ECG Basics

Leads-4 limb and 6 chest electrodes →electrical activity from 12 different viewpoints Limb leads- I , II , III , aVR , aVL , aVF -Frontal plane information Leads I , II and III are bipolar aVR , aVL , aVF are unipolar Precordial leads V1-6- provide information on horizontal plane ( unipolar )

Rate -Check calibration ie 10 mm = 1mV ECG trace speed @ 25 mm/sec 1 mm (small sqaure )= 0.04 sec 5 mm ( big square) = 0.2 sec Ventricular rate → 300/RR interval (number of big squares bet successive R waves )If rate irregular →Number of QRS in 30 squares multiplied by 10 Atrial rate →using number of squares bet P waves

Rhythm -Use 10 sec recording from lead II → to access rhythm Rate QRS Pattern-Regular / Irregular QRS Morphology ( Narrow or wide ) Atrial activity-P Waves ( absent / present ) < 0.08 sec P wave- QRS relationship Ventricular activity ? Broad , narrow or normal ?

Intervals and durations -PR interval 120-200 ms ( 3-5 small squares ) QRS complex 120 ms (3 small squares )Narrow QRS complexes < 100 msBroad complexes > 100 ms QT interval →is inversely proportional to...