Assessment of residual thrombus after venous thrombolytic regimens

We noticed substantial residual thrombus on intravascular ultrasound (IVUS) in many limbs despite restoration of flow after thrombolysis. Since thrombus burden has been tied to post-thrombotic syndrome (PTS), the frequency and extent of residual thrombus after thrombolysis is important. We present such an analysis below.

Sixty-seven limbs underwent (median age, 57; range, 24-83) pharmacomechanical thrombectomy (PMT) after deep venous thrombosis (DVT) (35 limbs) or iliac vein stent thrombosis (32 limbs). Assessment after PMT included venography and IVUS. If flow was not established or residual thrombus was present on IVUS examination, follow-up catheter-directed thrombolysis (CDT) up to 3 days was used to clear the thrombus.

PMT was successful in establishing flow across occluded segments in 82%, but complete lysis per IVUS was achieved in only 9% with residual thrombus present in 91% (18% occlusive) of treated limbs. Follow-up CDT was feasible in 48 limbs. This resulted in establishment of inline flow in nine additional limbs; complete thrombus clearance per IVUS was achieved in 15 others (many with prior inline flow with thrombus). Overall, 96% of limbs were patent, but as many as 69% of limbs had residual thrombus after treatment with one or both lytic regimens. There was significantly more complete clot clearance (P < .04) in virgin DVT compared with thrombosis in stented limbs. IVUS was significantly more sensitive (P = .03) than venography in estimating residual thrombus burden. However, there was no significant difference in PTS incidence whether the clot was completely lysed or not.

Venographic patency can be established in most limbs with DVT or stent thrombosis by PMT alone. Venographic patency was a poor guide to the presence and extent of residual thrombus. Follow-up CDT was useful in significantly increasing complete clot clearance, but residual thrombus remained on IVUS in over two-thirds of treated limbs overall. The implications of residual thrombus after inline flow has been re-established with thrombolytic regimens for the development of PTS are unknown.