Penile and Systemic Endothelial Function in Men with and without Erectile Dysfunction

Abstract

BackgroundAssessment of endothelial function can provide essential information about the mechanisms of cardiovascular disease. Emerging data show that erectile dysfunction (ED) can precede the symptoms of ischemic heart disease, and this suggests that endothelial dysfunction is the link between these two clinical entities. ObjectiveTo evaluate penile and systemic endothelial function in subjects with and without ED. Design, setting, and participantsFifty-nine subjects were enrolled in the study. According to their International Index of Erectile Function (IIEF) ED domain scores, they were divided into two groups: 40 patients with ED and 19 men without ED (control group). Hemodynamic measurements, penile endothelial function, and forearm endothelial function were assessed in all participants using veno-occlusive plethysmography. MeasurementsWe measured baseline blood flow in both the forearm and the penis and calculated the corresponding vascular resistances. Postischemic changes in blood flow were recorded serially in both organs for the evaluation of endothelial function. Area under the flow-time curve (AUC), and maximal blood flow after ischemia were considered to be the indices of endothelial function. Results and limitationsGeneral characteristics of the two groups of participants were comparable except for age (40.5±3.3 yr in the control group vs 53.3±2.3 yr in the ED group). Baseline forearm blood flow was similar in the two groups, but the penile blood flow was significantly lower in men with ED compared with that in the men without ED: 6.2±0.6 versus 8.6±0.6ml/min per 100ml of tissue (p=0.006). Penile vascular resistance was higher in the ED group compared with the control group. The indices of forearm endothelial function were comparable in both groups (p=0.70 for the AUCs). However, indices of penile endothelial function were significantly higher in the control group compared with those of the ED group (AUC: 950 units±130 vs 450±80 units, p=0.001). ConclusionsThe use of veno-occlusive plethysmography for evaluating penile endothelial function is simple and reliable and provides new information on the pathophysiology of ED at the level of penile vasculature. This is the first study that provides evidence of impaired penile endothelial function without the presence of a significant peripheral endothelial dysfunction. Furthermore, these results provide further support for the notion that the development of ED could predict the future onset of cardiovascular disease.