ECGs By Samantha Conroy and Sophie Harris MedSoc Teaching presents ECGs By Samantha Conroy and Sophie Harris

Normal Waveform

Normal Waveform Timings

Interpreting an ECG Check patient is correct Check date and time Check relevant clinical info Check speed and calibration

Interpreting an ECG 1) Rate --------------> 2) Rhythm------------> 3) Axis --------------> 4) P wave-------------> 5) PR interval -------> 6) QRS complexes--> 7) ST segment-------> 8) T wave ------------> Rutting Round Anuses Pays PRices when Qualifying for Sexually Transmitted Trachomatis

Rate Normal = 60-100 bpm Calculation: Rhythm Axis P wave PR QRS ST seg T wave Rate Normal = 60-100 bpm Calculation: 300 / number of large squares in R-R interval OR Number of QRS x 6 (because average strip is a measure of 10s)

Work out the rate

Rhythm Irregular / Regular? P wave for every QRS complex? Rate Rhythm Axis P wave PR QRS ST seg T wave Rhythm Irregular / Regular? P wave for every QRS complex? Sinus rhythm or not?

Atrial Fibrillation–different lengths between QRS Rate Rhythm Axis P wave PR QRS ST seg T wave Atrial Fibrillation–different lengths between QRS

Atrial Flutter – saw-toothed baseline, usually regular QRS Rate Rhythm Axis P wave PR QRS ST seg T wave Atrial Flutter – saw-toothed baseline, usually regular QRS Due to re-entry of depolarisation into the atria Atrial rate of 240-300 bpm Ventricular rate of 120-150

Axis Average direction of electrical depolarisation Rate Rhythm Axis P wave PR QRS ST seg T wave Axis Average direction of electrical depolarisation Look at leads I + II (also aVF to check)

P wave and PR interval P wave - Irregular / Regular? Rate Rhythm Axis P wave PR QRS ST seg T wave P wave and PR interval P wave - Irregular / Regular? P wave for every QRS complex? (sinus rhythm?) PR interval normal?

Short PR Wolff Parkinson White Syndrome Short PR Delta Wave Rate Rhythm Axis P wave PR QRS ST seg T wave Short PR Wolff Parkinson White Syndrome Short PR Delta Wave T inversion

Long PR = Heart Block 1st Degree – PR consistently longer than normal Rate Rhythm Axis P wave PR QRS ST seg T wave Long PR = Heart Block 1st Degree – PR consistently longer than normal 2nd Degree: Mobitz Type 1 (Wenckebach) – progressive increase in PR length until there is a missed QRS complex. It then resets this cycle Mobitz Type 2 – there is a ratio of P waves to QRS complexes (usually 1:1), that is 2:1 or 3:1 Symptomatic type 2 will need a pacemaker.

Rate Rhythm Axis P wave PR QRS ST seg T wave Long PR = Heart Block

Random PR 3rd Degree – dissociation between P waves and QRS complexes Rate Rhythm Axis P wave PR QRS ST seg T wave Random PR 3rd Degree – dissociation between P waves and QRS complexes Atria and ventricles have their own rhythms that do not correspond with each other Is an indication for a pacemaker.

Rate Rhythm Axis P wave PR QRS ST seg T wave Tall QRS complex Larger bulk of myocardium is depolarising, hence LVH/RVH Add R height in V1 and V6, if greater than 7 big sq (35 small sq) = hypertrophy. S wave depth in V1/2 + tallest R wave in V5/6 = LVH (Some Receive Love) Tallest R wave in V1/2 + deepest S in V5/6 = RVH (Rooney Shags Rio)

Rate Rhythm Axis P wave PR QRS ST seg T wave

Rate Rhythm Axis P wave PR QRS ST seg T wave Broad QRS complex Blockage of depolarisation, that makes the QRS broader (ie takes longer to travel through myocardium) Left = WiLLiaM Deep S in V1 (W) and tall R in V6 (M) Right = MaRRoW Tall R in V1 (M) and deep S in V6 (W)

Rate Rhythm Axis P wave PR QRS ST seg T wave Left Right

ST Elevation Is a full thickness MI (STEMI) Rate Rhythm Axis P wave PR QRS ST seg T wave ST Elevation Is a full thickness MI (STEMI)

ST Depression Rate Rhythm Axis P wave PR QRS ST seg T wave Caused by Ischemia of the myocardium, that can be demonstrated on an exercises tolerance test. Usually used to determine the severity of angina. Needs to be >2mm to be significant

Topics Not Covered T wave abnormalities Ventricular Tachycardia NSTEMI Electrolyte Disturbances / Digoxin Toxicity Pericarditis Changes during the progression of a STEMI