In the classification of pulmonary hypertension, Group 1 includes disorders that involve the small pulmonary muscular arteries. This group is known as:

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The key distinction here is that Group 1 refers to disorders that primarily affect the small pulmonary arteries, producing a pre-capillary form of pulmonary hypertension. This pattern of arterial involvement defines pulmonary arterial hypertension. The name emphasizes the arterial pathology and the pre-capillary rise in resistance, setting PAH apart from other PH groups caused by left heart disease (Group 2), lung disease/hypoxia (Group 3), chronic thromboembolic disease (Group 4), or miscellaneous etiologies (Group 5). So the group in question is known as pulmonary arterial hypertension, encompassing idiopathic, heritable, drug/toxin-associated, and various associated conditions linked to the small pulmonary arteries.