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Copyright © 2006 by Elsevier, Inc.
P-R
interval
0.16 sec
P T
R
QS
Q-T interval0.35 sec
Atrial depolarizatio
n
Ventricular depolarizatio
n
Ventricular repolarization
P
R
QS
T
Normal EKG
Copyright © 2006 by Elsevier, Inc.
Standardized EKGs
• Time and voltage calibrations are standardized as shown on figure 11-1.
Figure 11-1; Guyton & Hall
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
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
Copyright © 2006 by Elsevier, Inc.
Bipolar Limb Leads (cont’d)
Figure 11-7; Guyton & Hall
0.5 mV
1.2 mV
0.7 mV
Copyright © 2006 by Elsevier, Inc.
Other EKG Leads
• Chest Leads (Precordial Leads) known as V1-V6 are very sensitive to electrical potential
changes underneath the electrode.
Figure 11-9; Guyton & Hall
Copyright © 2006 by Elsevier, Inc.
Cardiac Cycle
Figure 9-5; Guyton & Hall
Copyright © 2006 by Elsevier, Inc.
Phases of the Cardiac Cycle
Copyright © 2006 by Elsevier, Inc.
Pressure and Volume Relationships in the Cardiac Cycle
Copyright © 2006 by Elsevier, Inc.
A Simple Model of Stroke Volume
Copyright © 2006 by Elsevier, Inc.
Factors Affecting Cardiac Output
Figure 20.20
