Artificial Pacemakers

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Information about Artificial Pacemakers

Published on October 15, 2008

Author: aSGuest1004


AV Blocks Artificial Pacemakers : AV Blocks Artificial Pacemakers EMS Professions Temple College AV Blocks : AV Blocks Disorders of conduction at AV Junction Categories First degree (1° AV Block) Second degree (2° AV Block) Type I Type II Third degree (3° AV Block or Complete AV Block) Analyze the Rhythm : Analyze the Rhythm AV Blocks : AV Blocks First Degree Prolonged AV conduction time PR interval > 0.20 seconds Characteristics of that of any other rhythm with a SINGLE sinus or atrial pacemaker site Associated with an underlying sinus or atrial rhythm!!! AV Blocks : AV Blocks First Degree Causes AV node ischemia/hypoxia Increased vagal or decreased sympathetic tone Drug effects Digitalis Beta blockers Calcium channel blockers Quinidine Pronestyl AV Blocks : AV Blocks First Degree Management Usually requires no specific treatment Treat the patient!!! Monitor for progression to higher degree block AV Blocks : AV Blocks Second Degree Definition More Ps than QRSs Every QRS caused by a P The pattern determines the type of 2° AV block Since requires presence of P waves, it also requires an underlying sinus or atrial rhythm AV Blocks : AV Blocks Second Degree Types Type I Variable Wenckebach phenomenon Type II Fixed Classical Analyze the Rhythm : Analyze the Rhythm AV Blocks : AV Blocks Second Degree Type I Definition PR interval lengthens Beat drops Pathophysiology Usually physiologic Increased vagal tone (Acute inferior MI, RVI) Drug effects (digitalis, beta blockers, CCBs) Frequently resolves AV Blocks : AV Blocks Second Degree Type I Good prognosis Specific therapy usually not necessary therapy, if indicated, most likely targeted towards bradycardia Treat the patient!!! Analyze the Rhythm : Analyze the Rhythm AV Blocks : AV Blocks Second Degree Type II Definition P waves fail to conduct without warning PR interval does not lengthen Characteristics Atrial rate > Ventricular rate QRS usually longer than 0.12 sec Usually 4:3 or 3:2 conduction ratio (P:QRS ratio) AV Blocks : AV Blocks Second Degree Type II Pathophysiology Organic lesions in bundle branches Usually occurs below bundle of His in the bundle branches (infranodal AV block) Intermittent block of conduction through one bundle and complete block in other Usually caused by Acute anterior or anteroseptal MI AV Blocks : AV Blocks Second Degree Type II Outlook Not good Usually associated with anterior or anteroseptal MI Frequent progression to complete AV block Requires pacemaker Worsened by digitalis, procainamide, lidocaine, propranolol, TCAs Analyze the Rhythm : Analyze the Rhythm AV Blocks : AV Blocks Complete Definition No conduction through AV node Independent atrial and ventricular rhythms Ventricular depolarization dependent on automaticity of ventricular pacemaker sites Pathophysiology AV node hypoxia/ischemia Myocardial infarction Increased vagal or decreased sympathetic tone AV Blocks : AV Blocks Complete Characteristics Atrioventricular dissociation Regular P-P and R-R but without association between the two Atrial rate > Ventricular rate QRS > 0.12 sec AV Blocks : AV Blocks Complete Outlook Junctional escape rhythm: good Ventricular escape rhythm: bad Warning Do NOT give lidocaine or other ventricular antidysrhythmics!!! AV Blocks : AV Blocks Management Treatment based on Sx/Sx Most common complication = Bradycardia IV/O2/ECG Monitor/12 lead ECG Atropine (not useful in 2° Type II or 3° AV Block) TCP (bridge to transvenous pacer) Catecholamine drip Prophylactic pacer application (standby) 2° Type II AV block 3° AV Block Analyze the Rhythm : Analyze the Rhythm Cardiac Pacemakers : Cardiac Pacemakers Definition Delivers artificial stimulus to heart Causes depolarization and contraction Uses Bradyarrhythmias Asystole Tachyarrhythmias (overdrive pacing) Cardiac Pacemakers : Cardiac Pacemakers Types Fixed Fires at constant rate Can discharge on T-wave Very rare Demand Senses patient’s rhythm Fires only if no activity sensed after preset interval (escape interval) Transcutaneous vs Transvenous vs Implanted Cardiac Pacemakers : Cardiac Pacemakers Cardiac Pacemakers : Cardiac Pacemakers Demand Pacemaker Types Ventricular Fires ventricles Atrial Fires atria Atria fire ventricles Requires intact AV conduction Cardiac Pacemakers : Cardiac Pacemakers Demand Pacemaker Types Atrial Synchronous Senses atria Fires ventricles AV Sequential Two electrodes Fires atria/ventricles in sequence Cardiac Pacemakers : Cardiac Pacemakers Problems Failure to capture No response to pacemaker artifact Bradycardia may result Cause: high “threshold” Management Increase amps on temporary pacemaker Treat as symptomatic bradycardia Cardiac Pacemakers : Cardiac Pacemakers Problems Failure to sense Spike follows QRS within escape interval May cause R-on-T phenomenon Management Increase sensitivity Attempt to override permanent pacer with temporary Be prepared to manage VF Cardiac Pacemakers : Cardiac Pacemakers Problems Inappropriate absence of pacer artifact Causes Depleted battery Circuit malfunction Oversense Management Decrease sensitivity Treat bradycardia Replace pacemaker Cardiac Pacemakers : Cardiac Pacemakers Problems Runaway pacemaker Rates of up to 400/minute Increasing rate = Emergency Causes Component failure Battery depletion Management Transport Enter site surgically, cut lead Some may be turned “off” by donut-shaped magnet Cardiac Pacemakers : Cardiac Pacemakers Special Considerations Pacemaker does NOT affect treatment of cardiac arrest Do NOT fire defibrillator directly over pacemaker generator Pacemakers may keep AEDs from advising shock Cardiac Pacemakers : Cardiac Pacemakers Transcutaneous Pacing Electrical vs Mechanical capture Tips for improving electrical capture Ensure adequate conductance Increase current (mA) Tips for improving mechanical capture Ensure the “tank” is topped off Increase the electrical rate Increase peripheral vascular resistance Cardiac Pacemakers : Cardiac Pacemakers Transcutaneous Pacing Realizations It is much easier to increase the electrical rate of depolarization than it is to increase the mechanical rate of contraction! You can’t create mechanical capture in dead muscle! Implanted Defibrillators : Implanted Defibrillators AICD Automated Implanted Cardio-Defibrillator Uses Tachyarrhythmias Malignant arrhythmias VT VF Implanted Defibrillators : Implanted Defibrillators Programmed at insertion to deliver predetermined therapies with a set order and number of therapies including: pacing overdrive pacing cardioversion with increasing energies defibrillation with increasing energies standby mode Effect of standby mode on Paramedic treatments Implanted Defibrillators : Implanted Defibrillators Potential Complications Fails to deliver therapies as intended worst complication requires Paramedic intervention Delivers therapies when NOT appropriate broken or malfunctioning lead parameters for delivery are not specific enough Continues to deliver shocks parameters for delivery are not specific enough and device senses a reset may be shut off (not standby mode) with donut-magnet

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