Cardiac Rhythm Interpretation

Sinus Node = Heart's Natural Pacemaker (60-100bpm at rest)

SA Node sends impulse to AV Node sends to Bundle of His sends to Purkinje Fibres moves the impulse through the Ventricles for contraction

         P wave = atrial depolarisation

QRS = ventricular depolarisation    T wave = ventricular repolarisation

ECG paper is calibrated in mm

Standard paper speed = 25mm/s

25 small squares = 5 big squares = 1 second

To calculate the heart rate = count the number of QRS Complexes on a six second ***** then multiply by 10 to get apporx. BPM

Normal PR interval = 120-200ms (3-5 small squares)

Normal QRS complex = 60-100ms (1.5-2.5 small squares)

Normal Rate: 60-100 BPM

For every P wave there is a QRS complex

Everything is regular

Non-shockable rhythms = Asystole and Pulseless Electrical Activity

Less than 60 BPM

Greater than 100 BPM

Chaotic Rhythm

Shockable Rhythms = Ventricular Fibrillation and Pulseless Ventricular Tachycardia

No discernable P wave

100-200 BPM

wide QRS complexes

Saw-tooth P wave

Prolonged P-R interval

PR interval progressively lengthens until eventually atrial impulse is not conducted and a QRS is dropped.

"going, going...gone! Wenckeback"

PR interval is consistent until intermittently dropped QRS complexes

"If some P's don't get through, then you have a mobitz 2!"

P waves have no association with QRS complexes

"if P's and Q's dont agree, then you have a 3rd degree!"