16.1 Pulmonary Embolism & Deep Vein Thrombosis

ABFM Family Medicine Certification Study Guide Exam

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1 Chapter 1: Exam Structure, Blueprint & Clinical Decision-Making

1.1 Exam Blueprint, FMCLA vs. One-Day Exam & Board Scoring 1.2 Clinical Reasoning, Test-Taking Strategy & Ambiguity Management 1.3 Evidence-Based Medicine & Clinical Practice Guidelines in Primary Care

2 Chapter 2: Healthcare Systems, Practice Management & Quality

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3 Chapter 3: Ethics, Law, Biostatistics & Health Equity

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4 Chapter 4: Lifestyle Counseling & Behavior Change

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5 Chapter 5: Nutrition, Physical Activity & Chronic Disease Prevention

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6 Chapter 6: Routine Adult Immunizations

6.1 ACIP Adult Respiratory Vaccines: Influenza, COVID-19, RSV & Pneumococcal 6.2 ACIP Adult Non-Respiratory Vaccines: Tdap, Shingrix, HPV & Hep B 6.3 Immunizations in Special Populations: Pregnancy, Asplenia & Immunocompromise

7 Chapter 7: Pediatric Health Maintenance & Surveillance

7.1 Newborn Examination & Early Postnatal Care 7.2 Well-Child Care, Developmental Surveillance & Milestones 7.3 Pediatric & Adolescent Screening: Vision, Hearing, Anemia & Lead 7.4 Pediatric Oral Health, Dental Screening & Fluoride

8 Chapter 8: Behavioral Health & Safety Screening

8.1 Primary Care Depression, Anxiety & Behavioral Health Screening 8.2 Domestic Violence, Intimate Partner Violence & Firearm Safety 8.3 Occupational Health & Recreational Safety Counseling

9 Chapter 9: Adult Preventive Screening: Cardiovascular & Metabolic

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10 Chapter 10: Adult Cancer Screening: Breast & Gynecologic

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11 Chapter 11: Adult Cancer Screening: Colorectal, Lung & Prostate

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12 Chapter 12: Sexual Health, Infectious Disease Screening & Contraception

12.1 Sexual Health Counseling & Risk-Reduction Strategies 12.2 STI Screening: Chlamydia, Gonorrhea, Syphilis & Trichomoniasis 12.3 Bloodborne Infectious Disease Screening: HIV & Hepatitis C

13 Chapter 13: Reproductive Life Planning, Lactation & Preoperative Care

13.1 Preconception Planning & Comprehensive Contraception Management 13.2 Lactation Support & Breastfeeding Counseling 13.3 Preoperative Medical Evaluation & Pre-Participation Sports Exam

14 Chapter 14: Emergent Cardiovascular Conditions

14.1 Acute Coronary Syndromes & Myocardial Infarction 14.2 Acute Chest Pain Risk Stratification & Triage 14.3 Acute or Critical Valvular Heart Emergencies

15 Chapter 15: Cardiac Arrhythmias, Heart Failure & Hypertensive Crises

15.1 Acute Atrial & Ventricular Arrhythmias 15.2 Acute Decompensated Heart Failure & Cardiogenic Shock 15.3 Hypertensive Emergency & Urgency Management

16 Chapter 16: Vascular & Thromboembolic Emergencies

16.1 Pulmonary Embolism & Deep Vein Thrombosis 16.2 Acute Aortic Syndromes & Peripheral Vascular Emergencies 16.3 Critical Limb Ischemia & Acute Arterial Occlusion

17 Chapter 17: Neurologic Emergencies: Stroke & Altered Consciousness

17.1 Acute Ischemic Stroke & Intracranial Hemorrhage 17.2 Syncope Evaluation & Status Epilepticus 17.3 Acute Delirium, Encephalopathy & Severe Confusion

18 Chapter 18: Neurologic Trauma & Acute Cranial Emergencies

18.1 Concussion, Moderate-to-Severe TBI & Intracranial Injury 18.2 Thunderclap & Acute Severe Secondary Headaches 18.3 Acute Ophthalmologic Emergencies

19 Chapter 19: Acute Abdominal, Pelvic & Gastrointestinal Emergencies

19.1 Acute Abdominal & Pelvic Pain Triage 19.2 Upper & Lower Gastrointestinal Bleeding 19.3 Acute Hepatic Failure, Cholangitis & Severe Jaundice

20 Chapter 20: Acute Pulmonary & Airway Emergencies

20.1 Acute Hypoxic Respiratory Failure & ARDS 20.2 Severe Community-Acquired Pneumonia & Empyema 20.3 Acute Severe Epistaxis & Airway Obstruction

21 Chapter 21: Acute Traumatic Injuries & Wound Care

21.1 Major Trauma Resuscitation & Initial Assessment 21.2 Burn Assessment, Inhalation Injury & Resuscitation 21.3 Laceration Management, Complex Wounds & Animal Bites

22 Chapter 22: Acute Orthopedic & Musculoskeletal Emergencies

22.1 Acute Ambulatory Fractures & Initial Splinting 22.2 Compartment Syndrome & Major Orthopedic Trauma 22.3 Septic Arthritis & Acute Microcrystalline Crises

23 Chapter 23: Severe Infections, Sepsis & Systemic Emergencies

23.1 Sepsis, Septic Shock & Initial Fluid Resuscitation 23.2 Necrotizing Soft Tissue Infections & Severe CNS Infections 23.3 Anaphylaxis Diagnosis, Epinephrine Dosing & Airway Protection

24 Chapter 24: Metabolic, Endocrine & Electrolyte Emergencies

24.1 Diabetic Ketoacidosis & Hyperosmolar Hyperglycemic State 24.2 Critical Electrolyte Emergencies: Dyskalemias & Dysnatremias 24.3 Severe Calcium Abnormalities & Acute Adrenal Crisis

25 Chapter 25: Hematologic, Urologic & Dental Emergencies

25.1 Severe Symptomatic Anemias & Coagulopathic Emergencies 25.2 Testicular Torsion, Priapism & Acute Urinary Retention 25.3 Urgent Odontogenic Infections & Dental Trauma

26 Chapter 26: Psychiatric, Behavioral & Obstetric/Gynecologic Emergencies

26.1 Suicidal Ideation, Acute Agitation & Behavioral Emergencies 26.2 Acute Physical & Sexual Assault Care 26.3 Life-Threatening Vaginal Bleeding & Ectopic Pregnancy 26.4 Environmental Heat Stroke & Severe Hypothermia

27 Chapter 27: Acute Head, Neck & Neurologic Symptoms

27.1 Primary Acute Headaches: Migraine, Tension & Cluster 27.2 Concussion & Minor Closed Head Injury Evaluation 27.3 Transient Ischemic Attack Evaluation & ABCD2 Risk Scoring

28 Chapter 28: Acute Cranial Nerves, Hearing & Sensory Symptoms

28.1 Peripheral Neuropathies: Bell's Palsy, Carpal Tunnel & Radiculopathy 28.2 Acute Tinnitus, Sudden Sensorineural Hearing Loss & Cerumen Impaction 28.3 Acute Dizziness, Benign Paroxysmal Positional Vertigo & Vestibular Neuritis

29 Chapter 29: Acute Upper Respiratory Tract Infections

29.1 Acute Viral Rhinosinusitis vs. Bacterial Rhinosinusitis 29.2 Acute Pharyngitis: Group A Streptococcus & Centor Criteria 29.3 Acute Otitis Media, Otitis Externa & Serous Effusion

30 Chapter 30: Acute Lower Respiratory Infections & Cough

30.1 Influenza, COVID-19 & Viral Respiratory Syndromes 30.2 Acute Bronchitis & Lower Respiratory Tract Infections 30.3 Ambulatory Community-Acquired Pneumonia

31 Chapter 31: Allergic, Nasal & Non-Infectious Pulmonary Conditions

31.1 Allergic Rhinitis & Acute Non-Anaphylactic Allergic Reactions 31.2 Acute Dyspnea in Ambulatory Care 31.3 Interstitial Lung Diseases & Sarcoidosis Presentation

32 Chapter 32: Acute Chest, Cardiac & Vascular Symptoms

32.1 Palpitations Evaluation & Arrhythmia Triage in Primary Care 32.2 Deep Vein Thrombosis & Superficial Thrombophlebitis 32.3 Ambulatory Hypotension & Orthostasis Evaluation

33 Chapter 33: Acute Upper Gastrointestinal Conditions

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34 Chapter 34: Acute Lower Gastrointestinal Conditions

34.1 Acute Infectious Diarrhea & Gastroenteritis 34.2 Acute Constipation & Functional Bowel Changes 34.3 Ano-Rectal Disorders: Hemorrhoids, Fissures, Abscesses & Pruritus Ani

35 Chapter 35: Inflammatory, Functional & Malabsorptive GI Disorders

35.1 Acute Flares of Inflammatory Bowel Disease 35.2 Irritable Bowel Syndrome: Diagnosis, Subtyping & Management 35.3 Celiac Disease & Malabsorption Syndromes

36 Chapter 36: Acute Abdominal, Hepatic & Biliary Disorders

36.1 Ambulatory Abdominal & Pelvic Pain Triage 36.2 Acute Cholecystitis, Biliary Colic & Pancreatitis 36.3 Acute Liver Injury & Viral Hepatitis

37 Chapter 37: Acute Abdominal Wall, Hernias & Dental Conditions

37.1 Abdominal Wall, Inguinal & Ventral Hernias 37.2 Acute Dental Pain, Odontogenic Abscess & Aphthous Ulcers 37.3 Acute Edema: Unilateral vs. Bilateral Diagnostic Evaluation

38 Chapter 38: Acute Infectious Dermatoses

38.1 Bacterial Skin Infections: Impetigo, Cellulitis & Cutaneous Abscesses 38.2 Fungal Skin Infections: Tinea Corporis, Cruris, Pedis & Onychomycosis 38.3 Viral Cutaneous Infections: Herpes Simplex, Zoster & Molluscum Contagiosum

39 Chapter 39: Inflammatory, Allergic & Autoimmune Dermatoses

39.1 Atopic Dermatitis, Contact Dermatitis & Eczematous Flares 39.2 Non-Infectious Rashes: Urticaria, Drug Eruptions & Erythema Multiforme 39.3 Cutaneous Malignancies & Premalignant Lesions: AK, BCC, SCC & Melanoma

40 Chapter 40: Acute Shoulder, Elbow & Upper Extremity Injuries

40.1 Rotator Cuff Pathology, Tendinopathy & Shoulder Impingement 40.2 Lateral & Medial Epicondylitis, Olecranon Bursitis & Elbow Sprains 40.3 Wrist & Hand Soft-Tissue Injuries: De Quervain, TFCC & Finger Sprains

41 Chapter 41: Acute Knee, Ankle & Lower Extremity Injuries

41.1 Meniscal Tears, Ligamentous Knee Injuries & Patellofemoral Pain 41.2 Ankle Sprains, Ottawa Ankle Rules & Achilles Tendinopathy 41.3 Plantar Fasciitis, Shin Splints & Overuse Syndromes

42 Chapter 42: Acute Ambulatory Fractures & Dislocations

42.1 Distal Radius, Scaphoid & Common Upper Extremity Fractures 42.2 Metatarsal, Clavicle & Common Lower Extremity Fractures 42.3 Joint Dislocation Management: Nursemaid's Elbow & Shoulder Subluxation

43 Chapter 43: Acute Axial Musculoskeletal Pain & Falls

43.1 Acute Low Back Pain: Red Flags, Strain & Disc Herniation 43.2 Acute Cervical Strain, Whiplash & Axial Neck Pain 43.3 Evaluation of Falls in Ambulatory & Older Patients

44 Chapter 44: Acute Inflammatory Arthropathies & Generalized Pain

44.1 Acute Inflammatory Arthritis & Spondyloarthropathies 44.2 Myalgias, Rhabdomyolysis & Post-Viral Pain Syndromes 44.3 Acute Non-Headache Pain Management Strategies

45 Chapter 45: Acute Renal, Urinary & Genitourinary Conditions

45.1 Uncomplicated UTI, Pyelonephritis & Acute Urethritis 45.2 Hematuria Workup & Glomerulonephritis 45.3 Nephrolithiasis & Acute Urinary Tract Obstruction

46 Chapter 46: Acute Male Genitourinary & Prostatic Conditions

46.1 Acute Prostatitis, Epididymitis & Orchitis 46.2 Acute Scrotal Pain: Torsion vs Appendage, BPH & Male Genital Emergencies 46.3 Acute Urinary Retention & Incontinence Evaluation

47 Chapter 47: Acute Women's Health & Early Pregnancy Care

47.1 Early Pregnancy Diagnosis, Dating & Initial Complications 47.2 Abnormal Uterine Bleeding & Acute Menstrual Disorders 47.3 Premenstrual Syndrome & Premenstrual Dysphoric Disorder

48 Chapter 48: Breast Disorders, STIs & Pediatric Elimination

48.1 Palpable Breast Mass, Mastitis & Nipple Discharge 48.2 Sexually Transmitted Infections: Diagnosis, Staging & CDC Guidelines 48.3 Pediatric Enuresis & Encopresis

49 Chapter 49: Systemic Signs, Metabolic Dysregulation & Miscellaneous Infections

49.1 Acute Fever, Sepsis Screening & FUO in Primary Care 49.2 Acute Hyperglycemia & Symptomatic Hypoglycemia 49.3 Electrolyte Abnormalities: Mild-to-Moderate Disturbances 49.4 Vector-Borne, Tick-Borne & Rickettsial Illnesses

50 Chapter 50: Chronic Cardiovascular Diseases: Hypertension & Ischemia

50.1 Essential Hypertension Management: 2025 AHA/ACC Guideline & JNC Strategies 50.2 Chronic Coronary Artery Disease & Post-MI Secondary Prevention 50.3 Chronic Heart Failure: HFrEF, HFpEF & Quadruple GDMT

51 Chapter 51: Chronic Vascular, Valvular & Dyslipidemic Diseases

51.1 Peripheral Arterial Disease & Claudication 51.2 Chronic Valvular Heart Disease & Murmur Evaluation 51.3 Lipid Disorders & ASCVD Risk-Based Statin Therapy

52 Chapter 52: Chronic Respiratory Diseases: Asthma & COPD

52.1 Chronic Asthma Management: GINA Stepwise SMART Therapy 52.2 Chronic Obstructive Pulmonary Disease: GOLD Recommendations 52.3 Solitary Pulmonary Nodule Evaluation & Fleischner Society Criteria

53 Chapter 53: Chronic Metabolic Diseases: Diabetes Mellitus

53.1 Type 2 Diabetes Management: ADA Pharmacotherapy Algorithms 53.2 Type 1 Diabetes: Basal-Bolus Insulin, CGMs & Diabetic Complications 53.3 Diabetic Microvascular & Macrovascular Disease Surveillance

54 Chapter 54: Obesity, Nutrition & Metabolic Bone Diseases

54.1 Medical & Behavioral Management of Obesity & Incretin Mimetics 54.2 Osteoporosis & Metabolic Bone Disease: DEXA, FRAX & Antiresorptives 54.3 Nutritional Deficiencies: Vitamin D, B12, Iron & Malnutrition

55 Chapter 55: Chronic Endocrine Disorders

55.1 Primary & Subclinical Hypothyroidism, Hyperthyroidism & Nodules 55.2 Adrenal Disorders: Addison's Disease & Cushing's Syndrome 55.3 Hypercalcemia, Hyperparathyroidism & Pituitary Disorders

56 Chapter 56: Chronic Kidney Disease & Venous Disorders

56.1 Chronic Kidney Disease: KDIGO Staging & Renoprotective Therapy 56.2 Chronic Venous Insufficiency, Stasis Dermatitis & Lymphedema 56.3 Chronic Electrolyte & Acid-Base Management in CKD

57 Chapter 57: Chronic Gastrointestinal & Hepatic Diseases

57.1 Gastroesophageal Reflux Disease, Barrett's Esophagus & Dyspepsia 57.2 Chronic Liver Disease: MASLD/NAFLD, Cirrhosis & Portal Hypertension 57.3 Viral Hepatitis B & C: Long-Term Monitoring & DAA Therapy

58 Chapter 58: Colorectal Surveillance & Chronic Pancreaticobiliary Care

58.1 Post-Polypectomy Colorectal Polyp Surveillance Guidelines 58.2 Chronic Pancreatitis & Exocrine Pancreatic Insufficiency 58.3 Chronic Nausea, Gastroparesis & Functional GI Disorders

59 Chapter 59: Chronic Musculoskeletal & Rheumatologic Disorders

59.1 Osteoarthritis: Hip, Knee & Hand Management 59.2 Spinal Conditions: Spinal Stenosis, Spondylolisthesis & Compression Fractures 59.3 Chronic Myopathies & Fibromyalgia Syndrome

60 Chapter 60: Chronic Neurologic & Neurodegenerative Disorders

60.1 Dementia: Alzheimer's, Vascular & Lewy Body Disease 60.2 Parkinson's Disease & Essential Tremor 60.3 Epilepsy: Chronic Antiseizure Medications & Post-Stroke Care

61 Chapter 61: Chronic Peripheral Nerves, Pain & Sensory Disorders

61.1 Diabetic & Chronic Peripheral Neuropathies 61.2 Chronic Pain Syndromes & Chronic Daily Headaches 61.3 Chronic Tinnitus, Presbycusis & Persistent Dizziness

62 Chapter 62: Chronic Psychiatric Disorders

62.1 Major Depressive Disorder & Generalized Anxiety Disorder 62.2 Bipolar Disorder: Maintenance Pharmacotherapy & Lithium Monitoring 62.3 Adult & Pediatric Attention-Deficit/Hyperactivity Disorder

63 Chapter 63: Chronic Behavioral Health & Neurodevelopmental Conditions

63.1 Chronic Behavioral Conditions: PTSD, OCD & Somatization 63.2 Autism Spectrum Disorder & Intellectual Disabilities 63.3 Eating Disorders: Anorexia Nervosa, Bulimia & Binge Eating

64 Chapter 64: Chronic Substance Use Disorders & Tobacco Cessation

64.1 Alcohol Use Disorder: Pharmacotherapy & Relapse Prevention 64.2 Opioid & Stimulant Use Disorders: MOUD & Harm Reduction 64.3 Longitudinal Tobacco Cessation Pharmacotherapy

65 Chapter 65: Chronic Dermatologic Conditions

65.1 Acne Vulgaris, Rosacea & Seborrheic Dermatitis 65.2 Chronic Plaque Psoriasis & Biologic Therapies 65.3 Chronic Eczema, Hidradenitis Suppurativa & Cutaneous Lupus

66 Chapter 66: Chronic Reproductive, Infectious & Geriatric Special Care

66.1 Chronic Menstrual Disorders, Infertility & Sexual Dysfunction 66.2 Menopause Management & Hormone Replacement Therapy 66.3 Chronic HIV Infection Management & Primary Care Integration 66.4 Gender-Affirming Primary Care & Hormone Therapy 66.5 Advance Care Planning, Palliative Care & End-of-Life Symptom Control

67 Chapter 67: Continuity Care: Sleep, Fatigue, Cancer, Pregnancy & the Adult Preventive Visit

67.1 Chronic Insomnia & Obstructive Sleep Apnea 67.2 Chronic Malaise, Fatigue & ME/CFS 67.3 Primary Care During Cancer Treatment & Survivorship 67.4 Routine Prenatal Care & Longitudinal Pregnancy Management 67.5 The Periodic Adult Health Examination & Medicare Annual Wellness Visit

16.1 Pulmonary Embolism & Deep Vein Thrombosis

Key Takeaways Explain This Topic AI

In patients with a low pretest probability of pulmonary embolism, meeting all 8 Pulmonary Embolism Rule-out Criteria (PERC) safely excludes PE (<1% probability) without obtaining a D-dimer assay or diagnostic imaging.

For patients older than 50 years with low or intermediate pretest probability, applying the age-adjusted D-dimer cutoff (Age × 10 µg/L FEU) significantly improves diagnostic specificity without compromising safety, preventing unnecessary CT pulmonary angiography.

Massive (high-risk) pulmonary embolism is defined by sustained systemic hypotension (SBP <90 mm Hg for >15 minutes, vasopressor requirement, or cardiac arrest); it mandates emergent systemic thrombolysis (alteplase 100 mg IV over 2 hours) or catheter-directed embolectomy alongside IV unfractionated heparin.

Direct oral anticoagulants (DOACs)—specifically apixaban (10 mg BID for 7 days, then 5 mg BID) and rivaroxaban (15 mg BID with food for 21 days, then 20 mg daily)—are first-line agents for hemodynamically stable VTE and do not require parenteral heparin lead-in.

Inferior vena cava (IVC) filters are strictly indicated for acute proximal VTE with absolute contraindications to anticoagulation, active life-threatening hemorrhage, or documented recurrent VTE despite therapeutic anticoagulation; retrievable filters should be removed once bleeding risk abates.

Last updated: September 2026

Pathophysiology of Venous Thromboembolism & Virchow's Triad

Venous thromboembolism (VTE), which encompasses deep vein thrombosis (DVT) and pulmonary embolism (PE), is the third most common cardiovascular emergency globally, trailing only acute myocardial infarction and stroke. Venous thrombi arise through the convergent pathophysiologic mechanisms historically identified as Virchow's Triad :

Hemodynamic Stasis : Impaired venous return and blood pooling—promoted by prolonged immobility (bed rest ≥ 3 \ge 3 ≥ 3 consecutive days, long-haul travel > 4 >4 > 4 hours), lower extremity orthopedic plaster casting, obesity, stroke with hemiplegia, or extrinsic venous compression (e.g., pelvic masses, pregnant uterus, or May-Thurner syndrome [compression of the left common iliac vein by the right common iliac artery]). Stasis permits accumulation of activated coagulation factors while preventing their clearance by hepatic circulation and endogenous inhibitors.

Endothelial / Vascular Wall Injury : Disruption of the vascular endothelium exposes subendothelial collagen, tissue factor, and von Willebrand factor, triggering platelet adhesion and the extrinsic coagulation cascade. Precipitating factors include major orthopedic trauma, pelvic and lower extremity fractures, hip or knee arthroplasty, indwelling central venous catheters, and prior intravenous drug use or phlebitis.

Hypercoagulability (Thrombophilia) : Systemic derangement of the procoagulant-anticoagulant balance. Hypercoagulable states are divided into:

Acquired : Active malignancy (adenocarcinomas of the pancreas, lung, gastrointestinal tract, and ovary secrete tissue factor-like procoagulants and mucins), pregnancy and the early puerperium (elevated fibrinogen, factors VII, VIII, X; decreased protein S), exogenous estrogens (combined hormonal contraceptives, hormone replacement therapy, selective estrogen receptor modulators like tamoxifen and raloxifene), antiphospholipid syndrome (lupus anticoagulant, anticardiolipin, anti-beta-2-glycoprotein I), nephrotic syndrome (urinary loss of antithrombin III), and heparin-induced thrombocytopenia (HIT).

Inherited : Factor V Leiden mutation (resistance to activated protein C; most common inherited thrombophilia in Caucasian populations), Prothrombin G20210A gene mutation, Antithrombin III deficiency (carries highest relative risk of thrombosis), Protein C deficiency, and Protein S deficiency.

Cardiopulmonary Hemodynamics of Pulmonary Embolism

When a thrombus dislodges from the deep venous system of the lower extremities (most commonly the iliofemoral or popliteal veins; calf vein DVTs embolize in < 10 % <10\% < 10% unless propagating proximally) or pelvic veins, it traverses the inferior vena cava, right atrium, and right ventricle, lodging within the pulmonary arterial circulation:

Mechanical Obstruction & Vasoconstriction : The physical occlusion of pulmonary arterial branches, compounded by the localized release of vasoconstrictive neurohumoral mediators (thromboxane A2 and serotonin from activated platelets), abruptly elevates pulmonary vascular resistance (PVR).

Right Ventricular Failure & The Spiral of Shock : The thin-walled right ventricle (RV) is physiologically unadapted to acute afterload spikes. When > 30 % >30\% > 30% to 50 % 50\% 50% of the pulmonary arterial bed is occluded, the RV dilates and wall tension surges. This produces severe tricuspid regurgitation and shifts the interventricular septum leftward (the echocardiographic "D-sign"). Leftward septal shifting impedes left ventricular (LV) diastolic filling, precipitating a dramatic reduction in LV stroke volume, systemic cardiac output, and mean arterial pressure.

Myocardial Ischemia : Elevated RV intracavitary pressure combined with systemic hypotension precipitously reduces right coronary artery perfusion pressure, inducing acute RV subendocardial ischemia, cardiogenic shock, and pulseless electrical activity (PEA) cardiac arrest.

Gas Exchange Derangements : V/Q mismatching results from alveolar dead space ventilation (ventilated alveoli lacking pulmonary perfusion). Concurrently, blood shunts toward non-embolized, hyperperfused lung zones, producing hypoxemia and reflex tachypnea mediated by vagal pulmonary J-receptors, leading to hypocapnia and respiratory alkalosis.

Clinical Prediction Rules & Triage Algorithms

Unstratified ordering of diagnostic imaging for suspected DVT and PE leads to contrast-induced nephropathy, radiation exposure, false-positive overdiagnosis, and prolonged emergency department lengths of stay. Validated clinical decision algorithms are mandatory.

Wells Criteria for Deep Vein Thrombosis

• Clinical Characteristic Points Awarded
• Active cancer (treatment ongoing, within past 6 months, or palliative) +1.0
• Paralysis, paresis, or recent plaster immobilization of the lower extremities +1.0
• Recently bedridden > 3 >3 > 3 days or major surgery within 12 weeks requiring anesthesia +1.0
• Localized tenderness along the distribution of the deep venous system +1.0
• Entire leg swollen +1.0

Calf swelling ≥ 3 \ge 3 ≥ 3 cm compared with the asymptomatic leg (measured 10 cm below tibial tuberosity) +1.0

• Pitting edema confined to the symptomatic leg +1.0
• Collateral non-varicose superficial veins +1.0
• Previously documented DVT +1.0
• Alternative diagnosis is at least as likely as DVT (e.g., Baker cyst, cellulitis, muscle tear) -2.0

Two-Tier Clinical Model :

Score < 2.0 <2.0 < 2.0 (DVT Unlikely) : Obtain high-sensitivity D-dimer assay. If D-dimer is negative ( < 500 <500 < 500 µg/L), DVT is ruled out. If positive, proceed to venous duplex ultrasonography.

Score ≥ 2.0 \ge 2.0 ≥ 2.0 (DVT Likely) : Proceed directly to compression venous duplex ultrasonography without relying on D-dimer.

Wells Criteria for Pulmonary Embolism

• Wells Parameter Points Awarded
• Clinical signs and symptoms of DVT (minimum of leg swelling and objective calf tenderness) +3.0
• An alternative diagnosis is less likely than PE (PE is the most likely or equally likely diagnosis) +3.0
• Heart rate > 100 >100 > 100 beats/min (tachycardia) +1.5
• Immobilization (bedridden ≥ 3 \ge 3 ≥ 3 consecutive days) OR surgery within prior 4 weeks +1.5
• Previous objectively documented DVT or PE +1.5
• Hemoptysis +1.0
• Active malignancy (treatment within 6 months or palliative) +1.0

Two-Tier Scoring (Standard Guideline Model) :

Score ≤ 4.0 \le 4.0 ≤ 4.0 (PE Unlikely) : Prevalence ~12%. Evaluate with the Pulmonary Embolism Rule-out Criteria (PERC) or quantitative D-dimer assay.

Score > 4.0 >4.0 > 4.0 (PE Likely) : Prevalence ~37%. Skip D-dimer; proceed immediately to Computed Tomographic Pulmonary Angiography (CTPA).

Three-Tier Scoring :

Low Risk (0–1 points): ~10% prevalence. Proceed to PERC or D-dimer.

Moderate Risk (2–6 points): ~30% prevalence. Proceed directly to quantitative D-dimer.

High Risk ( ≥ 7 \ge 7 ≥ 7 points): ~65% prevalence. Proceed directly to CTPA.

The Pulmonary Embolism Rule-out Criteria (PERC Rule)

The PERC rule was developed to eliminate unnecessary D-dimer testing and imaging in patients presenting with clinical suspicion of PE who have a LOW pretest probability (Wells score ≤ 4.0 \le 4.0 ≤ 4.0 or Low Risk). If a low-risk patient fulfills ALL 8 OF THE FOLLOWING CRITERIA , the probability of PE is < 1 % <1\% < 1% , and diagnostic workup halts without any blood testing or imaging:

• Age < 50 <50 < 50 years
• Heart rate < 100 <100 < 100 beats/min
• Oxygen saturation ( SaO 2 \text{SaO}_2 SaO 2 ​ ) ≥ 95 % \ge 95\% ≥ 95% on room air
• No prior history of venous thromboembolism (DVT or PE)
• No recent trauma or surgery requiring hospitalization within the preceding 4 weeks
• No hemoptysis
• No exogenous estrogen use (oral contraceptives, hormone therapy, or SERMs)
• No unilateral lower extremity swelling

Critical Rule : PERC is applied only when the pretest probability is low. If even a single criterion is positive (e.g., patient is 52 years old, or taking combined oral contraceptives), the PERC rule is "failed," and the clinician must obtain a quantitative D-dimer assay.

• Diagnostic Testing Cascade & Modalities
• Age-Adjusted D-Dimer Cutoffs

Quantitative D-dimer is a degradation product of cross-linked fibrin produced during endogenous fibrinolysis. High-sensitivity ELISA or immunoturbidimetric assays possess an exceptional negative predictive value ( > 99 % >99\% > 99% ), making a normal value ideal for ruling out VTE. However, circulating D-dimer physiologically increases with advancing age, pregnancy, malignancy, active inflammation, sepsis, and recent surgery, rendering the conventional fixed cutoff ( 500 500 500 µg/L or 0.50 µg/mL FEU) non-specific in older adults.

The Formula (for patients > 50 >50 > 50 years of age) : Age-Adjusted D-dimer Cutoff = Age (years) × 10 μ g/L FEU (or ng/mL FEU) \text{Age-Adjusted D-dimer Cutoff} = \text{Age (years)} \times 10\ \mu\text{g/L FEU (or ng/mL FEU)} Age-Adjusted D-dimer Cutoff = Age (years) × 10 μ g/L FEU (or ng/mL FEU) (or Age × 0.01 mg/L FEU \text{Age} \times 0.01\text{ mg/L FEU} Age × 0.01 mg/L FEU ).

Clinical Validation (ADJUST-PE Trial) : In a 78-year-old patient with low or intermediate pretest probability, a D-dimer result of 680 680 680 µg/L is elevated compared to the conventional 500 500 500 µg/L threshold, but falls below the age-adjusted cutoff of 780 780 780 µg/L ( 78 × 10 78 \times 10 78 × 10 ). PE is safely excluded without obtaining a CTPA, avoiding intravenous contrast, radiation, and unnecessary cost.

Diagnostic Imaging Modalities

Computed Tomographic Pulmonary Angiography (CTPA) :

Definitive Gold Standard : First-line diagnostic imaging modality for PE. Rapidly identifies filling defects within the main, lobar, segmental, and subsegmental pulmonary arteries.

Assessment of RV Strain : Provides immediate morphological evaluation of RV dilation (transverse RV/LV diameter ratio > 0.9 >0.9 > 0.9 on axial reformatted images) and reflux of IV contrast into the inferior vena cava, which independently predicts in-hospital mortality.

Contraindications / Cautions : Severe iodinated contrast allergy and severe acute or chronic renal failure (estimated GFR < 30 <30 < 30 mL/min/1.73m²). In unstable patients, moving to the CT scanner is hazardous.

Ventilation-Perfusion (V/Q) Scintigraphy :

Visualizes pulmonary capillary perfusion (via IV technetium-99m labeled macroaggregated albumin [Tc-99m MAA]) alongside alveolar ventilation (via inhaled xenon-133 or Tc-99m DTPA aerosol).

Strict Indications :

• Severe renal insufficiency (eGFR < 30 <30 < 30 mL/min/1.73m² or acute oliguric kidney injury);
• Documented severe, life-threatening anaphylactic hypersensitivity to iodinated contrast media;

Pregnancy with a normal baseline chest radiograph : V/Q scanning delivers a substantially lower radiation dose to maternal breast tissue than CTPA (reducing lifetime breast cancer risk) while maintaining high diagnostic accuracy when the baseline chest X-ray is clear.

Interpretation : A High-Probability scan ( ≥ 2 \ge 2 ≥ 2 large mismatched segmental perfusion defects without matching ventilation defects) diagnostic of PE ( > 85 % >85\% > 85% PPV); a Normal scan definitively excludes PE; Intermediate / Low Probability scans are indeterminate and mandate further testing (e.g., lower extremity venous ultrasound).

Venous Duplex Compression Ultrasonography :

First-line diagnostic study for suspected DVT. Complete compressibility of the venous lumen under direct transducer probe pressure is the single most sensitive and specific criterion for ruling out DVT. Non-compressibility, intraluminal echogenicity, and absence of Doppler flow augmentation confirm deep venous thrombosis.

If lower extremity ultrasound demonstrates a proximal DVT in a patient with suspected PE, anticoagulation is indicated immediately, often obviating the need for CTPA if renal function or contrast allergy is a concern.

Electrocardiography & Echocardiography Findings :

ECG : Sinus tachycardia is the most common rhythm abnormality ( > 40 % >40\% > 40% ). Classic signs of acute cor pulmonale include the S1Q3T3 pattern (deep S wave in lead I, prominent Q wave in lead III, and T-wave inversion in lead III; present in < 20 % <20\% < 20% of PE cases), new complete or incomplete right bundle branch block (RBBB), and T-wave inversions across anterior precordial leads (V1–V4).

Transthoracic Echocardiography (TTE) : Demonstrates RV enlargement, tricuspid regurgitant jet velocity > 2.8 >2.8 > 2.8 m/s, flattened interventricular septum, and McConnell's sign (severe hypokinesis of the mid-free RV wall with normal or hyperdynamic apical contraction; highly specific for acute PE).

Hemodynamic Risk Stratification & Clinical Staging

Once PE is diagnosed, management is dictated entirely by hemodynamic stability, right ventricular strain, and myocardial biomarker release :

PE Clinical Category Hemodynamic Criteria RV Dysfunction (Echo / CT) Myocardial Biomarkers (Troponin / BNP) Clinical Disposition & Primary Strategy

Massive (High Risk) ; Mortality 25–50% Sustained Hypotension : Systolic BP < 90 <90 < 90 mm Hg for > 15 >15 > 15 min, shock, vasopressor requirement, or cardiac arrest Markedly Present (RV dilation, McConnell sign) Markedly Elevated Immediate ICU admission; IV Unfractionated Heparin (UFH) bolus; emergent systemic thrombolysis (or catheter/surgical embolectomy)

Submassive (Intermediate Risk) ; Mortality 3–15% Normotensive : Systolic BP ≥ 90 \ge 90 ≥ 90 mm Hg Present (RV/LV > 0.9 >0.9 > 0.9 , septal shift) Elevated (Cardiac Troponin I/T, BNP / NT-proBNP) Hospital admission with continuous cardiac monitoring; therapeutic anticoagulation (DOAC, LMWH, or UFH); close surveillance for decompensation

Low Risk ; Mortality <1% Normotensive : Systolic BP ≥ 90 \ge 90 ≥ 90 mm Hg Absent (Normal RV size/function) Normal Early discharge or outpatient management; oral anticoagulation with direct-acting agent (DOAC)

Subclassification of Intermediate-Risk (Submassive) PE :

Intermediate-High Risk : BOTH right ventricular strain (echo or CTPA) AND elevated biomarkers (troponin or BNP) are present. These patients carry a substantial risk of secondary hemodynamic collapse; ICU or step-down admission is required, and rescue reperfusion teams should be alerted.

Intermediate-Low Risk : Either RV dysfunction OR an elevated biomarker is present, but NOT both. Managed with standard therapeutic anticoagulation on an inpatient telemetry ward.

Prognostic Clinical Scores (PESI and sPESI) : The Pulmonary Embolism Severity Index (PESI) and simplified PESI (sPESI) stratify 30-day all-cause mortality. An sPESI of 0 points (age < 80 <80 < 80 , no history of cancer, no chronic cardiopulmonary disease, heart rate < 100 <100 < 100 , SBP ≥ 100 \ge 100 ≥ 100 , SaO2 ≥ 90 % \ge 90\% ≥ 90% ) designates Low Risk and qualifies patients for consideration of early outpatient therapy.

• Acute Therapeutic Management & Anticoagulation Protocols
• 1. Direct Oral Anticoagulants (DOACs) — Preferred First-Line for Stable VTE

DOACs are now recommended over vitamin K antagonists (warfarin) and low-molecular-weight heparin for the acute and long-term treatment of VTE in patients without active cancer, severe renal dysfunction, or antiphospholipid syndrome:

Apixaban (Eliquis) : 10 mg orally twice daily for 7 days , followed by a maintenance dose of 5 mg orally twice daily . Key Exam Pearl : Apixaban does NOT require parenteral heparin lead-in.

Rivaroxaban (Xarelto) : 15 mg orally twice daily taken WITH FOOD for 21 days , followed by 20 mg orally once daily taken with food . Key Exam Pearl : Rivaroxaban does NOT require parenteral heparin lead-in.

Dabigatran (Pradaxa) (direct thrombin inhibitor) and Edoxaban (Savaysa) (factor Xa inhibitor): Require 5 to 10 days of initial parenteral anticoagulation (LMWH or UFH) prior to initiating oral therapy. Dabigatran dose: 150 mg BID; Edoxaban dose: 60 mg daily.

Advantages : Immediate onset of action, fixed dosing, no routine coagulation monitoring, and a > 50 % >50\% > 50% reduction in major life-threatening intracranial hemorrhage compared to warfarin.

2. Parenteral Anticoagulants

Low-Molecular-Weight Heparin (LMWH, Enoxaparin) :

Dosing : 1 mg/kg subcutaneously every 12 hours (or 1.5 mg/kg SC once daily). In severe renal impairment (CrCl < 30 <30 < 30 mL/min), dose is adjusted to 1 mg/kg SC once daily or switched to UFH.

Highly predictable bioavailability; anti-Xa monitoring is unnecessary except in extreme obesity (weight > 150 >150 > 150 kg), severe renal failure, or pregnancy.

Historical drug of choice in cancer-associated thrombosis (CAT), although DOACs (apixaban, edoxaban, rivaroxaban) are now also guideline-approved alternatives unless GI/GU luminal malignancies pose mucosal bleeding hazards.

Unfractionated Heparin (UFH) :

Dosing : 80 units/kg IV bolus , followed by a continuous maintenance infusion of 18 units/kg/hour , titrated to an activated partial thromboplastin time (aPTT) of 1.5 to 2.5 times control or therapeutic anti-Xa level (0.3 to 0.7 IU/mL).

Mandatory First-Line Choice for :

Hemodynamically unstable (massive) PE : Rapid half-life (~60–90 min) and full, immediate reversibility with protamine sulfate (1 mg per 100 units heparin administered in preceding 2 hours) should urgent systemic thrombolysis or surgical embolectomy be required;

Severe renal impairment (Creatinine clearance < 30 <30 < 30 mL/min) : UFH is cleared via the reticuloendothelial system and does not rely on renal excretion.

3. Reperfusion Therapy for Massive PE

Systemic Thrombolysis : Recommended for patients with Massive (High-Risk) PE presenting with sustained systemic hypotension (SBP < 90 <90 < 90 mm Hg) or cardiogenic shock, who do not have absolute bleeding contraindications.

Regimen : Alteplase (recombinant tPA) 100 mg IV infusion administered over 2 hours (or accelerated weight-based tenecteplase).

Mechanism : Cleaves plasminogen to plasmin, rapidly dissolving the obstructive pulmonary thrombus, reducing RV afterload, and reversing cardiogenic shock within hours.

Major Contraindications : Absolute contraindications include any prior intracranial hemorrhage, known structural cerebral vascular lesion, malignant intracranial neoplasm, ischemic stroke within 3 months, active internal bleeding (excluding menses), or recent major head/spinal trauma within 3 months.

Catheter-Directed Therapy (CDT) & Surgical Embolectomy :

Catheter-Directed Thrombolysis / Mechanical Thrombectomy : Delivers ultra-low-dose tPA (e.g., 0.5–1.0 mg/hr) directly into the clot via pulmonary artery infusion catheters, with or without ultrasound agitation or aspiration. Indicated for massive PE when systemic thrombolysis is contraindicated or has failed, or in selected intermediate-high risk patients deteriorating clinically.

Surgical Pulmonary Embolectomy : Open sternotomy with cardiopulmonary bypass to manually extract large central saddle emboli in patients with massive PE and absolute contraindications to thrombolysis.

4. Inferior Vena Cava (IVC) Filters

An IVC filter is an expandable metallic alloy device deployed into the infrarenal inferior vena cava to intercept dislodged lower extremity thrombi.

Strict Guideline Indications :

Absolute contraindication to full therapeutic anticoagulation (e.g., active major intracranial, retroperitoneal, or gastrointestinal hemorrhage; impending emergent major neurosurgery);

Active, life-threatening major bleeding occurring during therapeutic anticoagulation;

Recurrent, objectively verified pulmonary embolism occurring despite documented therapeutic levels of anticoagulation.

Filter Management & Retrieval Mandate : IVC filters do NOT reduce overall long-term mortality and increase the long-term risk of deep vein thrombosis and caval occlusion. Modern filters are retrievable and should be removed endovascularly as soon as the contraindication to anticoagulation resolves or bleeding risk diminishes (ideally within 2 to 6 months).

5. Duration of Anticoagulation Therapy

Provoked VTE by Major Transient Risk Factor (e.g., major surgery, orthopedic trauma, hospitalization for > 3 >3 > 3 days): 3 months of therapeutic anticoagulation , after which therapy is discontinued.

Unprovoked VTE or Persistent Risk Factor (e.g., active cancer, antiphospholipid syndrome, recurrent unprovoked events): Indefinite (extended) anticoagulation , with annual clinical assessments of bleeding risk versus recurrent thrombosis.

Loading diagram... Clinical Diagnostic & Therapeutic Algorithm for Suspected Pulmonary Embolism