Key Points Clinical Context: A single normal 12-lead ECG in the emergent setting does not exclude life-threatening conditions such as occlusion MI, PE, tamponade, tension pneumothorax, or aortic dissection. Serial…
Key Points: Treat the patient, not just the number or rhythm. Start with a 10-second stability check. If the rhythm explains hypotension, shock, ischemic chest pain, altered mentation, or severe…
Key Points Definition: The QRS axis reflects the net direction of ventricular depolarization and is expressed in degrees on the frontal plane. Why It Matters: Axis assessment is a fast,…
Key Points Definition: Right Axis Deviation (RAD) occurs when the QRS axis is > +90°, typically up to +180°. ECG Criteria: Negative QRS in Lead I Positive QRS in Lead…
Key Points Normal Axis Range: –30° to +90° Lead I: QRS complex is positive Lead aVF: QRS complex is positive → This combination confirms a normal QRS axis Frontal plane…
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) —…
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…
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…
Key Points SA Node: Initiates electrical impulses; primary pacemaker (60–100 bpm). AV Node: Slows conduction to permit ventricular filling. Bundle of His: Transmits impulses from the AV node to ventricles;…
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…
Key Points Do not fully trust computer interpretations of “normal” ECGs, they may miss significant abnormalities. Computer algorithms can miss early ischemic signs such as reciprocal changes in aVL and…
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…
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…
Key Points Definition: Right atrial enlargement (RAE) is an increase in the size of the right atrium, typically resulting from chronic pressure or volume overload, commonly related to cardiac or…
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 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…
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…
Key Points Definition: QRS voltage represents the amplitude (height) of the QRS complex on ECG, reflecting ventricular electrical activity during depolarization. High Voltage: Increased QRS voltage typically indicates ventricular hypertrophy—most…
Key Points Definition: QRS fragmentation (fQRS) refers to the presence of additional notches or spikes within the QRS complex, observed in at least two contiguous leads corresponding to a specific…
Key Points for EMS Providers: You are the first critical link in the chain of survival for ACS patients—your actions set the course for their care, directly impacting time to…