Despite the proven clinical efficacy of
phosphodiesterase inhibitors in the treatment of
erectile dysfunction (ED), some patients do not respond to the medication. By means of nailfold capillary microscopy in patients with concomitant
coronary artery disease (CAD) and ED, it was evaluated whether the extent of microvascular dysregulation predicts the responsiveness to
tadalafil (TAD) in terms of erectile function. The ED of each patient was assessed by the International Index of Erectile Function (IIEF). Patients presenting both, documented CAD and ED, showed a significantly reduced capillary red blood cell velocity (v(RBC)) at rest and after 3 min of
ischemia compared with age-matched controls. At 2 h after intake of 20 mg of TAD, a significant increase of v(RBC) at rest as well as during postischemic
hyperemia was found. Patients who reported no improvement of their ED after the use of TAD demonstrated no changes in the duration of postischemic (DpH)
hyperemia, or even a reduction of the DpH. The majority of the patients, who reported at least one successful sexual intercourse due to TAD, had a prolongation of DpH. We conclude that assessment of microvascular regulation by nailfold capillary microscopy can predict the probability of a treatment failure with
phosphodiesterase inhibitors in patients with ED. Moreover, as endothelial dysfunction is the common underlying pathophysiological process of ED and
cardiovascular diseases, the test may help to identify patients at risk for the development of
atherosclerosis and following cardiovascular events.