Low Intensity Extracorporeal Shockwave
The use of low intensity extracorporeal shockwave (LI-ESW) for the treatment of ED has its origins in the research performed in the 1990s by Young and Dyson who discovered the use of ultrasound and its effect to increase angiogenesis by increasing expression of vascular endothelial growth factor (VEGF) [Vardi et al. 2012; Young and Dyson, 1990]. Their research involved the use of ultrasound to promote the formation of new blood vessels in excised full thickness skin from adult rats. By exposing skin to 5 days of ultrasound at an intensity of 0.1 W/cm2 and frequency of 0.75 or 3.0 MHz, they demonstrated the formation of new blood vessels as assessed by microfocal X-ray techniques.
In 2010, a pilot study performed by Vardi and colleagues investigated the use of LI-ESW on men with ED who previously responded to oral phosphodiesterase type 5 inhibitor (PDE5-I). Only 20 men were enrolled in the study and the shockwave treatment consisted of 2 sessions per week for 3 weeks. LI-ESW was applied to the penile shaft and crura at five different nonspecific sites. The International Index of Erectile Function - Erectile Function (IIEF-EF) domain scores were used to measure responses at the end of treatment sessions. Results at 1 month follow up revealed a significant increase in IIEF-ED domain scores in all men and remained unchanged at 6 months follow up [Vardi et al. 2010]. Furthermore the study demonstrated significant increases in the duration of erections and penile rigidity [Vardi et al. 2010]. The study was the first to demonstrate the potential application of LI-ESW to the penile shaft to improve cavernosal hemodynamics. In May of 2012, Vardi and colleagues published the first randomized, controlled study to show that LI-ESW has positive short term clinical and physiological effects on ED for men who respond to PDE5-I. A total of 67 men were randomized to receive 12 sessions of LI-ESW or sham therapy. Erectile function and penile hemodynamics were assessed before the first treatment and after the final treatment using questionnaires and a venoocclusive strain gauge plethysmography [Vardiet al. 2012]. Results revealed an increase in IIEF-EF domain scores and achievement of sufficient penile rigidity in men who were previously unable to perform penetration. None of the participants had any adverse events or effects from treatment [Vardi et al. 2012]. Correlation of results revealed an increase in penile blood flow.
Based on the animal study, the mechanism of LI-ESW for ED is related to the increased expression of VEGF, smooth muscle and endothelial content through recruitment of endogenous mesenchymal stem cells [Qiu et al. 2013]. Recently, Liu and colleagues also published their research on the effects of different doses of low energy shock wave therapy on ED in diabetic induced rats. Rats were divided into five groups (normal control, diabetic control and three different doses of LI-ESW treated groups) [Liu et al. 2013]. The different doses of LI-ESW included 100, 200 and 300 shocks each treatment on the penile shaft three times a week for total of two weeks. Erectile function was evaluated using intracavernous pressure (ICP) 1 week after treatment commenced. Corpora were also harvested and stained histologically for the study to assess changes in smooth muscle content, endothelium, NO positive nerve fibers and expression of VEGF. The study's results revealed maximal therapeutic effect with the rats treated with 300 LI-ESW, with increased smooth muscle and endothelial contents, upregulation of VEGF, von Willebrand factor (vWF), alpha smooth muscle actin (α-SMA) and neuronal NO synthase (nNOS) in the corpora cavernosum [Liu et al. 2013].
Low intensity shockwave lithotripsy is currently not an approved therapy for ED and studies need still be conducted to optimize outcomes, dosage and frequency of treatments for patients. The technology and its applicability at present are intriguing and may soon provide a minimally invasive procedure to help patients achieve erection in addition to oral pharmacotherapy.