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 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 : Same findings as for Normal Sinus Rhythm except

– less than 60 bpm Normal Rhythms

• : Same findings as for Normal Sinus Rhythm except

– Heart Rate greater than 100 bpm Normal Rhythms

• Sinus : 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