pacemaker lecture.pptx

Defibrillators, Cardioversion and Pacemakers Knowledge Promise After today’s lecture I hope you have a better understanding of rhythm management devices, what they are, when and why we use them and how this information can help us be better perfusionists and patient advocates 2 • • • • • • • •...

Defibrillators, Cardioversion and Pacemakers Knowledge Promise After today’s lecture I hope you have a better understanding of rhythm management devices, what they are, when and why we use them and how this information can help us be better perfusionists and patient advocates 2 • • • • • • • • Menu / Objectives Introduction Understand the history of pacemakers Know the components that make up a pacemaker Know the types of pacemakers Understand pacemaker codes Understand the modes of pacemakers Examine the differences between cardioversion and defibrillation Evaluate EKG pacemaker strips (have some idea of what you are looking at! 3 Why learn about Pacemakers? • Pacemaker technology birthed with advent of cardiac surgery • Many cardiac patients c o m e t o th e O R w i t h p a c e m a kers and or defibrillators • Most all cardiac patients leave the OR on a temporary pacemaker • • Sometimes perfusionists manage this! Perfusionists are involved in pacemaker lead removals for infected pacemakers (sometimes using lasers so you get to wear cool glasses) • CPB standby to prevent potential disaster 9/27/2021 4 EKG Basics HR is 60 BPM – how many seconds between beats? XTRA credit for this one! Hint… frequency is 1 Hz Note that • R wave is about 1 mv • R-R interval is 1 sec or 1000 msec • P-R interval is about 200 msec (normal) • If longer could indicate heart block • Q-T interval is about 400 msec Pathologies requiring pacemakers? Effective cardiac pumping requires atria and ventricles to be activated rapidly and sequentially • Sinus node dysfunction • Acquired atrioventricular heart block – Prolonged PR 6 Why pace the atria? Atrial kick important for ventricular preload (20%) and maximizing cardiac output 7 Why do we need pacemakers? 8 Most experts agree that chronic beating of the heart is a good thing and that a blood pressure of zero is bad* (*findings have not been confirmed in prospective randomized trials) 9 Pacemakers Definition Fancy: A pacemaker ) is a (artificial device that medical pulses, uses electrical im delivered by electrodesacting the heart ng of cont muscles to the heart. regulate the beati • Less fancy – a wire in rt the hea emaker is to • The primary purpose of ate, either cemaker is a pac maintain an not ck in adequate heart r the heart's because the heart's native pa fast enough, Pacers can er (not or there is a blo electrical conduction slower) system. ONLY make the • Pacemakers Definition • Modern pacemakers are externally programmable • Allow the cardiologist to select the optimum pacing modes for individual patients • Some combine a pacemaker/defibrillator in a single implantable device - AICD • Others have multiple electrodes stimulating differing chambers (RA, RV, LV) to improve synchronization between atria and ventricles. 11 Current vs. Voltage Current (I) – milliamps • Flow of electrons in metal – myocardial depolarization • Pacemakers DELIVER current - a small “dose” (ma) of electrons every second • Current depends on voltage difference and impedance (Ohm’s law) Voltage (V) - millivolts • The “force” moving the current – battery chemistry • The “potential” of those electrons to do work once delivered – they don’t have to do anything, but could they wanted • Pacemakers also SENSE voltage (e.g. R or P waves) i f 12 • What do Pacemakers Do? Pace the heart (impulse formation and conduction) • • • Electrical current is sent to the heart in response to an applied voltage. This current is small and measured in milliamps (ma) When the heart can’t beat on its own this is a good thing Sense the heart • • The pacemaker measures the voltage produced by the heart when it contracts. The voltage is small and measured in millivolts (mv) Prevents R on T = VT, VF or Death 13 Perspect ive …extravascular pulse generator connected to 1 or more leads that traverse the venous system to contact myocardial tissue 14 Pac maker e History Pow er Rat h Implanta ble Leadle ss 15 Pacemaker History • 1930s: Hand crank!?!? – Hyman “an infernal machine that interferes with the will of God” • 1950s: Furman - Large AC powered pacemakers tethered to an extension cord • 1950s: Battery development – Mercury cell battery • • Lillehei / Bakken • Elmqvist / Senning 1960s: several companies, including ARCO in the USA, developed isotope powered pacemakers, but this development was overtaken by the development in 1971 of the lithium-iodide cell by Wilson Greatbatch. Lithium-iodide or lithium anode cells became the standard for future pacemaker designs 16 • Moments in Pacemaker History Wilson Greatbatch, a professed "humble tinkerer" who, working in his barn in 1958, in upstate New York, designed the first practical implantable pacemaker in the US, a device that has preserved millions of lives. • Tech. bought by Medtronic. 17 Transistorized / Wearable Rath 18 9/27/2021 • Implantati on 1 958: The first fully implantable pacemaker put in a human in the world • Patient: Arne Larsson in Solna, Sweden • Pacemaker designed by Rune Elmqvist and surgeon Åke Senning • Failed after three hours, 2nd one implanted lasted 3 days Arne went on to receive 26 different pacemakers during his lifetime. He died in 2001, at the age of 86, outliving the inventor as well as the surgeon. 196 1st in the U.S. – Chardack0: Greatbach device also incorporated a bipolar lead • • Rat h 1 9 Arne Larsson is the first human to receive an implanted pacemaker. He had been hospitalized with complete heart block and frequent Stokes- Adams attacks for 6 months. He was having 20 to 30 attacks daily and his prognosis was poor. Treatment was maximized with ephedrine, pentymal, atropine, isoprenaline, caffeine, digoxin and whisky. 20 Leadle ss Tech Present / Future 21 Components of a •Pacemaker Implantable pulse generator Leads IPG • Battery “Can” • • Circuitry Leads Cathode – negative • Anode – • Lead tips positive • • Body tissue – receives the voltage potential Anode Cathode 9/27/2021 22 Generat ors 23 Generator Placement 24 A look inside the “can” Rath 25 9/27/2021 A galvanic cell – current is produced by connecting an oxidation reaction to a reduction reaction in an electrolyte solution • Batteries convert chemical energy electrical into energy • Electrical current (positive Charge) runs from the positive terminal to the negative terminal • Electrons are negative and thus move in the opposite direction as the current • Electrons move alphabetically – from the lithium (A)node t0 the iodide (C)athode • The charge on electrodes depends on if the battery cell is driving the 26 electrons to the tissue (-) or if they are returning from the tissue back to the battery (+) Batter y Anode vs. Catho de Anod e • Electrons go Away • Electrochemical oxidation (loss of electrons) Cathod e • Electrons Come here • Electrochemical reduction (gain of electrons) 27 Pacemaker Leads are insulated wires • Deliver electrical impulses from the pulse generator to the heart • Sense cardiac depolarization • Must withstand mechanical torque, flexing and bending 28 Lea ds Bipolar Leads • Ground is close to the source (same wire) – lead tip (cathode -) to lead ring (anode +) • Electrons don’t travel as far • “Discrete” pacing spike • Favored for sensing – minimizes “oversensing” of extracardiac signals • Favored for “specificity” of pacing Unipolar Leads • Ground is somewhere else (lead tip to pulse generator) • Electrons travel farther – needs more energy to pace • Larger pacing spikes • Larger antenna for sensing / more interference 29 Bipolar Leads: Types of Lead s Unipolar Leads 30 3 1 Lead tips Passive fixation – tines lodge in fibrous meshwork Active fixation – screw in of heart or anywhere in (trabeculae heart chamber pectinate) Rath 32 9/27/2021 Lead Placem ent Endocardial stimulation • Transvenous to RA or RV • Coronary sinus to LV • Implantable (long term) Epicardial stimulation • Surface of heart • Temporary • Seen with cardiac surgery ops • In case of post op heart block 3 3 Ter ms Thresho •ldMinimum stimulation needed to pace the ventricle • Rate and pacing voltage initially set above native cardiac activity – then decreased until stimulation no longer results in a beat • Optimizing the pulse width and amplitude can significantly affect current drain and battery longevity • At implantation, a typical acceptable threshold is under 1.5 V with a pulse width of 0.5 ms • Can vary with scar tissue, circadian rhythm, hyperglycemia and viral infections • Steroid eluding pacing electrodes help by Sensitivity minimizing inflammation • Voltage level that must be exceeded to detect an R or P wave • To make a pacemaker more sensitive you must LOWER the sensitivity (mvolts) • Pacemakers typically are INHIBITED (don’t pace) when they sense native cardiac activity or noise (electrocautery) 3 4 Thresho ld Threshold vs. Sensitivit y Rat h S e n s i t i v i 3 5 Types of PermanentPacemakers • • • • • • Used to treat A-V Block Pulse generator inside body - subcutaneous Surgically implanted (sometimes in the OR) Trans-venous leads (bipolar or unipolar) Leads anchored (permanent fixation) to endocardium Programed before implantation 36 37 Need permanent pacemaker Complete Heart Block - Unrelated SA node firing with QRS escape rhythm Rhythm needs long term support 38 39 Pacemaker Pocket 4 0 Typ s of Pacemakers - orary e Temp • Uses • Pulse generator outside of body • Usually bipolar – no “can” for anode • For use while hospitalized • Epicardial (short term) • • Subclavian or Internal Lead placement Jugular Vein • Transvenous (passive fixation) • Emergency insertion if needed at bedside by “floating” electrode or placed using fluoroscopy • Post CPB Safety • Low Cardiac Output • Bradycardia • Heart Block • Bridge to Permanent 4 1 Temporary Pacemakers in the Cardiac OR -The pulse generator is attached to temporary wires placed while on CPB (during warming, Post XCL), before coming off pump – usual pacing rate of 80 BPM while coming off CPB -Atrial wires for coordination of heartrate – Afib (come out of right of sternum) -Atrial wires only will be of no use if pt has AV block -Ventricular wires in case of AV block (come out left of sternum) -2 epicardial wires per chamber (bipolar) or sometimes 1 epicardial wire cathode and skin anode (unipolar) 4 3 Avoid R on T I = INHIBITED - DOES NOT PACE T = TRIGGERED TO PACE 9/28/20 21 2021-09-29 15:26:56 -------------------------------------------If it only senses atrium, it can only respond to changes in P wave If it only sense ventricle it can’t respond to changes in the P wave, only the QRS 4 3 Common AAI: The atria are paced,Codes when the intrinsic atrial rhythm falls below the pacemaker's threshold. VVI: The ventricles are paced, when the intrinsic ventricular rhythm falls below the pacemaker's threshold. DVI: (A-V sequential) paces A and V, senses only V, inhibits w/activity VDD: The pacemaker senses atrial and ventricular events but can only pace the ventricle. This type of pacemaker is used in patients with a reliable sinus node, but with an AV- block. DDD: The pacemaker records both atrial and ventricular rates and can pace either chamber when needed. DDDR: As above, but the pacemaker has a sensor that records a demand for higher cardiac output (i.e. running from a lion) and can adjust the heart rate accordingly. VOO: Sometimes used in the OR when there is a lot of electrocautery interference – (00 license to kill!) ODO : this is an EKG (pacemaker joke) 4 4 Does not protect against AV block! A sensed – pace inhibited Atrial pacing and sensing 45 V sensed – pace inhibited NM L Ventricular pacing and sensing V paced 46 Asynchronous Pacing – goes no matter what! Can be Dangerous ! V paced NM L On T wave! NM L NM L Refracto ry Ventricular pacing in OR – Cautery can screw up sensing so you turn it off! 47 A sensed trigger ed V paced A paced V paced Atrial and Ventricular pacing and sensing A sensed V sensed inhibited V sensed – inhibite d A paced 4 8 Pacemaker Classification Codes Note the codes on the casing Can be seen on XRAY 4 9 Pacemaker modes of• Single-chamber use Pacemakers (RA or RV) • Dual-chamber Pacemakers (RA/RV or RA/LV) • Triple-chamber Pacemakers • Demand Pacemakers • Fixed-rate Pacemakers • Rate-responsive Pacemakers • Temporary Pacemakers • Permanent Pacemakers • ICDs (defibrillating capabilities) 5 9 • Single-Chamber Pacemakers One lead is placed into a chamber of the heart. This lead is placed either in the upper chamber (RA) or the lower chamber (RV). 51 Dual Chamber Two leads are placed into the heart. One is placed Pacemakers in the R atrium and the other in the R ventricle. This type of pacemaker more closely mimics a natural heart rate. 52 • • Triple-Chamber Pacemakers With a triplechamber pacemaker, one lead usually goes to the right atrium and the others stimulate both the right and left ventricles. It works to resynchronize the ventricles in a severely weakened heart. 53 Demand Pacemakers • • When the heart rate is too slow or it misses a beat, demand pacemakers, which monitor the heart's activity, will send an electrical pulse to set the heart back to a more normal rhythm Only pace when needed 54 Fixed-rate (asynchronous) Pacemakers • Fixed-rate pacemakers discharge steadily, regardless of the heart's natural electrical activity 55 Rate-Responsive IV have sensors •Pacemakers Rate-responsive pacemakers that adjust automatically to changes in your physical activity. They are designed to raise or lower the heart rate to meet the body’s needs. Comparison: 56 Types of Pacer Malfunctions • Failure to capture Pacer spike = no response • No p or ORS • Threshold may need to be increased • • Failure to pace • • No pacer spike present Failure to sense (under sensing) • Pacer fires anywhere in the cycle • Improper timing 57 Implantable Cardioverter / Defibrillators (ICD)  (ICDs) are designed primarily for the purpose of preventing sudden death from cardiac arrest due to tachycardia.  ICDs monitor the heart rhythm, and when the beat is normal, the device remains inactive.  If a tachycardia develops, the ICD sends an electrical shock to the heart to stop the abnormal rhythm and return the heartbeat to normal.  Resynchronize chambers 58 • Implantable CardioverterIdeal for patients with life-threatening Defibrillator ventricular arrhythmias • Termination of ventricular arrhythmias • Prevention of sudden-death • • Types of support • Bradycardia pacing • Anti-tachycardia pacing • Low-energy cardioversion • High-energy defibrillation Sophisticated detection algorithms • Ability to differentiate atrial fibrillation, sinus tachycardia and supraventricular tachycardia from ventricular tachycardia 5 9 60 Defibrillation vs. D Cardioversion e f ib r i l l a t i o n Sy n c hr o n i ze d C a r di o ve rs i on More energy needed (~200 Joules) Less energy needed (~50 For PEA (pulseless electrical For patients with an arrythmia joules) activity) like VF, narrow complex but with pulses VT Shock delivered anytime in cardiac cycle Shock delivered manually with external machine Tracks R wave and delivers shock away from T wave (prevents R on T) Shock delivered by computer 61 Concept of Defibrillation • Apply sufficient electrical current to cause simultaneous contraction (depolarization) of all cardiac cells • Stop the current • All cells should enter the refractory period at the same time • Normal intrinsic (sinus) electrical activity may then resume • Defibrillators can be external, trans-venous, or implanted, depending on the type of device used or needed 62 • AC Defibrillatio Application of an alternating current n Hz current applied for 250 to • 6 amps of 60 1000 msec • • Used prior to 1960 Problems • • • • Controlling the defibrillating current difficult Conversion rate low even with multiple attempts Cannot be used for converting atrial arrhythmias Could cause voltage drops across the hospital power line 63 • DC Defibrillatio 1962 – Dr. Bernard Lown developed successful DC defibrillator n • Design that is still commonly used • Electrical charge is stored - then released on demand • Energy release controlled by the operator • • 1 joule = 1 watt-second Requires application of high voltage over short time period to deliver the appropriate energy 64 External Defibrillators 65 Defibrillator Paddles Internal Paddles External Paddles 66 Rule of Thumb If you wake up and see this…probably not good 67 INDICATIONS: Defibrillat ion - Ventricular tachycardia (VT) – compromising (without a pulse) - Ventricular fibrillation (VF) 68 AICD Defibrillation 69 Defibrillated V-Fib 7 0 Defibrillated Pulseless V-Tach (unresponsive) 71 Ouch ! 72 • Synchronized Cardioversion Procedure by which an abnormally fast heart rate or cardiac arrhythmia is converted to a normal rhythm, using electricity or drugs. • Uses a therapeutic (lower) dose of electric current to the heart, at a specific moment in the cardiac cycle • Timing the shock to the R wave prevents the delivery of the shock during the vulnerable period (or relative refractory period) of the cardiac cycle, which could induce ventricular fibrillation • Usually timed to occur 30 • • msec after the peak R wave Want to avoid re-polarization (T wave) = VF Cannot do manually with any type of precision 73 Synchronized Cardioversion INDICATIONS:      Atrial fibrillation Atrial flutter Atrial tachycardia Ventricular tachycardia (with pulse) Supraventricular tachycardia 74 Cardioverted A-Fib 75 Pacemaker Rhythms you might see 7 6 Third Degree Heart Block with Ventricular Pacemaker 77 Pacemaker NonCapture 78 A-V Paced Rhythm w/PVC 79 The Rhythm You Will Deal With….A Lot Before termination of CPB some hearts don’t initiate normal SA Node activity well…It’s pacemaker time (temporary atrial and ventricular wires) 8 0 Class 81 9/27/2021 Knowledge Promise After today’s lecture I hope you have a better understanding of rhythm management devices, what they are, when and why we use them and how this information can help us be better perfusionists and patient advocates 8 2 Question s?