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…
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…
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…
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…
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…
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…
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…
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….
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…
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…
A 54-year-old man presents to the emergency department by EMS with acute shortness of breath. A prehospital ECG triggers a STEMI alert based on the computer interpretation. The tracing shows…
A 68-year-old man is brought to the emergency department by EMS with acute chest discomfort. The following prehospital ECG was obtained and shows concave ST elevation across multiple leads. The…
A 51-year-old man with lung cancer presents with shortness of breath and tachycardia. The arrival ECG shows an S1Q3 pattern and seems to support a familiar diagnosis that would normally…
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…
A 43-year-old woman with sharp left-sided chest pain and minimal cardiac risk factors has an initial ECG that is not diagnostic for STEMI. She looks stable, but one feature on…
Key Points: Traditional STEMI criteria miss many acute coronary occlusions. A substantial proportion of true OMIs do not meet classic millimetric STEMI thresholds. OMI is a pathophysiologic diagnosis, not an…
Key Points: Definition: Hypokalemic periodic paralysis (HPP) is a rare disorder characterized by episodic, reversible flaccid muscle weakness associated with a shift of potassium from the extracellular space into skeletal…
Key Points: Baseline ECG abnormalities do not protect patients from occlusion MI. They increase miss rates because they distort the ST segment and T waves. The core question is not…
Key Points: Lateral and high-lateral STEMI often present with subtle ST elevation and are commonly missed or labeled as nonspecific ST-T changes. Small-appearing ECG changes may represent true coronary occlusion…
Key Points: Inferior STEMI is the most common STEMI subtype and is frequently complicated by right ventricular and posterior involvement. Inferior occlusion may present with classic ST elevation, subtle ischemic…