Basics & Fundamentals
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Indeterminate QRS Axis Basics
Key Points Definition: An indeterminate QRS axis (also called “no man’s land”) occurs when the frontal QRS vector lies between –90° and ±180°, but no dominant direction is evident. ECG…
Right Axis Deviation Basics
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…
Right Axis Deviation DDx
Top 3 Emergent Causes of New Rightward Axis Deviation: When you encounter new right axis deviation on an ECG, immediately consider the following life-threatening conditions: Acute Right Heart Strain or…
LV Aneurysm vs. STEMI
Key Points Left Ventricular Aneurysm (LVA): Causes persistent ST elevation lasting more than 2 weeks post-MI, typically seen in the anterior leads but can also affect the inferior leads. Occurs…
Bifasicular 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 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…
Early Repolarization
Key Points Historical View: Early repolarization (ER) was long considered a benign cause of ST elevation, often called benign early repolarization (BER). Modern View: Certain ER patterns, now termed malignant…
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…
Intervals
Key Points Definition: ECG intervals measure the duration of electrical activity across different parts of the cardiac cycle. They reflect conduction times through the atria, AV node, ventricles, and repolarization…
Fascicular Ventricular Tachycardia
Key Points Definition: Fascicular VT is an idiopathic re-entrant tachycardia arising from the fascicles of the left bundle branch (LBB) within the Purkinje system. Mechanism: Re-entry within the Purkinje network,…
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) —…
Post-Thrombolytic Reperfusion ECG Findings
Key Points Clinical Indicators: Following thrombolytic therapy for STEMI, monitor for resolution of chest pain and ischemic symptoms alongside ECG changes. ECG Signs of Reperfusion: ST-Segment Resolution: ≥ 50% reduction…
Atrial Fibrillation with RVR
Key Points Most Common Sustained Arrhythmia: Atrial Fibrillation (AFib) is the most frequently encountered sustained arrhythmia in clinical practice, particularly among the elderly population. Misdiagnosis Risk: AFib is commonly misdiagnosed…
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…
Lead Misplacement
Key Points Proper lead placement is critical to avoid misdiagnoses that can lead to unnecessary interventions and patient harm. Misplaced precordial leads (V1-V6) can mimic ischemia and cause false MI…
Normal Cardiac Conduction
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;…
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…
Earliest Evidence of Occlusion MI
Key Points Dynamic Nature of ACS: Acute coronary syndromes (ACS) are complex and dynamic, with coronary arteries potentially undergoing reperfusion and reocclusion at any time. The ECG can provide real-time…
Computer Interpreted “Normal” ECGs
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…
Early Reciprocal Changes (OMI Pattern)
Key Points ACS Dynamics: ACS is complex and dynamic, with occluded arteries potentially reperfusing and reoccluding at any time. ECG Pattern Recognition: Mastering ECG pattern recognition in ACS is crucial…
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