Basics & Fundamentals
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Left Ventricular Hypertrophy (LVH)
Key Points: LVH reflects increased left ventricular muscle mass, usually from chronic pressure overload. Common causes include longstanding hypertension and aortic stenosis. ECG diagnosis is imperfect. Voltage criteria are specific…
Modified Sgarbossa Criteria: STEMI Equivalent Pattern
Key Points: LBBB and ventricular-paced rhythms can hide acute coronary occlusion because abnormal depolarization creates expected secondary ST-T changes. Occlusion MI can still be recognized when those ST changes are…
Persistent Juvenile T Wave Pattern
Key Points: Persistent juvenile T wave pattern is a benign normal variant that most often appears as shallow asymmetric T wave inversion in the right precordial leads, usually V1 to…
Atrial Flutter with Variable Conduction
Key Points: Mechanism: Typical atrial flutter arises from a large re-entry circuit in the right atrium. The atrial rate is usually near 300 beats per minute. ECG hallmark: Continuous “saw-tooth”…
Isorhythmic AV Dissociation
Key Points: Isorhythmic AV dissociation is a form of AV dissociation in which the sinus rate and junctional or ventricular escape rate are nearly identical, making the P waves and…
Third-Degree AV Block (Complete Heart Block)
Key Points: Third-degree AV block is complete failure of atrial impulses to conduct to the ventricles. The defining ECG feature is AV dissociation with no conducted P waves. The atrial…
Second-Degree AV Block Type I (Mobitz I/Wenckebach)
Key Points: Mobitz I is defined by progressive PR prolongation until a single P wave fails to conduct, after which the cycle resets. The block is usually at the AV…
Second-Degree AV Block with 2:1 Conduction
Key Points: Second-degree AV block with 2:1 conduction means every other P wave conducts and every other P wave is blocked. A single ECG with 2:1 conduction usually cannot be…
First-Degree AV Block
Key Points: First-degree AV block is defined by a PR interval greater than 200 ms with fixed 1:1 AV conduction and no dropped QRS complexes. It usually reflects delayed conduction,…
Second-Degree AV Block Type II (Mobitz II)
Key Points: Mobitz II is defined by sudden failure of AV conduction after at least 2 consecutive conducted beats with fixed PR intervals and no preceding PR prolongation. The block…
Atrial Flutter 2:1 Conduction
Key Points: Atrial flutter is a macro-reentrant atrial tachycardia, most commonly typical cavotricuspid isthmus-dependent right atrial flutter, with an atrial rate usually near 300 bpm. With 2:1 AV conduction, the…
Atrial Flutter
Key Points: Atrial flutter is a supraventricular tachyarrhythmia caused by a macro-reentrant circuit, most commonly typical cavotricuspid isthmus-dependent flutter in the right atrium. The atrial rate is usually about 250-350…
Flutter Waves (F waves): Basics
Key Points: Atrial flutter is a supraventricular tachyarrhythmia caused by a macro-reentrant circuit, most commonly typical cavotricuspid isthmus-dependent flutter in the right atrium. The atrial rate is usually about 250-350…
Advanced (High-Grade) AV Block
Key Points: Advanced or high-grade AV block is a severe second-degree AV block with 2 or more consecutive non-conducted P waves, such as 3:1 or 4:1 conduction. Do not force…
Appropriate Discordance
Key Points: Appropriate discordance refers to the expected secondary ST segment and T wave pattern seen with abnormal ventricular depolarization, especially LBBB and ventricular-paced rhythm. The ST segment and T…
QRS Morphology and ST-T Interpretation: Basics
Key Points: Read the QRS before you read the ST segment or T wave. Ventricular depolarization shapes repolarization. Narrow QRS usually reflects normal His-Purkinje conduction. Wide QRS suggests abnormal ventricular…
Preexcitation Syndromes: Overview
Key Points: Pre-excitation means an accessory pathway allows atrial impulses to reach the ventricle without traversing the AV node, producing early ventricular activation. A delta wave is the defining ECG…
Delta Waves: Basics
Key Points: Definition: A delta wave is a slurred upstroke at the very start of the QRS. It reflects early ventricular activation through an accessory pathway that bypasses the AV…
Short QT Syndrome
Key Points: Short QT Syndrome (SQTS) is a rare condition characterized by a shortened QT interval on the ECG, increasing the risk of atrial and ventricular arrhythmias, including sudden cardiac…
WPW Syndrome and Pseudo-MI Patterns
Key Points: WPW alters ventricular depolarization, producing secondary repolarization abnormalities that can mimic or mask myocardial infarction. ST-segment deviation in WPW is often non-ischemic, driven by abnormal activation via the…
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