Vasculogenic and Drug Induced ED
Erectile dysfunction (ED) is more frequent in patients with other signs of artherosclerotic disease such as ischaemic heart disease and arterial leg disease (20-22) and erectile dysfunction and cardiovascular disease share the same risk factors such as hypertension, diabetes mellitus, hypercholesterolemia and smoking (23,21).
Moreover, arterial lesions in the pudental arteries (penal erectile arteries) are much more common in men with ED than in the general population of a similar age. (24). Originally arterial disease was linked to ED by the French surgeon, Leriche in 1940. The cause for ED in such patients can be ascribed to the presence of a flow limiting stenosis (narrowing) caused by the artherosclerotic lesions, leading to a reduced blood flow to the corpus cavernosum (erectile tissue) during the erection process. This can lead to corporal veno-occlusive disorder (see below). Chronic ischaemia (oxygen deficiency) provoked by stenosis of the penile arteries is also associated with functional changes in the distal part of the penile vasculature such as decreased Nitric Oxide Synthase (NOS) activity and reduced endothelium dependent neurogenic NO-mediated relaxation in cavernosal tissue (25,26).
Two vascular factors are important in the onset of erection: adequate arterial inflow into the cavernosal arteries and an efficient veno-occlusive mechanism (trapping the blood inside the corpora cavernosa). Two types of vasculogenic ED can be theoretically distinguished:
Reduced penile blood flow leads to a relative impairment of oxygenation (ischaemia) of cavernosal tissue leading to atrophy of smooth cavernosal muscle and fibrosis. The resulting 'non-use atrophy',and smooth muscle dysfunction in turn prevents adequate compression of the subtunical venules inside the tunica albuginea with a breakdown in the veno-occlusive mechanism. Venous leakage develops, resulting in decreased rigidity or absence of erection.
Various kinds of drugs can induce ED. The prevalence of this aetiology is difficult to assess, as the underlying condition treated by the drugs may also cause ED (arteriosclerosis, depression, anxiety, etc). Often such patients are taking multiple medications making it difficult to determine the contribution of a single drug. There is little evidence to suggest modifying drug treatment can restore erectile function (except for hormones inducing hypogonadism). However, it is worth trying in most cases, while maintaining effective treatment of the primary condition. Many modern drugs in the classes shown are not associated with sexual side-effects in placebo controlled studies. Ask your GP for further information.