Abstract No. 506 - Venous pressure gradients during exercise in patients with iliac venous obstruction

Abstract

Venography and intervention of the iliac veins is commonly performed for lifestyle limiting symptoms such as lower extremity swelling, pain, venous ulcers and other stigmata of post-thrombotic syndrome related to iliac obstruction. Since some patients only experience symptoms with exercise and many patients experience an exacerbation of symptoms with exercise, a better understanding of the venous hemodynamics during exercise is needed. Six patients have undergone pelvic venography with exercise pressure measurements as part of the evaluation at the time of a planned intervention for iliac venous obstruction. Venous access was through the right internal jugular vein. Venous pressure gradients were measured across the perceived obstruction at rest in the supine position. These pressures were then assessed during moderate exercise (50-70% max heart rate) using a supine stationary exercise bike fixed to the fluoroscopy table. The normal contralateral iliac vein was also evaluated in the same manner. All patients underwent iliac venous angioplasty and stenting. Post-intervention rest and exercise gradients were then reassessed. Three patients had hemodynamically significant pressure gradients at rest (defined as 2mmHg or greater), with an average resting gradient ratio (common femoral vein pressure/IVC pressure) of 2.1 and an average exercise gradient ratio of 3.2. Two patients with in-stent venous stenosis had an average resting gradient ratio of 1.9 and an average exercise gradient of 2.9. Two patients with non-stented May-Thurner anatomy, one of whom had normal bilateral resting venous pressure gradients, had left to right internal iliac venous collateral flow at rest. Both of these patients developed venous pressure gradients of 3mmHg on the contralateral side during exercise as well as more significant gradients, average of 9.5mmHg, in the affected ipsilateral vein. All six patients had complete resolution of venous gradients at rest and during exercise following stent procedure. This preliminary experience indicates that exercise venous pressure measurements may play a role in defining the significance of venous obstruction.