Abstract Background Pulmonary Arterial Hypertension (PAH) is a form of pulmonary hypertension, where the narrowing of arteries in the lungs restricts blood flow and so increases pressure in the vessels. Studies have demonstrated that initial combination therapies are optimal for PAH management. However, prescription of monotherapy treatment is still prevalent as a first line therapy. Purpose The purpose of this research was to investigate prescribing trends of physicians for first line patients with PAH in the UK, Germany, Italy and Spain. We investigated the proportions of newly diagnosed patients and the prescription trends for monotherapy and combination therapy prior to and during the COVID-19 pandemic. Methods A multi-country, multi-centre online medical chart review study of patients with PAH was conducted between April – June of 2019, 2020 and 2021 respectively. Recruited from a large access panel, 178 treating cardiologists, pulmonologists & rheumatologists in the UK (n=16), Germany (n=55), Italy (n=55) and Spain (n=52) were screened for duration of practice in their speciality and caseload (≥5 PAH patients in the last 3 months), and provided data on 694 PAH patients (UK = 71, Germany = 206, Italy = 208, Spain = 209). Reported patient data pertained to medical chart information reflecting the prior year, i.e., Q2 2021 data reflected the 2020 period (advent of the COVID-19 pandemic). Results In this dataset, there has been a consistent decrease in the proportion of newly diagnosed (i.e. diagnosed within 12 months of being reported) patients reported from 2019 to 2020 and 2021. In 2019, 49% of the reported patients were diagnosed within the last 12 months. However, the newly diagnosed patient population dropped to 37% in 2020 and continued to drop to 27% in 2021. Despite this, there has been an increase in reported first line patients within the newly diagnosed segment from 74% in 2019, to 75% in 2020, then at 87% in 2021. This increase can be seen to coincide with the ongoing COVID-19 pandemic. In 2019, 58% of reported newly diagnosed patients were recorded as receiving monotherapy. This did drop to 33% in 2020; however, in 2021 monotherapy uptake increased to 47%. Of note, the usage of the endothelin receptor antagonist (ERA) drug class increased from 67% in 2019 to 83% in 2020 but dropped to 69% in 2021. Conclusions This data set suggests a decreasing trend in newly diagnosed patients and a gradual shift in treatment type to first line monotherapy prescription, which coincided with the height of the COVID-19 pandemic. More newly diagnosed patients (those diagnosed within 12 months of being reported) are receiving monotherapy treatment at the expense of combination therapy, and this has also coincided with the pandemic. Further investigation using comparator cohort is warranted to assess whether the challenges physicians faced during the pandemic has had a causal effect on the prescribing habits for PAH therapies. Funding Acknowledgement Type of funding sources: None.