Nailfold Capillaroscopy in PH

Pulmonary hypertension (PH) is an uncommon condition and can often be difficult to diagnose. It means elevated blood pressure in the lungs which can rapidly lead to failure of the right side of the heart and is ultimately fatal. Diagnosing PH currently involves a number of scans, breathing tests and often an invasive test called right heart catheterisation \[RHC\] (which involves inserting a tube into a large vein to measure the lung blood pressure from the). The investigators propose using a scan of the nailbeds called "Nailfold (Video) Capillaroscopy" to see whether this measurements correspond to the pressures that the investigators measure at the time of RHC and whether these measures change with treatment for PH. The investigators wish to answer the hypotheses that: 1. The measurements of the nailbed blood vessels are correlated with the invasive right heart catheter values across all groups of PH 2. The abnormalities seen in systemic sclerosis are reversible with treatment with pulmonary vasodilator drugs 3. This change will be significantly more than any change seen in other types of pulmonary hypertension with these drugs 4. Changes in the nailbed blood vessels with treatment will reflect changes in the usual parameters used to measure treatment response in PH: The scan uses a camera microscope connected to a laptop, does not involve radiation and can be completed within 30 minutes. The results are sent to the University of Manchester where they are analysed by computer software. If patients are found to have pulmonary hypertension and are started on medication (pulmonary vasodilators) to open up the blood vessels of the lungs, the investigators will then repeat the scan at this point. The investigators will compare the results between different forms of PH before and after treatment.