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1.4 Supraventricular Tachycardias, Ventricular Arrhythmias & Bradycardias
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
1.4 Supraventricular Tachycardias, Ventricular Arrhythmias & Bradycardias
Key Takeaways Explain This Topic AI
Conduction defects, bradyarrhythmias, tachyarrhythmias and cardiac resuscitation are all enumerated under the dysrhythmias blueprint subsection.
AV-nodal blocking agents are contraindicated in pre-excited atrial fibrillation because they accelerate conduction down the accessory pathway.
Mobitz II and third-degree AV block are infranodal, do not respond reliably to atropine, and require pacing.
Asymptomatic bifascicular block without syncope or higher-grade block does not require a pacemaker.
Channelopathies such as long QT and Brugada syndrome present with syncope or arrest in structurally normal hearts and are diagnosed from the resting ECG.
Last updated: August 2026
- 1. Supraventricular Tachycardias (SVT)
- AV Nodal Reentrant Tachycardia (AVNRT)
Mechanism: Dual AV nodal pathways (slow pathway with short refractory period; fast pathway with long refractory period) creating a micro-reentrant circuit within the AV node.
ECG: Regular narrow-complex tachycardia (140-220 bpm) with P waves buried within or immediately following the QRS complex (pseudo-r' in lead V1, pseudo-S in inferior leads).
Acute Treatment: (1) Vagal maneuvers (modified Valsalva with supine leg elevation); (2) IV Adenosine (6 mg rapid IV push through large antecubital vein followed by 20 mL saline flush; if no response within 1-2 min, administer 12 mg IV); (3) IV Diltiazem or Metoprolol if adenosine fails; (4) Synchronized cardioversion if unstable.
Definitive Treatment: Radiofrequency catheter ablation of the slow pathway (curative in >95% of cases).
AV Reentrant Tachycardia (AVRT) & Wolff-Parkinson-White (WPW) Syndrome
Mechanism: Congenital extranodal accessory pathway (Bundle of Kent) connecting atrium and ventricle, bypassing the AV node.
Baseline ECG Triad: Short PR interval (<120 ms), slurred QRS upstroke ( delta wave ), and widened QRS (>120 ms).
Orthodromic AVRT (90%): Conduction travels anterograde down the AV node and retrograde up the accessory pathway -> Regular narrow-complex tachycardia. Treat identical to AVNRT (vagal maneuvers, IV Adenosine).
Antidromic AVRT (10%): Conduction travels anterograde down the accessory pathway and retrograde up the AV node -> Regular wide-complex tachycardia.
Pre-Excited Atrial Fibrillation (AF + WPW):
ECG: Irregularly irregular, wide-complex tachycardia with bizarre, polymorphous QRS morphology and extremely rapid ventricular rates (>250-300 bpm) .
CRITICAL BOARD CONTRAINDICATION: AV nodal blocking agents ("ABCD": Adenosine, Beta-blockers, Calcium channel blockers [Diltiazem/Verapamil], Digoxin) are STRICTLY CONTRAINDICATED. Blocking the AV node diverts 100% of electrical impulses down the accessory pathway, which has a very short refractory period, precipitating ventricular fibrillation and cardiac arrest .
Treatment: Hemodynamically stable -> IV Procainamide (or IV Ibutilide) which prolongs the refractory period of the accessory pathway. Hemodynamically unstable -> Emergency Synchronized Direct-Current Cardioversion .
Definitive: Catheter ablation of the accessory pathway.
- 2. Ventricular Arrhythmias & Channelopathies
- Monomorphic Ventricular Tachycardia (VT)
Defined as >=3 consecutive ventricular beats at a rate >100 bpm with identical QRS morphology. Wide QRS complex (>120 ms).
ECG Signs of VT vs. SVT with Aberrancy:
AV Dissociation: P waves marching independently of wide QRS complexes (pathognomonic).
Capture Beats & Fusion Beats: Normal narrow QRS (capture) or hybrid hybrid QRS (fusion) demonstrating dual supraventricular and ventricular activation.
Concordance: Uniformly positive or uniformly negative QRS complexes across leads V1-V6.
Brugada Sign: Interval from onset of R wave to deepest nadir of S wave >100 ms in any precordial lead.
Management:
Pulseless VT: Immediate CPR + Defibrillation (unsynchronized 200 J biphasic) + Epinephrine + Amiodarone/Lidocaine.
Unstable with Pulse: Synchronized cardioversion (100-200 J).
Stable with Pulse: IV Amiodarone (150 mg over 10 min, then 1 mg/min for 6 hours) or IV Procainamide (20-50 mg/min until arrhythmia suppressed, hypotension ensues, or QRS widens >50%).
Polymorphic VT & Torsades de Pointes (TdP)
Torsades de Pointes: Polymorphic VT characterized by QRS complexes continuously twisting around the isoelectric baseline, occurring in the setting of prolonged baseline QT interval (QTc >500 ms) .
Causes of Prolonged QTc:
Electrolytes: Hypokalemia, Hypomagnesemia, Hypocalcemia.
Drugs: Antiarrhythmics (Sotalol, Dofetilide, Procainamide), Psychotropics (Haloperidol, Citalopram, Methadone), Antimicrobials (Macrolides, Fluoroquinolones, Azole antifungals), Antiemetics (Ondansetron).
Congenital Long QT Syndromes (LQTS): Romano-Ward (autosomal dominant), Jervell and Lange-Nielsen (autosomal recessive with sensorineural deafness).
Acute Management of Torsades de Pointes:
IV Magnesium Sulfate: 2 grams IV push over 1-2 minutes, repeated if necessary, regardless of baseline serum magnesium level.
Withdraw all QT-prolonging medications and vigorously recheck/correct potassium to >4.0-4.5 mEq/L.
Overdrive Transvenous Pacing or Isoproterenol Infusion: Increases heart rate to 100-110 bpm, which shortens ventricular repolarization and eliminates pauses that trigger TdP.
Unsynchronized defibrillation if degenerates to VF or hemodynamic collapse.
- 3. Bradycardias and Conduction Blocks
- Sinus Node Dysfunction (Sick Sinus Syndrome)
Manifests as persistent sinus bradycardia, sinus pauses/arrest (>3 seconds), or Tachycardia-Bradycardia Syndrome (paroxysms of AF alternating with severe sinus pauses). Permanent Pacemaker (PPM) is indicated when bradycardia is symptomatic.
Atrioventricular (AV) Blocks & Pacing Indications
AV Block Type Site of Block ECG Findings Clinical Behavior Permanent Pacemaker (PPM) Indication?
First-Degree AV Block AV Node (usually) PR interval > 200 ms (constant); every P wave is followed by a QRS Benign; asymptomatic NO (except rare symptomatic "pacemaker syndrome" with PR >300 ms)
Second-Degree Mobitz Type I (Wenckebach) AV Node (above His bundle) Progressive PR prolongation culminating in a non-conducted P wave; grouped beating Usually benign; physiological in young athletes; low risk of progression NO if asymptomatic. PPM only indicated if chronically symptomatic.
Second-Degree Mobitz Type II Infranodal (His-Purkinje system) Constant PR interval with intermittent, unpredictable dropped QRS complexes; wide QRS common High risk of sudden progression to complete heart block and asystole YES — Class I Indication for PPM in all patients, even if asymptomatic.
Third-Degree (Complete) AV Block Infranodal or AV Node Complete AV dissociation ; regular P-P intervals and regular R-R intervals; escape rate 30-40 bpm (wide QRS) or 40-60 bpm (narrow QRS) Severe bradycardia, syncope (Stokes-Adams attacks), heart failure, sudden death YES — Class I Indication for PPM in all patients (unless transient due to reversible Lyme carditis, hyperkalemia, or medication toxicity).
Acute Symptomatic Bradycardia Protocol:
Atropine: 1 mg IV push q3-5min (max 3 mg total). Note: Atropine is effective for AV nodal block (Mobitz I), but is INEFFECTIVE for infranodal block (Mobitz II / wide-QRS complete block).
If atropine fails or is contraindicated: Transcutaneous Pacing or IV Chronotropic Infusions ( Dopamine 5-20 mcg/kg/min or Epinephrine 2-10 mcg/min).
Emergent Transvenous Temporary Pacing while preparing for permanent pacemaker implantation.