ECG Basics

ECG BasicsNg Jit BengIntroductionPatient information Name, DOB etcVentricular rate, PR interval, QRS duration, QT/QTc interval, AxisInterpretation (Dont cheat)Paper speed, sensitivity, frequency, calibration

Conduction system of the heart

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Rate300 / number of big squares between 2 consecutive R waves1500/ number of small squares between 2 consecutive R wavesNumber of complexes on a rhythm strip x 6 (For irregular rhythms, not as accurate)RhythmTachycardic or bradycardic?Regular or irregular? If irregular, regularly irregular or irregularly irregular?Axis

Left axis deviation I positive, AVF negativeRight axis deviation I negative, AVF positiveExtreme axis (No mans land) I and AVF negative

Reaching - RADLeaving - LADCauses of right axis deviationNormal variant Infants, young children, young adultsRight ventricular hypertrophyRight heart strain PE etcChronic lung disease COPD etcDextrocardiaCauses of left axis deviationLeft ventricular hypertrophyLBBBVentricular ectopicsPaced rhythmExtreme axis deviationVentricular tachycardia

Heart rotates TOWARDS hypertrophy, AWAY from infarctionP waveAtrial depolarisation

P pulmonale, M mitrale

QRS segmentPathologic Q waves:- > 1mm wide> 2mm deep/ > of QRS complex

LVHSokolow/Lyon criteria for LVH R in V5 or V6 + S in V1 >35 mmCornell criteria for LVH R in AVL + S in V3 >28 mm in men, 20 mm in women

RVHIn AVR: R >5 mm, R>QIn V1: R/S ratio >1 and negative T wave, qR pattern, R>6mm, S10 mmR in V1 + S in V5 or V6 > 10 mmR/S ratio in V5 or V6 7 mm

LVH

RVH

ST segmentElevationCauses:-Acute myocardial infarctionPrinzmetal anginaPericarditisLBBBLVHBrugada syndromePaced rhythm

DepressionCauses:-IschaemiaPosterior MIDigoxinSVTRBBBPaced rhythm

T wave

ArrhythmiasHeart blocksFirst degree PR interval >200 ms

Second degreeMobitz Type 1 (Wenckebach) Progressive prolongation of PR interval, then dropped QRS complex

Mobitz Type II Intermittent non-conducted P waves without prolongation of PR interval

Third degree heart block (complete heart block) No relation betweeen P wave and QRS complexes

Ventricular tachycardia

Ventricular fibrillation

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