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Escape and Usurpation • Escape: Predominant pacemaker slows, lower pacemaker takes over at slower rate. An escape beat is a beat that comes in after a pause • Usurpation: Irritable lower pacemaker takes control and becomes new pacemaker at a faster rate, suppressing or inhibiting the previous pacemaker EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Figure 2-11 Escape EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Figure 2-12 Usurpation EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Paper • Graph paper that EKGs are printed on • Divided into small blocks 1 millimeter in height and width • Counting horizontally measures time (intervals) • Counting vertically measures amplitude EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Figure 2-13 EKG Paper EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. EKG Paper Delineations • • • • • • • One small block is 0.04 seconds Five small blocks = one big block One big block = 0.20 seconds 25 small blocks = 1 second Five big blocks = 1 second 1500 small blocks = 1 minute 300 big blocks = 1 minute EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. 12-Lead EKGs and Rhythm Strips • 12-Lead EKG: Printout of the heart’s electrical activity viewed from 12 different angles as seen in 12 different leads • A lead is an electrocardiographic picture of the heart’s electrical activity • Rhythm Strip: Printout of only one or two leads at a time EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Figure 2-14 (A) Single- and (B) double-lead rhythm strips. EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Benefit of Double-Lead Strips • Both leads show the same rhythm, just viewed from two different angles • Therefore both leads have the same rhythm, intervals, and heart rate EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Benefit of Double-Lead Strips • Two leads provide twice the chance of identifying the rhythm. For example, P waves may not be visible in one lead, but are very clear in the other • Having two leads shows how the same rhythm can look different in different leads EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Figure 2-15 12-Lead EKG EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Intervals • Measurement of time between the P-QRST waves and complexes • Measurements allow determination of heart’s efficiency at conducting its impulses down the pathway EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Intervals • PR: Measured from beginning of P to beginning of QRS • QRS: Measured from beginning of QRS to its end • QT: Measured from beginning of QRS to end of T wave EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Figure 2-16 Intervals EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Intervals Practice: Enlarged Rhythm Strip 1 PR__________ QRS__________ QT__________ EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Intervals Practice: Enlarged Rhythm Strip 2 PR__________ QRS__________ QT__________ EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved. Intervals Practice: Enlarged Rhythm Strip 3 PR__________ QRS__________ QT__________ EKG Plain and Simple, Third Edition Karen M. Ellis Copyright ©2012 by Pearson Education, Inc. All rights reserved.