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Pacemaker : overview Chennai: Feb2017
Title slide for this presentation. This presentation is an up-to-date overview of cardiac pacing for physicians and clinical staff referring patients for pacemaker therapy. For more about this presentation, see the companion binder Guidelines for Presenting Programs to Referring Physicians. This binder has guidelines and additional resources for presenting programs about cardiac pacing. Chennai: Feb2017
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The Implantable Pacemaker System
The Implantable Pulse Generator (IPG) : metal can (titanium) containing electronics/battery & an electrode or lead connector header Lead : Electrical connection between the pacemaker & the heart
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Unipolar & Bipolar Pacing
Anode (+) Anode (+) Cathode (-) Cathode (-)
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Indifferent electrode
A Bipolar Pacing System Contains a Lead with Two Electrodes Within the Heart. In This System, the Impulse: Flows through the tip electrode located at the end of the lead wire Stimulates the heart Returns to the ring electrode above the lead tip Anode Cathode The impulse: Travels down the lead wire to stimulate the heart at the tip electrode, which is the cathode (–) Travels to the ring electrode, which is the anode (+), located several inches above the lead tip Returns to the pulse generator by way of the lead wire Tip electrode coil Indifferent electrode coil
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Pacemaker Functions Stimulation of Cardiac Tissue
Sensing of natural (intrinsic) cardiac depolarization or contraction Diagnostic information
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Voltage, Current, and Impedance Are Interdependent
Voltage represents the force with which . . . Current (water) is delivered through . . . A hose, or lead, where each component represents the total impedance: The nozzle, representing the electrode The tubing, representing the lead wire Speakers Notes What to say: What to Do: What to Ask: Optional Information: Optional Resources: References: Speakers Notes What to say: What to Do: What to Ask: Optional Information: Optional Resources: References: Ohm’s Law Voltage = Current X Resistance (V=IR) Current = Voltage/Resistance As voltage increases, current increases As resistance decreases, current increases
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Pulse Duration (Width)
The Pacing Pulse t V = Pulse Amplitude in Volts (V) (say 2.5 V) t = Pulse Duration or Width in milliseconds (ms) (say 0.5 ms) R = Impedance of Pacing Circuit (ohms) (say 500 ohms) I = V/R = Current through pacing circuit (mA) = 2.5 V/ 500 ohms = A = 5 mA Pacing Pulse V Output Voltage t Pulse Duration (Width)
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Stimulation Threshold
Pacing Voltage Threshold – The minimum pacing voltage at any given pulse width required to consistently stimulate the heart causing it to contract
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Capture – Loss of Capture
Speakers Notes What to say: What to Do: What to Ask: Optional Information: Optional Resources: References: Capture Non-Capture Speakers Notes What to say: What to Do: What to Ask: Optional Information: Optional Resources: References: VVI / 60
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NBG Code for Pacing P: Simple programmable V: Ventricle V: Ventricle
Chamber Paced II Sensed III Response to Sensing IV Programmable Functions/Rate Modulation V Antitachy Function(s) P: Simple programmable V: Ventricle V: Ventricle T: Triggered P: Pace M: Multi- programmable A: Atrium A: Atrium I: Inhibited S: Shock D: Dual (A+V) D: Dual (A+V) D: Dual (T+I) C: Communicating D: Dual (P+S) O: None O: None O: None R: Rate modulating O: None S: Single (A or V) S: Single (A or V) O: None
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Single Chamber Pacemakers
Most basic type of pacemaker Works only on one chamber of the heart – usually the RV Paces the heart at a FIXED RATE programmed Inhibits pacing whenever a natural heartbeat is sensed by the pacemaker
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Single Chamber Pacemakers
Ventricular Single Chamber Pacing or VVI pacing Pacing Rate Pacing Rate Pace Sense Pace
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Single-Chamber System
AAI VVI Speakers Notes What to say: What to Do: What to Ask: Optional Information: Optional Resources: References:
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Dual Chamber Pacemakers
DDD, DDDR – sense & pace both atrium and ventricle VDD – Sense atrium, pace ventricle
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The four faces of dual chamber pacing
AV SEQUENTIAL PACING Atrial Pacing Rate – 60, AV Interval – 200 ms AV Synchronous Pacing :NATURAL ATRIAL CONTRACTION & VENTRICULAR PACING : VDD AV Interval = 150 ms Spontaneous Atrial Rate – 55 Spontaneous Atrial Rate – 110
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The four faces of dual chamber pacing
Atrial Pacing Rate = 70, Natural AV conduction NATURAL ATRIAL CONTRACTION WITH NORMAL AV CONDUCTION Spontanoeus Atrial Rate = 65, Spontaneous PR interval = 160 ms
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72 M with symptomatic bifasicular block with prolonged PR interval
#1 72 M with symptomatic bifasicular block with prolonged PR interval s/p DDD pacemaker 2 week ago, UTR 100/min Returns with history of atypical R sided chest pain and back pain SBP 70 mm Hg BP improved promptly with IV fluid and pt felt better
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Typical values LRL : 50-60/mt URL : 110-130/mt AV delay : 120-200/ms
PVARP : 250 ms VRP : 200 ms Blanking periods : < 50 ms
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Sensing of intrinsic heartbeats
Sensing is the ability of the pacemaker to “see” when a natural (intrinsic) depolarization is occurring Pacemakers record the Intracardiac Electrogram (EGM) by constantly recording the potential difference between the cathode and anode Depolarization Wave Processed by Device
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Scheduled pace delivered Optional Information:
Undersensing Pacemaker does not “see” the intrinsic beat, and therefore does not respond appropriately Scheduled pace delivered Speakers Notes What to say: What to Do: What to Ask: Optional Information: Optional Resources: References: Intrinsic beat Speakers Notes What to say: What to Do: What to Ask: Optional Information: Optional Resources: References: VVI / 60
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Oversensing VVI / 60 ...though no activity is present Marker channel shows intrinsic activity... An electrical signal other than the intended P or R wave is detected Pacing is inhibited Speakers Notes What to say: Oversensing will exhibit pauses in single chamber systems. In dual chamber systems, atrial oversensing may cause fast ventricular pacing without P waves preceding the paced ventricular events. What to Do: What to Ask: Optional Information: Optional Resources: References:
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Amplitude Threshold Testing
Keeping pulse width stable, decrement voltage until loss of capture @ 0.5ms 1.5V 1.0V .5V
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Intrinsic R wave Amplitude
Typical intrinsic R wave amplitude measured from pacing leads in the Right Ventricle are more than 5 mV in amplitude Intrinsic R wave in EGM Amplitude The Intrinsic R wave amplitude is usually much greater than the T wave amplitude
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Sensitivity Setting This is a value specified to the pacemaker in millivolts through programming. All ventricular electrogram deflections seen by the pacing lead that exceed the sensitivity setting will be identified by the pacemaker as intrinsic R waves The typical sensitivity setting that is programmed for Ventricular sensing is 2.5 mV
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Sensitivity Setting 5.0 5.0 2.5 2.5 Amplitude (mV) Amplitude (mV) 1.25 1.25 Time Time Sensitivity settings less than 2.5 mv – High sensitivity – can lead to oversensing Sensitivity settings greater than 2.5 mV – Low sensitivity – can lead to undersensing
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{ VVI Mode Pacing inhibited with intrinsic activity
Lower Rate Interval In inhibited modes (VVI/AAI), intrinsic events that occur before the lower rate interval expires will reset the lower rate interval, as shown in the example above. As with paced events, sensed events will also initiate blanking and refractory periods. VP VS VP Blanking/Refractory VVI / 60
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VVI TIMING V VP VP VP VS VP
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VVI TIMING V VP VP VP VS VP
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VVI TIMING V VP VP VP VS VP
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VVI TIMING V VP VP VP VS VP
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VVI TIMING V VP VP VP VS VP
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VVI TIMING V VP VP VP VS VP
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VVI TIMING V VP VP VP VS VP
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VVI TIMING V VP VP VP VP
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VVI TIMING V VP VP VP VS VP
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VVI TIMING V VP VP VP VS VP
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VVI TIMING V VP VP VP VS VP
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Sensed native R waves reset VVI timing
65/mt VVI VVI VVI VVI Fusion beat Sensed native R waves reset VVI timing
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Observation, Data, and Events Program
Presenting Rhythm and Rate Battery Status Lead Status Sensing Threshold Observation, Data, and Events Program During this workshop we will cover the steps outlined by the PBL STOP acronym. These steps are discussed in detail in subsequent slides.
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Diagnostic Information
With Medtronic ICDs and IPGs, important observations and diagnostic information is highlighted on the main Quick Look™ (initial interrogation) screen. The screen on the left is from an EnPulse pacemaker. The screen on the right is from an EnTrust ICD.
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Cardiac Compass® Management of atrial tachyarrhythmias
May help with assessment of: Rate-control therapy Rhythm-control therapy Risk for stroke1 This Cardiac Compass report is from a Medtronic EnPulse pacemaker. 1Glotzer TV, Hellkamp AS, Zimmerman J. et al., Atrial high rate episodes detected by pacemaker diagnostics predict death and stroke: Report of the Atrial Diagnostics Ancillary Study of the Mode Selection Trial (MOST). Circulation 2003;107:
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Potential Problems with Pacemakers
Battery Depletion Lead displacement or perforation Loss of capture and/or sensing Lead fracture or insulation break Increase in thresholds due to Drugs Electrolyte imbalance Interference from external electromagnetic sources Device malfunction
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Pacemaker Follow-up All the Information for Routine Follow-ups
Operating Mode Last Interrogation Longevity A&V Pacing Thresholds Arrhtymia Summary % Pace/Sense Histograms All of the information provided by the Quick Look II screen is also made available (automatically) in printed format via the Initial Interrogation Report. When Observations suggest that further investigation is warranted and/or troubleshooting is required, access to more detailed information can be found through the use of the QuickLink™ [>>] icon or via the Main Icons listed on the right-hand side of the display. To potentially assist clinicians with assessing rhythm-control and/or rate-control therapies used during management of atrial tachyarrhythmias, the Adapta Pacing System offers two observations: Number of days with > 4 hours of AT/AF. Notification if number 1 above is satisfied AND the ventricular response (rate) during those AT/AF episodes exceeded 100 bpm at least 5% of the time. Note: IF Rule #1 triggers (at least 1 day with > 4 hours AT/AF), then this is displayed instead of # of A. High Rate Episodes in Observations. A&V Pacing Lead Impedance Alert of situations that may require further investigation P&R wave Amplitudes
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Magnet Operation Varies across manufacturers and models
Medtronic Normal VOO, DOO mode 85 ppm No sensing, asynchronous pacing Medtronic ERI – VOO, DOO mode 65 ppm
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Special Precautions – EMI
General Principle Avoid proximity to powerful electric or magnetic fields Move away from the field if symptomatic Keep safe distance – 6 inches for electrical appliances Safe from Interference Microwave, TV, Washing Machine, Fridge, Vacum cleaners etc. Cordless phones Computer, printer, scanner, photcopier Possible interference Items with large magnets, e.g. speakers, car ignition systems Hand-held hair dryers Radiotransmitters Cellular Phones
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