Summary. Background: Recurrent thromboembolic events after an initial deep vein thrombosis (DVT) are relatively frequent. Residual thrombus in the affected veins on ultrasound scan at the completion of anticoagulant therapy has been described as a recurrence risk factor, and may have utility in stratifying those patients at risk. Objectives: The aims of the study were to correlate the risk of recurrence of DVT with the results of ultrasound at completion of oral anticoagulant therapy. A secondary aim was to review the mortality in this population. Patients: A cohort of 316 DVT patients was included. The patients were divided into those with completely clear vessels on follow-up scan (45%) and those with residual thrombus identified (55%). Results: The cumulative incidence of recurrence was 10% by 2 years and 23% by 5 years. Patients with residual thrombus on follow-up ultrasound were at higher risk of recurrence (hazard ratio [HR] 2.2, 1.19-4.21; P ¼ 0.012) which remained significant after multivariate adjustment for age, gender and malignancy (HR 2.2, 1.15-4.17; P ¼ 0.018). During follow-up, the cumulative mortality was 12% at 2 years and 27% by 5 years. The risk of death was increased in patients with residual thrombus on follow-up scan (HR 3.9, 1.93-7.71; P < 0.001) and this risk persisted after multivariate analysis of age, gender and malignancy (2.8, 1.37-5.72; P ¼ 0.005). The majority of deaths were due to malignancy (68%) however 10 (18%) died from vascular causes. There was a trend towards increased vascular death in the patients with residual thrombus on follow-up ultrasound scan, which did not reach significance (HR 4.1,; P ¼ 0.13). Conclusions: Consistent with previous cohort studies, recurrence risk is increased in patients with residual thrombus on ultrasound. The increased risk of death in patients with residual thrombus, with a trend towards increased vascular death, may suggest that failure of thrombus resolution is a marker of more global vascular dysfunction.

Withholding anticoagulation in patients with single subsegmental PE and negative serial bilateral CUS appears to be a safe and effective management strategy, with a low risk of VTE recurrence.

A 6-week duration of anticoagulation appears to be an effective and safe treatment for isolated axial distal DVT, with low rates of VTE recurrence and proximal propagation.

Background: Single subsegmental pulmonary embolism is increasingly diagnosed but the benefit to anticoagulate in the absence of concurrent deep vein thrombosis is not consistently established.Aims: To investigate the safety of an observational approach in patients with isolated subsegmental pulmonary embolism and the utility of the second lower limb ultrasound after 7 days.Methods: Prospective observational study of patients diagnosed with isolated subsegmental pulmonary embolism between July 2016 and July 2020 at North Shore and Waitakere Hospitals, Auckland. The primary outcome was the venous thromboembolism recurrence rate within 3 months of single subsegmental pulmonary embolism diagnosis. Secondary outcomes included all-cause mortality, bleeding complications and the percentage of deep vein thrombosis diagnosed at serial compressive ultrasounds (CUS) of lower limbs.Results: Among the 48 patients studied (two excluded due to revised diagnosis), no statistically significant differences were found in the baseline characteristics between the anticoagulated (n = 17) and observed (n = 31) groups. After patients with deep vein thrombosis were excluded, comparisons did not reveal significant differences in the primary outcome (0 vs 1 recurrent venous thromboembolism in the anticoagulated vs. observational groups respectively) and the secondary outcomes. In the observational cohort, 77.4% (n = 24) patients had repeat bilateral lower limb CUS after 7 days, and none had deep vein thrombosis diagnosed on the second CUS.Conclusions: Withholding anticoagulation was a feasible management option for this cohort of patients with single subsegmental pulmonary embolisms with an absence of deep vein thrombosis. The utility of a second lower limb ultrasound is questionable and would warrant further assessment in a prospective study.