Pulmonary embolism resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Rim Halaby; Pratik Bahekar, MBBS [2]; Chetan Lokhande, M.B.B.S [3]

Pulmonary embolism Resident Survival Guide Microchapters
Overview
Causes
FIRE
Diagnosis
Treatment
Do's
Don'ts

Overview

Pulmonary embolism (PE) is an acute obstruction of the pulmonary artery (or one of its branches). The obstruction in the pulmonary artery can be due to thrombus, air, tumor, or fat. Most often, this is due to a venous thrombosis (blood clot from a vein), which has been dislodged from its site of formation in the lower extremities. It has then embolized to the arterial blood supply of one of the lungs. This process is termed thromboembolism. PE is a potentially lethal condition. The patient can present with a range of signs and symptoms, including dyspnea, chest pain while breathing, and in more severe cases collapse, shock, and cardiac arrest. Pulmonary embolism can be classified based on the time course of symptom presentation (acute and chronic) and the overall severity of disease (stratified based upon three levels of risk: massive, submassive, and low-risk). PE treatment requires rapid and accurate risk stratification before the development of hemodynamic collapse and cardiogenic shock. Treatment consists of an anticoagulant medication, such as heparin or warfarin, and in severe cases, thrombolysis or surgery.

Causes

Life Threatening Causes

Life-threatening causes include conditions which result in death or permanent disability within 24 hours if left untreated.

• DVT
• Injury

Common Causes

• Antiphospholipid syndrome
• Antithrombin deficiency
• Factor V Leiden
• Hyperhomocysteinemia
• Long-distance air travel
• Malignancy
• Nephrotic syndrome
• Obesity
• Post surgery
• Pregnancy
• Protein C deficiency
• Protein S deficiency
• Prothrombin mutation

Classification

Pulmonary embolism can be classified based on the time course of symptom presentation (acute and chronic) and the overall severity of disease (stratified based upon three levels of risk: massive, submassive, and low-risk).

Massive Pulmonary Embolism

• An acute pulmonary embolism with:
  • Sustained hypotension (systolic blood pressure <90 mm Hg) for at least 15 minutes or requiring inotropic support. This is not due to other possible causes of hypotension such as arrhythmia, hypovolemia, sepsis, or left ventricular dysfunction.
  • Pulselessness
  • Persistent profound bradycardia (heart rate < 40 bpm with signs or symptoms of shock).

Submassive Pulmonary Embolism

An acute PE without systemic hypotension (systolic blood pressure >90 mm Hg) but with either, right ventricular dysfunction or myocardial necrosis.

1. Right ventricular dysfunction: It is defined by the presence of at least one of the following features,
   • Echocardiography findings:
     1. RV dilation (apical 4-chamber RV diameter divided by LV diameter > 0.9)
     2. RV systolic dysfunction
   • CT findings: RV dilation (4-chamber RV diameter divided by LV diameter > 0.9)
   • BNP > 90 pg/mL
   • N-terminal pro-BNP >500 pg/mL
   • EKG findings:
     1. New complete or incomplete right bundle-branch block
     2. Anteroseptal ST elevation or depression
     3. Anteroseptal T-wave inversion.
2. Myocardial necrosis: It is defined as the presence of either one of the following:
   • Elevation of troponin I (>0.4 ng/mL)
   • Elevation of troponin T (>0.1 ng/mL). .

Low-Risk Pulmonary Embolism

An acute pulmonary embolism without the life threatening clinical markers that define massive or submassive pulmonary emboli.

FIRE: Focused Initial Rapid Evaluation

A Focused Initial Rapid Evaluation (FIRE) should be performed to identify patients in need of immediate intervention.
Boxes in salmon color signify that an urgent management is needed.

Abbreviations: AVR: Aortic valve replacement; CK-MB: Creatine kinase myocardial type; ECG: Electrocardiogram; NSTEMI: Non ST elevation myocardial infarction; STEMI: ST elevation myocardial infarction; TTE: Transthoracic echocardiography

Identify cardinal findings that increase the pretest probability of pulmonary embolism ❑ Dyspnea at rest or with exertion ❑ Pleuritic pain ❑ Cough ❑ Tachycardia ❑ Accentuated P2 ❑ Wheezing ❑ Tachypnea ❑ Syncope ❑ Decreased breath sounds ❑ Calf or thigh pain and swelling ❑ Edema, erythema, tenderness, or a palpable cord in the calf or thigh ❑ Recurrent miscarriage in a previously pregnant female

Does the patient have any of the following findings of massive pulmonary embolism that require urgent management? ❑ >2- Pillow orthopnea ❑ Hypotension ❑ Jugular venous distension ❑ Right-sided S3 ❑ Parasternal lift ❑ EKG demonstrates, ❑ Atrial arrhythmias ❑ Right bundle branch block ❑ Inferior Q-waves ❑ Precordial T-wave inversion and ST-segment changes

Yes

No

❑ Perform D-dimer, level <500 ng/mL excludes the diagnosis in low pretest probability ❑ Erythrocyte agglutination assay (takes upto 2 min) ❑ Semi-quantitative latex agglutination assay (takes upto 5 min) ❑ Semi-quantitative rapid ELISA (takes upto 10 min) ❑ Qualitative rapid ELISA (takes upto 10 min) ❑ Quantitative latex agglutination assay (takes upto 15 min) ❑ Quantitative rapid ELISA (takes upto 30 min) ❑ CT Pulmonary angiography ❑ V/Q scan ❑ Normal V/Q scan excludes PE ❑ High clinical probability with high-probability V/Q scan has 95% chance of having PE ❑ Low clinical probability with low-probability V/Q scan has 4% chance of having PE

Proceed to the complete diagnostic approach below

Complete Diagnostic Approach

A complete diagnostic approach should be carried out after a focused initial rapid evaluation is conducted and following initiation of any urgent intervention.

Step 1: Establish The Diagnosis Of Pulmonary Embolism

In hospitals that have experience in performing and interpreting CT pulmonary angiography, the following flowchart approach can be adopted.

Determine chances of PE

Low chance

High chance

D-dimer

<500 ng/ml

>500 ng/ml

CT Pulmonary angiography

PE excluded

Negative

Positive

PE excluded

PE confirmed

Note: If there is a high clinical suspicion of pulmonary embolism, then anticoagulation can begin with a parenteral agent such as unfractionated heparin during the process of performing the diagnostic studies.

Treatment

Step 2: Use A Risk-Stratified Approach to Treat the Patient with Pulmonary Embolism

Confirmed PE

Assess Clinical Stability

Unstable

Stable

Blood pressure ≦ 90mm Drop in BP ≧ 40mm for > 15 min

Assess RV function Biomarkers of injury

Thrombolysis Catheter embolectomy Surgery

No Dysfunction + No injury

Dysfunction + No injury

Dysfunction + Injury

Anticoagulation Early discharge

Anticoagulation Ward admission

Thrombolytics ICU admission

Step 3: Assess Treatment Response and Need for Device Based Therapy

Acute PE confirmed

Anticoagulation contraindicated ?

Yes

No

IVC filter

Risk stratification

Low-risk PE

Submassive PE

Massive PE

Anticoagulation

Anticoagulation

Assess clinically for evidence of increased severity

Evidence of shock (SBP <90 mmHg) or respiratory failure

Is thrombolytic contraindicated?

Yes

No

Surgical emblectomy or catheter based interventions

Hold anticoagulation, give thrombolytics then resume anticoagulations

Patient shows clinical improvement

No

Yes

Surgical emblectomy or catheter based interventions

Continue anticoagulation

Do's

Don'ts

References