Arrhythmias are considered a prominent phenomenon in pulmonary hypertension (PH) as the disease progresses. According primarily to retrospective studies with up to 24 hours of monitoring, supraventricular tachycardias (SVT) can be found in 8-35% of patients, with significant impact on survival. Furthermore, a few prospective studies to date deploying short-term monitoring (10 minutes-24 hours) have revealed lower heart rate variability (HRV) in patients with pulmonary arterial hypertension (PAH). In ASPIRE arrhythmias and heart rate variability is being assessed via long term monitoring. Currently the the loop-recorder is considered the gold standard for long-term continuous cardiac montoring. A non-invasive continuous monitoring could be of a great benefit for the patients, and could potentially contribute to treatment optimization. The study will assess apple watches as a non-invasive tool compared to to the loop recorder, which is considered as the current gold standard. Additionally, the study seeks to assess apple watches for monitoring as an independent wearable for risk assessment in PH.