Core
Results:
Pericardial Tamponade
Key Points: Pericardial tamponade is a hemodynamic diagnosis, not just an ECG diagnosis. ECG may show sinus tachycardia, low-voltage QRS, and sometimes electrical alternans, but none are sensitive enough to…
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…
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…
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 1:1 Conduction
Key Points: Rare, high-risk rhythm. Atrial flutter with 1:1 conduction can produce ventricular rates of 240-320 bpm and may rapidly cause hypotension, ischemia, or collapse. Often mimics VT. The QRS…
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…
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…
Wolff-Parkinson White (WPW) Syndrome
Key Points: Pattern vs syndrome: WPW pattern is ECG evidence of pre-excitation without symptoms. WPW syndrome is pattern plus symptomatic tachyarrhythmia (palpitations, syncope, “seizure”, aborted sudden cardiac arrest). PR interval…
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…
Atrial Fibrillation with WPW (Pre-excited AF)
Key Points: Pre-excited AF is the most dangerous WPW rhythm. It can deteriorate quickly to VF because the accessory pathway may conduct atrial impulses to the ventricle at extreme rates….
WPW with Antidromic SVT (Antidromic AVRT)
Key Points: Antidromic AVRT is an AV re-entrant tachycardia that conducts antegrade down the accessory pathway and returns retrograde through the AV node (or another pathway), producing a regular wide-complex…
WPW with Orthodromic SVT (Orthodromic AVRT)
Key Points: Orthodromic AVRT is the most common tachyarrhythmia in WPW and presents as a regular narrow-complex SVT that is indistinguishable from AVNRT during the tachycardia. Mechanism: antegrade conduction down…
ECG Foundations: Vectors, Leads, & Activation
Key Points: An ECG records voltage differences over time. The ECG tracing is a plot where the horizontal axis is time and the vertical axis is voltage. Leads are viewpoints….
Bidirectional Ventricular Tachycardia (BiVT)
Key Points: BiVT is a regular wide-complex tachycardia with strict beat-to-beat alternation of QRS axis and/or bundle-branch pattern (often an approximately 180° frontal-plane axis flip). In adults, assume digoxin toxicity…
Occlusion MI: STEMI Criteria & Beyond
Key Points: The ECG’s primary role in ACS is detecting acute coronary occlusion. Acute coronary occlusion myocardial infarction (OMI) is a time-critical diagnosis that requires immediate reperfusion. Time is myocardium….
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