Basics & Fundamentals
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QRS Morphology & Proportionality
Key Points QRS Morphology Reflects Conduction Pathways: The shape and width of the QRS complex help differentiate between normal conduction, conduction delays, and ventricular-origin rhythms. QRS–T Wave Proportionality Signals Repolarization…
Right Bundle Branch Block (RBBB)
Key Points Definition: In RBBB, the right bundle branch of the heart’s electrical conduction system is blocked, preventing direct activation of the right ventricle (RV). As a result, RV activation…
Catecholaminergic Polymorphic VT (CPVT)
Key Points Definition: CPVT is a rare hereditary form of polymorphic ventricular tachycardia (VT) that is often triggered by emotional or physical stress, leading to potentially fatal arrhythmias such as…
Isoelectric Segment of the ECG
Key Points PR vs. TP Segment: The most accurate isoelectric baseline for assessing the magnitude of ST segment deviation is debated between the PR segment and the TP segment. Challenges…
Paced Rhythms
Key Points Paced Rhythms Overview: Paced rhythms, whether from right ventricular (RV) pacemakers, left ventricular (LV) pacemakers, or dual-chamber pacemakers, produce specific ECG changes due to the altered sequence of…
Fascicular Blocks
Key Points Definition: Fascicular blocks refer to conduction delays or blockages in the left bundle branch fascicles, which can affect the QRS complex and T waves on the ECG. Types:…
Osborn Wave
Key Points What Are Osborne Waves? Osborne waves are positive deflections at the junction of the QRS complex and the ST segment, also known as the J point. While they…
Atrial Septal Defect (ASD) & Crochetage Pattern
Key Points ASD Overview: Atrial septal defects (ASDs) are often diagnosed and corrected in childhood, but even uncorrected, patients may do well into early adulthood. Symptoms typically develop by age…
Atrioventricular Nodal Reentry Tachycardia (AVNRT)
Key Points Definition: AVNRT is a type of paroxysmal supraventricular tachycardia (SVT) caused by a reentry circuit within or around the AV node, leading to a narrow complex regular rhythm….
Atrioventricular Reciprocating Tachycardia (AVRT)
Key Points Definition: AVRT is a type of supraventricular tachycardia (SVT) caused by a macroreentrant circuit that involves an accessory pathway in addition to the normal AV nodal pathway, allowing…
Inverted U waves
Key Points Normal U Waves: Small (< 0.5 mm) deflections following the T wave, usually in the same direction, best seen in leads V2-V3. Their amplitude is typically ~10% of…
Terminal QRS Distortion (OMI Pattern)
Key Points Early Repolarization (ER): A common ECG finding that can produce widespread ST-segment elevation, often mimicking STEMI or acute pericarditis. ST Segment Morphology: Convex and horizontal ST-segment morphology is…
Hypermagnesemia
Key Points ECG Red Flags: Flattened P waves, prolonged PR/QT, peaked T waves, risk of AV block or asystole. Neuromuscular Suppression: Hyporeflexia, progressing to muscle weakness, respiratory depression, and potential…
J wave Basics
Key Points Definition: A J wave, also known as an Osborn wave, is a positive deflection immediately following the QRS complex at the J point. J waves are distinct from…
ST Segment Basics
Key Points Definition: The ST segment is the flat, isoelectric section of the ECG between the end of the QRS complex and the beginning of the T wave, representing the…
Left Anterior Fascicular Block (LAFB)
Key Points Anatomy of the Left Bundle Branch: The left bundle branch divides into two main fascicles: the left anterior fascicle (LAF) and the left posterior fascicle (LPF), both of…
Left Ventricular Hypertrophy (LVH)
Key Points Pathophysiology: Left ventricular hypertrophy (LVH) is a condition in which the muscle wall of the left ventricle becomes thickened due to chronic pressure overload, often from hypertension or…
PR Interval Basics
Key Points Definition: The PR interval is the time from the start of the P wave to the beginning of the QRS complex, representing the time it takes for the…
PR Segment Basics
Key Points Definition: The PR segment is the part of the ECG tracing between the end of the P wave and the start of the QRS complex, representing the delay…
Preexcitation Syndromes
Key Points Definition: Preexcitation syndrome, often synonymous with Wolff-Parkinson-White (WPW) syndrome, occurs when ventricular preexcitation is caused by a congenital accessory pathway in patients with symptomatic arrhythmias. Clinical Relevance: WPW…
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