Vascular Evaluation in Erectile Dysfunction

Evidence-Based Vascular Tests for ED and Recommendations

Aim to assist in deriving the classic diagnoses of arterial impairment and veno-occlusive dysfunction

Modalities 1. First Line: Intracavernous injection test OR Combined Intracavernosal Injection and Stimulation (CIS) 2. Second Line: Duplex Ultrasonography 3. Third Line: A) Dynamic Infusion Cavernosometry and Cavernosography B) Penile Angiography

Intracavernous injection test OR Combined Intracavernosal Injection and Stimulation It serves as a first-line evaluation of penile blood flow because of its very basic manner of administration and assessment. The test involves the intracavernosal injection of a vasodilator drug ± genital or audiovisual sexual stimulation, and the erectile response is observed and rated by an independent assessor. The test is designed to bypass neurologic and hormonal influences involved in the erectile response and allows the clinician to evaluate the vascular status of the penis directly and objectively.

Alternative regimens include: 1. alprostadil (10 to 20 μg) 2. combination of papaverine & phentolamine (Bimix, 0.3mL) 3. a mixture of all three of these agents (Trimix, 0.3 mL) Repeated dosing may be performed if the initial erectile response is poor.

The assessment is done periodically subsequently with rating of both rigidity and duration of response. A positive test is a rigid erectile response (unable to bend the penis) that appears within 10 min after the intracavernous injection and lasts for 30 min (EAU, 2016) Return to penile flaccidity is required before allowing the patient to leave the office, and if detumescencem does not occur spontaneously in approximately an hour after dosing, intracavernosal injection of a diluted phenylephrine solution (500 μg/mL) can be administered every 3 to 5 minutes until flaccidity returns.

A normal CIS test, based on the assessment of a sustainably rigid erection, is understood to signify normal erectile hemodynamics. Alternative diagnoses of psychogenic, neurogenic, or endocrinogenic ED may then be considered. False-positive results might occur in as many as 20% of patients with borderline arterial inflow (as defined by the measurement of 25 to 35 cm/s peak cavernous artery systolic flow on duplex ultrasonography) False-negative results are also possible and occur most commonly because of patient anxiety, needle phobia, or inadequate dosage. Overall, the test is inconclusive as a diagnostic procedure and a duplex Doppler study of the penis should be requested, if clinically warranted.

Duplex Ultrasonography Duplex ultrasound of the penis following pharmacostimulation or CIS represents second-line evaluation of penile blood flow. It is the most reliable and least invasive diagnostic modality for assessing ED. The technique consists of high-resolution (7.5 to 12 MHz) real time ultrasonography and color-pulsed Doppler, which serves to visualize the dorsal and cavernous arteries selectively and to perform hemodynamic blood-flow analysis.

Flow velocities are measured at baseline before injection and commonly every 5 minutes afterward up to 20 minutes. Cavernous arterial diameters may also be measured. Vascular anatomic communications between the paired cavernous arteries or between the dorsal and cavernous arteries should be noted. Erection quality should also be simultaneously assessed and rated.

Collateral circulation connecting the right dorsal artery (RDA) to the right cavernous artery (RCA), and the left cavernous artery (LCA) is shown by color duplex ultrasonography in a longitudinal view.

Artist’s conception of the changes in diameter and flow waveform in the cavernous arteries induced by intracavernous injection of prostaglandin E1 in a potent young man as demonstrated by duplex ultrasound. Forceful concentric pulsations are particularly noticeable during full erection

Normal cavernous arterial inflow: PSV consistently greater than 35 cm/s defines Cavernous artery acceleration time (i.e., PSV divided by systolic rise time) greater than 122 ms Cavernous arterial insufficiency: PSV < 25 cm/s

Cavernous veno-occlusive dysfunction (failure of erection maintenance despite adequate cavernous arterial inflow): 15 to 20 minutes after stimulatory onset: persistent high systolic flow velocities (PSV >25 cm/s) high end-diastolic flow velocities (EDV >5 cm/s), rapid detumescence Vascular resistive index (RI): PSV-EDV/PSV RI > 0.9: normal penile vascular function RI < 0.75 is consistent with veno-occlusive dysfunction