The use of anticoagulants to treat acute deep vein thrombosis (DVT) effectively prevents thrombus extension and recurrence, but it does not dissolve the clot, and many patients develop post-thrombotic syndrome (PTS). The landmark CaVenT open-label RCT examined whether additional treatment with catheter-directed thrombolysis (CDT) using alteplase reduced development of PTS.

The study involved 209 subjects (aged 18 to 75 years) recruited from 20 hospitals in the Norwegian southeastern health region with a first-time iliofemoral DVT within 21 days from symptom onset. They were randomised to receive conventional treatment (n=108) alone or additional CDT (n= 101). The two co-primary outcomes were frequency of PTS as assessed by Villalta score at 24 months, and iliofemoral patency after 6 months. At completion of 24 months' follow-up, data for clinical status were available for 189 patients (90%; 99 control, 90 CDT).

According to the intention to treat analysis:

• At 24 months, 37 (41•1%) patients allocated additional CDT presented with PTS compared with 55 (55•6%) in the control group (p=0.047).

• The difference in PTS corresponds to an absolute risk reduction of 14.4% (95% CI, 0.2 to 27.9), and the number needed to treat was 7 (95% CI, 4 to 502).

• Iliofemoral patency after 6 months was reported in 58 patients (65.9%) on CDT vs. 45 (47.4%) on control (p=0.012).

• 20 bleeding complications related to CDT included three major and five clinically relevant bleeds.

The researchers conclude from these findings that additional thrombolytic treatment reduced PTS compared with anticoagulation alone, but was associated with a small additional risk of bleeding, but this risk was considered acceptable in contrast to systemic thrombolytic treatment, and the effect size was in line with results for systemic treatment. They suggest that catheter-directed thrombolysis should be considered in patients with high proximal DVT and low risk of bleeding. Further data are awaited from completion of an ongoing trial.

An accompanying commentary commends the study investigators for a “tremendous contribution to the published literature on DVT.” They suggest that these data will help to preserve limb function in many patients with DVT by reducing the risk of incurable and debilitating PTS and thus serve as a powerful motivation to undertake CDT for symptomatic acute lower extremity DVT.