DVT/ Pulmonary Embolism
DVT
Blood clot in deep vein of the legs (90% proximal i.e. femoral vein and 10% distal i.e. posterior tibial vein)
Management
- Proximal DVT: Anticoagulate (Heparin, Warfarin, LMWH, DOAC). If contraindications, then IVC filter
- Massive proximal DVT: Thrombolytics or surgical thrombectomy
- Distal DVT: Anticoagulate (if contraindications the observe closely with ultrasound)
Risk Stratify
Commonly done using the Wells Score for DVT
Wells' Criteria for DVT
Pulmonary Embolism
Embolization of thrombus into pulmonary vasculature
Risk Stratification
| Classification of PE by Severity | Criteria |
|---|---|
| Massive PE | - Sustained hypotension (systolic blood pressure <90 mm Hg), not due to arrhythmia, hypovolemia, sepsis, or left ventricular dysfunction, and either lasting for at least 15 minutes or necessitating the administration of inotropes - Pulselessness - Persistent profound bradycardia (heart rate < 40 bpm) plus findings of shock |
| Submassive PE | - Right ventricular dysfunction OR myocardial necrosis - Absence of systemic hypotension (systolic blood pressure >90 mm Hg) |
| Low-risk PE | - Absence of hypotension, shock, right ventricular dysfunction, and myocardial necrosis |
Wells' Criteria for PE
Anticoagulation
Starting anticoagulation early is important. Typically, unfractionated heparin (UFH) is preferred because of its short half-life and reversibility. The dosing is usually as follows:
- Loading dose: 80 units/kg bolus
- Maintenance dose: 18 units/kg/hr
Monitor activated partial thromboplastin time (aPTT) with a goal of 1.5-2.5 times the upper limit of normal.
If the patient is at a high risk of bleeding, consider using a lower dose of UFH or choosing an alternative anticoagulant with a shorter half-life
Definitive Treatment
- Thrombolysis: This involves administering medication to dissolve the blood clot. The most commonly used medication is tissue plasminogen activator (tPA). The typical dose is 100 mg over 2 hours. However, the dose may need to be adjusted depending on the patient's condition, the size of the clot, and the risk of bleeding.
- Mechanical thrombectomy: This procedure involves inserting a catheter into the blood vessels to physically remove the clot. It's typically reserved for patients who are not candidates for thrombolysis or in whom thrombolysis has failed.
- Surgical embolectomy: This involves surgically removing the clot. It's generally reserved for patients who are not candidates for thrombolysis or mechanical thrombectomy, or in whom these therapies have failed
Contraindications for Thrombolysis
| Contraindications for Thrombolysis | Type of Contraindication |
|---|---|
| Brain/Spinal Cord Pathology | |
| Hemorrhagic CVA | Absolute |
| Ischemic CVA (within 3 months) | Absolute |
| Known vascular lesion (e.g., arteriovenous malformation) | Absolute |
| Recent brain or spinal surgery | Absolute if recent |
| Ischemic CVA (after 3 months) | Relative |
| CNS tumor | Relative |
| Diabetic retinopathy | Relative |
| Trauma/Surgery/Procedure | |
| Recent head trauma with fracture or brain injury (within 3 weeks) | Absolute |
| Major non-CNS surgery (within 2-3 weeks) | Relative |
| Recent puncture of non-compressible vessel | Relative |
| Bleeding History | |
| Serious active bleeding, excluding menses | Absolute |
| Recent internal bleeding (within 4 weeks) | Relative |
| Known coagulopathy | Relative |
| Coagulation Studies | |
| Platelets < 100,000 | Relative |
| Warfarin use with INR >1.7 | Relative |
| Fibrinogen <150 mg/dL | Relative |
| Anticoagulants | |
| Oral anticoagulation | Relative |
| Use of multiple anticoagulants, such as antiplatelet agents | Relative |
| Hypertension (HTN) | |
| History of chronic, severe, poorly controlled HTN | Relative |
| Blood pressure on presentation >180 systolic or >110 diastolic | Relative |
| Age | |
| Over 65-75 years old | Relative |
| Dementia | Relative |
| Specific Situations | |
| Pregnancy or first week postpartum | Relative |
| Infectious endocarditis | Relative |
| Advanced cirrhosis | Relative |
Ideal Fluid Balance in Massive PE
Excess preload may worsen right ventricular (RV) dilation, impairing cardiac function. In massive PE, most patients already have elevated filling pressures due to a failing RV. The potential risks of fluid generally outweigh the benefits in these patients
- Evaluate with ultrasound.
- If clear evidence of hypovolemia (e.g., small inferior vena cava (IVC) with respirophasic variation), give fluid judiciously and in small amounts.
- A small IVC should rarely occur in massive PE. If a small IVC is observed, carefully consider if the patient truly has a massive PE.
- If the IVC is dilated, do not give fluid.
- If the patient has already received a substantial volume of fluid, consider diuresis.
Inotropes & Vasopressors
Epinephrine is generally the front-line agent for inotropy in massive PE. It has beta-agonist activity that may cause pulmonary vasodilation, improves right ventricular contractility, and can block brady-asystolic arrest. Establishing an adequate mean arterial pressure (>65 mmHg) supports right ventricular function.
Vasopressin may be used as a second-line agent. It causes systemic vasoconstriction while causing pulmonary vasodilation, making it beneficial in pulmonary hypertension. The typical dose range is similar to sepsis dosing (0-0.06 U/min).
Inhaled Pulmonary Vasodilators
Inhaled pulmonary vasodilators may help improve oxygenation by enhancing ventilation-perfusion matching and improve hemodynamics by reducing afterload on the right ventricle. They counteract the vasoconstrictors released in response to the clot in PE
Interventional Radiology
Catheter-Directed Thrombolysis: catheters are placed into the pulmonary arteries to deliver a clot-dissolving medication called tissue plasminogen activator (tPA) directly to the site of the clot. However, there is limited evidence supporting the superiority of catheter-directed thrombolysis over peripheral administration of tPA
The traditional dose of tPA for catheter-directed thrombolysis is 0.5-1 mg/hour per catheter, totaling 12-24 mg delivered over 24 hours
Percutaneous Mechanical Thrombectomy: involves physically removing the clot using various devices. This approach is particularly useful for patients with high-risk submassive or massive pulmonary embolism (PE) who cannot undergo thrombolysis or have failed to respond to thrombolysis
Several devices are available for mechanical thrombectomy, including the Inari FlowTriever system, Penumbra Indigo embolectomy system, AngioVac, and AngioJet.
Surgical Thrombectomy: Surgical thrombectomy, previously considered a risky and ineffective procedure, has experienced a resurgence in the past decade. It can be considered for specific indications, such as patients with clot-in-transit across a patent foramen ovale (PFO) or those with massive PE and contraindications to thrombolysis
IVC Filter
There is insufficient evidence supporting the use of IVC filters, particularly in the context of submassive PE. The PREPIC-2 study, which evaluated IVC filter use in patients with large PE on anticoagulation, showed a trend towards harm.
IVC filters should be approached cautiously, considering the potential risks and benefits. If an IVC filter is used, a retrievable filter should be chosen and removed as soon as possible. Unfortunately, retrieval rates are low, and prolonged filter implantation increases the risk of complications.