1.12 Syncope: Reflex, Orthostatic & Cardiac Causes

ABIM Internal Medicine Exam

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

0.1 Exam Format, Question Types & the 2026 Blueprint 0.2 Eligibility, Registration, Fees & Exam-Day Logistics 0.3 Scoring, the Passing Standard & Score Reports 0.4 Building a Blueprint-Weighted Study Plan

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

4 Chapter 3: Gastroenterology & Hepatology (9% of Exam)

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

5 Chapter 4: Infectious Disease (9% of Exam)

4.1 Lower Respiratory Tract Infections & Sepsis Syndromes 4.2 Viral Respiratory Pathogens & Tuberculosis 4.3 Central Nervous System Infections 4.4 Skin, Soft Tissue, Bone & Joint Infections 4.5 Infective Endocarditis & Cardiovascular Infection 4.6 Clostridioides difficile & Catheter-Related Bloodstream Infection 4.7 HIV Diagnosis, Antiretroviral Therapy & Prevention 4.8 Opportunistic Infections & Sexually Transmitted Infections 4.9 Fever of Unknown Origin, Neutropenic Fever & Toxic Shock 4.10 Travel-Related Illness, Vector-Borne Disease & Outbreaks 4.11 Infection Prevention, Nosocomial Infection & Postexposure Prophylaxis 4.12 Rheumatic Fever, Poststreptococcal Disease, Enteric & Hepatic Infections

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

7 Chapter 6: Rheumatology & Orthopedics (9% of Exam)

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

9 Chapter 8: Medical Oncology (6% of Exam)

8.1 Breast, Lung, Colorectal & Prostate Cancer 8.2 Oncologic Emergencies 8.3 Genitourinary & Gynecologic Malignancies 8.4 Head and Neck, Bone & Soft Tissue Cancer and Cancer of Unknown Primary 8.5 Complications of Cancer & Its Treatment 8.6 Cancer Prevention, Survivorship & Psychosocial Care

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

11 Chapter 10: Neurology (4% of Exam)

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

12 Chapter 11: Psychiatry & Behavioral Health (4% of Exam)

11.1 Major Depressive Disorder & Medical Mimics 11.2 Antidepressant Pharmacotherapy & Treatment-Resistant Depression 11.3 Bipolar Disorder, Mood Stabilizers & Lithium Toxicity 11.4 Anxiety, Stress-Related & Obsessive-Compulsive Disorders 11.5 Alcohol Use Disorder & Withdrawal 11.6 Pharmacotherapy for Alcohol & Opioid Use Disorder 11.7 Toxidromes, Psychiatric Emergencies & Suicide Risk Assessment 11.8 Psychotic, Somatic Symptom, Factitious & Personality Disorders 11.9 Eating Disorders, Sleep Disorders & Sexual Health

13 Chapter 12: Dermatology (3% of Exam)

12.1 Dermatitis, Papulosquamous & Inflammatory Dermatoses 12.2 Acne, Rosacea & Cutaneous Infections 12.3 Herpes Zoster & Autoimmune Blistering Diseases 12.4 Nodules, Tumors & Cutaneous Oncology 12.5 Dermatologic Emergencies & Severe Cutaneous Adverse Reactions 12.6 Pigment Disorders, Alopecia, Nail Disease & Photosensitivity 12.7 Vascular Dermatoses, Environmental Injury & Cutaneous Signs of Systemic Disease

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

18 Chapter 17: Miscellaneous - Ethics, Patient Safety & Quality Improvement (2% of Exam)

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

1.12 Syncope: Reflex, Orthostatic & Cardiac Causes

Key Takeaways Explain This Topic AI

The syncope blueprint subsection enumerates reflex (vasovagal and situational) syncope, orthostatic hypotension, and cardiac syncope of structural and electrical origin.

Syncope during exertion or while supine, or preceded by palpitations, suggests a cardiac cause and warrants admission and monitoring.

A prodrome of nausea, warmth, diaphoresis and tunnel vision with an identifiable trigger characterizes reflex syncope.

Orthostatic hypotension is defined by a fall of at least 20 mmHg systolic or 10 mmHg diastolic within three minutes of standing.

Tilt-table testing and prolonged rhythm monitoring are second-line tests; history, examination and a 12-lead ECG identify most causes.

Last updated: August 2026

1. The Only Question That Matters

Syncope is transient loss of consciousness from global cerebral hypoperfusion, with spontaneous complete recovery. ABIM lists it as a named subsection under Cardiovascular Disease with three categories: reflex syncope (vasovagal and situational) , orthostatic hypotension , and cardiac syncope (structural and electrical) .

The exam task is never "what is the diagnosis" in isolation. It is: is this cardiac? Reflex syncope has an excellent prognosis. Cardiac syncope carries meaningful short-term mortality, and the correct answer in those vignettes is admission and monitoring rather than reassurance and discharge.

2. Historical Features That Discriminate

• Feature Suggests reflex/orthostatic Suggests cardiac
• Position at onset Standing, prolonged Supine or seated
• Relation to exertion After exertion During exertion
• Prodrome Nausea, warmth, diaphoresis, tunnel vision None, or palpitations only
• Trigger Pain, fear, micturition, cough, defecation, venipuncture None
• Recovery Slow, with fatigue Rapid and complete
• Injury Uncommon Facial or head injury from unguarded fall
• Age at first episode Adolescence to young adult Older, or new onset after 50
• Cardiac history Absent Structural disease, low ejection fraction, prior infarct
• Family history Unremarkable Sudden death before age 40

Three features carry disproportionate weight and should be treated as red flags in isolation: syncope during exertion , syncope while supine , and syncope preceded by palpitations .

3. Reflex (Neurally Mediated) Syncope

Reflex syncope results from an inappropriate autonomic response — vasodilation, bradycardia, or both. Subtypes:

Vasovagal: the classic form, triggered by prolonged standing, heat, pain, emotional distress or the sight of blood, with a well-developed autonomic prodrome.

Situational: triggered by a specific act — micturition, defecation, coughing, swallowing, or weightlifting.

Carotid sinus hypersensitivity: in older patients, triggered by head turning, shaving or a tight collar.

Management is largely non-pharmacologic: trigger avoidance, liberal salt and fluid intake if no contraindication exists, and physical counter-pressure maneuvers (leg crossing with tensing, handgrip, arm tensing) at the first symptom. Midodrine or fludrocortisone are reserved for recurrent, disabling episodes. Pacing has a narrow role limited to documented, recurrent asystolic reflex syncope in older patients.

4. Orthostatic Hypotension

The definition is quantitative: a fall of at least 20 mmHg systolic or 10 mmHg diastolic within three minutes of standing . Measure supine after five minutes, then at one and three minutes standing — a seated-to-standing measurement misses cases.

The presence or absence of a compensatory heart-rate rise separates the two mechanisms:

Compensatory tachycardia present: volume depletion, hemorrhage or medication effect.

Compensatory tachycardia absent (neurogenic): autonomic failure from diabetic autonomic neuropathy, Parkinson disease, multiple system atrophy or amyloidosis.

Culprit drugs are a favorite: alpha-blockers, diuretics, nitrates, tricyclic antidepressants, antipsychotics and dopaminergic agents. Reviewing and deprescribing the medication list precedes any new prescription.

5. Cardiac Syncope

Structural causes obstruct output or impair filling:

Severe aortic stenosis — exertional syncope is one of the three cardinal symptoms and mandates evaluation for valve replacement.

Hypertrophic cardiomyopathy — outflow obstruction worsens with the reduced preload of exertion.

Pulmonary embolism and cardiac tamponade — acute obstruction to filling or output.

Aortic dissection and acute myocardial infarction .

Electrical causes are arrhythmic:

Bradyarrhythmias: sinus node dysfunction, high-grade AV block.

Ventricular tachycardia , particularly with prior infarct or reduced ejection fraction.

Inherited channelopathies: long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia.

6. The ECG Is the Highest-Yield Test

Every syncope patient gets a 12-lead ECG . Findings that convert a benign story into an urgent one:

• ECG finding Implication
• Prolonged QT interval Long QT syndrome, torsades risk
• Coved ST elevation in V1–V2 Brugada syndrome
• Delta wave with short PR Pre-excitation
• Q waves, low ejection fraction markers Prior infarct, scar-related VT
• Bifascicular block, Mobitz II, complete heart block Intermittent high-grade block
• Epsilon wave, T inversion in V1–V3 Arrhythmogenic right ventricular cardiomyopathy
• Left ventricular hypertrophy with deep septal Q waves Hypertrophic cardiomyopathy
• 7. Diagnostic Sequencing

History, physical examination including orthostatic vital signs, and 12-lead ECG. This trio identifies the cause or the risk category in most patients.

Echocardiography when structural disease is suspected by history, murmur or ECG.

Rhythm monitoring matched to episode frequency: inpatient telemetry for high-risk patients, ambulatory monitoring for frequent episodes, and an implantable loop recorder for infrequent, unexplained, high-risk syncope.

Exercise testing for exertional syncope.

Tilt-table testing only when reflex syncope is suspected but the diagnosis remains uncertain after the above.

Two tests that are commonly ordered and rarely helpful: routine head CT and carotid ultrasonography . Syncope is global hypoperfusion; carotid disease causes focal deficits, not transient global loss of consciousness. Neuroimaging is warranted only when head trauma occurred or when focal neurologic findings are present.

8. Seizure Versus Syncope

Brief myoclonic jerking occurs in up to 90% of syncopal episodes and does not indicate a seizure. Features favoring seizure are a preceding aura, prolonged tonic-clonic activity, lateral tongue biting, and postictal confusion lasting minutes . Recovery from syncope is prompt and orientation returns immediately.