Hemodynamics in penile cavernosal arteries during pharmacologically induced erection in monkeys in comparison to humans

Introduction. Currently, studying of penile erection mechanisms continues to be relevant. However, invasive methods of examination in humans present some difficulties. In this connection assessment of blood flow in cavernosal arteries was performed in monkeys, by means of invasive measurement of intracavernosal pressure and systemic blood pressure during pharmacologically induced erection. Materials and methods. 13 monkeys (anubis baboon) and 15 patients with normal erectile function were examined using doppler ultrasonography after intracavernosal injection of alprostadil (10 mg). All monkeys were sedated before examination. In 11 monkeys intracavernosal pressure (ICP) and pressure in common femoral artery were measured. Results. Blood flow dynamics in cavernosal artery in monkeys was similar to blood flow dynamics in humans. After injection of alprostadil (prostaglandin E1), peak systolic velocity (PSV) increased, blood flow in diastole was present with increase of end diastolic velocity (EDV), resistive index (RI) decreased. In group of monkeys after 117±23 sec and in group of patients after 227±31 sec after injection PSV, EDV and mean velocity (Vmean) started to decrease and RI started to increase. After 342±66 sec in group of monkeys and after 1180±116 sec in group of patients diastolic backflow was present, PSV increased and EDV decreased progressively down to the values common for the flaccid state of the penis. The maximum Vmean in monkeys was seen at ICP of 39,8±3,7 mm Hg and mean arterial pressure 77,7±3,1 mm Hg. Backflow in diastole appeared when ICP exceeded diastolic arterial pressure (DAP). At maximal velocity of backflow ICP was 77,6±5,2 mm Hg, and DAP was 65,5±3,3 mm Hg. Linear blood flow velocity in monkeys was not significantly different from values measured in humans in all phases of erection that were examined. Conclusions. Blood flow dynamics in cavernosal artery of a monkey during erection are similar to blood flow dynamics of a human. Blood flow dynamics are associated with pressure gradient between mean systemic blood pressure and ICP. Diastolic backflow appears when ICP exceeds DAP.