Hypertension (persistently elevated blood pressure) is a major risk factor for heart disease
and stroke. Hypertensive individuals show a reduced exercise capacity, which is present from
a very early stage and contributes to their increased cardiovascular risk. Sildenafil belongs
to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors, and it works by
enhancing the effects of nitric oxide, a substance that dilates blood vessels and increases
blood flow. We hypothesize that sildenafil, because of its effect on nitric oxide and blood
flow, will improve exercise capacity in hypertensive patients. Therefore, the main aim of the
study is to investigate the effects of PDE5 inhibition on exercise capacity and vascular
function in hypertension, and to compare these effects in hypertensive patients and healthy
controls.