ECG Seminar Diagnostic Aids PDF

ECG Seminar Diagnostic Aids FdSc Veterinary Nursing Level 5 Contents Revision of the cardiac conduction cycle What is an ECG? Setting up an ECG 2 REVISION OF THE CARDIAC CYCLE 3 ECG Stands for? What is it?...

ECG Seminar Diagnostic Aids FdSc Veterinary Nursing Level 5 Contents Revision of the cardiac conduction cycle What is an ECG? Setting up an ECG 2 REVISION OF THE CARDIAC CYCLE 3 ECG Stands for? What is it? 4 Electrical control of the heart 5 The electrical impulse is a measurable occurrence Cardiac muscle is quite hefty! By placing electrodes on the skin surface around the body, we can measure the electrical activity as it passes around the heart We do this using an ECG 6 7  Limb Leads The difference in the electric potential between the two points is plotted on a trace and is called a ‘lead’ Cables are attached to RF, LF and LH Lead I: RF is the negative pole, LF is the positive pole Lead II: RF is the negative pole, LH is the positive pole Lead III: LH is the positive pole, LF is the negative pole A cable may also be attached to the RH as a reference point 8 2nd heart sound: semilunar valves close 1st heart sound: 9 AV valves close ECG components of the cardiac cycle P wave: represents atrial depolarization QRS wave: represents ventricular depolarization T wave: Represents ventricular repolarization 10 ECG Trace Height of trace shows voltage changes:10mm per mV → each mm represents 0.1mV Length of trace shows timing of different parts of cardiac cycle: 25mm/sec → each mm represents 0.04 seconds. 11  Uses of ECG? Assess: –the rate and regularity of heartbeats –the size and position of the chambers –the presence of any damage to the heart Used to assess: Heart condition, anaesthesia, toxaemia, electrolyte disturbance (e.g. GDV) 12 SETTING UP AN ECG 13 Electrodes Crocodile clips - old style can be traumatic if conscious, newer one less traumatic e.g. ‘comfy clips’ Adhesive pads Comfy clip 14 Electrode Attachment Crocodile clips – elbows and stifles 15  Electrode Attachment Adhesive pads – paw pads (or axilla and groin) - minimal hair 16 Electrode Conductive Gel Need good electrical contact with skin Electrical conductive gel – needed for crocodiles (pads already have gel) If long coat, need to clip 17 Cable Colours UK USA 18 Patient Positioning Right lateral recumbency normally, but can do in other positions e.g. sternal if respiratory distress. Hold limbs/use pads so limbs separate from each other. 19 24 Hour Holter 20 Interference Two possible sources: Electrical Movement 21 Electrical Interference If occurs: 22 Movement of the Patient If occurs: 23 Why do an ECG? To determine heart rate To determine heart rhythm When to do an ECG? Arrhythmia Drug toxicity Electrolyte disturbance Emergency Anaesthesia monitoring Post surgical e.g. GDV 24 ECG Interpretation: Systematic Approach Heart Rate (bradycardia, tachycardia, normal) Heart Rhythm (regular, regularly irregular, irregular) Is there a QRS complex for every P wave? Is there a P wave for every QRS complex? Are P wave and QRS consistently related? What is the QRS morphology? 25 Heart Rate and Rhythm Rate: Count number of QRS complexes in a given time e.g. if trace running at 25mm/sec, 250mm represents 10 seconds. Rhythm: Does P-QRS-T pattern repeat with same distances between the components? 26