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# Lec18(cvs)

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### Lec18(cvs)

1. 1. How to Analyze a Rhythm<br />
2. 2. Rhythm Analysis<br />Step 1: Calculate rate.<br />Step 2: Determine regularity.<br />Step 3: Assess the P waves.<br />Step 4: Determine PR interval.<br />Step 5: Determine QRS duration.<br />
3. 3. Step 1: Calculate Rate<br />Option 1<br />Count the # of R waves in a 6 second rhythm strip, then multiply by 10.<br />Interpretation?<br />3 sec<br />3 sec<br />9 x 10 = 90 bpm<br />
4. 4. Step 1: Calculate Rate<br />Option 2 <br />Find a R wave that lands on a bold line.<br />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)<br />R wave<br />
5. 5. Step 1: Calculate Rate<br />Option 2 (cont) <br />Interpretation?<br />300<br />150<br />100<br /> 75<br /> 60<br /> 50<br />Approx. 1 box less than 100 = 95 bpm<br />
6. 6. Step 2 : Determine Regularity<br />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<br />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<br />
7. 7. Step 2: Determine regularity<br />Look at the R-R distances (using a caliper or markings on a pen or paper).<br />Regular? Occasionally irregular? Regularly irregular? Irregularly irregular?<br />Interpretation?<br />R<br />R<br />Regular<br />
8. 8. Step 3: Assess the P waves<br />Are there P waves?<br />Do the P waves all look alike?<br />Do the P waves occur at a regular rate?<br />Is there one P wave before each QRS?<br />Interpretation?<br />Normal P waves with 1 P wave for every QRS<br />
9. 9. Step 4: Determine PR interval<br />Normal: 0.12 - 0.20 seconds.<br /> (3 - 5 boxes)<br />Interpretation?<br />0.12 seconds<br />
10. 10. Step 5: QRS duration<br />Normal: 0.04 - 0.12 seconds.<br /> (1 - 3 boxes)<br />Interpretation?<br />0.08 seconds<br />
11. 11. Rhythm Summary<br />Rate 90-95 bpm <br />Regularity regular<br />P waves normal<br />PR interval 0.12 s<br />QRS duration 0.08 s<br />Interpretation?<br />Normal Sinus Rhythm<br />
12. 12. NSR Parameters<br />Rate 60 - 100 bpm <br />Regularity regular<br />P waves normal<br />PR interval 0.12 - 0.20 s<br />QRS duration 0.04 - 0.12 s<br />
13. 13. Generation of the Electrocardiogram<br />
14. 14. Key Points to Remember regarding Vector Analysis<br />A wave of depolarization traveling towards a positive electrode results in a positive deflection in the ECG trace.<br />2. A wave of depolarization traveling away from a positive electrode results in a negative deflection.<br />3. A wave of repolarization traveling toward a positive electrode results in a negative deflection.<br />4. A wave of repolarization traveling away from a positive electrode results in a positive deflection.<br />
15. 15. Atrial Depolarization and the Inscription of the P-wave<br />SA node<br />AV node<br />Delay (no electrical activity) before the beginning of ventricular depolarization due to AV node function<br />0<br />90<br />
16. 16. Ventricular Depolarization and the Inscription of the QRS complex<br />
17. 17. Ventricular Repolarization and the Inscription of the T-wave<br />
18. 18. Flow of Electrical Currents in the Chest Around the Heart <br />Ventricular depolarization starts at the ventricular septum and the endocardial surfaces of the heart.<br />The average current flows from negative to positive in the direction in the direction from the base of the heart to the apex.<br />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).<br />
19. 19.
20. 20. +<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />+<br />Flow of Electrical Currents in the Chest Around the Heart<br />Mean Vector Through the Partially Depolarized Heart<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />_<br />
21. 21. ECG leads and their Axis<br />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<br />
22. 22. ECG Leads<br />The standard ECG has 12 leads:<br />3 Standard Limb Leads<br />3 Augmented Limb Leads<br />6 Precordial Leads<br />The axis of a particular lead represents the viewpoint from which it looks at the heart.<br />
23. 23. Three Bipolar Limb Leads <br />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<br />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<br />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<br />
24. 24. Leads I, II, & III together(“Einthoven’s triangle”)<br />
25. 25. Normal Electrocardiograms Recorded from the Three Standard Bipolar Limb Leads<br />Recordings of the electrocardiograms in leads I, II, and III. <br />
26. 26. Augmented Unipolar Limb Leads<br />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. <br />When the positive terminal is on the right arm, the lead is known as the aVR lead<br />when on the left arm, the aVL lead<br /> and when on the left leg, the aVF lead<br />
27. 27. Summary of the “Limb Leads”<br />LEAD AVR<br />LEAD AVL<br />-30o<br />-150o<br />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.<br />0o<br />LEAD I<br />60o<br />LEAD II<br />120o<br />90o<br />LEAD III<br />LEAD AVF<br />
28. 28. Chest Leads (Precordial Leads)<br />V1 - 4th intercostal space - right margin of sternum<br />V2 - 4th intercostal space - left margin of sternum<br />V3 - linear midpoint between V2 and V4<br />V4 - 5th intercostal space at the mid clavicular line<br />V5 - horizontally adjacent to V4 at anterior axillary line<br />V6 - horizontally adjacent to V5 at mid- axillary line<br />
29. 29. Chest Leads (Precordial Leads)<br />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.<br />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<br />
30. 30. Determining the electrical axis from standard lead electrocardiograms<br />Plotting the mean electrical axis of the ventricles from two electrocardiographic leads (leads I and III)<br />
31. 31. Left axis deviation in a hypertensive heart (hypertrophic left ventricle)<br />
32. 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<br />