Basics & Fundamentals
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Bifascicular Block
Key Points Definition: Conduction block in any two of the three fascicles: right bundle branch (RBB), left anterior fascicle (LAF), or left posterior fascicle (LPF). High-Risk OMI Pattern: New RBBB…
Bundle Branch Blocks
Key Points: Bundle branch blocks widen the QRS, usually to 120 ms or more, because ventricular depolarization is delayed through one of the main bundle branches. The two classic patterns…
Dextrocardia
Key Points Dextrocardia is a congenital condition where the heart is located on the right side of the thorax. Situs inversus totalis refers to complete reversal of all thoracic and…
Interval Interpretation
Key Points: Intervals are your ECG safety rails. Before you get seduced by ST segments and T waves, lock down PR, QRS, and QT/QTc. They frequently reveal the real danger…
Fusion Beats
Key Points Definition: A fusion beat occurs when two impulses — one from the normal conduction system (typically supraventricular) and one from an ectopic ventricular focus (e.g., during VT) —…
Normal Sinus Rhythm
Key Points Definition: Normal sinus rhythm (NSR) refers to the heart’s rhythm when impulses originate from the sinoatrial (SA) node, the heart’s primary pacemaker. This rhythm suggests that electrical impulses…
History of the “STAT ECG”
Key Points The ECG is a cornerstone of acute care medicine, offering immediate, non-invasive insight into cardiac function in critically ill patients. Its evolution spans over a century, from rudimentary…
Pseudonormalization of T Waves
Key Points Definition: Pseudonormalization is the apparent normalization of previously inverted T waves, often signaling reocclusion of a coronary artery that had recently reperfused. Mechanism: During reperfusion, ischemic T wave…
Escape-Capture Bigeminy
Key Points Escape-capture bigeminy is a unique rhythm characterized by alternating escape beats and normally conducted sinus beats, resulting in a bigeminal (paired) rhythm pattern. It typically occurs in patients…
Ventricular Escape Rhythms
Key Points Wide QRS Complex Rhythm: Ventricular escape rhythms (aka idioventricular rhythms) are characterized by a wide QRS duration (>120 ms), absent or dissociated P-waves, and a regular, slow ventricular…
Sinus Tachycardia
Key Points Definition: Sinus tachycardia is a regular rhythm originating from the sinoatrial (SA) node, defined by a heart rate >100 bpm in adults or above age-adjusted norms in children….
Ashman Phenomenon
Key Points Definition: Ashman phenomenon is an aberrant intraventricular conduction pattern triggered by cycle-length variation. It is most often seen in atrial fibrillation but can appear in any supraventricular rhythm….
Sinoatrial Nodal Reentry Tachycardia (SANRT)
Key Points Mechanism: SANRT is a rare type of paroxysmal supraventricular tachycardia (SVT) that operates through a similar mechanism as AV nodal reentry tachycardia (AVNRT), with the reentry loop occurring…
Atrial Tachycardia
Key Points: Definition: Atrial tachycardia is a supraventricular arrhythmia characterized by rapid atrial depolarizations from one or more ectopic foci outside the SA node. Atrial Rate: > 100 bpm, typically…
Trifascicular Block
Key Points Definition: Trifascicular block describes ECG evidence of impaired conduction across all three fascicles: right bundle branch (RBB), left anterior fascicle (LAF), and left posterior fascicle (LPF). Common Usage:…
Sinus Bradycardia
Key Points: Definition: Sinus bradycardia is a rhythm originating from the sinoatrial (SA) node with a rate < 60 bpm. Physiological Occurrence: Common in young, healthy adults, athletes, and during…
Sinus Node Dysfunction (Sick Sinus / Brady-Tachy Syndrome)
Key Points Spectrum, not one rhythm: Look for sinus brady, pauses, arrest, alternating atrial tachyarrhythmias (AF, flutter, ATach). Symptoms matter: Syncope, presyncope, fatigue usually come from cerebral/systemic hypoperfusion, especially after…
Slow Atrial Fibrillation
Key Points Definition: Atrial fibrillation with a slow ventricular response, usually < 60 bpm. ECG: Irregularly irregular rhythm, no discrete P waves, slow R-R intervals. Common causes: AV-nodal blockers (digoxin,…
Sinoatrial Exit Block
Key Points Definition: SA exit block occurs when the sinus node generates impulses that are blocked before they can activate the right atrium, leading to dropped P waves on the…
Unifasicular Block
Key Points Definition: Unifascicular block refers to conduction delay or interruption in a single fascicle of the ventricular conduction system: the right bundle branch (RBB), left anterior fascicle (LAF), or…
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