Abnormal Sinus Rhythms Tachycardia means a fast heart

Abnormal Sinus Rhythms (cont’d) • Bradycardia means a slow heart rate usually less than

Sinoatrial Block • In rare instances impulses from S-A node are blocked. • New pacemaker is region of heart with the fastest discharge rate, usually the A-V node. Note: no P waves and slow rate Figure 13 -4; Guyton & Hall Copyright © 2006 by Elsevier, Inc.

First Degree Heart Block AV Node SA Node H T Delay Prolonged P-R Interval

Second Degree Heart Block AV Node SA Node H T Intermittent Blocked Conducted Blocked

Third Degree Complete Block • Total block through the A-V node or A-V bundle • P waves are completely dissociated from QRST complexes • Ventricles escape and A-V nodal rhythm ensues HR = 37 Figure 13 -7; Guyton & Hall Copyright © 2006 by Elsevier, Inc.

Premature Atrial Contractions Figure 13 -9; Guyton & Hall Copyright © 2006 by Elsevier,

Premature Ventricular Contractions (PVC’s) Figure 13 -3; Guyton & Hall Copyright © 2006 by

Atrial Paroxysmal Tachycardia • Paroxysmal means a series of rapid heart beats suddenly start and then suddenly stop. • Can be stopped with a vagal reflex or quinidin or procainimide • P wave is inverted if origin is near A-V node • Occurs by re-entrant pathways Figure 13 -12; Guyton & Hall Copyright © 2006 by Elsevier, Inc.

Ventricular Paroxysmal Tachycardia • Usually does not occur unless there has been ischemic damage • Quinidine increases refractory period of cardiac muscle and can eliminate the problem Figure 13 -13; Guyton & Hall Copyright © 2006 by Elsevier, Inc.