NTI 2010 Cardiovascular Boot Camp Bradyarrhythmias and Treatment Cynthia Webner MSN, RN, CCNS, CCRN, CMC Cardiovascular Nursing Education Associates www.cardionursing.com 1 2 Understanding Arrhythmias Physiologically Potential Causes of Bradycardias in Critical Care What does P wave represent? Can we see sinus node? What does normal PR interval represent? (prolonged?) What does skinny QRS represent? Wide QRS?? What pacemaker options exist? What should be the end result of each sinus impulse? • • • • • • • Propofol Cardiac disorders and medications Vasovagal CNS injury Rule of thumb: Hypothyroid Pace if cause cannot Hypothermia be reversed. Multiple other 4 3 SA Block (SA Exit Block) • Type I and Type II • Signs of Wenckebach • Fixed P to P • Dropped P waves • Typically transient • • • • • • SA Block • Quality of sinus node cells • Sinus discharge versus atrial activation Healthy young people Trained athletes Digitalis toxicity Other antiarrhythmics Infarction / myocarditis Part of SSS 5 Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com 6 1 Sinus Arrest or Sinus Pause Sick Sinus Syndrome • Failure of impulse formation • Impossible definitive diagnosis on surface ECG • Clue: PP intervals of cycle cannot be walked out across the pause and end on P wave • • • • Disorders of impulse generation and conduction Failure of escape pacemakers Susceptibility to atrial tachyarrhythmias Bradycardia / tachycardia syndrome • Long pause after tachycardia (overdrive suppression) • Syncope 40% SSS: coronary atherosclerosis 5-10% SSS: ideopathic cardiomyopathy 7 Heart Blocks – AV Blocks 8 2nd Degree AV Blocks • Classification • One P Wave at a time fails to conduct to ventricle • Type I (Wenckebach) – 1st Degree – 2nd Degree • Type I (Wenckebach) • Type II – Conduction fails in AV node • Type II – High Grade – Third Degree – Conduction fails below the AV node and usually involves both bundles 9 10 Wenckebach (2nd Degree Type I) – Sinus node fires regularly – Disease in AV node – Group beating is noted – First P-R of group of often longer than normal with progressive lengthening of the P-R until a beat is not conducted – In absence of BBB QRS is normal 11 Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com – Conduction ratios may be 2:1, 3:2, 4:3 etc. – May develop 2:1 conduction if sinus rate increases • Verify the block is still type I • P-R longer than normal • Absence of prolonged QRS – Treatment: Often none • Acutely with symptoms: Atropine or TTVP 12 2 2nd Degree Type (Wenckebach) 2nd Degree AV Block Type II • • • • Similar to Type I however no progressive lengthening of P-R interval Disease within or below bundle of His P-R interval is fixed with normally conducted beats QRS: wide • If 2:1 conduction look for: – Normal P-R interval with conducted beats – Wide QRS complex • Treatment: Usually requires permanent pacing 13 Third Degree AV Block – Complete Heart Blocks - High Grade AV Block • • • • • • 14 – No atrial impulses are conducted to the ventricles – One form of AV dissociation – Ventricular Rate: Maintained by junctional escape (narrow QRS) or ventricular escape (wide QRS) – Symptomatic if develops acutely – May be well tolerated if develops overtime – Treatment: Perm. Pacer Two or more consecutive atrial impulses are blocked. P waves: Regular, but 2 or > fail to conduct to the ventricles QRS: Narrow in type I & wide in type II Ventricular Rate: Slow, often symptomatic Treatment: Atropine for Type I Pacing for Type II - Usually 15 Third Degree (Complete) Heart Block 16 Junctional Escape and Rhythm • HR 35-60 beats per minute • P’ waves may or may not be associated with QRS complexes • QRS complexes same as sinus beats 17 Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com 18 3 Ventricular Escape Beats II V1 19 20 20 Medications that Increase Heart Rate Idioventricular Ventricular Rhythm • Sympathomimetics that increase heart rate (β1 receptors) – Dopamine – Epinephrine – Isuprel (no longer used except with cardiac transplants) II 21 21 – Atropine – Note: Will only work in the location of parasympathetic nervous system fibers – Clinical Clue: Skinny or wide QRS 22 Implantation of Permanent Pacer Pacing Basics 23 Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com • Para Sympatholytics that increase heart rate (block parasympathetic nervous system) 24 4 Bipolar vs. Unipolar System Pacemaker Function 25 Pace • Ability of the pacemaker to send a stimulus to the myocardium • Identified by a pacemaker spike on the ECG Capture • Ability of the pacing stimulus to depolarize chamber being paced • Identified by a pacemaker spike that is immediately followed by a P wave or a QRS complex on the ECG 26 Pacing Sense • Ability of the pacemaker to recognize and respond to intrinsic cardiac depolarization • Identified by pacing when no intrinsic beats and not pacing when intrinsic beats are present 27 Capture – Two consecutive pacer spikes • Spikes should appear regularly unless pacer is inhibited by sensed intrinsic activity 28 Sensing • Pacing stimulus results in depolarization of chamber being paced • Each spike should be followed by a QRS unless it falls in heart’s refractory period 29 Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com • Identify automatic pacing interval (pacing rate) • Pacemaker sees and responds to intrinsic activity • Must be given opportunity to sense – Must be in demand mode – There must be intrinsic activity to be sensed 30 5 Revised NASPE/BPEG Generic Code for Antitachycardia Pacing Position I Position II AAI Pacing – Atrial Inhibited Position III Position IV Position V AAI Chamber(s) Paced Chamber(s) Sensed Response to Sensing Rate Modulation Multisite pacing Paces the Atrium O=None O=None O=None O=None O=None AAI R=Rate modulation A=Atrium Senses the Atrium AAII AA A=Atrium A=Atrium T=Triggered V=Ventricle V=Ventricle I=Inhibited V=Ventricle D=Dual (A+V) D=Dual (A+V) D=Dual (T+I) D=Dual (A+V) Atrial sensing inhibits atrial pacing 31 (Bernstein et al., 2002) 32 VVI Pacing – Ventricular Inhibited Pacing Modes AAI VVI Paces the Ventricle VVI Senses the Ventricle VVI Ventricular sensing inhibits ventricular pacing 33 34 Dual Chamber Pacers VVI Pacing • Provide AV synchrony – Maintains atrial kick – Improves hemodynamics in those with heart blocks • Tracks atrial activity – Ventricular pacing occurs in response to atrial activity – Improved hemodynamics • Decreased incidence of pacemaker syndrome 35 Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com 36 6 DDDR Pacing DDDR Paces both Atrium and Ventricle DDDR Senses both Atrium and Ventricle DDDR 1. 2. Atrial sensing inhibits atrial pacing and triggers ventricular pacing Ventricular sensing inhibits ventricular and atrial pacing 38 37 Basic Pacemaker Timing Basic Pacemaker Timing Refractory Period • AV Interval Brief period of time when pacer is not allowed to look for intrinsic events Can be lengthened or shortened to eliminate in appropriate sensing – Period of time between an atrial event (sensed “P” wave or atrial pace) and a paced ventricular event • VV Interval – Period of time from ventricular complex to ventricular complex Absolute Refractory Period • VA Interval Nothing can be sensed Relative Refractory Period – Ventricular complex to atrial activity – Also called AEI or atrial escape interval Allows sensing but pacer will not respond 40 39 DDD Pacing: AV Sequential Pacing State Basic Pacemaker Timing • Low Rate – Lowest rate allowed by the pacer before a paced beat is initiated • High Rate – Upper rate limit – Highest rate that can be achieved and still maintain AV synchrony 41 Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com 42 7 DDD Pacing: Atrial Pacing Ventricular Sensing State DDD Pacing: Atrial Tracking Ventricular Pacing State 43 44 DDD Pacing: Atrial Sensing and Ventricular Sensing State 46 45 Effect of RV Pacing • RV pacing results in mechanical desynchronization (mechanical LBBB) • Increased hospitalizations and mortality for HF (DAVID Trial) • No improvement in mortality, HF hospitalizations or stroke free survival when compared to VVI (MOST Trial, CTOPP Trial) • Patients who survived to the 3-month follow-up had worse 12month event-free rates when the percentage of right ventricular pacing by ICD interrogation was 41% to 100% (75.9%) than when less than 40% (86.9%) (P=.09) (DAVID Trial) • AAI pacing demonstrates improved outcomes • Reducing RV pacing to less than 10% in patients with dual chamber pacemakers reduced the relative risk of developing persistent atrial fibrillation by 40% compared to conventional 47 dual chamber pacing (SAVE PACe Trial) Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com Managed Ventricular Pacing 48 8 Minimizing Right Ventricular Pacing Managed Ventricular Pacing – AAIR mode with mode switching – VVI mode with low rate for those being paced as defibrillation back up only – Long AV delays – Managed ventricular pacing 49 – AV search historesis 51 52 50 #1 What is your priority when it appears that the pacemaker is not working? Troubleshooters Toolbox Rhythm strip V1 or the lead that best allows evaluation of the pacemaker Pacemaker information Type Programmed parameters Intervals Special features Calipers Magnet 53 Chest x-ray Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com Questions to Ask • Are there pacemaker spikes? 54 9 Questions to Ask Questions to Ask • Is there evidence of pacemaker capture Ventricular after a pacemaker spike? Capture • Does the pacemaker sense appropriately – Inhibit the pacemaker when a natural beat occurs? Sensed appropriately – Activate pacing when no intrinsic beat occurs Atrial Capture 55 56 What are the three major malfunctions with pacemakers? Failure to ______? • Failure to Fire • Failure to Capture • Failure to Sense Fire? – Oversensing – Undersensing Capture? Sense? 58 57 Troubleshooting Pacemakers • Causes of Failure to Fire Failure to ___________? • Interventions for Failure to Fire – Pacer turned off – Loose or broken connection – Lead displacement – Battery depletion – Oversensing 59 – Emergently treat patient as condition requires – Check connections if temporary – Replace battery or pulse generator – Lead repositioning or replacement – Convert pacer to asynchronous mode – to assess for sensitivity issues Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com Fire? Capture? Sense? 60 10 Troubleshooting Pacemakers Failure to __________? • Causes of Failure to • Interventions for Failure to Capture Capture – Position patient on left side – May need lead repositioned or replaced – Increase mA – Chest x-ray, Labs – Monitor for tamponade, diaphragmatic pacing – Lead displacement – Increased pacing thresholds – Acute MI – Chamber perforation Fire? Capture? Sense? 62 61 Sensitivity: “The Fence” Troubleshooting Pacemakers • Causes of Oversensing (Seeing Too Much) • Causes of Undersensing (Not Seeing) Sensitivity too low (fence too high) Pacer can’t see QRS Sensitivity too high (fence too low) Pacer “hallucinates” 63 Troubleshooting Pacemakers • Interventions for Undersensing • Interventions for Oversensing – Decrease sensitivity (turn mV number higher) – Decrease MA if set very high – Chest X-ray to verify position and check for lead fractures – Remove from EMI – Ensure that all equipment is properly grounded – Emergently treat patient as condition requires – Position on left side – Lead repositioning (by MD) – Set in demand mode – Increase sensitivity (lower mV number) – Check connections – Treat PVC’s 65 Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com – Fence too high – doesn’t see QRS – Asynchronous mode – Sensitivity set too low – Intrinsic ventricular activity in refractory period – Lead tip not in place with myocardium – Low QRS voltage (drugs, electrolyte imbalance, disease) – Break in connection, Faulty generator, Battery failure – Fence too low – sees too much – Sensitivity set too high – Electromagnetic interference – Myopotentials 64 True or False: When you place the magnet over a permanent pacemaker the pacemaker should pace. 66 11 Magnet Mode Let’s Practice DDDR Pacer Beware of the Magnet! FUNCTIONS DIFFERENTLY WITH ICD’S Turns sensing circuit off in permanent pacemakers (without ICDs) Pacemaker paces asynchronously (no regard for intrinsic activity) Identifies battery end of life Determines lead location RV Pacing LV Pacing Risk of pacemaker impulse occurring on the T wave Should be used with caution Avoid use in those patients susceptible to ventricular arrhythmias: Fresh MI Hypokalemia 67 Fire? Capture? Sense? Let’s Practice DDDR Pacer 68 Let’s Practice VVI Pacer Fire? Capture? Fire? Sense? Capture? 69 70 Sense? Let’s Practice VVI Pacer 71 Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com Fire? Capture? Sense? 72 12 Let’s Practice VVI Pacer Let’s Practice DDDR Pacer Fire? Capture? Sense? Fire? Capture? 74 73 Sense? Congratulations!!! 75 Cynthia Webner MSN, CCNS, CCRNCMC 2010 Cardiovascular Nurisng Education Associates www.cardionursing.com 76 13