Heart Anatomy + ECG Aaqid Akram MBChB (2013) Clinical Education Fellow

Brachiocephalic Trunk L Subclavian Artery L Common Carotid Artery Arch of the Aorta Superior Vena Cava Pulmonary Artery L Pulmonary Vein L Atrium Mitral Valve (Bicuspid) Chordae Tendinae Papillary Muscle Endocardium Myocardium Septum Aortic Valve (Semilunar) Inferior Vena Cava L Ventricle R Ventricle Tricuspid Valve Pulmonary Valve R Atrium Fossa Ovalis

Ligamentum Arteriosum R Coronary Artery Circumflex Artery L Anterior Descending Artery

Cardiac Cycle

Introduction Wash Hands Introduce yourself Confirm patient + ALLERGY STATUS Explain investigation to patient Gain verbal consent Offer chaperone (Chest will be exposed) – If opposite sex you require a chaperone for your own safety

The ECG Machine Power (plugged/battery) Demographics Paper All leads intact Stickers available Scale – vertical axis (0.1mV = 1mm = 1 small square)

Placing Stickers

There’s only 10 leads…. How can it be a 12 lead ECG?

Interpreting an ECG Demographics Obvious abnormality Rate Rhythm Axis P wave PR Interval QRS Complex ST segment T wave Summary

Rate 1500 small squares (0.04 seconds) = 60s No of small squares between R-R = x 1500/x = ventricular rate per minute If normal calibration  rhythm strip = 50 large squares (0.2seconds) = 10 seconds Count QRS complexes on rhythm strip Multiply by 6 = ventricular rate per minute

Rhythm Sinus = p wave before every QRS Complex Regular = QRS complexes equidistant – Mark 3 R-R points on the edge of a paper – Move to next three complexes – Do the marks on the paper correlate to the R waves?

Axis

P Wave T Wave

P wave Atrial depolarisation (Sino Atrial Node) 2-3 mm high 0.06 – 0.12 seconds duration Usually positive deflection throughout ECG Peaked/enlarged = atrial hypertrophy Inverted = retrograde/reverse conduction Absent = conduction by route other than SA

PR Interval Impulse from atria to AV Node, Bundle of His, bundle branches 0.12 – 0.2 seconds duration Short = impulse did not originate from SA Long = AV Block

1 st Degree Heart Block 1 st Degree: – QRS complex after every P wave – Prolonged PR Interval – No Rx necessary unless symptomatic

2 nd Degree Heart Block Mobitz Type 1 (Wenckebach): – Each successive impulse from SA node delayed slightly longer than previous impulse – A QRS complex is dropped – Cycle repeats

2:1 Heart block xx x x xx Mobitz Type 2: – Occasional SA impulses fail to cause ventricular depolarisation – Regular P waves, but some dropped QRS complexes 2 nd Degree Heart Block

3 rd Degree Heart Block Complete Heart Block: – Impulses from atria cannot pass the AV node – Atria depolarise independently to ventricles – Life threatening

QRS Complex Deep wide Q waves may suggest old infarct Total duration <0.12 seconds >0.12 seconds = ventricular conduction delay

Bundle Branch Block Bundle branch fails to conduct impulses Ventricles contract at slightly different times Block further down the bundle = hemiblock Cell-cell conduction slower than via specialised pathway therefore prolonged depolarisation New Left Bundle Branch Block = ACS

QT Interval Time from ventricular depolarisation to ventricular repolarisation Varies according to heart rate QTc = corrected QT interval to 60bpm Males <450 ms / Females <470 ms Prolonged QT interval increases risk of life threatening arrhythmias

Torsades de Pointes

Drugs affecting QT Interval DrugType AmiodaroneAntiarrhytmic AmitriptyllineAntidepressant ChlorpromazineAntipsychotic/antiemetic ClarithromycinAntibiotic DroperidolSedative/antiemetic ErythromycinAntibiotic FluoxetineAntidepressant HaloperidolAntipsychotic KetoconazoleAntifungal LevofloxacinAntibiotic MethadoneOpiate agonist QuinidineAntiarrhythmic SertralineAntidepressant SotalolAntiarrhythmic SumatriptanAnti migraine

ST Segment Segment affected if acute ischaemia/infarction Elevation = >1mm Depression = >0.5mm

T Wave Ventricular repolarisation Usually upright deflection Tented T waves = hyperkalaemia/myocardial injury Inverted T wave = ischaemia Camel Hump = hidden P/U wave

Summary Present all positive findings and important negative findings. Advise on urgency of management.

Supraventricular Tachycardia

Atrial Flutter

Atrial Fibrillation

Ventricular Tachycardia

Ventricular Fibrillation

Asystole

Any Questions? Thank You