Basics & Fundamentals
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Paced Rhythms
Key Points Ventricular pacing changes depolarization, so ST–T segments often look “abnormal.” Expect appropriate discordance: ST/T deflect opposite the main QRS polarity. RV pacing (most common) ≈ LBBB pattern: wide…
Himalayan T Waves
Key Points Tall, broad-based T–U fusion that looks like a mountain peak, usually from severe hypokalemia; think high torsades risk until proven otherwise. Hallmark is prolonged repolarization: QT appears long…
Pediatric ECG: Basics
Key Points Pediatric ECGs are not scaled-down adult ECGs. Right axis deviation, large R waves in V1, and T wave inversions in V1 to V3 are expected in healthy children….
Pseudo-Wellens Waves
Key Points: Pseudo-Wellens waves are anterior T-wave patterns that mimic the biphasic or deeply inverted T waves of true Wellens syndrome but are caused by non-LAD, non-ischemic physiology. These normal-variant…
Wellens Waves
Key Points Wellens waves are anterior precordial T wave abnormalities (biphasic or deeply inverted) most often in V2–V3, occasionally extending to V1 and V4–V6. They signal a high likelihood of…
T Wave Alternans
Key Points: Definition: Beat-to-beat alternation in T wave amplitude or morphology with stable P waves and QRS complexes. Significance: A visible marker of ventricular electrical instability. Strongly associated with torsades,…
Torsade de Pointes (TdP)
Key Points Definition: TdP is a specific subtype of polymorphic ventricular tachycardia associated with a prolonged QTc interval. It often presents with a “twisting” pattern on ECG but can be…
Ventricular Tachycardia (VT): Core Overview
Key Points VT is a ventricular-origin rhythm: ≥3 consecutive ventricular beats, QRS >120 ms, rate usually 120–250 bpm. Types include monomorphic VT, polymorphic VT, torsades (PMVT with long QT), ventricular…
Prominent Upright T Wave in V1
Key Points: Normal T Wave in V1: The normal ECG typically shows a flat or inverted T wave in lead V1 in sinus rhythm. An upright T wave in V1 can…
Premature Atrial Complexes (PACs)
Key Points PACs are early atrial depolarizations from an ectopic focus that create a premature P wave with a different morphology and axis than the sinus P wave, usually followed…
Atrial Fibrillation (AFib)
Key Points Prevalence: The most common sustained cardiac arrhythmia, particularly prevalent among elderly individuals, associated with increased stroke, heart failure, and mortality risks. Mechanism: Caused by chaotic, multiple reentry circuits…
Post-Cardiac Arrest ECGs
Key Points Early post-ROSC ECGs often mislead. Within the first 8–10 minutes, transient global ischemia and catecholamines can exaggerate ST changes. Plan a repeat at 10–15 minutes before making cath…
First-Degree AV Block
Key Points Defined by a PR interval >200 ms with consistent 1:1 AV conduction and no dropped QRS complexes. Conduction delay is most often at the AV node; His–Purkinje delay…
Premature Junctional Complexes (PJCs)
Key Points PJCs are premature impulses from ectopic foci in or near the AV junction. ECG hallmark is a narrow premature beat with an absent or retrograde P wave. Retrograde…
J Point: Basics
Key Points The J point is the junction where QRS ends and the ST segment begins. It is a location, not a waveform. ST deviation is judged at the J…
Blocked Premature Atrial Complexes (PACs)
Key Points Definition: early ectopic atrial beats that do not conduct to the ventricles. You see a premature P wave with no following QRS and a pause that is usually…
J Wave: Basics
Key Points Definitions: The J point is the QRS–ST junction (a location). A J wave is an added deflection at or just after that point (notch or slur). Why it…
Premature Complexes (PACs, PJCs, & PVCs) Overview
Key Points: Premature complexes are early depolarizations arising from the atrium, AV junction, or ventricle which interrupt the expected sinus rhythm. Rapid classification by origin: look for a P wave…
Osborn (J) Wave: Basics
Key Points An Osborn wave is a notch or slur at the J point that becomes more prominent as core temperature falls. Most visible in inferolateral and precordial leads; can…
Premature Ventricular Complexes (PVCs)
Key Points PVCs are early ventricular depolarizations that produce a wide QRS with secondary ST-T changes and are usually followed by a full compensatory pause. No preceding P wave. A…
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