Conceptual Reconsideration of the Classification of Pulmonary Hypertension

Figures

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  Figure 1. Diverse Etiologies of PH The figure illustrates the different PH cases along the pulmonary circulation. These cases can be classified into 3 major categories on the basis of the predominant site of obstruction: 1) pulmonary arterial large-vessel stenosis (blue), including CTEPH, PA sarcoma, and vasculitis; 2) pulmonary microvasculopathy (purple), encompassing PAH and related small-vessel disorders such as PVOD; and 3) pulmonary venous large-vessel stenosis (red), such as fibrosing mediastinitis–associated PV stenosis and stenosis induced by pulmonary vein isolation. CTEPH = chronic thromboembolic pulmonary hypertension; FM = fibrosing mediastinitis; HPAH = heritable pulmonary arterial hypertension; IPAH = idiopathic pulmonary arterial hypertension; LD = lung disease; LHD = left heart disease; PA= pulmonary artery; PAH = pulmonary arterial hypertension; PCH = pulmonary capillary hemangiomatosis; PH = pulmonary hypertension; PPS = peripheral pulmonary artery stenosis; PV = pulmonary vein; PVI = pulmonary vein isolation; PVOD = pulmonary veno-occlusive disease; TA = Takayasu arteritis.

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  Central Illustration. Pathophysiology-Based Binary Framework of Pulmonary Hypertension PH is categorized according to 2 major pathophysiological mechanisms: pulmonary large-vessel stenosis (potentially revascularizable) and pulmonary microvasculopathy (predominantly pharmacotherapy-focused), with specific etiologies and treatment strategies corresponding to each category. CTEPH = chronic thromboembolic pulmonary hypertension; IpcPH = isolated postcapillary pulmonary hypertension; PH = pulmonary hypertension; PPS = peripheral pulmonary artery stenosis.

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  Figure 2. Diagnostic Pathway Based on the Binary Framework The figure illustrates the “SPC” (stenosis-PH-comorbidity) strategy, which stratifies diagnosis into 3 domains. (S) Stenosis assessment: Noninvasive imaging (typically V/Q scan and/or CTPA/V) serves as the filter to screen for PLVS. (P) PH evaluation: RHC defines the definitive hemodynamic status. (C) Comorbidity assessment: Concurrent assessment determines whether comorbidities are contributing to symptoms or limiting therapeutic interventions. aV/Q scanning is well established for CTEPH but may be insensitive to other forms of pulmonary large-vessel stenosis; a negative result should not preclude pulmonary computed tomography angiography when clinical suspicion persists. bIndicated for IPAH, HPAH, or drug-induced PAH according to the current PH guideline. CTPA/V = computed tomography pulmonary angiography/venography; IpcPH = isolated postcapillary pulmonary hypertension; PLVS = pulmonary large-vessel stenosis; PMV = pulmonary microvasculopathy; RHC = right heart catheterization; V/Q = ventilation/perfusion; other abbreviations as in Figure 1.

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  Figure 3. Therapeutic Pathway Based on the Binary Framework The figure outlines the treatment decision-making process for PH, distinguishing between pulmonary large-vessel stenosis and pulmonary microvasculopathy. An important modifying factor in this process is the presence of severe cardiopulmonary comorbidities. If present, therapeutic efforts should prioritize optimization of comorbid conditions. In their absence, patients are directed toward mechanism-specific strategies: revascularization for large-vessel stenosis or pharmacological therapy for microvascular involvement, including etiology-specific treatments, PAH-targeted therapies, and high-dose CCB therapies in appropriately selected patients. aRestricted to patients with a positive acute vasoreactivity test. CCB = calcium-channel blocker; other abbreviations as in Figure 1.