it is essential to differentiate between them since PVOD has a worse prognosis and requires specific management. Indeed, PVOD patients are characterized by poor response to PAH-approved drugs, which can lead to pulmonary edema and clinical deterioration. Due to the lack of effective treatments, early referral to a lung transplantation center is crucial.

The role of cardiopulmonary exercise testing in identifying and monitoring pulmonary veno-oclusive disease: a case report

Background

Pulmonary veno-occlusive disease (PVOD) is a subgroup of pulmonary arterial hypertension (PAH) where vascular remodelling affects mainly the post-capillary vessels. It is characterized by a particularly worse prognosis and by the risk of developing life-threatening pulmonary oedema, especially after PAH-targeted therapy. Therefore, suspicion of PVOD is crucial to guide the patient’s management. In the absence of specific genetic or histological findings, diagnosis has traditionally relied on the recognition of non-invasive indicators associated with a high likelihood of PVOD. The cardiopulmonary exercise testing (CPET) arises as a promising additional tool both to identify these patients and to guide their management.

Case summary

We report the case of a young female patient with dyspnoea and clinical suspicion of PVOD. The diagnostic workup is thoroughly described stressing the valuable and readily accessible information that CPET can provide, in addition to the data of radiological and lung function tests. Once diagnosed, she was started on PAH-targeted therapy with subsequent improvement. The patient underwent a complete reassessment with satisfactory findings, including those of the CPET.

Discussion

Pulmonary veno-occlusive disease diagnosis is still one of the most difficult tasks that pulmonary hypertension physicians have to deal with. An accurate and timely PVOD diagnosis can be challenging, as it is to decide the most appropriate timing of referal to the lung transplant team, and CPET may serve these purposes. Through this case, we would like to review one of the typical clinical courses that PVOD may present and how to analyse the information provided by the diagnostic tests.