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ECG Basics & Fundamentals
Key Points About The Basics of ECG Interpretation: Electrocardiography Defined: An ECG records the heart’s electrical activity in real time, offering a rapid window into rhythm, rate, and conduction. Core…
ECG Basics and Fundamentals: A stepwise approach to ECG interpretation and how to use differential diagnoses to make critical clinical diagnoses
A 40-year-old man presents to the ED with altered mental status and appears critically ill. The following ECG is obtained:
ECG Tags
- & Myocardial Ischemia
- 11th Annual UMEM ECG Competition
- 12th annual UMEM Residency ECG competition
- 13th annual ECG competition
- 1st degree AV Block
- 1st degree AVB
- 2:1 AV Block
- 2:1 AVB
- 2:1 Conduction
- 2015 ECG Competition
- 2015 ECG Competition Part II
- 2016 ECG Competition
- 2017 ECG Competition Part II
- 2018 ECG Competition Part II
- 2019 ECG Competition
- 2020 ECG Competition
- 2024 ECG Competition
- 2025 ACC/AHA/ACEP/NAEMSP/SCAI Clinical Practice Guidelines for the Management of Patients with Acute Coronary Syndromes
- 2025 ACS guidelines
- 3rd degree AV block
- 5 Step Approach
- 5-FU
- aberrancy
- Aberrant conduction
- Abnormal ECG
- Abnormal P wave Axis DDx
- Abnormal STAT ECG
- absent p waves
- Accelerated idioventricular rhythm
- accelerated junctional rhythm
- Acidosis
- ACS
- ACS mimics
- ACS RIsk Factors
- Acute Chest Pain
- Acute Chest Pain DDx
- Acute Coronary Syndromes (ACS)
- Acute MI
- Acute Pericarditis
- Acute Pericarditis vs. STEMI
- Adenosine
- Adenosine sensitive VT
- Advanced AV block
- Afib
- Afib with WPW
- AI
- AI interpreted ECGs
- AIVR
- Algorithm Limitations
- Altered Mental Status Emergencies
- AMI
- Amiodarone
- and Lead II R-wave-peak-time (RWPT) algorithms
- Anemia
- anemia in ACS
- Anterior STEMI
- Anterior T wave inversions
- antidromic
- antidromic SVT
- Aortic Dissection
- Approach to ECG
- Approach to ECG interpretation
- Appropriate Discordance
- April Fools
- arrhythmogenic cardiomyopathy
- Arrhythmogenic right ventricular cardiomyopathy
- Arrhythmogenic right ventricular dysplasia/cardiomyopathy
- Arrhythmogenic RV Dysplasia
- Artifact
- artifact vs. malignant arrhythmias
- artifact vs. torsades
- artifact vs. ventricular fibrillation
- Artifact vs. ventricular rhythm
- artifact vs. ventricular tachycardia
- Artificial Intelligence
- ARVC
- ARVD
- ASD
- Ashman
- Ashman phenomenon
- Aslanger
- Aslanger Pattern
- Aslanger's Pattern
- Atherosclerosis
- Athlete’s ECG
- atrial arrhythmias
- atrial bigeminy
- Atrial dysrhythmias
- Atrial fibrillation
- Atrial Fibrillation (AFib)
- atrial fibrillation with complete heart block
- Atrial Fibrillation with RVR
- Atrial Fibrillation with SVT
- Atrial Fibrillation with WPW
- Atrial flitter
- Atrial flutter
- Atrial Flutter 1:1 Conduction
- atrial flutter 2:!
- atrial flutter 2:1 conduction
- atrial flutter mimics
- Atrial Flutter with Variable Conduction
- Atrial parasystole
- Atrial septal defect
- Atrial Septal Defect (ASD) & Crochetage Pattern
- Atrial tachycardia
- Atrifact
- Atrioventricular blocks
- Atrioventricular Blocks (AVB) Summary
- Atrioventricular Nodal Reentry Tachycardia
- Atrioventricular Reciprocating Tachycardia
- Attending Level Curriculum
- AV Block
- AV Block: Second-Degree
- AV Blocks
- AV Dissociation
- AV dissociation without complete heart block
- AVB
- AVB: 1st degree
- AVB: 2nd degree
- AVBs
- AVD
- aVL
- AVNRT
- aVR
- Axis
- axis basics
- Barcelona criteria
- Basics
- basics and fundamentals
- Bayesian
- Bazett formula
- BBB
- BBBs & Paced Rhythms vs. STEMI
- Benign early repolarization
- BER
- Beta-Blocker (BB) and Calcium Channel Blocker (CCB) Toxicity
- bidirectional ventricular tachycardia
- bifascicular block
- bifid p waves
- bigeminy
- Biphasic T-waves
- Bix rule
- Bizzare rhythm
- Blocked PAC’s
- Board review
- bpm
- brady
- brady tachy syndrome
- bradyarrhythmia
- Bradycardia
- Bradycardia DDx
- BRASH syndrome
- Brs
- Brugada
- Brugada Pattern
- Brugada Sign
- Brugada syndrome
- Brugada Syndrome (BrS)
- Buried P Waves
- Buried T wave
- CAD
- cannabis
- cannabis toxicity
- Cardiac arrest
- cardiac risk factors
- Cardiac tamponade
- cardiogenic shock
- Cardiovascular effects of marijuana
- Cardioversion
- Catecholaminergic Polymorphic VT (CPVT)
- CCB toxicity
- Cerebral T waves
- CHB
- Chemotherapy
- Chest Pain
- chest pain differentials
- child
- child ecg
- Chronic Obstructive Pulmonary Disease
- Classic STEMI Criteria
- clumped beats
- Clumped or Grouped Beats
- cocaine
- cocaine chest pain
- Cocaine toxicity
- Complete Heart Block
- Computer ECG interpretation
- Computer interpreted ECGs
- Computer interpreted electrocardiograms
- congenital long QT syndrome
- congenital short QT syndrome
- COPD
- coronary angiography
- Corrected QT interval
- COVID-19
- Crochetage
- Crochetage pattern
- ddx
- DDx for TWIs in V1-V3
- de Winter
- de Winter T-wave
- de Winter T-waves
- defibrillation
- Delta waves
- deWinter
- deWinter T-waves
- Dextrocardia
- differential diagnoses
- differential diagnoses for left axis deviation
- Diffuse ST elevation
- Diffuse ST Elevation DDx
- Diffuse ST-segment Elevation
- Diffuse STE
- dig effect
- digoxin
- Digoxin effect
- Digoxin toxicity
- DKA
- Dominant R wave
- Dominant R wave in aVR
- Dominant R wave in V1
- dresslers
- dresslers syndrome
- dynamic ecg changes
- Dysrhythmia
- Dysrhythmia in LVADs
- Dysrhythmias
- Earliest ECG Evidence of Occlusion MI
- Earliest Evidence of Occlusion MI
- Early cardiac ischemia
- Early ECG evidence of ischemia
- Early ischemia
- Early ischemic changes
- Early reciprocal changes
- Early Repolarization
- early repolarization vs/ STEMI
- early signs of cardiac ischemia
- early signs of ischemia
- Early STEMI
- ecg 101
- ECG Basics
- ECG competition
- ECG Competition 2023
- ECG Evidence of Reperfusion After Occlusion
- ecg history
- ECG in ACS
- ECG interruptions
- Ectopic atrial rhythm
- Ectopic beats
- electrical alternans
- Electrical storm
- Electrocardiographic polyuria
- Electrographic polyuria
- Electrolytes
- Elevated intracranial pressure
- Emergent cath lab activation
- EMS
- EMS cases
- EMS ECG
- EMS ECGs
- EMS ECGs in Acute Coronary Syndromes (ACS)
- Epsilon waves
- escape rhythm
- escape rhythms
- Escape-Capture
- Escape-Capture Bigeminy
- evolution of ecg
- Evolving STEMI
- extreme axis deviation
- Extreme Axis Deviation Basics
- Extreme Axis Deviation DDx
- Extreme Axis Deviation Differentials
- failure to capture
- failure to pace
- failure to sense
- Fascicular blocks
- fever
- First-Degree AV Block
- Flattened T Waves
- Flutter Waves (F waves)
- Foundational Resident
- Framingham formula
- Fridericia formula
- Fusion Beats
- generic PMVT
- GERD
- Griffith
- grouped beats
- Guidelines
- HCM
- Heart block
- heart rate
- heart rate and rhythm basics
- heart rate basics
- heart rhythm
- heart rhythm interpretation
- High grade AV block
- high grade AV blocks
- high lateral STEMI
- high left ventricular voltages and 'dagger like' Q waves
- high risk pe
- High Voltage
- High-Grade (Advanced AV Block)
- high-risk pulmonary embolism
- Himalayan T-waves
- history of ecg
- History of presenting illness
- HOCM
- Hodges formula
- Hypeacute T waves
- hyperacute
- Hyperacute T-waves
- Hypercalcemia
- Hyperkalemia
- Hyperkalemia emergencies
- hyperkalemia mimics
- Hyperkalemia vs. STEMI
- Hyperkalemia vs. VT
- Hyperkalemic paralysis
- Hyperkalemic Periodic Paralysis
- Hyperkalemic Periodic Paralysis (“Impressive Syndrome”)
- Hypermagnesemia
- Hypertrophic
- Hypertrophic Cardiomyopathy
- Hypertrophic obstructive cardiomyopathy
- Hypocalcemia
- Hypokalemia
- hypokalemia emergencies
- Hypokalemic paralysis
- hypokalemic periodic paralysis
- Hypomagnesemia
- hyponatremia
- Hypothermia
- Idioventricular rhythms
- Impressive syndrome
- in-training exam
- inappropriate sinus tachycardia
- incomplete right bundle branch block
- indeterminate axis
- Indeterminate Axis DDx
- Indeterminate Axis differentials
- indeterminate QRS axis
- inferior STEMI
- inservice exam
- intermittent
- Intermittent WPW
- intervals
- Intracranial hemorrhage
- Intractable chest pain
- inverted P Waves
- Inverted T Waves
- Inverted U-waves
- IRBBB
- Irregular rhythm
- irregular rhythms
- Ischemia
- Ischemia & Infarction
- Ischemic T-waves
- Isoelectric baseline
- Isoelectric segment
- Isoelectric Segment of the ECG
- Isolated Posterior STEMI
- Isorhythmic AV dissociation
- Isorhythmic AVD
- ITE prep
- ITE review
- J point
- J wave
- J-waves
- Jervell
- Jervell and Lange-Nielsen Syndrome
- JLNS
- Josephson Sign
- Josephson’s sign
- junctional escape
- junctional escape capture bigeminy
- junctional escape rhythms
- junctional rhythm
- Junctional rhythms
- Junctional Tachycardia
- Juvenile T wave inversions
- Juvenile T waves
- Juvenile T-wave pattern
- kid
- kid ecg
- kids
- killer differentials
- LAD
- LAD OMI
- LAE
- LAFB
- Lange
- Large T Wave DDx
- Large T-waves
- LBBB
- LBBB DDx
- lead misplacement
- lead V1
- left anterior fascicular block
- Left Atrial Enlargement
- Left axis deviation
- left axis deviation ddx
- left bundle branch block
- left posterior fascicular block
- Left Ventricular Hypertrophy (LVH)
- Left ventricular hypertrophy vs. STEMI
- lewis
- Lewis lead
- LGL
- life savers
- limb lead misplacement
- Limb lead reversal
- Literature review
- Long QT
- Long QT Interval DDx
- Long QT-interval
- Long QTc
- long ST segment
- Low Voltage
- low voltage differential
- Low voltage QRS
- Low Voltage QRS DDx
- LPFB
- LQT1 (KCNQ1 Mutation)
- LQT2 (KCNH2 Mutation)
- LQT3 (SCN5A Mutation)
- LQTS
- LV Aneurysm
- LV Aneurysm vs. STEMI
- LVAD
- LVAD Dysrhythmias
- LVADs
- LVH
- LVH vs. STEMI
- LVH with strain pattern
- Lyme carditis
- Marijuana
- marijuana toxicity
- Massive STEMI
- MAT
- Mechanisms of ACS
- Metabolic Emergencies
- Methamphetamine Toxicity
- MI
- mimics
- misplaced leads
- Mobitz
- Mobitz conduction
- Mobitz I
- Mobitz I (Wenckebach)
- Mobitz I or Mobitz II: How to tell the difference
- Mobitz II
- Mobitz II (Hay)
- Mobitz II AV block
- modified lead
- Modified Sgarbossa criteria
- Monomorphic Ventricular Tachycardia
- monomorphic VT
- Multifocal atrial tachycardia
- Myocarditis
- Myxedema
- Na channel blocker toxicity
- narrow & irregular tachycardia
- narrow & regular tachycardia
- Narrow complex and regular rhythms
- Narrow complex irregular rhythms
- Narrow complex irregular tachycardia
- Narrow Complex Regular Tachycardia
- narrow complex regular tachycardia differential
- Narrow Complex Tachycardia
- narrow qrs bradycardia
- Narrow QRS Bradycardia DDx
- New Q Waves
- New RBBB and LAFB
- Nielsen
- Nikelekam T-waves
- No clear P waves DDx
- no man's land
- Non-conducted P wave (P:QRS>1) DDx
- non-conducted P waves
- non-conducted PACs
- Non-STE ACS
- Non-sustained Ventricular tachycardia
- Non-sustained VT
- Nonspecific intraventricular conduction delay
- nonsustained
- nonsustained ventricular tachycardia
- Nonsustained VT
- normal
- Normal Cardiac Conduction
- Normal ECG
- normal heart rate
- Normal Heart Rate Ranges by Age
- normal lead placement
- normal qrs axis
- Normal R wave progression
- Normal Sinus Rhythm
- Normal STAT ECG
- Normal variant patterns
- normal variant ST elevation
- Normal variants
- Not Enough P Waves (P:QRS < 1) DDx
- Not normal ecg
- NSVT
- Occlusion MI
- Occlusion MI - STEMI Criteria & Beyond
- Occlusion MI patterns
- OMI
- OMI pa
- OMI Pattern
- OMI Pattern: ST Depression V1-V4
- OMI Patterns in Left Bundle Branch Block
- OMI Patterns in Ventricular Paced Rhythms
- OMI Patterns: STEMI (-) Occlusion MI
- Opiate Toxicity
- orthodromic
- orthodromic SVT
- Osborn waves
- overdose
- p mitrale
- p pulmonale
- p waves
- P.E.
- PAC
- PAC’s
- Paced rhythms
- Pacemaker
- Pacemaker emergencies
- pacemaker malfunction
- Pacer
- palpitations
- Pauses and clumped beats
- PE
- PE vs. STEMI
- peaked P waves
- Pediatric ECG
- Pediatric ECG Interval Table
- Pediatrics
- Pericardial effusion
- Pericardial Tamponade
- Pericarditis
- pericarditis vs acs
- Pericarditis vs. STEMI
- Periodic paralysis
- Persistent juvenile T-wave pattern
- PFO
- PGY-2 (Intermediate) Resident Curriculum
- PGY-3 (Advanced) Resident Curriculum
- PGY1 Curriculum
- PJC
- PJCs
- PJTW
- plaque rupture
- plaque vulnerability
- PMVT
- Pokey T wave
- Polymorphic Ventricular Tachycardia
- Polymorphic VT
- Polyuria
- Poor R-wave progression
- post arrest ECG
- post cardiac arrest ECGs
- post-arrest
- Post-Arrest ECG for Dysrhythmias
- Post-Arrest ECG for Ischemia
- Post-arrest NSTE-ACS
- Post-arrest STEMI
- post-cardiac arrest ecg
- post-mi pericarditis
- Post-Thrombolytic Reperfusion ECG Findings
- Posterior MI
- Posterior Occlusion MI
- POSTERIOR OMI
- Posterior STEMI
- Posterior STEMI Criteria
- postural orthostatic tachycardia syndrome
- Potpourri
- POTS
- PR interval
- PR segment
- PR segments
- Pre-hospital ECG
- precordial lead misplacement
- precordial swirl
- preexcitation
- preexcitation syndrome
- Preexcitation syndromes
- preexcited af
- preexcited atrial fibrillation
- Pregnancy
- Prehospital ECG
- premature atrial complexes
- Premature beats
- Premature complexes
- premature contractions
- premature junctional complexes
- Prolonged QT
- Prolonged QT interval
- prolonged QTc
- Proper ECG Lead Placement
- proper lead placement
- proportionality
- PRWP
- Pseudo Wellens
- Pseudo-Wellens waves
- Pseudonormalization of T-waves
- Pulmonary Embolism
- pulmonary hypertension
- Pulse tapping artifact
- pulse-tapping
- PVC
- PVCs
- PVT
- Q-waves
- QRS
- QRS axis
- qrs axis basics
- QRS Complexes
- QRS fragmentation
- QRS Fragmentation (fQRS)
- QRS morphology
- qrs voltage
- QRS-interval
- QRS-T proportionality
- QT interval
- QT Interval Basics
- QTc interval
- R wave basics
- R waves
- R-on-T phenomenon
- R-wave
- R-wave in V1
- R-wave progression
- RAD
- RAE
- rapid af
- rapid afib
- rapid atrial fibrillation
- rate & rhythm
- RBBB
- Really wide complex tachycardia
- reciprocal changes
- Recommended ECG Books
- Reflux
- refractory ischemia
- Regular Really Wide Complex Tachycardia
- Regular Rhythm
- Regular Wide Complex Tachycardia
- Regularized atrial fibrillation
- Regularly Irregular Rhythm
- repeat ecg
- repolarization abnormalities
- Rescue PCI
- Resolved ST segment elevation
- Resources & Recommendations
- Respiratory variation
- Retrograde P waves
- Reverse R wave progression
- Revised Sgarbossa Criteria
- Rhythm
- Rhythm Interpretation
- right atrial enlargement
- Right axis
- Right Axis Deviation
- Right Axis Deviation + STE DDx
- Right Axis Deviation + STE Differential
- Right Axis Deviation Basics
- Right Axis Deviation DDx
- Right bundle branch block
- right heart strain
- Right sided leads
- Right Ventricular (RV) STEMI Criteria
- Right Ventricular Hypertrophy
- Rightward axis
- rollercoaster T waves
- RRWCT
- RV MI
- RV Outflow Tract Tachycardia (RVOT)
- RV STEMI
- rvh
- RVH with strain
- RVMI
- RWCT
- S wave
- S waves
- s5
- SAH
- Salvador Dali
- SANRT
- SCAD
- second degree av block
- Second-Degree AV Block Type I (Mobitz I / Wenckebach)
- Second-Degree AV Block Type II (Mobitz II)
- Second-Degree AV Block with 2:1 Conduction
- segments
- Seizure
- Seizures
- Septal STEMI
- Serial ECG
- Serial ECGs
- Severe Hyperkalemia
- Severe hypothyroidism
- Sgarbossa
- Sgarbossa Criteria
- Shark fin morphology
- Shark fin STEMI
- Short PR interval
- Short QT
- Short QT interval
- Short QT Syndrome
- Short QTc
- Shortened QT
- SHS
- sick sinus syndrome
- Sinoatrial Exit Block
- Sinoatrial Nodal Reentry Tachycardia
- Sinoatrial Nodal Reentry Tachycardia (SANRT)
- Sinus arrest
- sinus arrhythmia
- sinus bradycardia
- sinus inversus totalis
- Sinus Node Dysfunction
- Sinus Node Dysfunction (Sick Sinus Syndrome
- sinus rhythm
- Sinus rhythms
- Sinus Tachycardia
- situs inversus
- situs inversus totalis
- Sloof Lirpa Sign
- Slow Atrial fibrillation
- slow ventricular tachycardia
- slow vt
- Sodium channel blocker toxicity
- South Africa
- South Africa sign
- South African
- South African Flag Sign
- spiked
- Spiked Helmet sign
- spiked-helmet
- Spodick Sign
- Spodick’s Sign
- Spontaneous Coronary Artery Dissection
- Spontaneous Coronary Artery Dissection (SCAD)
- ST
- ST depression
- ST depression differential
- ST Depression in V1-V4 DDx
- ST depression V1-V4
- ST Elevation
- ST Elevation DDx
- ST Elevation in aVR DDx
- ST segment elevation
- ST Segment Elevation in aVR with Multi Lead ST Segment Depression
- ST-segment
- ST-segment depression
- stat
- stat ecg
- stat ecgs
- STD
- STE
- STE differential diagnosis
- STE in aVR
- steeple sign
- Steeple sign in V1
- STEMI
- STEMI Criteria
- STEMI Criteria & STEMI Equivalent Patterns
- STEMI equivalent
- STEMI equivalents
- STEMI mimics
- STEMI vs. acute pericarditis
- STEMI vs. Early repolarization
- STEMI vs. Severe Hyperkalemia
- stepwise approach
- strain
- Stress Testing
- Stress tests
- Student Level Curriculum
- Subtle ST elevation
- Subtle ST Segment Elevation (STE)
- subtle stemi
- Supraventricular tachycardia
- Supraventricular Tachycardia (SVT)
- Sustained VT
- SVT
- synchronization
- Syncop
- Syncope
- syncope ddx
- syncope differentials
- syncope emergencies
- Systematic approach to ECG
- T wave
- T wave inversion differential
- T Wave Inversion in V1-V3 DDx
- T wave inversions in V1-V3
- T wave morphology
- T-wave abnormalities
- T-wave alternans
- T-wave inversion
- T-wave inversions
- T-waves
- Tachycardia
- Takotsubo Cardiomyopathy
- Takotsubo Cardiomyopathy vs. STEMI
- Tall R wave in aVR
- Tall R wave in V1
- Tamponade
- TCA
- TCA overdose
- TCA toxicity
- TdP
- Terminal QRS distortion
- Terminal QRS Distortion (OMI Pattern)
- the basics
- The Bix Rule
- The Bix Rule – Unmasking Atrial Flutter
- The Curriculum
- third degree AV block
- Third-Degree AV Block (Complete Heart Block)
- Thrombolytics
- too many P waves
- Too Many P Waves (P:QRS>1) DDx
- Top 10 cases of the past 10 years
- Torsades
- Torsades de pointes
- Torsades de Pointes risk
- torsades de points
- Toxicologic Emergencies
- Toxicology
- TP segment
- Transient STEMI
- Tremor artifact
- trifascicular block
- Trigeminy
- Troponin
- troponins
- TWI
- Type A Wellens
- Type B Wellens
- U-waves
- Understanding ECG Artifacts
- unifascicular
- unstable angina
- unstable bradycardia
- unstable tachyarrhythmia
- unstable tachycardia
- Upright T waves in V1
- urgent cath
- V1
- v1-v2 placed too high
- V1/V2
- vasospasm
- Ventricular aneurysm
- Ventricular dysrhythmias
- ventricular escape rhythms
- Ventricular fibrillation
- ventricular fibrillation mimics
- Ventricular Flutter
- Ventricular rhythm
- Ventricular rhythms
- Ventricular Tachycardia
- Ventricular Tachycardia (VT)
- Ventricular tachycardia mimics
- Ventricular tachycardia vs. SVT with aberrant conduction
- Ventricular Tachycardiak
- Vereckei aVR
- VF
- voltage
- VT
- VT mimics
- VT vs. SVT with Aberrancy
- w Voltage
- waveforms
- waves
- WCT
- Wellens
- Wellens waves
- Wellens’ syndrome
- Wide & Regular Tachydysrhythmia DDx
- wide complex irregular tachycardia
- Wide complex QRS
- wide complex regular tachycardia
- Wide complex tachycardia
- Wide QRS
- Wide QRS (BBBs & Paced Rhythms) vs. STEMI
- wide qrs bradycardia
- Wide QRS Complex DDx
- wide qrs differential
- Wide QRS interval
- wide vs. narrow QRS
- Wolff Parkinson White
- Wolff-Parkinson White (WPW) Syndrome
- WPW
- wpw syndrome
- WPW syndrome and Pseudo-MI patterns
- WPW vs STEMI
- WPW with Antidromic SVT
- WPW with atrial fibrillation
- WPW with Orthodromic SVT
- WPW with SVT
- Young patients
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