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 Theres 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 = 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 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