Vasculogenic Impotence: Role of the Pelvic Steal Test

0022-534 7/82/1282-0300$02.00/0 THE JOURNAL OF UROLOGY Copyright© 1982 by The Williams & Wilkins Co.

Vol. 128, August Printed in U.S.A.

VASCULOGENIC IMPOTENCE: ROLE OF THE PELVIC STEAL TEST IRWIN GOLDSTEIN,* MIKE B. SIROKY, RONALD L. NATH, THOMAS N. McMILLIAN, JAMES 0. MENZOIAN AND ROBERT J. KRANE From the Departments of Urology and Vascular Surgery, Boston University Medical Center, Boston, Massachusetts

ABSTRACT

A new dynamic pelvic flow test is described that measures differential right and left corporeal artery blood pressure changes with exercise. Previous penile blood flow measurements have been made at rest. It is well known that exercise may unmask vascular pathological conditions not apparent at rest. Furthermore, cases have been reported that document potency at rest and impotence following exercise. As a result exercise was used to stress the pelvic vasculature in 97 patients chosen from vascular and urology clinics. A decrease of 0.15 or more in penile-brachial index with exercise was found to be statistically abnormal. A total of 23 patients (27 per cent) fulfilled the criteria for positive pelvic steal testing. In this group there we.re high incidences of smoking (52 per cent), hypertension (52 per cent) and diabetes (30 per cent). Although 70 per cent of these patients had at least occasional morning erections 78 per cent complained of loss of erection with exercise. The pelvic steal test detected vascular pathological conditions in 17 patients (20 per cent) previously missed by resting penile-brachial index measurements. Nocturnal penile tumescence studies in these patients demonstrated poor quality erections and correlated with the intermediate penile-brachia! index values. Angiographic data performed in 5 of 23 patients corroborated the pathophysiology of a pelvic steal condition in each case. The pelvic steal test is simple to perform and markedly improves the sensitivity and yield of penile blood pressure measurements. The test appears to have better results in patients with suspected vasculogenic impotence and intermediate resting penile-brachial index values. V asculogenic impotence occurs when there is an insufficient supply of arterial inflow into the corpora cavernosa. The diagnosis may be suggested by history and physical examination, corroborated by nocturnal penile tumescence monitoring and established by the measurement of penile blood pressures. The incidence of this syndrome is dependent on several factors, such as the techniques and criteria used to measure objectively penile blood flow and the particular patient population studied. One common and reproducible method for the determination of pelvic hemodynamics has been transcutaneous Doppler ultrasound.1-4 Penile systolic pressure can be recorded with a 2.5 cm. cuff placed at the base of the penis. Compared to brachial systolic pressure the resultant penile-brachia! index provides an objective interpretation of pelvic blood flow. The penile-brachial index has been evaluated extensively in patients with aortoiliac occlusive disease undergoing vascular reconstruction. It has been shown that an index <0.6 is diagnostic of vasculogenic impotence, between 0.6 and 0.75 is compatible with but not necessarily diagnostic of vasculogenic impotence and >0. 75 is consistent with normal pelvic hemodynamics. 5 Using these criteria the incidence of unequivocal vasculogenic impotence in patients with aortoiliac occlusive disease has been found to be 37 per cent. 5 Presently, penile-brachial index measurements are obtained under resting conditions. For several reasons this assessment may be inadequate. Investigators have shown that exercise may reveal vascular pathological conditions that previously have been unrecognized in the resting state. 6- 1 For example, the well known subclavian steal syndrome involves a worsening of brain symptoms associated with exercise of the corresponding upper extremity. 6 • 7 The pathophysiology of the subclavian steal syndrome involves stenosis of the root of the subclavian artery or

°

Accepted for publication October 30, 1981. Editor's note. This paper was awarded a prize in the AUA Essay Contest sponsored by the American Urological Association. * Requests for reprints: Department of Urology, Boston University School of Medicine, 75 E. Newton St., Boston, Massachusetts 02118.

of the brachiocephalic trunk with subsequent reversal of blood flow in the vertebral artery. This condition is only apparent after exercise. Similarly, others have realized the role of treadmill exercise testing for evaluation of peripheral vascular disease_ 10-12 There exists in the pelvic circulation an analogue to the subclavian steal syndrome. In 1978 Michal and associates reported on a patient with intermittent right gluteal claudication who was able to achieve erections at rest. 13 However, coital movement resulted in immediate detumescence and right gluteal claudication. Two considerations become apparent when the inadequacy of the resting penile-brachial index is assessed in patients complaining of impotence. First, vascular pathological conditions in the internal iliac or internal pudendal arterial system may be unmasked by the measurement of penile arterial pressures before and after exercise. Second, a vascular condition may exist whereby exercise may convert potency into impotence. Encouraged by these realizations we examined the effect of stress on the pelvic vasculature by lower extremity exercise. MATERIALS AND METHODS

To gain further experience with the objective assessment of pelvic hemodynamics, exercise testing was performed on 47 patients chosen from a vascular clinic, 35 from a urology clinic and 14 age-matched potent controls. Patients were placed in the supine position on an examining table. With a 9. 7 kHz. Doppler probe systolic occlusion pressures were recorded in the brachial, dorsalis pedis, posterior tibial, cavemosal and dorsal penile arteries (fig. 1). The resting penile-brachial index was defined as the ratio of the cavernosal to the brachial systolic resting pressures. Patients then were asked to flex and extend the ankles against a resistance for a maximum of 3 minutes or to the point of claudication or extreme fatigue. Systolic occlusion pressures were recorded again in these same arteries immediately following the exercise. This exercise Doppler study was termed the pelvic steal test. 300

urology

1T_4.ELE

V sscular Clinic

56 (19-92) 40 49 74 Diabetic(%) Potent(%)

Impotent(%)

l? 19 18

Urology Clinic 36 52 (22-75) 31 39

14 56 (43-71)

21 21

6

14

17 11 89

100 0

14

an even

3 to 4 times

-, ..,,-,.,,.,.. - studies. 1Q''"'''u•e1 vasculogenic 5 groups, on resting penileThis arbitrary classification was made to in whom exercise testing had the most S11,rrn11u:ar1t lowering effect. In g-roup l penile-brachial index values were §Uf?:li!:6S1C1Ve Of db'CU1UiMCHH, ,rcmr,,-Q,nc•c, because they Were values vasculogenic imEach c,cc.n,n,,r SUE;g,est;rve of vascuu,alo>Ho

The resultant left and after exercise then V>/STe blood flow. A total of le &.ad effect

Of 12 7 further a[SO underwent [J!olUtelJlU<~> WaS done under anesthesia Ginestie and Romieu. 14 Additional organic testing for erectile dysfunction was done with endocrinologic screening (serum testosterone, luteinizing hormone and prolactin) in 46 patients and sacral latency testing15 in 17. RESULTS

Table l describes the characteristics of the 97 patients. Vascular clinic patients chosen at random demonstrated a high

index values the in values 1;;,;as controls ~40 yearn old ~"·S"·''&'·" in sexual intercourse. wac.,u,~, index values and standard de,;iabefo:re and after exercise are shown in exercise did not :sii~IllHCaJ.H ln·cw>1"1n0.14 was statistically abnormal

302

GOLDSTEIN AND ASSOCIATES TABLE

No. pts. Mean penile-brachia! index value at rest: Rt. Lt Mean exercise penile-brachia! index value: Rt. Lt.

2. Results in 55 patients with suspected or psychogenic impotence Group 1

Group 2

Group 3

Group4

Group 5

13

5

12

7

18

0.61 ± 0.08 0.56 ± 0.17

0.58 ± 0.33 0.58 ± 0.33

0.68 ± 0.04 0.68 ± 0.04

0.76 ± 0.07* 0.77 ± 0.08*

0.89 ± 0.07* 0.88 ± 0.11*

0.55 ± 0.11 0.50 ± 0.19

0.63 ± 0.32 0.64 ± 0.33

0.68 ± 0.09 0.54 ± 0.25

0.65 ± 0.10* 0.67 ± 0.10

0.83 ± 0.06 0.82 ± 0.13*

All values are expressed as mean ± standard deviation. Values are considered normal if the penile-brachia! index is >0. 75, intermediate if the index is between 0.6 and 0.75 and abnormal if the index is <0.6. Groups were based on resting penile-brachia! index. Group 1-both penile-brachia! index values abnormal, group 2-1 abnormal and 1 normal value, group 3-both values intermediate, group 4-1 normal and 1 intermediate value and group 5-both values normal. • Statistically significant difference between mean resting and exercising penile-brachial indexes.

TABLE 3.

Meanpenile-brachial indexes before and after exercise in age-matched potent controls

TABLE

4. Ratio of average resting to average exercising penile-

brachial index in all patients excluding controls Rt.

Lt.

No. Pts.

0. 74/0.57 (0.17)

0.69/0.44 (0.25)

23

0.70/0.69 (0.01)

0. 71/0.68 (0.03)

60

Mean ± Standard Deviation Mean penile-brachia! index at rest: Rt. Lt. Mean exercising penile-brachia! index: Rt. Lt. Mean changes in penile-brachia! index with exercise

0.86 ± 0.09 0.86 ± 0.10 0.83 ± 0.09 0.84 ± 0.09 -0.06 ± 0.04

(within 2.5 per cent error). Thus, we considered a positive pelvic steal test to be any decrease in penile-brachia! index of ~0.15. A total of 23 patients (27 per cent) fulfilled the criteria for positive steal testing (that is the penile-brachia! index decreased ~0.15 during exercise). Mean patient age was 58 years, with a range of 45 to 91 years. There were high incidences of smoking and hypertension (52 per cent), and diabetes (30 per cent). Of the patients 78 per cent claimed loss of erection with exercise. Morning erections were present in 70 per cent and were described most commonly as semi-erections. Table 4 describes additional characteristics of the pelvic steal test. The average ratio of resting to exercising penile-brachia! index in these 23 patients was 0. 74/0.57 on the right (average difference 0.17) and 0.69/0.44 on the left sides (average difference 0.25). In comparison, the remaining 60 patients (excluding controls) had an average ratio of 0. 70/0.69 on the right and 0. 71/0.68 on the left sides. Table 5 illustrates the average penile-brachia! index values categorized by nocturnal penile tumescence qualitative grade in patients undergoing pelvic steal testing. Grade 3 nocturnal penile tumescence analysis was associated with an average decrease in penile-l?rachial index of 0.10, while grade 2 analysis was associated with a smaller decrease of 0.02. It appears that while total numbers of nocturnal penile tumescence studies are small the impression is that patients least suggestive of having vasculogenic impotence by resting Doppler determination and by moderately well maintained erections on nocturnal penile tumescence analysis had the greater decreases ofpenile-brachial index values on pelvic steal testing. Of 23 patients 10 (43 per cent) had unilateral changes in pelvic steal testing, while 13 (57 per cent) had bilateral changes. The pelvic steal test was positive in 9 patients in whom both resting penile-brachia! indexes were >0.75 and in 8 in whom resting penile-brachia! indexes were <0.75 and >0.6. Therefore, the pelvic steal test was useful in detecting vascular pathological conditions in 17 of 83 patients (20 per cent) at risk for vasculogenic impotence (excluding controls) based on resting penilebrachial index values. Vasculogenic impotence would have been missed in these patients undergoing resting Doppler studies. Nocturnal penile tumescence studies were performed on 5 of the 23 patients. Using the qualitative analysis described previously, 4 patients had 2 slow rising, poorly maintained erections (grade 2) and 1 had 3 moderately well maintained erections (grade 3).

Pos. steal test (av. difference) * Neg. steal test (av. difference) Total No. pts.

83

• Of the patients with positive steal tests and normal or near normal pelvic hemodynamics at rest, 9 (10.8 per cent) had both resting penile-brachia! indexes >0.75 and 8 (9.6 per cent) had either resting index between 0.6 and 0.75. TABLE 5. Average penile-brachia[ indexes categorized by 4-point nocturnal penile tumescence analysis in patients undergoing pelvic steal testing

Nocturnal Penile Tumescence Grade*

No. pts. Rt. and lt. resting indexes Rt. and lt. exercising indexes Av. decrease in penile-brachia! indexes with exercise

0-1

2

3

4

1 0.51 0

7 0.65 0.63 0.02

7 0.72 0.62 0.10

1 1.04 0.97

* 0-1-no erections or minimal baseline deflection, 2-0 to 2 slow rising erections with poorly maintained deflection, 3-3 erections with moderately well maintained deflection and 4-G;3 immediate erections with well maintained deflection.

In 5 patients in whom arteriographic studies were performed the physiology of the pelvic steal condition was corroborated by arteriography. Two cases are reported that illustrate positive pelvic steal testing. CASE REPORTS

Case 1. A 59-year-old man complained of erectile dysfunction during an 18-month interval. The patient had normal libido and ejaculation. He experienced occasional morning erections and was able to achieve a semi-erection during foreplay. Loss of erection occurred following vaginal penetration and during copulation. A nocturnal penile tumescence study demonstrated poorly maintained erections (grade 2) (fig. 2). There was no significant medical history of hypertension. The patient denied taking any medication. He had smoked >2 packs of cigarettes per day for many years. Endocrine evaluation was within normal limits. Resting penile-brachia! indexes were 0.66 on the right and left sides. Following exercise the penile-brachia! index was 0.44 on the right and 0.41 on the left sides. Pelvic and bilateral selective internal iliac arteriograms were performed via a right femoral artery puncture, which demonstrated occlusion of both internal pudenda! arteries and the presence of abnormal pelvic collaterals between the obturator artery (internal iliac artery system) and profunda femoris (external iliac system) (fig. 3). Case 2. A 61-year-old white man had progressive impotence during a 5-year interval. The patient described a semi-erection that was firm enough for vaginal penetration. However, loss of erection occurred on numerous occasions during copulation

'{eport l

Coror.n

£...i

Dtflectim1 cm

15

30

45

60

Minutes

FIG. 2. Nocturnal penile tumescence study demonstrates penile coronal and base deflection during sleep. Deflection is minimal and poorly maintained. ·

DISCUSSION

erections. There \A1as a but he took no medication had smoked but had 10 years ago. penile tumescence study demon· strated partial erections (grade 2) (fig. 4). Endocrine evaluation and sacral latency responses were within normal limits. Resting penile-brachial indexes also were within normal limits (0.79 on the right and 0.93 on the left sides). However, following exercise the penile-brachial index decreased to 0.50 on the right and 0.56 on the left sides. Pelvic and bilateral selective internal iliac arteriograms performed via right femoral artery percutaneous catheterization demonstrated an abnormal internal pudenda! artery with an abrupt amputation in the perinea! segment at the urogenital diaphragm (fig. 5).

The penile arterial inflow can. be evaluated a Doppler ultrasound flow detectoro Several investigators have established the of this technique. 1- 5 In Queral and associates demonstrated that Doppler determination of penile blood flow closely predicted erectile capacity in patients undergoing bypass graft procedures for aortoiliac occlusion. 5 They found that an abnormal preoperative Doppler result was associated invariably with impotence and that if the Doppler determination was increased postoperatively >70 per cent of these previously impotent patients had restored erectile capacity. Doppler determinations of the penile circulation are expressed best as a ratio of penile systolic blood pressure to brachial systolic blood pressure, that is the penile-brachial index. Penile-brachial index measurements usually have been

304

GOLDSTEIN AND ASSOCIATES

NOCTURNAL PENILE TUMESCENCE Case Report 2

Corona Deflection

cm

Base Deflection

2-

0----·/\_,__ ~__,___ 2-

cm

's

1

Minutes

FIG. 4. Nocturnal penile tumescence study demonstrates penile coronal and base deflection during sleep. Deflection is slightly better than previous case but it is short-lived.

FIG. 5. Hypogastric arteriogram demonstrates widely patent gluteal and ischiorectal segments (arrowheads) of internal pudenda! artery. Bifurcation of internal pudenda! artery into perinea! segment (straight arrow) and superficial perinea! artery are normal. There is abrupt amputation of perinea! segment at urogenital diaphragm.

expressed only as resting values. During actual sexual intercourse a resting penile-brachia! index measurement may not be the most sensitive expression of erectile capacity for several reasons. First, sexual intercourse is not a resting event. The copulating phase of intercourse requires movement of calf, thigh and buttock muscles, all of which must have increased blood flow to satisfy metabolic demands. The response of the pelvic circulation to exercise-induced increased arterial flow through the external iliac artery cannot be assessed with resting penile-brachia! index measurements. Second, several analogues occur in medicine for exercise-related flow phenomena not apparent at rest. For example, symptoms of blood flow impairment or claudication of the lower extremities, coronary artery and cerebral arteries or angina may only be expressed following exercise. 6 • 7• 10- 12 In a similar fashion penile arterial blood flow impairment or vasculogenic impotence may only be expressed following exercise. Michal and associates described an impotent patient who

suffered right gluteal claudication, which illustrates the potential for exercise-induced impotence.13 A schematic arteriogram demonstrated occlusion of the right common iliac artery and stenosis of the left internal iliac artery (fig. 6). The right external iliac artery was reconstituted from the left side via the left internal iliac artery and pelvic collaterals. At operation blood flow in the right internal iliac artery was found to be reversed. Although no hemodynamic study was performed these investigators postulated that coital movement created increased flow through the left external iliac. Thus, a steal of arterial flow away from the pelvic collaterals and right external iliac artery occurred, resulting in impotence and right gluteal claudication. This steal syndrome was resolved by right common iliac endarterectomy, following which the patient experienced return of erection and loss of claudication. At our institution we were intrigued by the recurrent association of certain findings in some impotent men. These patients complained of erectile dysfunction that was positional or exercise-related but there were occasional semirigid erections. Physical examination revealed a poorly palpable penile pulse. In these patients sacral latency testing15 and endocrinologic profiles were within normal limits. On nocturnal penile tumescence monitoring erections were less frequent, short-lived and poorly maintained. Many of these patients appeared to fulfill the clinical criteria for vasculogenic impotence. However, the penile-brachia! index values sometimes were >0.75 but, most commonly, were in the intermediate zone between 0.75 and 0.6. It was in these patients that exercise testing was most useful. We found that a change in penile-brachia! index induced by exercise was abnormal if the decrease was >0.15. In the series by Queral and associates 2 patients who were potent preoperatively became impotent after vascular reconstruction. 5 In both patients a decrease in penile-brachia! index of >0.1 occurred. Thus, these investigators observed that sufficient pelvic hemodynamic changes induced by an operation resulted in impotence when the penile-brachia! index decreased by 0.1. Nath used these criteria and arbitrarily chose a decrease in penile-brachia! index of 0.1 with exercise as being significant. 16 We found that the criteria of Queral and associates, when applied to pelvic steal testing, appeared to overestimate the positive yield. 5 An attempt was made to compare nocturnal penile tumescence monitoring with penile-brachia! index values obtained during pelvic steal testing. Intermediate penile-brachia! indexes were associated with poor quality erections (table 5). Clinical nocturnal penile tumescence monitoring was described first by Karacan in 197017 and has been used since to provide objective

305

VASCULOGEN:IC IMPOTENCE

A

B

REST - FLOW REVERSED IN INTERNAL I LI AC

@

- CD

EXERCISE - PREFERENTIAL FLOW TO (L) EXTERNAL ILIAC AWAY FROM CD INTERNAL ILIAC

INTERNAL ILIAC, PELVIC COLLATERALS SUPPLY (R) EXTERNAL ILIAC

FIG. 6. Schematic arteriogram demonstrates pelvic steal syndrome. A, at rest flow in right external iliac is supplied by left internal iliac and pelvic collaterals as result of right common iliac occlusion. B, with exercise flow in right external iliac and pelvis is diminished as blood preferentially flows to left lower extremity.

data for the differential diagnosis of impotence. There has been discussion in the literature concerning the possibility of psychogenically impotent patients having impaired nocturnal penile tumescence readings. 17· 18 Of the patients studied by Karacan 20 per cent found to have impaired nocturnal penile tumescence did not have demonstrable organic disease known to cause impotence and it was believed that those patients had subtle psychological deficits not detected by available techniques. 19 It is possible that some of the patients had unrecognized vascular disease. To resolve this issue larger studies are needed, which will compare nocturnal penile tumescence recordings with new objective evaluations of impotence, such as pelvic steal and sacral latency testing. 15 Of the 97 patients in this study 12 underwent arteriograms to confirm the presence of vasculogenic impotence. We compared dorsal artery penile pressure to cavernosal artery penile pressures before and after exercise in this group (table 6). The results differed in 5 of these patients. In patient 8 reliance on dorsal artery resting pressure would have resulted in missed pathology. In patients 9 to 11 the dorsal artery resting pressure underestimated the cavernosal artery resting pressure but the latter pressures also were suggestive of vascular pathology. In patient 12 (8 per cent) exercise testing was abnormal in the cavernosal arteries but not in the dorsal artery. It appears that while dorsal arterial pressures closely approximate cavernosal arterial pressures the former are less representative of erectile capacity. Cavernosal arterial pressures also allowed for localization of suspected vascular lesions, whereas dorsal arterial pressures did not. In conclusion, the vessels to the corpora cavernosa often have obliterations and hemodynamically significant stenoses. In such situations collateral beds develop with reversal of blood flow in some on these arteries. At rest collaterals may provide sufficient blood flow to the pelvis and sufficient filling of the corpus cavernosum to allow for penile erections. However, with exercise dilated muscle beds in the calf and thigh create a pressure decrease in the lower extremities. In normal situations this exercise-related flow demand is met simply by increasing blood flow through the external iliac artery. Two patterns of vascular disease exist that would explain the syndrome of potency at rest and impotence with exercise. The external iliac artery is occluded or significantly stenosed so that flow is reconstituted by 1) internal iliac collaterals (fig. 6) or 2)

TABLE

6. Comparison of cavernosal artery and dorsal artery penile

pressures Cavernosal Artery Pt. No.

Dorsal Artery Lt.

Rt.

Agreement 1 2 3 4

5 6 7

0.38/0 0.76/0.75 0.69/0 0.71/0.67 0.61/0.83 0.47 /0.42 0.66/0.41

0.30/0 0.86/0.66 0.69/0 0.71/0.47 0.68/0.75 0.47 /0.48 0.66/0.44

0.35/0 0.86/0.66 0.73/0 0.75/0.53 0.68/0.58 0.47 /0.48 0.66/0.41

Disagreement 8

9 10 11

12

0.73/0 0.67/60 0.63/0.47 0.57/0.62 0.93/0.56

0.47 /0 0.70/0 0.67 /0.51 0.57/0.62 0.79/0.50

0.9/0.42 0.44/0 0/0 0/0 0.81/0.69

All values express the ratio of penile-brachia] index to penile-brachia! exercising index.

external iliac collaterals (fig. 7). In each case exercise-related lower extremity pressure decreases create preferential blood flow away from the internal iliac artery. In the first situation the patient generally seeks help from the vascular surgeon because of concomitant lower extremity claudication. However, in the second case the patient seeks help from the urologist and there is no complaint of claudication but there is a history of exercise-related erectile dysfunction. Owing to the presence of morning erections and the existence of erections on nocturnal penile tumescence monitoring this syndrome often has been unrecognized, undiagnosed and difficult to explain. We believe that the pelvic steal test, by predicting exercise-related impotence, will add significant new dimensions to the clinical diagnosis of vasculogenic impotence. In summary, the incidence of vasculogenic impotence in patients with peripheral arterial disease is significantly higher than appreciated previously and may well be the most common cause of secondary impotence in men >40 years old. Screening for vasculogenic impotence should include history, physical examination, nocturnal penile tumescence monitoring and penile blood pressure. Nocturnal penile tumescence monitoring of

306

GOLDSTEIN AND ASSOCIATES

EXTERNAL ILIAC COLLATERALIZATION OF OBSTRUCTED INTERNAL ILIAC (NO CLAUDICATION)

A

B

FIG. 7. Schematic arteriogram demonstrates pelvic steal syndrome. A, right internal iliac artery is obstructed. Blood flow to pelvis originates from left internal iliac artery. B, additional pathological condition, such as left internal and left external iliac stenoses, is represented. Blood flow to pelvis at rest may be sufficient for normal erectile function. With exercise flow is preferential to left external iliac. This later situation may result in erectile dysfunction after exercise.

poor quality erections appears to correlate with intermediate penile-brachial indexes. Monitoring of penile blood pressures by the dorsal artery instead of the cavernosal artery appears to be associated with an 8 per cent error in diagnosis. The pelvic steal test appears to improve markedly the sensitivity and yield of blood pressure measurements and, thus, facilitates the diagnosis of vasculogenic impotence, especially in those patients who have intermediate penile-brachial indexes. A decrease in penile-brachia! index of i;;;0.15 with exercise is considered the criterion for a positive pelvic steal test. A larger series involving >400 patients presently is being undertaken. REFERENCES 1. Abelson, D.: Diagnostic value of the penile pulse and blood pressure: a Doppler study of impotence in diabetics. J. Urol., 113: 636, 1975. 2. Barry, J. M. and Hodges, C. V.: Impotence: a diagnostic approach. J. Urol., 119: 575, 1978. 3. Engel, G., Burnham, S. J. and Carter, M. F.: Penile blood pressure in the evaluation of erectile impotence. Fertil. Steril., 30: 687, 1978. 4. Malvar, T., Baron, T. and Clark, S. S.: Assessment of potency with the Doppler flowmeter. Urology, 2: 396, 1973. 5. Queral, L. A., Whitehouse, W. M., Jr., Flinn, W. R., Zarins, C. K., Bergan, J. J. and Yao, J. S. T.: Pelvic hemodynamics after aortoiliac reconstruction. Surgery, 86: 799, 1979. 6. Reivich, M., Holling, H. E., Roberts, B. and Toole, J. F.: Reversal of blood flow through the vertebral artery and its effect on cerebral circulation. New Engl. J. Med., 265: 878, 1961. 7. Sammartino, W. F. and Toole, J. F.: Reversed vertebral artery flow. The effect oflimb exercise and hypertensive agents. Arch. Neurol., 10: 590, 1964. 8. Kountz, S. L., Laub, D. R. and Connolly, J. E.: "Aortoiliac steal" syndrome. Arch. Surg., 92: 490, 1966. 9. Trippel, 0. H., Jurayj, M. N. and Midell, A. I.: The aorto-iliac steal: a review of this syndrome and a report of one additional case. Ann. Surg., 175: 454, 1972. 10. Carter, S. A.: Response of ankle systolic pressure to leg exercise in mild or questionable arterial disease. New Engl. J. Med., 287: 578, 1972.

11. Kempczinski, R. F. and Rutherford, R. S.: Current status of the vascular diagnostic laboratory. Adv. Surg., 12: 1, 1978. 12. Bruce, R. A.: Exercise testing of patients with coronary heart disease. Principles and normal standards for evaluation. Ann. Clin. Res., 3: 323, 1971. 13. Michal, V., Kramar, R. and Pospichal, J.: External iliac "steal syndrome". J. Cardiovasc. Surg., 19: 355, 1978. 14. Ginestie, J. F. and Romieu, A.: Radiologic Exploration of Impotence. Hague: Martin us Nijhoff Medical Division, 1978. 15. Krane, R. J. and Siroky, M. B.: Studies in sacral-evoked potentials. J. Urol., 124: 872, 1980. 16. Nath, R. L.: The multidisciplinary approach to vasculogenic impotence. Surgery, 89: 124, 1981. 17. Karacan, I.: Clinical value of nocturnal erection in the prognosis and diagnosis of impotence. Med. Aspects Hum. Sex., 4: 27, 1970. 18. Fisher, C., Schiavi, R., Lear, H., Edwards, A., Davis, D. M. and Witkin, A. P.: The assessment of nocturnal REM erection in the differential diagnosis of sexual impotence. J. Sex Marital Ther., 1: 277, 1975. 19. Karacan, I.: Impotence: psyche vs soma. Medical World News, p. 28, June 1976.

EDITORIAL COMMENT The authors have made a significant contribution to the evaluatioi, of vasculogenic impotence by means of measuring the systolic penilebrachial pressure index after exercise. The 2 important aspects of this paper are 1) pelvic steal testing was able to detect vascular pathology in an additional 20 per cent of patients at risk for vasculogenic impotence, not previously detected by resting Doppler studies and 2) they have quantified that a significant decrease between resting and exercise penile-brachia! indexes is i;;;0.15. However, one must keep in mind that such noninvasive vascular testing evaluates an entire arterial system and does not localize the site of stenosis or obstruction. Arteriographic studies are needed for accurate localization, after which some patients will be found to be surgically correctable and others will require conservative management, that is no smoking, aspirin and dipyridamole. Joseph L. Romolo 1727 Fernaldo Point Lane Santa Barbara, California 93108