3. Step 1: Calculate Rate Option 1 Count the # of R waves in a 6 second rhythm strip, then multiply by 10. Interpretation? 3 sec 3 sec 9 x 10 = 90 bpm
4. Step 1: Calculate Rate Option 2 Find a R wave that lands on a bold line. Count the # of large boxes to the next R wave. If the second R wave is 1 large box away the rate is 300, 2 boxes - 150, 3 boxes - 100, 4 boxes - 75, etc. (cont) R wave
6. Step 2 : Determine Regularity Regular: If the difference between the longest R-R interval in the ECG and the shortest R-R interval is less than 0.12 second Irregular: If the difference between the longest R-R interval in the ECG and the shortest R-R interval is greater than 0.12 second
7. Step 2: Determine regularity Look at the R-R distances (using a caliper or markings on a pen or paper). Regular? Occasionally irregular? Regularly irregular? Irregularly irregular? Interpretation? R R Regular
8. Step 3: Assess the P waves Are there P waves? Do the P waves all look alike? Do the P waves occur at a regular rate? Is there one P wave before each QRS? Interpretation? Normal P waves with 1 P wave for every QRS
14. Key Points to Remember regarding Vector Analysis A wave of depolarization traveling towards a positive electrode results in a positive deflection in the ECG trace. 2. A wave of depolarization traveling away from a positive electrode results in a negative deflection. 3. A wave of repolarization traveling toward a positive electrode results in a negative deflection. 4. A wave of repolarization traveling away from a positive electrode results in a positive deflection.
15. Atrial Depolarization and the Inscription of the P-wave SA node AV node Delay (no electrical activity) before the beginning of ventricular depolarization due to AV node function 0 90
18. Flow of Electrical Currents in the Chest Around the Heart Ventricular depolarization starts at the ventricular septum and the endocardial surfaces of the heart. The average current flows from negative to positive in the direction in the direction from the base of the heart to the apex. At the very end of depolarization the current reverses from 1/100 second and flows toward the outer walls of the ventricles near the base (S wave).
21. ECG leads and their Axis The ECG is measured by placing skin electrodes on the body surface at different locations and connecting these electrode in different configurations to a voltage amplifier and recorder
22. ECG Leads The standard ECG has 12 leads: 3 Standard Limb Leads 3 Augmented Limb Leads 6 Precordial Leads The axis of a particular lead represents the viewpoint from which it looks at the heart.
23. Three Bipolar Limb Leads To record limb lead I, the negative terminal of the electrocardiograph is connected to the right arm and the positive terminal to the left arm To record limb lead II, the negative terminal of the electrocardiograph is connected to the right arm and the positive terminal to the left leg To record limb lead III, the negative terminal of the electrocardiograph is connected to the left arm and the positive terminal to the left leg
24. Leads I, II, & III together(“Einthoven’s triangle”)
25. Normal Electrocardiograms Recorded from the Three Standard Bipolar Limb Leads Recordings of the electrocardiograms in leads I, II, and III.
26. Augmented Unipolar Limb Leads In this type of recording, two of the limbs are connected through electrical resistances to the negative terminal of the electrocardiograph, and the third limb is connected to the positive terminal. When the positive terminal is on the right arm, the lead is known as the aVR lead when on the left arm, the aVL lead and when on the left leg, the aVF lead
27. Summary of the “Limb Leads” LEAD AVR LEAD AVL -30o -150o Each of the limb leads (I, II, III, AVR, AVL, AVF) can be assigned an angle of clockwise or counterclockwise rotation to describe its position in the frontal plane. Downward rotation from 0 is positive and upward rotation from 0 is negative. 0o LEAD I 60o LEAD II 120o 90o LEAD III LEAD AVF
28. Chest Leads (Precordial Leads) V1 - 4th intercostal space - right margin of sternum V2 - 4th intercostal space - left margin of sternum V3 - linear midpoint between V2 and V4 V4 - 5th intercostal space at the mid clavicular line V5 - horizontally adjacent to V4 at anterior axillary line V6 - horizontally adjacent to V5 at mid- axillary line
29. Chest Leads (Precordial Leads) In leads V1 and V2, the QRS recordings of the normal heart are mainly negative because, the chest electrode in these leads is nearer to the base of the heart than to the apex. Conversely, the QRS complexes in leads V4, V5, and V6 are mainly positive because the chest electrode in these leads is nearer the heart apex, which is the direction of electropositivity during most of depolarization
30. Determining the electrical axis from standard lead electrocardiograms Plotting the mean electrical axis of the ventricles from two electrocardiographic leads (leads I and III)
32. High-voltage electrocardiogram in congenital pulmonary valve stenosis with right ventricular hypertrophy. Intense right axis deviation and a slightly prolonged QRS complex also are seen
