Clinical relevance of symptomatic superficial-vein thrombosis extension: Lessons from the CALISTO study

Abstract

The clinical relevance of symptomatic extension of spontaneous, acute, symptomatic, lower-limb superficial-vein thrombosis (SVT) is debated. We performed a post hoc analysis of a double-blind trial comparing fondaparinux with placebo. The main study outcome was SVT extension by day 77, whether to ≤3 cmor >3 cm from the sapheno-femoral junction (SFJ). All events were objectively confirmed and validated by an adjudication committee. With placebo (n 5 1500), symptomatic SVT extension to ≤3cmor >3 cmfrom the SFJ occurred in 54 (3.6%) and 56 (3.7%) patients, respectively, inducing comparable medical resource consumption (eg, anticoagulant drugs and SFJ ligation); subsequent deep-vein thrombosis or pulmonary embolism occurred in 9.3% (5/54) and 8.9% (5/56) of patients, respectively. Fondaparinux was associated with lower incidences of SVT extension to ≤3 cm(0.3%; 5/1502; P 3 cm (0.8%; 12/1502; P