NUR 105 Basic ECG Interpretation

What is an ECG? • An ECG is a simple, noninvasive procedure. Electrodes are placed on the skin of the chest and limbs then connected in a specific order to a machine that, when turned on, measures electrical activity all over the heart. Output usually appears on a long scroll of paper that displays a printed graph of activity on a computer screen. 12 Lead ECG • The standard 12-lead electrocardiogram is a representation of the heart's electrical activity recorded from electrodes on the body surface. • The spikes and dips in the tracings are called waves. 12-lead ECG • 12-lead ECG – 10 electrodes required to produce 12-lead ECG. • Electrodes on all 4 limbs (RA, LL, LA, RL) • Electrodes on precordium (V1–6) – Monitors 12 leads (V1–6), (I, II, III) and (aVR, aVF, aVL) – Allows interpretation of specific areas of the heart • Inferior (II, III, aVF) • Lateral (I, aVL, V5, V6) • Anterior (V1–4) 3 & 5 Lead Cardiac Monitoring • Monitor cardiac functioning • Controlled from central monitor room at most acute facilities • Printable or electronic strips are available and place in chart at desired times during 24 hour period 3-Electrode System • 3-electrode system – Uses 3 electrodes (RA, LA and LL). – Monitor displays the bipolar leads (I, II and III) – To get best results – Place electrodes on the chest wall equidistant from the heart (rather than the specific limbs) 5-electrode system • 5-electrode system – Uses 5 electrodes (RA, RL, LA, LL and Chest) – Monitor displays the bipolar leads (I, II and III) – AND a single unipolar lead (depending on position of the brown chest lead (positions V1–6)) Understanding the ECG Grid • ECG tracings are recorded on grid paper. The horizontal axis of the EKG paper records time, with black marks at the top indicating 3 second intervals. • Each second is marked by 5 large grid blocks. Thus each large block equals 0.2 second. The vertical axis records EKG amplitude (voltage). Two large blocks equal 1 millivolt (mV). Each small block equals 0.1 mV. • Within the large blocks are 5 small blocks, each representing 0.04 seconds.