1. Copyright © 2006 by Elsevier, Inc. P-R interval 0.16 sec P T R Q S Q-T interval 0.35 sec Atrial depolarization Ventricular depolarizatio n Ventricular repolarization P R Q S T Normal EKG

2. Copyright © 2006 by Elsevier, Inc. Standardized EKGs Time and voltage calibrations are standardized as shown on figure 11-1. Figure 11-1; Guyton & Hall

3. Copyright © 2006 by Elsevier, Inc. Heart Rate Calculation R-R interval = 0.83 sec Heart rate = (60 sec) / (0.83 sec) = 72 beats/min min beat

4. Copyright © 2006 by Elsevier, Inc. Bipolar Limb Leads Bipolar means that the EKG is recorded from two electrodes on the body. Figure 11-6; Guyton & Hall

5. Copyright © 2006 by Elsevier, Inc. Bipolar Limb Leads (cont’d) Figure 11-7; Guyton & Hall 0.5 mV 1.2 mV 0.7 mV

6. Copyright © 2006 by Elsevier, Inc. Other EKG Leads Chest Leads (Precordial Leads) known as V 1 - V 6 are very sensitive to electrical potential changes underneath the electrode. Figure 11-9; Guyton & Hall

7. Copyright © 2006 by Elsevier, Inc. Cardiac Cycle Figure 9-5; Guyton & Hall

8. Copyright © 2006 by Elsevier, Inc. Phases of the Cardiac Cycle

9. Copyright © 2006 by Elsevier, Inc. Pressure and Volume Relationships in the Cardiac Cycle

10. Copyright © 2006 by Elsevier, Inc. A Simple Model of Stroke Volume

11. Copyright © 2006 by Elsevier, Inc. Factors Affecting Cardiac Output Figure 20.20