Diabetes and vascular impotence: does insulin dependence increase the relative severity?

Diabetes is a well documented risk factor for vascular erectile dysfunction (ED). We evaluated the relative roles of insulin dependence (IDDM) vs oral agent controlled diabetes (NIDDM) in predicting the etiologies and severity of ED: arterial insufficiency (AI), venous leakage (CVOD), and mixed vascular disease. The impact of additional risk factors were also analyzed: hypertension (HTN), coronary artery disease (CAD), and smoking (SM).

Retrospective data on 105 patients complaining of impotence who underwent pharmacotesting with PGE1 (Caverject) and color duplex Doppler was reviewed. Penile blood flow study (PBFS) data following a period of privacy and self-stimulation was compared. PBFS diagnostic criteria were: AI for peak systolic velocity (PSV) < 25 cm/s; CVOD for PSV > or = 35 cm/s and resistive index (RI) < 0.9; mixed vascular disease for PSV > or = 25 cm/s, PSV < 35 cm/s and RI > 0.9. Consistent dosing of PGE1 was used; 6 mcg for age < 60 y and 10 mcg for age > or = 60 y. Patients were NIDDM (79 out of 105) and IDDM (26 out of 105). Mean ages for NIDDM and IDDM were respectively 60, and 55 y. The relative significance of insulin dependence was assessed by Student's t-test.

The most common etiology of ED was arterial insufficiency: mean PSV's did not significantly vary and were: 23.5 cm/s for NIDDM, and 21.6 cm/s for IDDM. PBFS parameters did not vary significantly for the risk factors of SM or HTN and diabetes. Mean peak systolic velocities were significantly different among diabetics with coronary artery disease: NIDDM/CAD, 22.9 cm/s compared to IDDM/CAD, 14.8 cm/s (P = 0.006).

We found among the 105 diabetics the most common etiology of vascular ED based on Doppler criteria was arterial insufficiency, 64%. Statistical analysis of additional risk factors (SM, HTN, CAD) suggested that patients with IDDM and CAD have more severe cavernosal arterial insufficiency than patients with NIDDM and CAD. This data tends to support the theory that microangiopathy is the predominant factor in diabetic impotence, and that insulin dependent diabetes with 'large vessel' coronary heart disease have a similar pathology in the 'small vessels' regulating penile inflow which is unfortunately worse than their non-insulin dependent counterparts.