liminfoECG Reference
Free reference guide: ECG Reference
About ECG Reference
The ECG Interpretation Reference is a comprehensive, searchable guide to electrocardiogram reading that covers six major categories: normal waveforms, intervals and segments, arrhythmias, conduction disorders, axis and hypertrophy, and ischemia with infarction. Each entry includes diagnostic criteria with specific numeric thresholds, morphology descriptions, clinical significance, and differential diagnosis considerations used in real-world ECG interpretation.
The arrhythmia section covers atrial fibrillation (AF) with CHA2DS2-VASc scoring, atrial flutter with sawtooth wave identification, ventricular tachycardia (VT) with Brugada differentiation criteria, ventricular fibrillation (VF) with ACLS treatment protocols, and supraventricular tachycardia (SVT) including AVNRT, AVRT, and focal AT subtypes. The conduction disorders section details all three degrees of AV block, Mobitz I vs Mobitz II differentiation, and bundle branch block patterns (RBBB rsR' pattern, LBBB broad notched R wave) with associated clinical causes.
For ischemia assessment, the reference includes STEMI diagnostic criteria with sex-specific ST elevation thresholds, coronary artery territory mapping (LAD anterior V1-V4, LCx lateral I/aVL/V5-V6, RCA inferior II/III/aVF), MI evolution stages from hyperacute to chronic, and standard 12-lead electrode placement. Voltage criteria for LVH (Sokolow-Lyon, Cornell) and RVH are also covered with associated ECG findings like strain patterns and axis deviation.
Key Features
- Normal waveform morphology with amplitude and duration thresholds for P wave, QRS complex, T wave, and U wave
- Interval reference including PR (0.12-0.20s), QT/QTc with Bazett formula, and ST segment elevation/depression criteria
- Arrhythmia identification guide for AF, atrial flutter, VT, VF, and SVT with treatment protocols
- AV block differentiation (1st, 2nd Mobitz I/II, 3rd degree) with pacemaker indications
- Bundle branch block patterns: RBBB (rsR' in V1-V2) and LBBB (broad notched R in V5-V6) with Sgarbossa criteria
- STEMI diagnosis with coronary artery mapping and sex-specific ST elevation thresholds
- LVH/RVH voltage criteria (Sokolow-Lyon, Cornell) with associated ECG findings
- Bilingual Korean/English content with full-text search and category-based filtering
Frequently Asked Questions
What are the criteria for normal sinus rhythm on ECG?
Normal sinus rhythm requires: heart rate 60-100 bpm, P wave present before every QRS and upright in lead II, PR interval 0.12-0.20 seconds, QRS duration less than 0.12 seconds, regular RR intervals, QTc less than 0.45s (male) or 0.47s (female), and electrical axis between -30 degrees and +90 degrees.
How do I differentiate VT from SVT with aberrancy?
Use the Brugada criteria in sequence: (1) absence of RS complex in all precordial leads V1-V6 suggests VT, (2) RS interval greater than 100ms in any precordial lead suggests VT, (3) AV dissociation (P waves independent of QRS) confirms VT, (4) morphological criteria specific to RBBB or LBBB pattern. Wide-complex tachycardia should be treated as VT until proven otherwise.
What ST elevation thresholds indicate STEMI?
STEMI requires new ST elevation in 2 or more contiguous leads: at least 1mm (0.1mV) in limb leads, at least 2mm in V2-V3 for males (2.5mm if under 40), and at least 1.5mm in V2-V3 for females. Coronary territory mapping: anterior (LAD) = V1-V4, lateral (LCx) = I, aVL, V5-V6, inferior (RCA) = II, III, aVF.
How do I distinguish Mobitz I from Mobitz II second-degree AV block?
Mobitz I (Wenckebach) shows progressive PR prolongation before a dropped QRS, with gradually shortening RR intervals. The block is at the AV node level and is usually benign. Mobitz II shows constant PR intervals with sudden unexpected QRS drops, the block is infrahisian (His bundle or below), QRS is often wide, and it carries risk of progression to complete heart block requiring a pacemaker.
What are the ECG criteria for left ventricular hypertrophy (LVH)?
Two commonly used voltage criteria: Sokolow-Lyon requires S wave in V1 plus R wave in V5 or V6 of 35mm or greater. Cornell criteria requires R wave in aVL plus S wave in V3 greater than 28mm for males or 20mm for females. Associated findings include left axis deviation, ST-T strain pattern in V5-V6, widened QRS, and possible left atrial enlargement.
How do I identify RBBB vs LBBB on ECG?
RBBB shows rsR' pattern (M-shape or rabbit ears) in V1-V2 with wide S wave in V5-V6 and lead I. LBBB shows deep QS or rS in V1 with broad notched R wave in V5-V6, I, and aVL. Both require QRS duration of 0.12 seconds or greater. New LBBB with chest pain is treated as a STEMI equivalent using Sgarbossa criteria.
What is the QTc and when is prolongation dangerous?
QTc is the corrected QT interval adjusted for heart rate using the Bazett formula: QTc = QT divided by the square root of RR. Normal values are less than 0.45s for males and 0.47s for females. QTc greater than 0.50 seconds carries significant risk for Torsades de Pointes. Common causes include drugs (quinidine, amiodarone, haloperidol), electrolyte abnormalities (low K, Ca, Mg), and congenital long QT syndromes.
Does this ECG reference support both Korean and English?
Yes, the reference provides complete bilingual content in both Korean and English. All 28+ ECG entries across six categories are fully translated with identical clinical detail, diagnostic criteria, and treatment notes. The language switches automatically based on your locale preference, and the search function works across both languages.