After the proper questions are asked regarding psychological contributions to ED, the focus becomes more on the patient's pre-existing health problems.
The second category of erectile dysfunction relates to problems with blood vessels. In general terms, there are two types of blood vessels, arteries and veins. Arteries carry blood away from the heart. The blood then circulates through the body and tissues and returns to the heart in blood vessels known as veins. Erection problems can stem from diseases of either type of blood vessel. These problems are probably the most common reason for erectile dysfunction.
In order to achieve an erection blood must flow into the penis through arteries. The blockage that develops in arteries, atherosclerosis, limits the proper flow of blood to the penile tissues. Imagine if you were trying to fill a large tub with water from a garden hose, but the garden hose had a very slow flow because someone pushed a stone into hose that became stuck. It would take a longer time to fill the tub, of course. Similarly, when an artery is filled with a calcium deposits (atherosclerosis) the blood flow is slower and the erection cannot be maintained. This is the same problem that occurs in the heart in people that have heart attacks. It is common for heart disease to first be picked up by men complaining of erectile dysfunction. The arteries of the penis are no different from those of the heart. If "hardening" is occurring in the penile arteries, it is likely happening elsewhere (the heart). Men are usually very aware of their ability to achieve an erection; therefore, they report problems to their family doctor. It is the physician's job to make sure that the disease (arterial disease) affecting the penis is not affecting the other major arteries in the patient's body. This can be done by checking the person's cholesterol level and performing an EKG (electrical tracing of the heart).
Problems can also occur with the veins, something known as venous leak. Remember that once blood enters the penis for an erection, the veins (the blood vessels that take the blood back to the heart from the penis) are compressed slowing the flow of blood out of the penis. This maintains the erection. Venous leak occurs when blood is leaked out of the penis from the veins and the penis does not stay hard or the erection is lost. Imagine trying to blow up a balloon with a pinpoint hole in it. You would blow and blow, but the leak of air out of the balloon from the hole would prevent it from ever being fully blown up.