Pacemaker Automatic Features Module 10

Pacemaker Automatic Features Module 10
Student Notes This module will teach you the baseline information necessary for working toward more advanced knowledge in pacemaker operation. Depending on your background, this module may allow you to meet the objective of this module. It is possible that you may require additional supplemental materials to enhance your knowledge or provide more practice. If you feel this is necessary, ask your instructor for suggestions on books or other tools. Instructor Notes This module should take approximately 2 hours to cover. To deliver this module the following materials are recommended: Printed participant guides for each participant Overhead projector and screen Optional: whiteboard or flip chart While delivering the module engage the learners by asking questions and getting them to talk based on their previous knowledge. Evaluate the learners by delivering the knowledge check at the end of this module. An acceptable score is 90%. World Headquarters Medtronic, Inc. 710 Medtronic Parkway Minneapolis, MN USA Internet: Tel: (763) Europe Medtronic International Trading Sàrl Route du Molliau Ch Tolochenaz Switzerland Tel: (41 21) Asia-Pacific Medtronic International, Ltd. 16/F Manulife Plaza The Lee Gardens, 33 Hysan Avenue Causeway Bay Hong Kong Tel: (852) Canada Medtronic of Canada Ltd. 6733 Kitimat Road Mississauga, Ontario L5N 1W3 Tel: (905) Toll-free: 1 (800) Medtronic USA, Inc. Toll-free: 1 (800) (24-hour technical support for physicians and medical professionals) Latin America Medtronic USA, Inc. Doral Corporate Center II 3750 NW 87th Avenue Suite 700 Miami, FL 33178 USA Tel: (305) UC d EN Medtronic, Inc. Minneapolis, MN February 2008

Topics Atrial and Ventricular Capture Management® Sensing Assurance
Auto Adjusting Sensitivity Lead Monitor and Polarity Switch Rate Response Student Notes Here are the topics for this module. Instructor Notes

Capture Management® Objectives
Describe the value of Atrial and Ventricular Capture Management® Recall the basic operation of ACM and VCM Identify how to program ACM and VCM Student Notes Here are the objectives. Instructor Notes

Capture Management® Why is it important? How is it conducted?
Patient Safety Device Longevity Troubleshooting Information How is it conducted? Automatic algorithms that mimic what a person would do in a clinic Student Notes By now you should be capable of running and obtaining an accurate in-office threshold test for the atrium and ventricle. We now introduce the concept of a pacemaker doing this testing automatically. Why is this important? Patient Safety—Threshold results taken more often can allow for automatic output changes as patients’ conditions change Device Longevity—A smaller safety margin may be acceptable if adaptability happens on a more regular basis Troubleshooting Information—If a problem does arise, trended threshold information may help to pinpoint the source of the problem Instructor Notes prompt the class to list reasons as to why this will be important Transition to next slide with the “how” answer. Ask how. Solicit answers from the class. Come to the consensus that the pacemaker must mimic how an in office threshold test and management of output is performed.

Capture Management® - Three Categories
Assess Patient’s Rhythm Determine Threshold Program Appropriately Student Notes All of these steps can be grouped into 3 general categories: Assess Patient’s Rhythm Assess patient’s rhythm (rate, type) Determine Threshold Decide pacing rate or AV delay to force pacing Tell the patient that you are going to start the test Start the test at an output that should definitely achieve capture Decrement the output Look for loss of capture Call capture 1 step above loss Program Appropriately Program appropriate safety margin Make the point that the pacemaker does these same steps automatically, but that it must follow rigid pre-defined guidelines.) Instructor Notes Since you agree that the pacemaker must mimic what a follow-up person must do, let’s first walk through those steps. Have different people offer the steps of a threshold test, write them down on a white board or flip chart. Get a good comprehensive list and put it in order. Advance through the list on the slide and agree that this is a pretty good comprehensive list of steps that will achieve an appropriate threshold.

Capture Management® Manual Testing Automated Testing
Assess Patient’s Rhythm Determine Threshold Program Appropriately Manual Testing Automated Testing Assess patient’s rhythm (rate, type) Stability Check Student Notes The first step to managing capture thresholds is assessing the patient’s rhythm. This may be second nature to a very experienced follow-up person, because you may not even realize that you have already assessed the rhythm. The device has to be very methodical about this and does it by conducting what we will call a stability check. Instructor Notes

Capture Management® Assess Patient’s Rhythm Determine Threshold Program Appropriately When you get ready to run a threshold test manually: What questions do you ask? Why do you ask these questions? Would you run a ventricular threshold test on a patient whose underlying rhythm is AF with a ventricular response of 120 bpm? NO Student Notes Now that you see that the Capture Management® Feature obtains a threshold in a similar fashion as running the test manually, let’s walk through each step the pacemaker takes in more detail—starting with the assessment of the patient’s rhythm. First ask the question: “Would you run a ventricular threshold on a patient who’s underlying rhythm is AF with a ventricular response of 120 bpm?” Get the class to answer no, and then discuss why? Too fast to pace Not safe—may induce a ventricular arrhythmia Patient become more symptomatic What questions do you ask when you look at a patient’s rhythm with the purpose of preparing for a threshold test? (be thorough, and realize that these questions may be automatic to you) Try to get at least the following questions out of the class: What is the patient’s heart rate? What is the type of rhythm? (AF, Brady, Block, etc.) Is there pacing? Why do you ask these questions? To know if the test can be ran To know what rate or AV delay will force pacing Patient safety Instructor Notes transition to the automated side

Capture Management® VCM Stability check
Assess Patient’s Rhythm Determine Threshold Program Appropriately VCM Stability check Are conditions favorable to conduct a search? What is the rate? (typically lower than 90 – 100 bpm) What is rhythm? (defined by few VR/AR/VSP/PVC) Are there feature interaction? (No RDR or Mode Switch in progress) If conditions are unfavorable, what do you think happens? The threshold test is postponed If conditions are favorable Move on to determining the threshold Student Notes The pacemaker decides in it’s own way if it should run the threshold test. Even though the rules are much more ridged, the pacemaker asks its own set of questions for the same reason you ask you questions. When you are in front of the patient you can end the test if the patient becomes symptomatic. You can also come up with a creative way of getting a threshold even if there are a lot of PVCs or sensing issues. For example, it may be appropriate for you to switch to VOO to force ventricular pacing (feel free as the instructor to bring up other ways that you can get a threshold in difficult situations). The device, on the other hand, does not have this luxury. Since the device has limited ways to conduct its test, the patient’s rhythm must meet certain criteria before it begins its test. Through the Stability Check, the device decides if conditions are favorable to conducting a threshold VCM Stability check Are conditions favorable to conduct a search? What is the rate? If USR/UTR >135 then rate must be < 100 If USR/UTR then < 95 If USR/UTR <125 then <90 Sensor < ADL Rate What is rhythm Few VR/AR/VSP/PVC Feature interaction? No RDR therapy in progress Not transitioning DDDR-DDIR-DDDR If conditions unfavorable, search is postponed Instructor Notes

Assess Patient’s Rhythm Determine Threshold Program Appropriately Manual Testing Automated Testing Decide how to pace Choose the type of test-amplitude decrement, pulse width decrement, or strength duration Choose the type of test-always strength duration Start pacing Test paces, backup paces, and support cycles Threshold search Identify Loss of Capture (LOC) Evoked response sensing Call capture threshold one step above LOC Confirm capture at one step above LOC Student Notes It’s now time to learn how the device determines a ventricular threshold on its own. This step involves several different actions. As you can see from the chart, each action that the device does has a correlating action that you could do manually. Now we are going to walk through each action from the prospective of the device and how it is similar to what you do when in the office with the patient. Instructor Notes

Capture Management® Decide how to pace
Assess Patient’s Rhythm Determine Threshold Program Appropriately Decide how to pace Why do you need to decide how to pace? To force pacing What are your options for forcing pacing? Increase the rate in a non-tracking mode (VVI/R, DDI/R) How much? Decrease the AV delay in a tracking mode (DDD/R) Student Notes Why do you need to decide how to pace? To force pacing—which ensures that delivered test paces have a chance to stimulate and not compete with intrinsic conduction So now you are ready to force pacing with the intention of running a threshold test. Different options depending the mode Non-tracking (VVI, DDIR) – the rate must be increased Tracking mode (DDD, DDDR) – the AV delay must be shortened or as short as it is when In non-tracking mode—the lower rate on test paces is set to the fastest V-V interval seen on any support cycle or seen during the stable rhythm check plus 15 bpm or minus 150 ms, whichever results in a faster rate. In tracking mode—the AV delay of the test cycle = shortest AV during stability – 15 ms Instructor Notes

Capture Management® Choose the type of test
Assess Patient’s Rhythm Determine Threshold Program Appropriately Choose the type of test The device runs a strength duration test for Ventricular Capture Management 1.50 V Pulse Width Threshold 1.25 V Student Notes In a clinic it is common to manually run only an amplitude auto decrement test. The device runs the strength duration test. Instructor Notes 1.0 V 0.75 V Amplitude Threshold 0.5 V 0.4 ms 1.0 ms

Capture Management® Test paces, backup paces, and support cycles
Assess Patient’s Rhythm Determine Threshold Program Appropriately Test paces, backup paces, and support cycles Test pace- pace delivered to determine capture Backup pace- pace delivered immediately following each test pace to ensure there are no dropped beats Q: If you start running a threshold test on a pacer dependent patient, and immediately see Loss of Capture, what do you do? A: Stop the test Student Notes (Instructor: Ask the question: “If you start running a threshold test on a pacer dependent patient, and immediately see loss of capture, what do you do?” A: Stop the test You stop the test because you cannot have the patient go without ventricular activity for too long. Explain that the device does not allow for there to be any pause in ventricular activity. It does this by providing a backup pace after each test pace. More specifically, the patient is protected against actual LOC by an automatic back-up pace that occurs 110 ms after each test pace, at programmed outputs. This is step is a little different than the way an in-office threshold test would be run. Instructor Notes

Capture Management® Test paces, backup paces, and support paces
Assess Patient’s Rhythm Determine Threshold Program Appropriately Test paces, backup paces, and support paces Support cycles- a series of three events (paced or sensed) that allow for the heart to function as it would without being tested Q: As you are running a threshold test on a patient at an accelerated rate to force pacing, the patient becomes extremely symptomatic, what do you do? A: Stop the test Student Notes Answer: Stop the test You stop the test because you do not want the patient to feel these symptoms. The device cannot determine if symptoms arise from pacing, so it does not allow for the pacing rate or AV delay to be different for very long. It does this by allowing for support cycles in between each test pace. Instructor Notes Ask the question: “As you are running a threshold test on a patient at an accelerated rate to force pacing, the patient becomes symptomatic, what do you do?”

Ventricular Capture Management®
Test & Back-up Pace Test & Back-up Pace Support Events Student Notes Pacing Threshold Search (PTS) In EnPulse®, the threshold search is conducted by decreasing the amplitude at a 0.4ms pulse width until an evoked response is no longer sensed. The amplitude is increased until the evoked response is confirmed on at least 3 consecutive pacing cycles. This value is doubled. The threshold is reported at 0.4ms pulse width. The clinician controls the test frequency (every 15 min –1/week, nominal 1/day at rest), the minimum adapted output, and the voltage safety margin. The minimum pulse width is 0.4 ms. The patient is protected against actual LOC by an automatic back-up pace that occurs 110 ms after each test pace, at programmed outputs. During the programmable acute phase, thresholds are tested but outputs are not decreased, until this phase has completed. Instructor Notes

Capture Management® Threshold Search Starting Output Starting Output
Assess Patient’s Rhythm Determine Threshold Program Appropriately Threshold Search Starting Output Start at an output that capture should occur Capture Management® starts its threshold search at the previous measured threshold value Starting Output Decrement Output When you are performing a threshold, how do you shorten the test? Student Notes The threshold search includes the output that you start at, the decrement of the output, and the output that you stop the test at. Just like performing a threshold test on a patient in a clinic, the mechanism for finding capture is to first find where loss of capture occurs. To do this the output is decremented in steps until the clinician identifies loss of capture. This also assumes that the starting output has capture. Another goal while searching for the threshold is for the test to run for as little time as possible. Possible answers include: Minimize the number of paces between decrements, start at an output just above the threshold Capture Management® starts its threshold search at the previous measured threshold value. (more detail: The test Amplitude is set at the last Amplitude result from the previous pacing threshold search or at 0.75 V if no previous search has been done. Pulse Width is set at 0.4 ms.) Instructor Notes When you are performing a threshold, how do you shorten the test? Discuss the possible answers: minimize the number of paces between decrement, start at an output close to previous threshold (in the chart, or the listed threshold on the QuickLookTM screen, cut the output in half (this assumes 2x safety margin was programmed). Emphasize that starting at an output of the previous threshold (or very close) will minimize the test time which reduces the amount of time that the patient has to be paced a rate different than normal operation. Ending Output

Capture Management® Threshold Search Decrement Output
Assess Patient’s Rhythm Determine Threshold Program Appropriately Threshold Search Decrement Output Lower output (amplitude or pulse width) one step at a time Ventricular Capture Management® performs Strength Duration Test Tests amplitude at 0.4 ms PW Tests PW at 2X amplitude threshold Atrial Capture Management® performs an Amplitude Decrement Test Starting Output Decrement Output Student Notes The output is then decremented in steps until the clinician identifies loss of capture. Instructor Notes Ending Output

Capture Management® Threshold Search Ending Output
Assess Patient’s Rhythm Determine Threshold Program Appropriately Threshold Search Ending Output Capture Management® confirms capture Starting Output What do you do when you see Loss of Capture (LOC)? Decrement Output Programmer Stop the test Analyzer Increase output to confirm capture Student Notes The output that you stop the test at is one step below the threshold. Therefore, you call capture one step above the first output that you lost at. Since Capture Management® is testing the threshold automatically its mechanism for determining threshold is more like using the analyzer—in that it confirms capture. After Capture Management® sees loss of capture, the output is increased until capture is confirmed on at least 3 consecutive pacing cycles. Instructor Notes Ask, “What do you do when you see loss of capture?” Answer: Stop the test by lifting the programmer pin and letting normal operation start back up. You can also bring up testing thresholds on the analyzer. Ask the question: “what do you do when you lose capture on the analyzer?” Discuss that you come up on the output immediately to confirm capture Ending Output

Capture Management® Identify Loss of Ventricular Capture vs.
How do you identify Loss of Capture (LOC) when running a ventricular pacing threshold? VVI DDD vs. Student Notes Now that you know how the device does a capture threshold search, it is time to understand how the device identifies loss of capture. Let’s look at what the device knows: It knows exactly when it delivered a pace Let’s build off that strength. If it knows exactly when the pace occurs—it can make a pretty good judgment about what it should “see” immediately following that pace. That is exactly what it does. It looks for what is called an evoked response. Ventricular capture verification algorithms rely on evoked response sensing to determine if a pacing pulse has captured the myocardium. The characteristics of this evoked response, in a sense it’s shape, is how the pacemaker determines if a test pulse has captured the myocardium. Instructor Notes Ask, “How do you identify loss of capture when running a ventricular pacing threshold?” Look for responses like: See a pacing spike without ventricular activity after it See a change in rate There is ventricular activity after the pacing spike, but it is narrow (non-paced looking)

Evoked Response Sensing
All ventricular capture verification algorithms: Rely on sensing the evoked response to the test pace The characteristics of this response is how the pacemaker determines if the myocardium is captured If the characteristics of the evoked response signal differ from what is expected, the pacemaker assumes LOC Evoked response sensing can be affected by Lead tissue interface (acute vs. chronic lead) Lead Polarization Tip-to-Ring spacing Lead tip design Other factors Student Notes All capture verification algorithms rely on evoked response sensing to determine if a pacing pulse has captured the myocardium. The characteristics of this evoked response, in a sense it’s shape, is how the pacemaker determines if a test pulse has captured the myocardium. Evoked response sensing can be affected by: The lead tissue interface, for example trauma at the lead tip Polarization – not lead polarity, but polarization at the lead tip- see next slide Tip-to-ring spacing Lead tip design Other factors Instructor Notes

Capture Management® Identify Loss of Atrial Capture
How do you identify capture when you run an atrial pacing threshold? Student Notes Atrial capture can be much more difficult to see on a surface ECG: the p-wave can be difficult to see because it is very small or there is too much baseline noise. Even during a follow-up you may not use the presence of a p-wave as determining capture. If you cannot see a p-wave during follow-up, you can still assess atrial capture implementing these other concepts. ACM does not use evoked response sensing. Rather, ACM finds capture by utilizing the same concepts that you use if seeing a p-wave is difficult. Instructor Notes Ask: How do you identify capture when you run an atrial pacing threshold? Possible answers: P-wave R-wave at the appropriate time after the A-pace (increase in ventricular rate) No intrinsic p-waves competing with the pacing rate

No Atrial Sense in the AV Interval (Capture)
Capture Management® Atrial Chamber Reset Method Device makes sure that there are no intrinsic atrial events competing with the pacing rate Test AP Student Notes There are two methods for atrial capture management®: Arial Chamber Reset Method and AV Conduction Method. These two algorithms do not compete against one another. The Atrial Chamber Reset method tries to run first, but it requires the Periods of slow(er) sinus rhythm -or- Periods of intact AV conduction Atrial Chamber Reset (ACR) method Designed for patients with stable sinus rhythm Atrial Chamber Reset evaluates capture by observing the response of the intrinsic atrial rhythm to the atrial test pace. A test pace which captures should interrupt the underlying escape rhythm and reset the sinus node. A test pace which fails to capture the atrium will NOT reset the sinus node. An atrial sensed event is observed (after the test pace) falling in its AV delay. In other words, the absence of this atrial sense indicates that the test pace captured the myocardium and reset the sinus node. Instructor Notes No Atrial Sense in the AV Interval (Capture)

Capture Management® AV Conduction Method
Device looks for a conducted R-wave at the predicted time after an atrial pace Student Notes AV Conduction (AVC) method Designed for patients with intact AV conduction Each test pace is followed by a back-up pace (AVC only) A captured test pace will result in a VS occurring within an expected “window” based on the intrinsic AV interval from the test pace A non-captured test pace will result in a VS occurring within an expected “window” based on the intrinsic AV interval from the back-up pace The AV Conduction method (AVC) uses ventricular sensing to determine atrial capture, thus 1:1 AV conduction is required. Since a loss of atrial capture in this methodology could result in a dropped ventricular beat, to reduce symptoms and promote safety, this method also uses a backup atrial safety pace (delivered at programmed polarity and at least 2.5V and 1.0 ms). Instructor Notes Note that the backup pace is delivered after every test pace in AVC, but no marker is recorded for this event. Only a slight change in EGM can be observed. The device algorithm for AVC relies on being able to accurately detect when the VS event occurs, with respect to when it is expected to occur, based upon the timing relationship established during the stability check, and reaffirmed during the Support pacing cycles. AP-VS interval following test pace is monitored; if timing is consistent with support pace “expected” window, device records as capture. AP-VS events that result from back-up paces (LOC) will lag by approximately 70 ms from the “expected” window of a test pace.

Assess Patient’s Rhythm Determine Threshold Program Appropriately Manual Testing Automated Testing Program appropriate safety margin Follow programmed rules Student Notes Now that you see that the Capture Management® Feature obtains a threshold in a similar fashion as running the test manually, let’s walk through each step the pacemaker takes in more detail. Instructor Notes

Capture Management® Assess Patient’s Rhythm Determine Threshold Program Appropriately Adapts the output downward in one step decrements (0.125V) Never below the programmable Minimum Amplitude (Nominal = 2.5V) Applies the programmable safety margin (Nominal = 2X) to the amplitude at 0.4 ms pulse width Adapts upward, as needed, to maintain the safety margin Acute Phase Output may rise Will not adapt downward until the Acute Phase expires (N=112 days) Student Notes Instructor Notes

Advanced Pacemaker Operations Tools to Manage Pacemaker Sensing
Student Notes Instructor Notes

Sensitivity Management Objectives
State a reason why fixed sensing safety margins may not be adequate Identify three clinical areas affected by inappropriate sensing Recall two of the mechanisms for managing sensing automatically Student Notes Sensing Assurance provides clinicians with the confidence that an appropriate sensitivity is programmed in changing conditions. This feature is programmed Nominal - ON. Instructor Notes

Sensitivity Management
Programming a fixed sensing safety margin may not accommodate for these and other potential changes What factors can change a patient’s P- and R-wave amplitudes? Antiarrhythmia Medications Lead Maturation Atrial Arrhythmias Exercise Ventricular Arrhythmias Myocardial Infarction Student Notes Fixed sensing values may not be adequate to manage patients. Advanced pacing systems should be able to accommodate changing patient conditions. Instructor Notes Lead off this discussion, ask the class, “what factors can change a patient’s P and R-wave amplitudes?” Answers include: Lead maturation Myocardial infarction Antiarrhythmia medications Exercise Atrial Arrhythmias Ventricular Arrhythmias

Normal Operation Therapy Diagnostics Student Notes You now know reasons why a fixed sensing safety margin may not be adequate. Now let’s shift our focus to clinical problems with inappropriate sensing. This can be broken down into 3 key areas. Normal Operation Undersensing may result in sub-optimal hemodynamics, for example a loss of AV synchrony Oversensing may result in pacemaker inhibition and a return of patient symptoms and/or initiation of a pacemaker mediated tachycardia (PMT) Inappropriate Mode Switch behavior (too often or not at all) Therapy Pacemakers designed to utilize intrinsic conduction or modify pacing therapy in response to arrhythmia rely on reliable and accurate sensing to function. Diagnostics Mode Switching relies (in part) on consistent atrial sensing during atrial tachyarrhythmias To help guide therapy decisions, accurate arrhythmia detection is necessary for devices to accurately report arrhythmia burden, duration, frequency, etc. Instructor Notes

Sensing Assurance Adapts Sensitivity based on target safety margins, to automatically provide safe sensing margins Adequate High Low 5.6x Sensitivity 4x Sensitivity Atrial Bipolar Current Sensitivity 0.5 mV 2.0 mV 2.8 mV Student Notes Two approaches to automatic sensitivity changes are sensing assurance and auto adjusting sensitivity. If the pacemaker has the capability to automatically change sensing it has either one or the other, not both. Sensing Assurance provides clinicians with the confidence that an appropriate sensitivity is maintained under changing patient conditions. This feature is programmed Nominal - ON. Instructor Notes At completion of Implant Detection, Sensing Assurance begins monitoring the peak amplitude of sensed signals. Each non-refractory sensed event (AS or VS) is monitored by measuring the ratio of the peak amplitude of the P- or R-wave to the sensitivity setting. For a bipolar, atrial lead, the “Adequate” waveform amplitudes will range between 2.0 and 2.8 mV, (that is, 4.0X - 5.6X of 0.5 mV) at nominal/shipped settings. If the pacemaker detects several “low” waveforms, the operating sensitivity setting is decreased by one step, that is, down to 0.35 mV, in an attempt to shift the Target Sensing Margin downward to place the top of the waveform between the 4.0 and 5.6 X limits. If, on the contrary, the pacemaker detects several “high” waveforms, the operating sensitivity setting is automatically increased by one step in an attempt to place the top of the waveform within the target limits. Adaptation does not occur immediately. 17 consecutive events must be “low” to increase the sensitivity, 36 events to decrease the sensitivity. In the case of a mix of low, adequate, and high events, the adjustments occur more gradually, or if paced events are also intermingled with sensed events. If fewer than 60% of events are high (or low), or if the pace to sense ratio is greater than 5:1, no sensitivity adjustment is made. During periods of infrequent sensing, the pacemaker maintains a long-term running average of the sensitivity adjustments and will adjust sensitivity thresholds toward the long-term average. Note: Sensing Assurance boundaries for an Atrial bipolar lead restrict sensitivity settings to adapt only between the values of 0.18 mV and 0.5 mV. Therefore, at nominal sensitivity of 0.5 mV, Sensing Assurance can only adapt sensitivity to lower numbers (increased sensitivity). ASK: What’s the clinical need for this feature? ANSWER: Pacemakers designed to utilize intrinsic events, or modify pacing therapy in response to an arrhythmia, rely on accurate sensing in order to function properly.

Auto Adjusting Sensitivity Adjusts the sensitivity fence on a beat-by-beat basis Student Notes Auto Adjusting Sensitivity is applied on a beat-to-beat basis for both paced and sensed events (as shown above). Whether a beat is paced or sensed will determine the level of adjustment and the time decay. For example, a sensed ventricular event will decrease sensitivity to 75% of peak EGM with a maximum of 8X the programmed value and a time decay of 450 ms. A complete description of auto-adjusting sensitivity behavior follows. Note: If the programmed sensitivity value exceeds 0.3 mV in the ventricle or 1.2 mV in the atrial, the threshold is not adjusted. Instructor Notes

Rate Response Student Notes Instructor Notes

Rate Response Objectives
State the clinical reason for rate response pacing Recall why rate response pacing works List the implantations industry uses for rate response pacing Student Notes Instructor Notes

Rate Responsive Pacing
Introduced in the mid-80’s by Medtronic Why was it one of the most significant developments in pacing? When one exercises, metabolic demand increases. To meet this demand, cardiac output needs to increase. What contribution does increasing heart rate make to increasing the cardiac output? Click for Answer Student Notes In this context of basic timing and alterations to basic timing, another topic to consider is Rate Responsive Pacing. In terms of adding value to pacemaker therapy it is hard to overstate the importance of this innovation. Prior to rate responsive pacing, pacemaker patients had devices which provided a fixed rate only. If a patient had an unreliable sinus node, whether from chronic AF or SSS, and they got a pacemaker – they received a device which could only provide pacing a preset-programmable rate. Obviously this may not have provided a rate to meet metabolic demands. Instructor Notes Up to a 500% increase over the resting cardiac output. No other component of cardiac output has this significant of a contribution.

This is designated by the “R” in DDDR, AAIR, or VVIR… It is accomplished by using a sensor to indicate changing metabolic demand The sensor then modifies the pacing rate Think of it as a dynamic lower rate or dynamic escape interval DDDR means: The heart will not be paced at rates below 60 bpm The heart may be paced at rates between bpm, based on the information from the rate response sensor The heart will not be paced at rates above 130 bpm Student Notes At its simplest, rate response is really a dynamic lower rate. The escape rate, the A-A interval, is under the control of a sensor which tries to mimic the sinus node and respond to changing metabolic needs. If metabolic demand rises and the current A-A interval does not meet the programmed criteria for rate at that level of metabolic need, the pacemaker simply begins pacing at a faster rate. Think of it like this: An accelerometer, a common rate response sensor, is similar to a pendulum. As the patient moves about this ‘pendulum’ swings back and forth. The pacemaker is designed to measure the rate of the pendulum swinging and convert that motion into a rate. The pacemaker compares the current rate to the “pendulum’s” rate and uses the faster of the 2. When programming rate response we still program a lower rate, and under normal circumstances the pacemaker will not operate at rates less than this. However, it will operate at faster rates when called upon to do so by its sensor. Instructor Notes

Rate Response Sensors Many types have been developed with various advantages and disadvantages Motion-based Sensors Advantages Disadvantages Piezoelectric crystal Fast to respond, easy to program, less expensive to make Motion based. May not be as accurate with sustained exercise. Accelerometer Metabolic Sensors Minute Ventilation (MV) Accurate, uses rate and depth of respirations Slow to respond, increased battery consumption Q-T interval Accurate Slow to respond, requires Ventricular Pacing Temperature Not always reliable Increased battery consumption, special lead Student Notes Over the years a variety of rate-response sensors have been used. Piezo-electric crystals were among the first and are still used in some devices in operation today. Accelerometers are also very common and probably the most frequently used sensor today. Both of these attempt to mimic the Sinus Node by responding to patient movement or motion. Minute ventilation (MV) is also a common sensor used and can closely match metabolic need however is slower to respond and does consume the battery somewhat to operate. Q-T sensor have been very successfully used by one manufacturer but these are gradually becoming less popular because they require ventricular pacing to establish a QT interval. Other sensors have been tried, most notably thermo-sensors, but were found to be less reliable. Instructor Notes

Rate Response Sensors In use today Accelerometer
Piezo-electric crystal Combination of MV + Accelerometer or MV + P-E crystal Combination of QT + Piezo-electric crystal Student Notes A variety of new sensors are under clinical investigation or development however the accelerometer remains popular because it is simple, relatively inexpensive to manufacture and install, reliable, predictable, simple to program and above all, meets the needs of the typical pacemaker patient. Instructor Notes

Rate Response Rate responsive (also called rate modulated) pacemakers provide patients with the ability to vary heart rate when the sinus node cannot provide the appropriate rate Rate responsive pacing is for patients who may benefit from increased pacing rates concurrent with increases in activity, such as: Patients who are chronotropically incompetent (heart rate cannot reach appropriate levels during exercise, or meet other metabolic demands) Patients in chronic atrial fibrillation with too slow of a ventricular response to meet metabolic demands Student Notes Instructor Notes

Cardiac output (CO) is determined by the combination of stroke volume (SV) and heart rate (HR) SV X HR = CO Changes in cardiac output depend on the ability of the HR and SV to respond to metabolic requirements Student Notes Instructor Notes

SV reserves can account for increases in cardiac output of up to 50% HR reserves can nearly triple total cardiac output in response to metabolic demands Student Notes Most of the pacing population relies heavily on rate reserves to increase cardiac output because stroke volume reserves are diminished. Instructor Notes

When the need for oxygenated blood increases, the pacemaker ensures that the heart rate increases to provide additional cardiac output Adjusting Heart Rate to Activity Normal Heart Rate Rate Responsive Pacing Fixed-Rate Pacing Student Notes Instructor Notes Daily Activities

A Variety of Rate Response Sensors Exist
Those most accepted in the market place are: Activity sensors that detect physical movement and increase the rate according to the level of activity Minute ventilation sensors measure the change in respiration rate and tidal volume via transthoracic impedance readings Student Notes Other sensors that measure QT interval, central venous temperature, stroke volume, etc., are either not available or have gained limited acceptance. Instructor Notes

Activity sensors employ a piezoelectric crystal that detects mechanical signals produced by movement The crystal translates the mechanical signals into electrical signals that in turn increase the rate of the pacemaker Piezoelectric crystal Student Notes Instructor Notes

Minute Ventilation (MV) is the volume of air introduced into the lungs per unit of time MV has two components: Tidal volume - the volume of air introduced into the lungs in a single respiration cycle Respiration rate - the number of respiration cycles per minute Student Notes Instructor Notes

Minute ventilation can be measured by calculating the changes in electrical impedance across the chest cavity to calculate changes in lung volume over time Student Notes Increased tidal volume and rate increase transthoracic impedance, which increases the pacing rate. Instructor Notes

Status Check Evaluate this rhythm strip IPG is programmed to 60-130bpm
What are the atrial and ventricular rates? What operation is in effect? Click for Answer Student Notes Instructor Notes A and V rates are about 79 bpm Rate responsive pacing in the atrium with intrinsic AV conduction

Brief Statements Indications
Implantable Pulse Generators (IPGs) are indicated for rate adaptive pacing in patients who ay benefit from increased pacing rates concurrent with increases in activity and increases in activity and/or minute ventilation. Pacemakers are also indicated for dual chamber and atrial tracking modes in patients who may benefit from maintenance of AV synchrony. Dual chamber modes are specifically indicated for treatment of conduction disorders that require restoration of both rate and AV synchrony, which include various degrees of AV block to maintain the atrial contribution to cardiac output and VVI intolerance (e.g. pacemaker syndrome) in the presence of persistent sinus rhythm. Implantable cardioverter defibrillators (ICDs) are indicated for ventricular antitachycardia pacing and ventricular defibrillation for automated treatment of life-threatening ventricular arrhythmias. Cardiac Resynchronization Therapy (CRT) ICDs are indicated for ventricular antitachycardia pacing and ventricular defibrillation for automated treatment of life-threatening ventricular arrhythmias and for the reduction of the symptoms of moderate to severe heart failure (NYHA Functional Class III or IV) in those patients who remain symptomatic despite stable, optimal medical therapy and have a left ventricular ejection fraction less than or equal to 35% and a QRS duration of ≥130 ms. CRT IPGs are indicated for the reduction of the symptoms of moderate to severe heart failure (NYHA Functional Class III or IV) in those patients who remain symptomatic despite stable, optimal medical therapy, and have a left ventricular ejection fraction less than or equal to 35% and a QRS duration of ≥130 ms. Contraindications IPGs and CRT IPGs are contraindicated for dual chamber atrial pacing in patients with chronic refractory atrial tachyarrhythmias; asynchronous pacing in the presence (or likelihood) of competitive paced and intrinsic rhythms; unipolar pacing for patients with an implanted cardioverter defibrillator because it may cause unwanted delivery or inhibition of ICD therapy; and certain IPGs are contraindicated for use with epicardial leads and with abdominal implantation. ICDs and CRT ICDs are contraindicated in patients whose ventricular tachyarrhythmias may have transient or reversible causes, patients with incessant VT or VF, and for patients who have a unipolar pacemaker. ICDs are also contraindicated for patients whose primary disorder is bradyarrhythmia.

Brief Statements (continued)
Warnings/Precautions Changes in a patient’s disease and/or medications may alter the efficacy of the device’s programmed parameters. Patients should avoid sources of magnetic and electromagnetic radiation to avoid possible underdetection, inappropriate sensing and/or therapy delivery, tissue damage, induction of an arrhythmia, device electrical reset or device damage. Do not place transthoracic defibrillation paddles directly over the device. Additionally, for CRT ICDs and CRT IPGs, certain programming and device operations may not provide cardiac resynchronization. Also for CRT IPGs, Elective Replacement Indicator (ERI) results in the device switching to VVI pacing at 65 ppm. In this mode, patients may experience loss of cardiac resynchronization therapy and / or loss of AV synchrony. For this reason, the device should be replaced prior to ERI being set. Potential complications Potential complications include, but are not limited to, rejection phenomena, erosion through the skin, muscle or nerve stimulation, oversensing, failure to detect and/or terminate arrhythmia episodes, and surgical complications such as hematoma, infection, inflammation, and thrombosis. An additional complication for ICDs and CRT ICDs is the acceleration of ventricular tachycardia. See the device manual for detailed information regarding the implant procedure, indications, contraindications, warnings, precautions, and potential complications/adverse events. For further information, please call Medtronic at and/or consult Medtronic’s website at Caution: Federal law (USA) restricts these devices to sale by or on the order of a physician.

Brief Statement: Medtronic Leads
Indications Medtronic leads are used as part of a cardiac rhythm disease management system. Leads are intended for pacing and sensing and/or defibrillation. Defibrillation leads have application for patients for whom implantable cardioverter defibrillation is indicated Contraindications Medtronic leads are contraindicated for the following: ventricular use in patients with tricuspid valvular disease or a tricuspid mechanical heart valve. patients for whom a single dose of 1.0 mg of dexamethasone sodium phosphate or dexamethasone acetate may be contraindicated. (includes all leads which contain these steroids) Epicardial leads should not be used on patients with a heavily infracted or fibrotic myocardium. The SelectSecure Model 3830 Lead is also contraindicated for the following: patients for whom a single dose of 40.µg of beclomethasone dipropionate may be contraindicated. patients with obstructed or inadequate vasculature for intravenous catheterization.

Disclosure NOTE: This presentation is provided for general educational purposes only and should not be considered the exclusive source for this type of information. At all times, it is the professional responsibility of the practitioner to exercise independent clinical judgment in a particular situation.

Pacemaker Automatic Features Module 10

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Pacemaker Automatic Features Module 10

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