Page 2362 - Hematology_ Basic Principles and Practice ( PDFDrive )

2104 Part XII Hemostasis and Thrombosis

PROGNOSIS OF VENOUS THROMBOEMBOLISM on walking. When symptoms are acute or subacute in onset, a
diagnosis of postthrombotic syndrome should be considered only
Untreated or inadequately treated VTE is associated with a high after recurrent DVT has been excluded by objective testing. There is
complication rate, which can be decreased markedly by adequate no single definitive diagnostic test for the postthrombotic syndrome,
anticoagulant therapy. Approximately 20% of untreated asymptom- but a history of objectively documented DVT, appropriate clinical
atic calf vein thrombi and 20%–30% of untreated symptomatic calf findings, and evidence of venous reflux or outflow obstruction on
vein thrombi extend into the popliteal vein; in the majority of cases venous ultrasonography constitute sufficient evidence to make this
this occurs within 1 week. When extension occurs and is untreated, diagnosis.
it is associated with a 40%–50% risk of clinically detectable PE. The frequency with which postthrombotic syndrome occurs after
Patients with proximal DVT who receive inadequate treatment have VTE is controversial, with contemporary studies reporting incidence
a 47% risk of recurrent VTE over 3 months. Approximately 10% of rates of 20%–80%. Severe postthrombotic syndrome occurs in
symptomatic PE cases are estimated to be fatal within 1 hour of approximately 5%–10% of patients. Risk factors for postthrombotic
symptom onset. Anticoagulant therapy reduces the mortality associ- syndrome include proximal location of thrombosis (especially femoral
ated with PE; without therapy, mortality rates are as high as 30%. or iliac veins), ipsilateral recurrent thrombosis, older age, obesity, and
Clinically detectable recurrence occurs in fewer than 3% of patients inadequate anticoagulant treatment.
with proximal DVT during anticoagulant therapy. The most impor- Postthrombotic syndrome can cause significant disability and
tant determinant of VTE recurrence following discontinuation of impairs quality of life. The clinical severity of postthrombotic syn-
anticoagulant therapy is the presence or absence of identifiable risk drome can be assessed using the Villalta scale, a validated scoring
factors at diagnosis. VTE associated with transient surgical or non- system. Treatment for acute DVT may reduce the long-term risk of
surgical risk factors are associated with lower rates of VTE recurrence postthrombotic syndrome. In addition, there is conflicting evidence
compared with those that are unprovoked (idiopathic). After 3 regarding the effectiveness of below-knee graduated compression
months of treatment for VTE associated with a transient surgical or stockings for reducing the risk of postthrombotic syndrome in
nonsurgical (e.g., exogenous hormone use, immobility) risk factor, patients with DVT. Other conservative measures may include exer-
12-month VTE recurrence rates are 1% and 5%, respectively. Sub- cise, limb elevation, compression bandages, pharmacologic manage-
sequent recurrence rates are 0.5% and 2.5% per year. In contrast, the ment of edema, and careful attention to skin care.
recurrence rate after at least 3 months of anticoagulant therapy for a
first episode of unprovoked VTE is approximately 10% within the
first 12 months and 5% per year thereafter. Patients with malignancy Chronic Thromboembolic Pulmonary Hypertension
and those with a second episode of unprovoked VTE have high
recurrence rates, up to 15% within 12 months and 7.5% per year Chronic thromboembolic pulmonary hypertension (CTEPH) is a
thereafter following anticoagulant discontinuation. rare complication typically occurring within 2 years of acute PE.
Patients with CTEPH present with exertional dyspnea that may
LONG-TERM COMPLICATIONS OF VENOUS progress to dyspnea at rest. With worsening pulmonary hypertension,
patients may report signs or symptoms of right ventricular dysfunc-
THROMBOEMBOLISM tion such as lower extremity edema. CTEPH should be considered
in patients presenting with signs and symptoms consistent with
Postthrombotic Syndrome pulmonary hypertension, especially if they have a history of VTE or
risk factors for VTE.
The postthrombotic syndrome is caused by venous hypertension, Echocardiography is a useful, noninvasive method of evaluating
usually resulting from valve damage. Valve damage results in malfunc- estimated systolic pulmonary artery pressure, right atrial enlarge-
tion of the muscular pump mechanism, which leads to increased ment, right ventricular systolic dysfunction, and septal displacement
pressure in the deep calf veins during ambulation. The high pressure suggesting pulmonary hypertension. Ventilation/perfusion (V/Q)
ultimately renders the perforating veins of the calf incompetent, so lung scanning has higher sensitivity for CTEPH than computed
that blood flow is directed from the deep veins into the superficial tomography (CT) pulmonary angiogram and is the preferred initial
venous system during muscular contraction. This leads to edema and diagnostic test in this setting. Subsequent CT pulmonary angiogram
impaired viability of subcutaneous tissues and, in its most severe is then used to exclude competing diagnoses that can cause perfusion
form, to venous ulceration. Outflow obstruction initially may be defects on V/Q scanning.
bypassed by the development of collateral veins, but with time, the Medical therapy for CTEPH includes anticoagulation, and pul-
veins distal to the obstruction become dilated, and their valves monary vasodilatory and remodeling therapies that are not curative
become incompetent. and modestly improve symptoms. Medical therapy is administered at
In patients whose thrombosis extends into the iliofemoral veins, specialized centers and is reserved for patients who are not surgical
the leg swelling at initial presentation may not resolve entirely. This candidates or as a bridge to surgical intervention. Surgical manage-
is in contrast to patients with less extensive proximal vein thrombosis, ment with pulmonary thromboendarterectomy is the only potentially
in whom the swelling may subside after initial treatment but recur curative treatment option and is conducted at specialized centers.
months or years later. Other symptoms and signs of the postthrom-
botic syndrome may be delayed for 5–10 years after the initial
thrombotic event. These symptoms include pain in the calf that is DIAGNOSIS OF VENOUS THROMBOEMBOLISM
relieved with rest and leg elevation, skin pigmentation and induration
around the ankle and lower third of the calf, and ulceration in the The diagnosis of VTE is based on objective testing as opposed to
region of the medial malleolus. clinical assessment, which may be subjective.
Patients with extensive thrombosis involving the iliofemoral vein
frequently have greater disability and may have venous claudication,
characterized by incapacitating, bursting pain with exercise. This Deep Venous Thrombosis
complication rarely occurs in patients with thrombosis involving the
more distal veins. Clinical Manifestations
The clinical spectrum of the postthrombotic syndrome varies
from a course that may mimic acute DVT to one of persistent leg DVT classically causes swelling, pain, and erythema of the affected
pain that is worse at the end of the day and is associated with extremity. Proximal vein lower extremity DVT is more likely to be
dependent edema, stasis pigmentation, and, in its most severe form, symptomatic than calf vein thrombosis. Patients with massive throm-
skin ulceration. Rarely, patients may complain of venous claudication bosis involving the iliac and femoral veins may present with