Group 5 Pulmonary Hypertension: Multiple Systemic Diseases, Multiple Mechanisms of Pulmonary Hypertension, and Multiple Management Challenges

Group 5 pulmonary hypertension (PH) with unclear and/or multifactorial mechanisms includes a wide variety of conditions associated with PH, and the mechanisms by which PH develops vary dramatically depending on the underlying condition. Indeed, in many group 5 conditions, such as sarcoidosis, multiple distinct drivers of PH are present concurrently in a single patient, with the predominant factor depending on the predisposing disease phenotype. For this reason, thorough diagnostic evaluation to most accurately phenotype every patient with group 5 PH is essential. Treatment of these patients should begin by fully characterizing and optimizing the management of their underlying disease, often in conjunction with disease experts. Initial targets of PH treatment include identifying and correcting factors that worsen PH, such as volume overload and hypoxemia, as well as a complete PH evaluation, searching for other undiagnosed causes of PH (e.g., congenital heart disease or chronic thromboembolic disease). Data to guide treatment with therapies specific to pulmonary arterial hypertension (PAH) are inadequate for any specific recommendations, and adverse effects in group 5 patients are common. If these therapies are considered, evaluation by a multidisciplinary team that includes a PH specialist is recommended. Factors in the selection of PAH therapies should include consideration of the dominant physiologic features of the underlying disease, the severity of hemodynamic and right ventricular abnormalities, the risk of adverse drug effects, and any known contraindications to PAH-specific medications based on the underlying condition. Vigilant monitoring following initiation of PAH-specific therapy is critical, as the clinical effects are hard to predict, and untoward events, such as uncovering pulmonary veno-occlusive disease, may occur. Collaborative care by a multidisciplinary team of experts is key to the management of this challenging patient population.