QRS
Results:
Bundle Branch Blocks
Key Point Types: The two main BBBs are Right Bundle Branch Block (RBBB) and Left Bundle Branch Block (LBBB). Impact on ECG: Both widen the QRS (>120 ms) and produce…
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) —…
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 RBBB delays right ventricular activation. The left ventricle depolarizes normally via the left bundle; the right ventricle is activated late through myocardial spread. ECG hallmark: wide QRS and…
STEMI vs Wide QRS (BBBs & Paced Rhythms): DDx
Key Points Wide QRS & Repolarization Abnormalities: Bundle branch blocks (BBBs) and ventricular-paced rhythms (RV, LV, BiV) cause abnormal ventricular depolarization, leading to secondary ST segment and T wave changes—even…
Occlusion MI in Ventricular Paced Rhythms: STEMI Equivalent Pattern
Key Points 1. Paced Rhythms and Acute MI Detection: Ventricular paced rhythms significantly alter ST segment and T wave morphology, complicating acute myocardial infarction (MI) recognition. Accurate ECG interpretation in…
Occlusion MI in Left Bundle Branch Block: STEMI Equivalent Pattern
Key Points LBBB Does Not Exclude Acute Coronary Occlusion: LBBB alters ventricular activation, leading to expected secondary ST/T abnormalities. However, acute occlusion myocardial infarction (OMI) can and must still be…
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…
Appropriate Discordance
Key Points Definition: Appropriate discordance is a normal repolarization pattern in which the ST segment and T wave are directed opposite to the main QRS vector. It reflects expected changes…
Left Bundle Branch Block (LBBB): DDx
Key Point Overview: Left bundle branch block (LBBB) is an intraventricular conduction delay that results from a block in the left bundle branch of the heart’s electrical conduction system. It…
QRS Voltage: Basics
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…
ECG Foundations: Waveforms, Intervals, Conduction, and Leads
Key Points: Electrocardiography Defined: An ECG records the heart’s electrical activity in real time, offering a rapid window into rate, rhythm and conduction. The ECG measures changes in voltage between…
Wide QRS Bradyarrhythmia: DDx
Key Point Wide QRS bradycardias usually reflect infranodal conduction disease (His–Purkinje or below), making them much more dangerous than narrow QRS bradycardias. These rhythms often lead to hemodynamic instability and…
Polymorphic Ventricular Tachycardia (PMVT)
Key Points Definition: PMVT is a ventricular tachycardia characterized by beat-to-beat variations in QRS morphology, axis, and duration, reflecting multiple ventricular foci or reentrant circuits. Clinical Importance: PMVT is often…
Nonsustained Ventricular Tachycardia
Key Points Definition: NSVT is defined as ≥3 consecutive ventricular beats, QRS duration >120 ms, rate typically 100-250 bpm (usually > 120 bpm), lasting less than 30 seconds without causing…
QRS Fragmentation (fQRS)
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…
New RBBB and LAFB in ACS: OMI Pattern
Key Points Pattern Recognition: New-onset Right Bundle Branch Block (RBBB) and Left Anterior Fascicular Block (LAFB) occurring together is a high-risk ECG finding. Often associated with proximal Left Anterior Descending…
Left Bundle Branch Block (LBBB)
Key Points Definition: LBBB occurs when electrical conduction through the left bundle branch is delayed or blocked, resulting in asynchronous and delayed activation of the left ventricle (LV) and a…
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