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Chronotropic Incompetence

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Discussion of chronotropic incompetence as a class I indication for pacemaker therapy.

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Chronotropic Incompetence

  1. 1. Chronotropic Incompetence & Adaptive Rate Pacing Frank W Meissner, MD FACP, FACC, FCCP, FASNC, CPHIMS, CCDS February 18, 1009
  2. 2. Greatest Equations of All 1+1=2 Time C=2πr iγ⋅δΨ=mΨa2=b2+C2a/b=c/d E=hν ν=Η0δ eiπ+1=0 S = k(logW)F=maδ C=Blog2(1+S/N) S=0 E=mc2PV=nRT I=V/R
  3. 3. Greatest Equations of All 1+1=2 C=2πr Time iγ⋅δΨ=mΨ E=hνa2=b2+C2 ν=Η0δa/b=c/d S = k(logW) eiπ+1=0 C=Blog2(1+S/N)F=maδ E=mc2 S=0PV=nRT I=V/R CO=SV⋅HR
  4. 4. 4
  5. 5. Chronotropic Incompetence: AMathematical Definition CO= ⋅HR SV
  6. 6. Chronotropic Incompetence Clinical Definition of Chronotropic Incompetence: • The inability of the heart to regulate its rate appropriately in response to physiologic stress1 • Generally recognized types of Chronotropic Incompetence (CI) 2 : Failure to achieve Max Heart Rate (MHR) A delay in achieving MHR Inadequate sub-maximal and recovering heart rate Rate instability during exercise 1. Chronotropic incompetence as defined by H. Weston Moses, in “A Practical Guide to Cardiac Pacing.” 2. Lukl, J. et al. “Incidence and Significance of Chronotropic Incompetence in Patients Indicated for Primary Pacemaker Implantation of Pacemaker Replacement.” PACE September 1999, Vol 22 (p.1284-1291) 6
  7. 7. Why is Chronotropic Incompetence a Problem?Generally recognized symptoms of chronotropic incompetence: Failure to achieve maximum heart rate (MHR) A delay in achieving MHRInadequate sub-maximal and recovering heart rate Rate instability during exerciseChronotropic incompetence is a Class I indication 7
  8. 8. Clinical Clues Suggesting CI• What complaints do you hear from Chronotropically Incompetent patients who aren’t properly treated? • “I’m just getting older” • “I frequently feel fatigued” • “I can’t do the things I used to do” • “I have to cut my yard on two different days” • “When I’m active I feel lightheaded”• You may hear these complaints from: • Patients with pacemakers who do not have optimized therapy • Patients without pacemakers 8
  9. 9. Chronotropic Incompetence Prevalence What is the prevalence of chronotropic incompetence (CI) in the pacemaker population?5 Lukl J, Doupal V, Sovava E, et al. Incidence and significance of chronotropic incompetence in patients with indications for primary pacemaker implantation or pacemaker replacement. PACE. 1999;22:1284-1291. 9
  10. 10. Chronotropic Incompetence Prevalence What is the prevalence of chronotropic incompetence (CI) in the pacemaker population? 42% 5 n=211 CI prevalence in patients with: Atrial Fibrillation = 67% Sick Sinus Syndrome = 49% AV Block = 30%5 Lukl J, Doupal V, Sovava E, et al. Incidence and significance of chronotropic incompetence in patients with indications for primary pacemaker implantation or pacemaker replacement. PACE. 1999;22:1284-1291. 9
  11. 11. CI is a Progressive Disease• It is important to monitor all of your patients, even your chronotropically competent patients• CI is progressive and worsens over a short period of time Sub analysis6 Pacemaker less than 2 yrs: 53% Pacemaker more than 4 yrs: 70% n=386 Gwinn N, Leman R, et al. Chronotropic incompetence: A common and progressive finding in pacemaker patients. Am Heart J. 1992;123:1216-1219. 10
  12. 12. The Ability to Generate Elevated Heart Rates Benefits All Age Groups• How many times a day does the average person under age 65 raise his or her heart rate above 90 beats per minute? 11
  13. 13. The Ability to Generate Elevated Heart Rates Benefits All Age Groups• How many times a day does the average person under age 65 raise his or her heart rate above 90 beats per minute? 178 times per day7 7 Mianulli M, Birchfield D, Yakimow K, et al. Do elderly pacemaker patients need rate adaptation – implications of daily heart rate behavior in normal adults. PACE.1996;19(pt II):681(abstract). 11
  14. 14. The Ability to Generate Elevated Heart Rates Benefits All Age Groups• How many times a day does the average person under age 65 raise his or her heart rate above 90 beats per minute? 178 times per day7• How many times a day does the average person over age 65 raise his or her heart rate above 90 beats per minute? 7 Mianulli M, Birchfield D, Yakimow K, et al. Do elderly pacemaker patients need rate adaptation – implications of daily heart rate behavior in normal adults. PACE.1996;19(pt II):681(abstract). 11
  15. 15. The Ability to Generate Elevated Heart Rates Benefits All Age Groups• How many times a day does the average person under age 65 raise his or her heart rate above 90 beats per minute? 178 times per day7• How many times a day does the average person over age 65 raise his or her heart rate above 90 beats per minute? 151 times per day7 All patients benefit from the ability to raise their heart rates! 7 Mianulli M, Birchfield D, Yakimow K, et al. Do elderly pacemaker patients need rate adaptation – implications of daily heart rate behavior in normal adults. PACE.1996;19(pt II):681(abstract). 11
  16. 16. What should their heart rate be?Chronotropic Assessment Exercise Protocol (CAEP) 12
  17. 17. Wilkoff Mathematical Model of the Cardiac Chronotropic Response to Exercise Normal predicted heart rate for an individual at a submaximal stage of exercise:Wilkoff et al. J Electrophysiol 3:176-180, 1989
  18. 18. Exercise Heart Rate Response and MortalityLauer et al. JAMA 1999;281:524-529
  19. 19. CI & Cardiac DeathLauer et al., JAMA.1999:281:524-529
  20. 20. Physiologic Responses and Rate-Adaptation
  21. 21. Physiologic Responses and Rate-Adaptation
  22. 22. Characteristics of an Ideal Sensor for Rate-Responsive Pacing
  23. 23. Characteristics of an Ideal Sensor for Rate-Responsive Pacing• Reliable• Consistent• Durable• Efficient• Easily implanted• Physiologically appropriate
  24. 24. Activity SensorsPiezoelectric crystals bonded to the inside of the pulse generator housing – sense vibration, causing a minute change in the shape of the crystals’ structure and a voltage proportional to the force is generatedAccelerometer – monitors body motion in the anteroposterior direction which converts the change in velocity or direction of motion to electrical signals
  25. 25. Activity Sensors
  26. 26. Accelerometer Signal ProcessingAccelerometers sense the electrical signal generated from body motion to deliver a proportional pacing response Activity threshold Sensor signalsMedium Sitting Walking Running 22
  27. 27. Accelerometer Summary End activity MSRPacing rate (ppm) REACTION RECOVERY RESPONSE LRL THRESHOLD Start activity 23
  28. 28. Activity SensorsDisadvantages:• PE crystals are sensitive to pressure (lying face-down or turning on box spring mattress can lead to inappropriate increase in heart rate)• PE crystal-based devices fail to increase HR appropriately as treadmill incline or grade is increased while the speed of walking is constant (Accelerometer does better)• PE crystal–based devices show a more dramatic increase in HR when walking down stairs than climbing stairs (accelerometer is better in this situation)• Both sensors are more responsive to lower body than upper body exercises• PE crystal devices in unipolar mode can lead to sensor-mediated pacemaker tachycardia if generator flipped in pocket (pocket stimulation)• Both sensors fail to respond appropriately to emotional stress, swimming, isometric exercises, stationary bicycle riding
  29. 29. Minute Ventilation Minute Ventilation Sensor• Should this man’s heart rate be the same for both levels of activity? 25
  30. 30. Review of Minute Ventilation • Minute ventilation is the product of respiratory rate (breaths/minute) and tidal volume Tidal Volume Respiration Period VE = true minute ventilation MV = minute ventilation using impedance measurement 26
  31. 31. Minute Ventilation Sensor• An excitation signal is sent between the can and ventricular ring electrode (the largest electrodes)• The waveform is designed to minimize interaction with monitoring equipment by: – Having an amplitude 1/3 the size of that used by competitive MV devices (320 µA vs. 1000 µA) – Providing a balanced waveform (less polarization artifact) 320 uA 50mS 80 uS
  32. 32. Minute Ventilation Minute Ventilation Transthoracic Impedance MeasurementsOhm’s Law R=V/I Indifferent Electrode 28
  33. 33. Minute Ventilation Blended Sensor Restores Chronotropic Competence10 1.0 1 Normal11 0.9 Accelerometer Sensors only .92 Minute do 60% of the job of restoring Ventilation 0.8 competence. Blended Sensor 0.7 .60 0.6 % Heart Rate Accelerometer 0.5 Only 0.4 0.3 0.2 0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 % Metabolic Rate10 Chronotropic competence is defined by: Wilkoff BL, Corey J, Blackburn G. A mathematical model of cardiac chronotropic response to exercise. J Electrophysio. 1989;3(3):176–180. Refer to Physician’s System Guide for more information on adaptive-rate therapy. Additional clinical performance was assessed using INSIGNIA Ultra clinical data with the AutoLifestyle feature programmed On. Data on file. 11 Wilkoff BL, Corey J, Blackburn G. A mathematical model of cardiac chronotropic response to exercise. J Electrophysio. 1989;3(3):176–180. 29
  34. 34. There is a BIG difference in how sensors work Example: Patient Playing Golf 30
  35. 35. Let’s look at a simple example An accelerometer and an MV pacemaker that are pacing at 60 ppm will deliver the same baseline cardiac output. 31
  36. 36. Let’s look at a simple example1. An accelerometer and an MV pacemaker that are pacing at 60 ppm will deliver the same baseline cardiac output.2. Upon exercise, the two pacers will produce two different heart rates (90 and 106 ppm). Both pacers will produce incremental CO for the patient. 32
  37. 37. Small difference in HR means a big difference in CO1. An accelerometer and an MV pacemaker that are pacing at 60 ppm will deliver the same baseline cardiac output. 53%2. Upon exercise, the two pacers will produce two different heart rates (90 and 106 ppm). Both pacers will produce incremental CO for the patient.2. In this example, at a pacemaker rate of 106 ppm there will be an incremental CO that is 53% higher than the incremental CO produced by the pacemaker going at 90 ppm. This is a simple outcome of: CO = HR x SV 33
  38. 38. Small difference in HR means a big difference in CO That’s a lot more blood.1. An accelerometer and an MV pacemaker that are pacing at 60 ppm will deliver the same baseline cardiac output. 53%2. Upon exercise, the two pacers will produce two different heart rates (90 and 106 ppm). Both pacers will produce incremental CO for the patient.2. In this example, at a pacemaker rate of 106 ppm there will be an incremental CO that is 53% higher than the incremental CO produced by the pacemaker going at 90 ppm. This is a simple outcome of: CO = HR x SV 33
  39. 39. Is 53% more Oxygen a big deal? 50% More O2Denver Houston 18,000 feet Sea Level 34
  40. 40. Pacemaker Indications – Class I• Sinus node dysfunction with documented symptomatic bradycardia, including frequent sinus pauses that include symptoms• Symptomatic chronotropic incompetence• Symptomatic sinus bradycardia that results from required drug therapy for medical conditions. 35
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  43. 43. Questions??????????

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