Acute Lower Extremity Deep Venous Thrombosis: Surgical and Interventional Treatment

Morbidity

PTS is the clinical condition defined by the signs and symptoms resulting from acute DVT. This is usually the consequence of ambulatory venous hypertension resulting from valve reflux and/or chronic luminal obstruction. Studies have shown that patients with PTS have a significant reduction in their quality of life (QoL). ^, The severity of the patient’s acute DVT is predictive of post-thrombotic morbidity, especially when it involves the iliofemoral (IF) segment. Patients with IFDVT are a clinically relevant subset of patients with acute DVT. They have occlusion of their single venous outflow channel from the leg, often resulting in severe post-thrombotic morbidity when treated with anticoagulation alone. In a prospective observational study of anticoagulation for acute DVT, IFDVT was found to be the most powerful predictor of severe PTS (HR 2.23). Labropoulos et al. monitored venous pressures in patients with PTS after treatment for their acute DVT. They found that patients who were treated for IFDVT had the highest venous pressures. This confirmed prior observations that IFDVT patients treated by anticoagulation alone had ambulatory venous hypertension, with 40% demonstrating venous claudication and up to 15% developing venous ulceration within 5 years. The morbidity of PTS escalates with ipsilateral thrombotic recurrence. A meta-analysis of outcomes after treatment for acute DVT demonstrated that recurrence occurs more commonly in patients harboring a large burden of thrombus.

Etiology

The pathophysiology of post-thrombotic venous disease is ambulatory venous hypertension, defined as elevated venous pressure during exercise. ^, Ambulatory venous pressure is linearly linked to the consequences observed with chronic post-thrombotic venous disease, such as swelling, pigmentation, and lipodermatosclerosis. Microcirculatory changes leading to dermal breakdown follow.

The anatomic components contributing to ambulatory venous hypertension are venous valvular incompetence and luminal obstruction. The most severe post-thrombotic morbidity is associated with the highest venous pressures, which often occur in patients with both valvular incompetence and luminal venous obstruction. ^, Although valvular function can be reliably assessed with ultrasound, techniques are not yet available to assess the relative contribution of venous obstruction to the pathologic venous hemodynamics leading to clinical post-thrombotic morbidity ( Fig. 149.1 ). Neither ascending phlebography performed and interpreted by a skilled radiologist nor the maximal venous outflow test performed in an accredited vascular laboratory identified venous obstruction in the patient presented (see Fig. 149.1 ). A cross-section of the proximal femoral vein removed during a classic Linton procedure clearly showed recanalization channels through what was once occlusive thrombus, resulting in chronic obstruction of a large percentage of the luminal surface area. Venous hemodynamics can be affected before imaging techniques detect obstruction. Our inability to noninvasively quantify obstruction has led physicians to underappreciate its contribution to post-thrombotic pathophysiology. Luminal venous obstruction causes the most severe forms of PTS, especially when it involves the common femoral and iliac veins. Obstruction of the distal popliteal vein is also associated with significant PTS. Therefore, treatment strategies for thrombus removal should be developed during the initial encounter in patients with severe symptoms, and, if successful, can eliminate obstruction, and should significantly reduce the incidence of PTS. We and others have observed that successful elimination of thrombus can preserve venous valve function.

Experimental observations in canine models of acute DVT have shown that successful thrombolysis preserves endothelial function and valve competence. ^, These experimental observations appear to translate into improved clinical outcomes when put into the perspective of natural history studies of acute DVT treated with anticoagulation alone. Investigators have found that distal valve incompetence can develop in patients with persistent venous obstruction treated with anticoagulation alone, even when the distal veins are not initially involved with thrombus. When spontaneous lysis occurred, defined as clot resolution within 90 days, valve function was frequently preserved. These investigators confirmed that the combination of valvular incompetence and venous obstruction was associated with the most severe post-thrombotic morbidity. ^, It is intuitive that elimination of acute venous thrombus restores luminal patency and increases the likelihood that valve function will be preserved.

Recurrence

An underappreciated but important benefit of successful thrombus removal is the reduction in the rate of recurrent DVT. As mentioned earlier, patients with IFDVT have an exceptionally high recurrence rate compared with those having less extensive thrombosis. ^, Hull et al. performed a systematic review and showed that treated patients with a large thrombus burden had a greater risk of recurrence than those with a smaller thrombus burden. As noted previously, Baekgaard and colleagues observed an unexpectedly low 3-year recurrence after CDT for IFDVT. Aziz and Comerota observed that patients with IFDVT treated with catheter-directed techniques appeared to have a low recurrence rate. Upon further analysis, the benefit accrued to those patients who had successful thrombus removal, whereas those with the bulk of the thrombus remaining (unsuccessful lysis) had a significantly higher recurrence rate.

Valve Function

Vogel et al. addressed the issue of whether pharmacomechanical techniques compromised valve function, presumably due to direct valve injury. In a sequential analysis of CDT versus pharmacomechanical thrombolysis (PMT), there did not appear to be any adverse effect on valve function. The important observations were that valves functioned best in patients who had successful thrombolysis. An interesting observation was that 35% of the veins in the noninvolved limbs had incompetent valves. This suggests that in a third of patients, valve dysfunction predates the onset of the acute DVT. This was confirmed in a prospective, nested case-controlled study.