How to rule out pulmonary embolism

How-to rule-out
pulmonary embolism
Michael Aref, MD, PhD
Hospitalist, Carle Physician Group
Adjunct Assistant Professor, Department of Nuclear, Plasma, and Radiological
Engineering, UIUC
Clinical Instructor, Department of Medicine, UICOM-UC

Objectives
• Risk Factors
• Signs and Symptoms
• Laboratory Findings
• Diagnostic Test Findings
• Clinical Pretest Probability
• Imaging Modalities
• Low Pretest Probability
• Medium Pretest Probability
• High Pretest Probability
• Special Cases
• Empiric Anticoagulation

Strong (OR > 10)
Patient-related Setting-related

• Hip or leg fracture

• Hip or knee replacement

• Major general surgery

• Major trauma

• Spinal cord injury

European Society of Cardiology Guidelines on the Diagnosis and Management of Acute Pulmonary Embolism, European Heart Journal (2008) 29:2276-2315

Moderate (OR 2-9)

• Chronic heart failure • Arthroscopic knee surgery
• Chronic respiratory failure
• Hormone replacement / oral • Central venous lines
contraceptive therapy

• Malignancy • Chemotherapy

• Paralytic stroke
• Pregnancy/postpartum
• Previous VTE
• Thrombophilia


Weak (OR < 2)

• Increasing age • Bed rest > 3 days

• Obesity • Immobility due to sitting
(i.e. prolonged travel)
• Pregnancy/antepartum
• Laparoscopic surgery
• Varicose veins


Sx PE conﬁrmed PE excluded
(n = 219) (n = 546)
Dyspnea 80% 59%

Pleuritic chest pain 52% 43%

Substernal pain 12% 8%

Cough 20% 25%

Hemoptysis 11% 7%

Syncope 19% 11%


PE conﬁrmed PE excluded
Signs
(n = 219) (n = 546)
Tachypnea
70% 68%
(≥ 20/min)
Tachycardia
26% 23%
(≥ 100/min)

Signs of DVT 15% 10%

Fever
7% 17%
(> 38.5°C)

Cyanosis 11% 9%


• Respiratory alkalosis on ABG
• Hypoxemia not corrected with tachypnea
(hypoxemia + hypocapnia + elevated pH)
• Increased A-a gradient
• 20% of pulmonary embolism without
signiﬁcant A-a gradient or hypoxemia
• Elevated BNP
• Increased right ventricular strain
• Positive troponin
• Myocardial ischemia (?diffuse hypoxic injury/
cardiac strain/prothrombotic state)


CXR
• Atelectasis
• Parenchymal inﬁltrates
• Elevated diaphragm
• Enlarged hilum
• Enlarged mediastinum
• Cardiomegaly
• Pleural effusion
• Oligemia (Westermark’s sign)
• Prominent central pulmonary artery (Fleischer’s sign)
• Pleural-based area of increased opacity (Hampton’s hump)
• Pulmonary edema

www.ebmedicine.net

Westermark’s sign

www.wikiradiography.com

Hampton’s hump

emedicine.medscape.com

EKG

• RV strain
• T-wave inversion in V -V 1 4

• QR in V 1

• New RBBB (incomplete/complete)
• SQ T I III III


SIQIIITIII

3.bp.blogspot.com

Clinical Pretest
Probability

Canadian rule
• Patient has clinical features
compatible with pulmonary Probability Factors
embolism deﬁned as:
Dyspnea and/or tachypnea
± hemoptysis
High (a) and (b)
± pleuritic chest pain

• And two other factors: Intermediate (a) or (b)
(a) absence of another reasonable
clinical explanation
Low no
(b) presence of a major risk factor

British Thoracic Society Guidelines for the Management of Suspected Acute Pulmonary Embolism, Thorax (2003) 58:470-484

Modiﬁed Well’s Score
Previous VTE 1.5
Recent surgery or immobilization 1.5
Cancer 1.5
Hemoptysis 1
HR > 100/min 1.5
Signs of DVT 3
Alternative diagnosis less likely than PE 3

Thromb Haemost (2000) 83:416–420
Ann Intern Med. (2001) 135:98–107

Modiﬁed Well’s Score
3 level clinical probability
Low 0-1
Intermediate 2-6
High ≥7

2 level clinical probability
PE unlikely ≤4
PE likely >4
Thromb Haemost (2000) 83:416–420
Ann Intern Med. (2001) 135:98–107

Revised Geneva Score
Age > 65 years old 1
Previous VTE 3
Surgery or fracture within 1 month 2
Active malignancy 2
Unilateral lower limb pain 3
Hemoptysis 2
HR 75-94/min 3
HR ≥ 95/min 5
Pain on lower limb deep vein palpation and unilateral edema 4

Annals of Internal Medicine (2006) 144:165–171

Revised Geneva Score

Low ≤3

Intermediate 4-10

High ≥11

Annals of Internal Medicine (2006) 144:165–171

CT Angiogram

• Cost: $1739
• Effective Whole Body Radiation Dose:
1.6-8.3 mSv
• ACR Appropriateness Criteria Rating 9

Diagnostic Pathways in Acute Pulmonary Embolism: Recommendations of the PIOPED II Investigators, American Journal of Medicine (2006) 119:1048-1055
acsearch.acr.org

CT Angiogram /
CT Venogram
• Effective Whole Body Radiation Dose: an additional
5.7 mSv

• First line imaging test

• Radiation dosing can be limited by limiting
venography to femoral and popliteal veins

• ACR Appropriateness Criteria Rating 7 (if
suspicion for DVT is high and/or if US
inconclusive)

acsearch.acr.org

Pulmonary Scintigraphy
• Cost: $917

• Effective Whole Body Dose: 1.2-2.0 mSv

• In pregnant women and women of reproductive
age this may be the imaging modality of choice

• ACR Appropriateness Criteria Rating 6 (If chest x-
ray is negative and CTA is contraindicated or
nondiagnostic)

acsearch.acr.org

Venous Ultrasound
• Cost: $631

• No radiation

• Detects DVT in 13-15% of suspected pulmonary
embolism

• Detects DVT in 29% of proven pulmonary
embolism

• ACR Appropriateness Criteria Rating 7 (if CXR
negative and strong clinical suspicion)

acsearch.acr.org

Low Clinical Pretest
Probability

(-)ve
(+)ve D-dimer
D-dimer

CT Angiogram
CT Angiogram / CT Venogram (femoral and popliteal veins)

Negative Positive
NPV 96% PPV 58%
NPV 97% PPV 57%

Segmental PPV 68%
Main or Lobar PPV 97%
Subsegmental PPV 57%

No Rx No Rx * Rx


*Options
• Repeat CT Angiogram or CT Angiogram/Venogram
if Poor Quality
• If CT Angiography only
• Venous Ultrasound
• MRI Venography
• Pulmonary Scintigraphy
• Digital Subtraction Angiography
• Serial Ultrasound


Intermediate
Clinical Pretest
Probability

(-)ve
(+)ve D-dimer
D-dimer

CT Angiogram

CT Angiogram / CT CT Angiogram Positive
Venogram Negative Negative PPV 92%
NPV 92% NPV 89% PPV 90%

No Rx No Rx * Rx


*Options
• Repeat CT Angiogram or CT Angiogram/Venogram
if Poor Quality
• MRI Venography
• Pulmonary Scintigraphy
• Digital Subtraction Angiography
• Serial Venous Ultrasound


High
Clinical Pretest
Probability

CT Angiogram

Negative Positive
NPV 60% PPV 96%
NPV 82% PPV 96%

* Rx


*Options

• MRI Venography


Allergy to Iodinated
Contrast
• D-dimer if low or intermediate clinical pretest
probability

• Mildly allergic patients may be treated with
corticosteroids prior to CT imaging

• Severely allergic patients should be imaged with
venous ultrasound and pulmonary scintigraphy

• Options include serial venous ultrasound or
gadolinium-enhanced CT angiography


Impaired Renal
Function
probability

• Venous ultrasound and if positive, treatment is
indicated

• Pulmonary scintigraphy if venous ultrasound is
negative

• Options: serial venous ultrasound


Pregnancy

probability

• Venous ultrasound and if positive, treatment is
indicated

• Pulmonary scintigraphy = CT angiogram for
radiation dose, equivocal recommendations


Hemodynamically
Unstable
• Bedside echocardiography and venous
ultrasonography
• RV enlargement or poor right ventricular function,
in an appropriate clinical setting, can be interpreted
as positive for pulmonary embolism
• Positive venous ultrasound, in an appropriate
clinical setting, can be interpreted as positive for
pulmonary embolism
• If the combination of the above negative, CT
angiography indicated when the patient stabilizes


• Low Clinical Pretest Probability

• No recommendations

• Intermediate Clinical Pretest Probability

• Therapeutic anticoagulation may be appropriate

• High Clinical Pretest Probability

• Initiate therapeutic anticoagulation


Pulmonary Embolism
Rule-out Criteria

J Thromb Haemost. 2010 Nov 22. doi: 10.1111/j.1538-7836.2010.04147.x. [Epub ahead of print]

The Pulmonary Embolism Rule-out Criteria (PERC) rule does not safely exclude pulmonary
embolism.
Hugli O, Righini M, Le Gal G, Roy PM, Sanchez O,Verschuren F, Meyer G, Bounameaux H, Aujesky D.
Emergency Department, University Hospital of Lausanne University, CHUV-Lausanne, Switzerland Division of Angiology and Hemostasis, Department of Internal Medicine, Geneva
University Hospital and Faculty of Medicine, Geneva, Switzerland Université Européenne de Bretagne, EA3878 (GETBO), Université de Brest, INSERM CIC 0502, CHU de la Cavale
Blanche, Brest Cedex, France Centre Hospitalier Universitaire d'Angers, Service des Urgences, Angers Cedex 9, France Service de Pneumologie et Soins Intensifs, Hôpital Européen
Georges Pompidou, Paris, France Université catholique de Louvain, Cliniques universitaires Saint-Luc, Acute Medicine Department, Accidents and Emergency Unit, Brussels, Belgium
Université Paris Descartes; APHP. Hôpital Européen Georges Pompidou, Service de pneumologie, Paris, France Division of Angiology and Hemostasis, Department of Internal Medicine,
Geneva University Hospital and Faculty of Medicine, Geneva, Switzerland Division of General Internal Medicine, Ofﬁce: PKT2, D 562, Bern University Hospital, Bern, Switzerland.
Abstract
Background: The Pulmonary Embolism Rule-out Criteria (PERC) rule is a clinical diagnostic rule designed to exclude pulmonary embolism (PE) without further testing.
We sought to externally validate the diagnostic performance of the PERC rule alone and combined with clinical probability assessment based on the revised Geneva
score. Methods: The PERC rule was applied retrospectively to consecutive patients who presented with a clinical suspicion of PE to six emergency departments, and
who were enrolled in a randomized trial of PE diagnosis. Patients who met all eight PERC criteria (PERC((-)) ) were considered to be at very low risk for PE. We
calculated the prevalence of PE among PERC((-)) patients according to their clinical pretest probability of PE. We estimated the negative likelihood ratio of the PERC
rule to predict PE. Results: Among 1,675 patients, the prevalence of PE was 21.3%. Overall, 13.2% of patients were PERC((-)) . The prevalence of PE was 5.4% (95% CI:
3.1 - 9.3%) among PERC((-)) patients overall and 6.4% (95% CI: 3.7 - 10.8%) among those PERC((-)) patients with a low clinical pretest probability of PE. The PERC rule
had a negative likelihood ratio of 0.70 (95% CI: 0.67 - 0.73) for predicting PE overall, and 0.63 (95% CI: 0.38-1.06) in low-risk patients. Conclusions: Our results suggest
that the PERC rule alone or even when combined with the revised Geneva cannot safely identify very low risk patients in whom PE can be ruled out without additional
testing, at least in populations with a relatively high prevalence of PE.

How to rule out pulmonary embolism

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