Basics & Fundamentals
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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…
Pulmonary Embolism (PE)
Key Points ECG Findings in PE: No single ECG pattern is diagnostic of acute PE, and ECG findings are typically nonspecific. However, certain ECG patterns, especially those indicating right heart…
Persistent Juvenile T wave Pattern
Key Points Benign Variant: Persistent juvenile T waves (PJTW) represent a benign ECG finding and require no further evaluation in the absence of clinical symptoms or concerning findings. Typical Distribution:…
Atrial Flutter with Variable Conduction
Key Points Mechanism: Typical atrial flutter arises from a large re-entry circuit in the right atrium. The atrial rate is usually near 300 beats per minute. ECG hallmark: Continuous “saw-tooth”…
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…
Abnormal P Wave Axis DDx
Key Points Normal Sinus Rhythm: In a normal rhythm, the sinus node initiates atrial depolarization, resulting in a P wave with a normal axis: upright in lead II, inverted in…
ECG Foundations
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…
Flutter Waves (F waves)
Key Points Mechanism: Produced by a macro-reentrant circuit within the right atrium. Atrial Rate: Typically ~300 bpm (range 240–360 bpm). ECG Appearance: Characteristic saw-tooth baseline undulations without an isoelectric interval….
Electrical Alternans
Key Points Classically associated with pericardial tamponade but seen in fewer than 30% of confirmed cases. Combination of low-voltage QRS + sinus tachycardia strongly suggests pericardial effusion/tamponade. Always perform rapid…
Pericardial Effusion
Key Point Always consider pericardial effusion in any patient with new low-voltage QRS complexes combined with sinus tachycardia. Prompt bedside ultrasound (POCUS) prevents diagnostic delays and potentially catastrophic outcomes. Classic…
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…
Acute Coronary Syndromes (ACS)
Key Points ECG First: The ECG is the most important initial test for suspected ACS. STAT ECGs help identify acute coronary occlusion MI (OMI) that require emergent reperfusion. Time-Sensitive Dx:…
Sodium Channel Blocker Toxicity
Key Points Recognizing the Danger: Sodium channel blocker toxicity can present with a variety of ECG changes that are critical to recognize, especially in patients with altered mental status or…
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…
Hypocalcemia
Key Points Prolonged QTc as the Hallmark ECG Change: Hypocalcemia primarily lengthens the ST segment, leading to a prolonged QTc interval, increasing the risk of arrhythmias like Torsades de Pointes…
Acute Pericarditis
Key Points Diagnostic Challenge: Acute pericarditis symptoms and ECG findings can closely resemble STEMI/ACS, leading to frequent diagnostic uncertainty in acute care. Critical Importance: Rapid and accurate differentiation from STEMI…
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…
EMS ECGs in Acute Coronary Syndromes (ACS)
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…
Hypercalcemia
Key Points Shortened QTc interval is the hallmark ECG finding of hypercalcemia, primarily due to a shortened ST segment duration. Hypercalcemia can mimic acute STEMI on ECG (pseudoinfarction pattern due…
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