Normal Sinus Rhythm Lancashire & South Cumbria Cardiac Network ECG Interpretation • A mystery? • An enigma? • Confusing? • Difficult? Criteria - P wave • P Wave represents atrial depolarisation. • An upright rounded P-wave in leads II, III and AVF, and an inverted P-Wave in AVR which precede each QRS Complex. • The P wave does not exceed 2.5mm in height. • It does not exceed 3mm in width. • A biphid P wave is seen in lead V1. Criteria - PR interval • PR Interval • 0.12 - 0.20seconds. • Delay at AV node » Protect ventricles » Allow for ventricular filling Criteria QRS complex • QRS Complex represents ventricular depolarisation. • Should not exceed 0.12 seconds in duration. • Should not exceed 27mm in height. • Sharp narrow complex • RS in V1, QRS in V6 Criteria T wave • The deflection produced by repolarisation of the ventricles. • No clearly defined range • General rule - T wave should not be more than 1/2 the height of the preceding QRS Criteria - QT interval •QTcInterval • Should not exceed 0.42 seconds (QTc). • QT interval corrected to the heart rate. Correction Calculation QTc = measured Qt interval √ cycle length Criteria U wave • The origin is uncertain • May represent repolarisation if the IVS • May represent slow conduction of ventricular myocardium • Prominent U waves are abnormal • Usually most visible in V1-V4 Nomenclature - QRS • The 1st negative deflection - Q • The 1st positive deflection - R • The 2nd negative deflection or If a negative follows a positive - S Nomenclature -QRS Nomenclature - QRS Nomenclature - QRS • Waves > 0.5mv (5mm) high • Capital letters e.g. QRS • Waves < 0.5mv (5mm) high • Lower case e.g. qrs Intervals • P wave duration measured? • PR interval measured? • QRS interval measured? • QT interval measured? Amplitudes • P wave height measured? • QRS height measured? Segments • PR segment measured? • ST segment measured? 1mm = 0.1mv 1mm = 0.04s Paper P speed QRS segments Pr Int QT Interval Limb leads • Measurements - lead II •QRS Axis •P wave Axis Chest Leads • Progression of R waves throughout the chest leads • Transitional Zone • Phases of Activation Depolarisation Stages 1 3 2 Typical complexes in the Pre- cordial leads RVRVIVSIVSLVLV V1 V2 V3 V4 V5 V6 Progression of R waves throughout the chest leads • Size of the R wave should increase from V1 to V6. • V4 Usually at the Apex (Transitional Zone where the first negative wave appears). Normal Rhythms • Sinus Bradycardia: Same findings as for Normal Sinus Rhythm except – Heart Rate less than 60 bpm Normal Rhythms • Sinus Tachycardia: Same findings as for Normal Sinus Rhythm except – Heart Rate greater than 100 bpm Normal Rhythms • Sinus Arrhythmia: Same findings as for Normal Sinus Rhythm except – The R - R Interval is Irregular Normal Rhythms !!! • *Sinus Arrest* • Considered a ‘Sinus rhythm’ but is abnormal Summary • Checklist • Criteria ECG INTERPRETATION • If the normal ECG is known then interpretation of abnormals becomes easier.