The Case for Managing Calf Vein Thrombi With Duplex Surveillance and Selective Anticoagulation

Pulmonary Emboli at Presentation

PE at presentation with calf DVT should be clearly distinguished from PE that occurs during duplex surveillance of the calf. When fatal PE is the presenting symptom (Table 1) and isolated calf thrombosis is the only site of thrombosis, the association between fatal PE and calf DVT may be seriously overestimated at 13%-25%.2, 3, 4 Embolization of a more proximal thrombus in the thigh or higher, leaving residual clot in the calf, can never be excluded in such cases. In showing the leg venograms

Pulmonary Emboli During Surveillance

In contrast to the high rate of PE at the time of presentation, the incidence of symptomatic PE during surveillance is 0%-6.3% (Table 2), with no deaths attributable to PE. The lower rates of PE in patients undergoing surveillance support the contention that such an approach is safe if executed with a reliable follow-up protocol. The low rate of serious PE associated with isolated calf vein thrombi under surveillance can be at least partly explained by self-selection—those at highest risk,

Risk of Propagation

Propagation to the popliteal veins or higher is associated with a higher risk of PE¹ and postthrombotic syndrome¹⁶ than thrombus that remains confined to the infrapopliteal level. Anticoagulation, or placement of an inferior vena cava (IVC) filter in those with contraindications to anticoagulation, remains the standard of care for patients with thrombus extending into the popliteal vein or higher. Proximal propagation to the popliteal vein or higher occurs in 8%-15% of isolated calf vein

Randomized Controlled Trials (RCTs)

The ongoing controversy over the management of calf DVT is fueled by the absence of RCTs comparing anticoagulation with duplex surveillance plus selective anticoagulation. There are 4 RCTs evaluating the duration of anticoagulation for calf DVT.20, 21, 22, 23 Of these, the study of Lagerstedt and colleagues²⁰ is most commonly cited by proponents of routine anticoagulation. Among symptomatic patients, all of whom received heparin for 5 days, the 23 cases treated with 3 months of warfarin had no

Influence of DVT Pharmacologic Prophylaxis on Propagation

DVT prophylaxis with low molecular weight heparin or unfractionated heparin may reduce both the incidence of DVT and the rate of proximal extension from the calf in hospitalized patients. Among 3116 elective abdominal surgery patients in 4 studies reviewed by Giannoukas and coworkers,26, 27, 28, 29, 30 6.4% of patients had thrombosis despite heparin prophylaxis and proximal extension occurred in 0.6%. In contrast, among the 380 patients who developed calf vein thrombi in the absence of heparin

Predictors of Propagation

Clinical factors could theoretically identify those patients at high risk for clot propagation, recurrence, or PE during duplex surveillance. Unfortunately, there is little evidence supporting predictors of thrombus propagation, possibly because of the limited number of patients included in individual series. In 1 of the larger studies, Lohr and coworkers³¹ examined 192 patients with isolated calf vein thrombosis and found no factors, including malignancy, obesity, trauma, estrogen use,

Risk for Postthrombotic Syndrome (PTS)

The incidence of PTS symptoms after isolated calf DVT ranges from 8% to 57%, the majority being CEAP (current standard of reporting on chronic venous insufficiency) clinical Class 2 and 3 with pain, varicose veins and/or swelling. Less than 5% will develop significant symptoms of C4-C6 disease, and of these, lipodermatosclerosis or stasis dermatitis will be the predominant finding. Ulceration is a rare event (Table 4).

When weighing the benefits and risks of treating all cases of calf vein

Risk of Bleeding From Anticoagulation

The risk of major bleeding associated with anticoagulation is not insignificant. Although the definition of major bleeding is variable, most would define major bleeding as those events that are intracranial or retroperitoneal or result in hospitalization or blood transfusion. Linkins and coworkers³⁶ reported a meta-analysis of 29 RCTs and 4 cohort studies, including 10,757 DVT patients treated with vitamin K antagonists. During the first 3 months of treatment, major bleeding occurred in 2.1%

Cost of Treatment

It is estimated that up to 36%¹⁸ of the 800,000 cases of venous thrombotic events annually in the USA are isolated to the calf. If patients can be anticoagulated as outpatients, the cost is slightly higher than that for duplex scan surveillance (Table 5). However, if patients require hospitalization, the costs are likely significantly higher than surveillance alone.

American College of Chest Physicians (ACCP) Guidelines

The 2008 ACCP guidelines³⁷ suggest 3 months of anticoagulation for isolated calf DVT that are not provoked (ie, idiopathic). This is a weak grade 2B recommendation based on uncertainty about the magnitude of benefits over risks; it was given a level B for moderate-quality evidence. If anticoagulation is contraindicated, the ACCP recommends IVC filters for proximal DVT, but does not make any recommendations regarding isolated calf DVT, nor do they suggest an alternative to anticoagulation, such

Conclusions

In summary, controversy persists regarding the roles of routine anticoagulation for all calf DVT versus selective anticoagulation based on duplex surveillance. Selective treatment is supported by the low incidence of serious pre- and postthrombotic syndrome after isolated calf vein thrombi as well as the not insignificant risk of bleeding complications associated with routine anticoagulation. Disadvantages of surveillance include the 3%-15% risk of proximal propagation to the popliteal vein or