Impotence in older men may be a major unrecognized risk factor for heart attack or stroke, according to new research. Fortunately, for men who have developed an impotence problem, a simple, non-invasive medical test appears capable of detecting whether that problem might be related to a risk of heart attack or stroke. Those at risk can then take steps to prevent more serious medical complications from developing.
That conclusion is based on studies from the Sepulveda Veterans Administration Medical Center (SVAMC) in Los Angeles, where investigators have developed a new index called the penile brachial pressure index (PBPI) comparing blood flow through the penis with blood flow through the brachial artery.
The brachial artery is the main artery of the upper arm. Since its blood flow generally stays normal throughout life, the artery is a standard against which blood flow in other areas of the body is compared.
The theory behind the penile brachial pressure index is based on the fact that vascular disease accounts for about half the impotency seen in patients over the age of 40. In these men, impotency occurs when arteries delivering blood to the penis become blocked or occluded by a build-up of fatty deposits. When blood flow is prevented, erection becomes impossible.
When such blockage occurs in arteries transporting blood to the brain or heart, a stroke or heart attack can result. Investigators thus reasoned that since penis arteries are similar in size to arteries carrying blood to the heart and brain, reduced penile blood flow might indicate a risk of future stroke or heart attack.
John Morley, M.D., director of SVAMC's Geriatric Research, Education and Clinical Center, said other research supports this theory.
Medical Histories Reviewed
Investigators have found that up to two-thirds of male heart attack patients had had previous problems with impotence. Assuming the same problem that caused impotence may have triggered the heart attack or stroke, Morley decided to review the medical histories of 130 of SVAMC's patients who had undergone an evaluation called a Doppler blood flow study as part of a routine evaluation for impotence. Doppler scanning, a type of ultrasound imaging, provides a non-invasive means of measuring internal blood flow. By comparing reduced blood flow to the penis with that through the brachial artery, Morley created a simple ratio that would suggest the extent of arterial blockage to the penis--and perhaps elsewhere.
When Morley compared the results of each person's PBPI with his medical records to determine who had gone on to experience either a heart attack or a stroke, he found that penile blood flow could be used to predict such vascular accidents.
"What we found," Morley said, "was that of those patients who had a PBPI below 0.65--which is what we considered our cut-off for severe vascular disease--26% had some form of major vascular accident over the next two years, either a myocardial infarction (heart attack) or a cerebrovascular accident (stroke)."
Yet very few patients (just under 5%) with PBPIs greater than 0.65 had any kind of major vascular accident during the study period.
"It makes perfect sense," Morley said. When arteries begin to occlude, he explained, it is not an isolated event, but something that occurs throughout the body. Such blocked arteries are best known for their ability to cause a heart attack or a stroke, but such blockages, he said, are not limited to the heart and brain.
Morley found that his index fared well against exercise treadmill testing, which currently is considered the best means of predicting a heart attack.
In the past, penile blood flow has mainly been used in the diagnosis of impotence, but Morley believes his study suggests a much larger role for this relatively simple measurement technique.
"I think there is no question that if you develop impotence and (are) over the age of 50, this is suggesting that you are at high risk for developing vascular disease in other parts of your body," Morley said.
If Doppler testing confirms reduced penile blood flow, he said, "that patient is at major risk for other vascular disease, and appropriate medical management needs to be instituted immediately."
Such patients, Morley said, should be treated "just as aggressively" as someone complaining of angina, the chest pain most often associated with heart disease.
If impotence is indeed a major factor for either a stroke or heart attack, a good sexual history now becomes a critical part of any medical examination given to an older male, Morley said.
Unfortunately, he added, physicians often have trouble discussing sexual function with their patients. "It amazes me, but here it is the late 1980s and doctors still have trouble discussing anything with their patients related to sex.
"Yet," Morley continued, "I think this is about as firm a proof as you're going to get as to why a good sexual history is an important part of the workup of any male coming to a general practitioner."