In-stent recurrent stenosis in stents placed in the lower extremity venous outflow tract.

PURPOSE: This study was undertaken to describe development of in-stent recurrent stenosis (ISR) in stents placed in the iliocaval outflow tract and to examine possible contributing factors.

METHOD: After iliocaval balloon angioplasty and stent insertion to treat chronic nonmalignant obstruction, single-plane transfemoral venography was performed at least once in 324 limbs, twice in 123 limbs, three times in 40 limbs, and four times in 4 limbs. ISR was measured with a caliper, and expressed as percentage diameter reduction of patent lumen on the venograms. Left-right limb ratio was 2.3:1; thrombotic-nonthrombotic disease ratio, 1.2:1; negative-positive thrombophilia test ratio, 1.6:1; and above-below inguinal ligament stent placement ratio, 4.5:1. Median stent length was 9 cm (range, 4-35 cm), and median lumen area before and after stenting was 0.41 cm(2) (range, 0-1.65 cm(2)) and 1.70 cm(2) (range, 0.65-4.00 cm(2)), respectively. Limbs were divided into groups with no ISR, any degree of ISR, greater than 20% diameter reduction, and greater than 50% diameter reduction. Cumulative ISR and patency rates were analyzed. Possible contributing factors were examined.

RESULTS: At 42 months, only 23% of limbs demonstrated no ISR. Cumulative rate of limbs with greater than 20% diameter reduction was 61%, and of limbs with greater than 50% diameter reduction was 15%. Patient gender or sidedness of the treated extremity did not affect outcome. At 36 months, limbs with thrombotic disease had higher ISR rates than did limbs without thrombotic disease (63% and 41% of limbs with >20% narrowing, and 23% and 4% of limbs with >50% narrowing, respectively; P <.01). Similarly, higher rates of ISR were found in patients with thrombophilia and long stents extending below the inguinal ligament. Primary, assisted primary, and secondary patency rates for the entire population at 3 years were 75%, 92%, and 93%, respectively. There was a significant increase in ISR in individual limbs, but analysis of groups of stents did not unequivocally show progression.

CONCLUSION: Severe (>50%) ISR of iliofemoral venous stents is uncommon over the short term. The three major risk factors appear to be presence of thrombotic disease, positive thrombophilia test results, and stent extending below the inguinal ligament (long stents). Although stented limbs that eventually became occluded during the study demonstrated similar risk factors, no conclusion regarding a cause-effect relationship can be drawn from the present data. Whether late occlusion is due to acute thrombosis or to gradual development of true intimal hyperplasia requires further study.