5.6 Pulmonary Embolism: Diagnosis, Risk Stratification & Anticoagulation

ABIM Internal Medicine Exam

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1 Chapter 0: The ABIM Exam, Blueprint & Study Strategy

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2 Chapter 1: Cardiovascular Disease (14% of Exam)

1.1 Ischemic Heart Disease & Acute Coronary Syndromes 1.2 Antithrombotic Therapy, Secondary Prevention & Mechanical Complications of MI 1.3 Atrial Fibrillation, Atrial Flutter & Stroke Prevention 1.4 Supraventricular Tachycardias, Ventricular Arrhythmias & Bradycardias 1.5 Heart Failure: Classification, Staging & Guideline-Directed Medical Therapy 1.6 Device Therapy, HFpEF & the Cardiomyopathies 1.7 Valvular Heart Disease & Endocarditis Prophylaxis 1.8 Pericardial Disease & Acute Aortic Syndromes 1.9 Hypertension: Classification, Diagnosis & Secondary Causes 1.10 Hypertensive Crises & Dyslipidemia 1.11 Adult Congenital Heart Disease & Coarctation of the Aorta 1.12 Syncope: Reflex, Orthostatic & Cardiac Causes 1.13 Cardiac Physical Examination, Murmurs & Antithrombotic Selection

3 Chapter 2: Endocrinology, Diabetes & Metabolism (9% of Exam)

2.1 Diabetes Mellitus: Diagnosis, Glycemic Targets & Pharmacotherapy 2.2 Insulin Therapy, Hyperglycemic Emergencies & Chronic Complications 2.3 Thyroid Function Testing & Hypothyroidism 2.4 Thyrotoxicosis, Thyroid Storm & Thyroid Nodules 2.5 Adrenal & Pituitary Disorders 2.6 Hypercalcemia, Hypocalcemia & Disorders of Mineral Metabolism 2.7 Osteoporosis & Paget Disease of Bone 2.8 Ovarian, Testicular & Reproductive Endocrine Disorders 2.9 Hypoglycemia, Endocrine Tumors, Polyglandular Syndromes & Severe Hypertriglyceridemia

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3.1 Esophageal Disease 3.2 Stomach & Duodenal Disease and Gastrointestinal Hemorrhage 3.3 Inflammatory Bowel Disease 3.4 Celiac Disease & Irritable Bowel Syndrome 3.5 Diverticular Disease & Colorectal Cancer Screening 3.6 Viral Hepatitis, Steatotic & Alcohol-Associated Liver Disease 3.7 Cirrhosis & the Complications of Portal Hypertension 3.8 Acute Pancreatitis 3.9 Chronic Pancreatitis & Biliary Tract Disease 3.10 Inherited, Autoimmune & Drug-Induced Liver Disease 3.11 Small Intestinal Disease, Ischemia & Gastrointestinal Complications of HIV

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6 Chapter 5: Pulmonary Disease (9% of Exam)

5.1 COPD: Diagnosis, GOLD Classification & Initial Pharmacotherapy 5.2 Interventions That Reduce COPD Mortality & Exacerbation Management 5.3 Asthma: Diagnosis, Stepwise Therapy & Status Asthmaticus 5.4 Interstitial Lung Disease & Idiopathic Pulmonary Fibrosis 5.5 Sarcoidosis, Hypersensitivity Pneumonitis & Occupational Lung Disease 5.6 Pulmonary Embolism: Diagnosis, Risk Stratification & Anticoagulation 5.7 Pulmonary Hypertension & Sleep-Disordered Breathing 5.8 Acute Respiratory Distress Syndrome & Mechanical Ventilation 5.9 Pleural Disease, Empyema & Pneumothorax 5.10 Bronchiectasis, Cystic Fibrosis & Restrictive Lung Disease 5.11 Evaluation of Cough, Dyspnea, Hemoptysis & the Solitary Pulmonary Nodule

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6.1 Rheumatoid Arthritis: Diagnosis & Systemic Manifestations 6.2 Antirheumatic Pharmacotherapy & the Spondyloarthropathies 6.3 Gout: Pathophysiology & Acute Management 6.4 Urate-Lowering Therapy & Calcium Pyrophosphate Deposition Disease 6.5 Osteoarthritis 6.6 Systemic Lupus Erythematosus 6.7 Systemic Sclerosis, Sjogren Syndrome & Inflammatory Myopathies 6.8 The Vasculitides 6.9 Regional Musculoskeletal Syndromes, Back Pain & Sports Injuries 6.10 Other Primary Rheumatic Disorders & Mixed Connective Tissue Disease 6.11 Osteonecrosis & Metabolic Bone Disease

8 Chapter 7: Hematology (6% of Exam)

7.1 Approach to Anemia & the Microcytic Anemias 7.2 Macrocytic, Normocytic & Hemolytic Anemias 7.3 Hemoglobinopathies, Thalassemias & Paroxysmal Nocturnal Hemoglobinuria 7.4 Platelet Disorders, Thrombocytopenia & the Bleeding Patient 7.5 Coagulation Factor Disorders, Thrombophilia & Anticoagulant Reversal 7.6 Acute Leukemias, Chronic Leukemias & Myeloproliferative Neoplasms 7.7 Lymphomas & Plasma Cell Disorders 7.8 Myelodysplastic Syndrome, Myeloproliferative Neoplasms & Porphyria 7.9 Transfusion Medicine & Late Complications of Transplantation

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10 Chapter 9: Nephrology & Urology (6% of Exam)

9.1 Acute Kidney Injury: Staging, Etiology & Urine Microscopy 9.2 Glomerular Disorders & Nephrotic Syndrome 9.3 Nephritic Syndromes, RPGN & Indications for Renal Replacement Therapy 9.4 Chronic Kidney Disease: Staging & Progression Retardation 9.5 Complications of Chronic Kidney Disease: Anemia, CKD-MBD & Acidosis 9.6 Hyponatremia, Hypernatremia & Water Balance 9.7 Potassium Disorders & Systematic Acid-Base Analysis 9.8 Renal Tubular Acidosis & Nephrolithiasis 9.9 Prostate Disorders, Urinary Incontinence & Other Urologic Conditions 9.10 Cystic Kidney Disease, Obstructive Uropathy, Tubulointerstitial Disease & Hematuria

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10.1 Acute Ischemic Stroke: Syndromes & Reperfusion 10.2 Transient Ischemic Attack, Secondary Prevention & Hemorrhagic Stroke 10.3 Headache & Facial Pain 10.4 Seizures, Epilepsy & Movement Disorders 10.5 Multiple Sclerosis & Neuromuscular Junction Disorders 10.6 Motor Neuron Disease & Acute Peripheral Neuropathy 10.7 Cranial Neuropathies & Neuro-Ophthalmology 10.8 Peripheral Neuropathies, CNS Tumors & Other Neurologic Disorders

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14 Chapter 13: Obstetrics & Gynecology / Women's Health (3% of Exam)

13.1 Contraception, Preconception Care & Teratogenicity 13.2 Hypertensive Disorders of Pregnancy & Gestational Diabetes 13.3 Thyroid Disease & Venous Thromboembolism in Pregnancy 13.4 Menopause & Menopausal Hormone Therapy 13.5 Abnormal Uterine Bleeding, Endometrial Disease & Gynecologic Cancer Screening 13.6 Breast Disorders & Diseases of the Vulva and Vagina 13.7 Menstrual Disorders, Fibroids, Endometriosis & Early Pregnancy Complications

15 Chapter 14: Geriatric Syndromes (3% of Exam)

14.1 Comprehensive Geriatric Assessment & Frailty 14.2 Falls, Gait Assessment & Polypharmacy 14.3 Urinary Incontinence & Pressure Injuries in Older Adults 14.4 Mild Cognitive Impairment, Dementia & Its Subtypes 14.5 Delirium & the Pharmacotherapy of Cognitive Disorders 14.6 Palliative Care, Hospice & Advance Care Planning 14.7 Chronic Wounds, Nutrition, Swallowing, Constipation & Hip Fracture 14.8 Sensory Impairment, Dizziness, Elder Mistreatment & Care Settings

16 Chapter 15: Allergy & Immunology (2% of Exam)

15.1 Anaphylaxis: Recognition & Emergency Management 15.2 Urticaria & Angioedema 15.3 Drug Allergy, Desensitization & Adult Immunodeficiency 15.4 Food Allergy, Insect Venom Hypersensitivity, Serum Sickness & Contrast Reactions 15.5 Rhinitis, Conjunctivitis, Eosinophilic & Mast Cell Disorders

17 Chapter 16: Preventive Medicine, Immunization & Clinical Epidemiology

16.1 The USPSTF Framework & Evidence-Based Cancer Screening 16.2 Cardiovascular & Metabolic Screening and Primary Prevention 16.3 Adult Immunization & Vaccines in Special Populations 16.4 Clinical Epidemiology, Biostatistics & Study Design

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17.1 Principles of Bioethics & Decisional Capacity 17.2 Informed Consent, Treatment Refusal & Special Scenarios 17.3 Surrogate Decision-Making, Advance Directives & Confidentiality 17.4 Patient Safety Science, Medical Error & Diagnostic Reasoning 17.5 Quality Improvement Methods, Health Disparities & Health Equity

19 Chapter 18: Perioperative Medicine & Medical Consultation

18.1 Preoperative Cardiovascular Risk Assessment 18.2 Preoperative Pulmonary Risk & Perioperative Medication Management 18.3 Perioperative Anticoagulation, Bridging & Postoperative Complications

20 Chapter 19: Ophthalmology (1% of Exam)

19.1 The Acute Red Eye & Ophthalmic Emergencies 19.2 Painless Vision Loss & Chronic Ophthalmic Disease 19.3 Uveitis, Scleritis & Orbital Disease

21 Chapter 20: Otolaryngology & Dental Medicine (1% of Exam)

20.1 Dizziness, Vertigo & Epistaxis 20.2 Ear Disorders, Hearing Loss & Upper Respiratory Infections 20.3 Oral Cavity, Salivary Gland, Laryngeal & Taste and Smell Disorders

5.6 Pulmonary Embolism: Diagnosis, Risk Stratification & Anticoagulation

Key Takeaways Explain This Topic AI

Pulmonary embolism, idiopathic pulmonary arterial hypertension, cor pulmonale, superior vena cava syndrome and hepatopulmonary syndrome are enumerated under pulmonary vascular disease.

D-dimer is useful only to exclude pulmonary embolism in low or intermediate pretest probability and has no role when probability is high.

Massive pulmonary embolism with sustained hypotension is an indication for systemic thrombolysis in the absence of contraindications.

Right ventricular strain with elevated troponin defines submassive embolism, which warrants monitoring rather than routine thrombolysis.

Provoked embolism is treated for three months, whereas unprovoked embolism warrants consideration of extended anticoagulation based on bleeding risk.

Last updated: August 2026

Pulmonary vascular emergencies and chronic sleep-related breathing disorders require prompt recognition and evidence-based risk stratification. ABIM exam questions rigorously evaluate the sequential diagnostic algorithm for pulmonary embolism, advanced hemodynamic classifications of pulmonary hypertension, guideline-directed targeted therapeutics, and the clinical management of obstructive sleep apnea versus obesity hypoventilation syndrome.

1. Acute Pulmonary Embolism (PE): Pathophysiology & Diagnostics

Pulmonary embolism is the third leading cause of cardiovascular mortality worldwide. Emboli typically originate in the deep venous system of the lower extremities (iliac, femoral, popliteal veins) and occlude branches of the pulmonary arterial bed.

Pathophysiologic Cascade

Right Ventricular (RV) Failure: Occlusion of >30–50% of the pulmonary vascular bed abruptly increases RV afterload -> acute RV dilation, hypokinesis, and ischemia -> leftward bowing of the interventricular septum (D-shaped LV on short-axis echo) -> impaired LV diastolic filling -> decreased stroke volume, systemic hypotension, cardiogenic shock, and pulseless electrical activity (PEA) arrest.

Gas Exchange Abnormalities: (1) Increased alveolar dead space (areas with ventilation but absent perfusion, V/Q = infinity); (2) Right-to-left intrapulmonary and intracardiac shunting (via patent foramen ovale reopening); (3) V/Q mismatch and reflex bronchoconstriction due to inflammatory mediator release (serotonin, thromboxane A2).

Stepwise Diagnostic Algorithm

Loading diagram... Clinical Diagnostic Algorithm for Suspected Acute Pulmonary Embolism

Clinical Decision Rules & Scoring Systems

Wells Clinical Prediction Rule for PE:

• Clinical signs/symptoms of DVT (+3.0 points)
• Alternative diagnosis less likely than PE (+3.0 points)
• Heart rate > 100 beats/min (+1.5 points)
• Immobilization (>=3 days) or surgery within past 4 weeks (+1.5 points)
• Previous objectively diagnosed DVT or PE (+1.5 points)
• Hemoptysis (+1.0 point)
• Active malignancy with treatment within 6 months or palliative (+1.0 point)

Two-Tier Stratification: PE Unlikely (<=4.0 points); PE Likely (>4.0 points).

Three-Tier Stratification: Low risk (0–1 point); Intermediate risk (2–6 points); High risk (>=7 points).

PERC Rule (Pulmonary Embolism Rule-Out Criteria):

Applied only to patients with LOW pre-test probability (Wells <2). If ALL 8 criteria are met, the probability of PE is <1% and PE is ruled out without laboratory or imaging tests:

• Age < 50 years
• Pulse < 100 beats/min
• SaO2 >= 95% on room air
• No prior DVT or PE
• No recent surgery or trauma within 4 weeks
• No hemoptysis
• No exogenous estrogen use (OCPs, HRT)
• No unilateral lower extremity swelling

Age-Adjusted D-Dimer Cutoff:

In patients aged > 50 years with low or intermediate clinical probability, use the age-adjusted formula: Cutoff = Age (years) x 10 mcg/L (fibrinogen equivalent units) or ng/mL. (e.g., for a 75-year-old, cutoff is 750 mcg/L rather than standard 500 mcg/L). Increases specificity by ~20% without compromising sensitivity.

Imaging Modalities:

CT Pulmonary Angiography (CTPA): First-line test of choice in stable patients.

V/Q Lung Scan: Diagnostic test of choice when CTPA is contraindicated (severe renal impairment with eGFR < 30 mL/min/1.73m2, severe anaphylactoid iodinated contrast allergy, or pregnancy with a normal baseline chest radiograph). Interpreted via modified PIOPED criteria: A normal V/Q scan excludes PE; a high-probability scan with high clinical suspicion confirms PE; indeterminate/non-diagnostic scans require further imaging (e.g., lower extremity venous duplex ultrasound).

2. Risk Stratification & Acute PE Management

Therapeutic management is dictated strictly by hemodynamic stability, RV strain, and myocardial biomarker release.

Clinical Risk Categories

PE Risk Category Hemodynamics RV Function (Echo / CT) Cardiac Biomarkers (Troponin / BNP) Guideline-Directed Acute Management

Massive (High Risk) Hypotension: Sustained SBP < 90 mmHg for >=15 min, shock, requiring inotropes, or drop in SBP >=40 mmHg. Severe RV dilation, hypokinesis, McConnell sign. Frequently elevated. Immediate Systemic Thrombolysis (IV Alteplase 100 mg over 2h) + IV Unfractionated Heparin (UFH) bolus/infusion.; If lysis contraindicated: Emergent Surgical Embolectomy or Catheter-Directed Thrombectomy.

Submassive (Intermediate Risk) Normotensive (SBP >= 90 mmHg). RV Dysfunction present (RV/LV diameter ratio >= 0.9 on CT/Echo, TAPSE <16 mm). Elevated Troponin I/T or elevated BNP/NT-proBNP. Therapeutic Anticoagulation (LMWH, Fondaparinux, or UFH) + ICU/Step-Down Monitoring .; Intermediate-High Risk (both RV strain & +troponin): Close surveillance for rescue thrombolysis/catheter embolectomy if shock develops.; Intermediate-Low Risk (only one present): Anticoagulation alone.

Low Risk Normotensive (SBP >= 90 mmHg). Normal RV size and function. Normal Troponin and BNP. (PESI Class I-II / sPESI = 0). Direct Oral Anticoagulant (DOAC) therapy (Apixaban, Rivaroxaban). Outpatient management or early discharge (<24–48h) is safe.

Anticoagulation Selection & Duration

Direct Oral Anticoagulants (DOACs): First-line treatment for acute VTE in patients without contraindications:

Apixaban: 10 mg PO BID for 7 days, then 5 mg PO BID.

Rivaroxaban: 15 mg PO BID with food for 21 days, then 20 mg PO daily.

Dabigatran / Edoxaban: Requires initial 5–10 days of parenteral anticoagulation (LMWH/UFH) prior to oral transition.

Special Patient Populations:

Antiphospholipid Syndrome (APLS): In patients with high-risk "triple-positive" APLS (lupus anticoagulant + anticardiolipin + anti-beta-2-glycoprotein I), Warfarin with a target INR 2.0–3.0 is the anticoagulant of choice . The TRAPS trial demonstrated that DOACs (Rivaroxaban) significantly increase arterial thromboembolic events (stroke, MI) compared to Warfarin; DOACs are contraindicated in triple-positive APLS.

Cancer-Associated Thrombosis (CAT): Oral factor Xa inhibitors (Apixaban, Rivaroxaban, Edoxaban) or LMWH (Enoxaparin 1 mg/kg SC q12h). In patients with unresected gastrointestinal or genitourinary luminal malignancies, LMWH or Apixaban is preferred due to lower mucosal bleeding rates.

Severe Renal Impairment (CrCl < 15–30 mL/min): IV Unfractionated Heparin transitioned to Warfarin (target INR 2.0–3.0) is preferred.

Duration of Anticoagulation:

Provoked PE by a major transient risk factor (major surgery, trauma, hospitalization >=3 days): Exactly 3 months of therapeutic anticoagulation.

Unprovoked PE, recurrent VTE, or persistent major risk factors: Indefinite (extended) anticoagulation with periodic reassessment of risk-benefit ratio.

Inferior Vena Cava (IVC) Filter Indications:

IVC filters do not reduce long-term mortality and increase recurrent DVT risk. Retrievable filters are indicated strictly for:

Absolute contraindication to therapeutic anticoagulation in acute VTE (e.g., active major internal bleeding, recent hemorrhagic stroke).

Recurrent objectively confirmed PE despite proven therapeutic anticoagulation .