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

1. Chronotropic Incompetence
& Adaptive Rate Pacing
Frank W Meissner, MD
FACP, FACC, FCCP, FASNC, CPHIMS, CCDS
February 18, 1009

2. Greatest Equations of All
1+1=2
Time
C=2πr
iγ⋅δΨ=mΨ
a2=b2+C2
a/b=c/d
E=hν
ν=Η0δ
eiπ+1=0
S = k(logW)
F=maδ
C=Blog2(1+S/N)
S=0
E=mc2
PV=nRT
I=V/R

3. Greatest Equations of All
1+1=2
C=2πr
Time iγ⋅δΨ=mΨ
E=hν
a2=b2+C2
ν=Η0δ
a/b=c/d S = k(logW)
eiπ+1=0 C=Blog2(1+S/N)
F=maδ
E=mc2
S=0
PV=nRT
I=V/R
CO=SV⋅HR

4. 4

5. Chronotropic
Incompetence: A
Mathematical Definition
CO= ⋅HR SV

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. Why is Chronotropic
Incompetence a Problem?
Generally recognized symptoms of chronotropic
incompetence:
Failure to achieve maximum heart rate (MHR)
A delay in achieving MHR
Inadequate sub-maximal and recovering heart rate
Rate instability during exercise
Chronotropic incompetence is a Class I indication
7

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. 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. 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. 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=38
6 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. 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. 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. 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. 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. What should their heart rate be?
Chronotropic Assessment Exercise Protocol (CAEP)
12

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. Exercise Heart Rate Response and
Mortality
Lauer et al. JAMA 1999;281:524-529

19. CI & Cardiac Death
Lauer et al., JAMA.1999:281:524-529

20. Physiologic Responses and Rate-Adaptation

21. Physiologic Responses and Rate-Adaptation

22. Characteristics of an Ideal Sensor
for Rate-Responsive Pacing

23. Characteristics of an Ideal Sensor
for Rate-Responsive Pacing
• Reliable
• Consistent
• Durable
• Efficient
• Easily implanted
• Physiologically appropriate

24. Activity Sensors
Piezoelectric 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 generated
Accelerometer – monitors body motion in the
anteroposterior direction which converts the change in
velocity or direction of motion to electrical signals

25. Activity Sensors

26. Accelerometer
Signal Processing
Accelerometers sense the electrical signal generated from body
motion to deliver a proportional pacing response
Activity threshold
Sensor signals
Medium
Sitting Walking Running
22

27. Accelerometer
Summary
End activity
MSR
Pacing rate (ppm)
REACTION RECOVERY
RESPONSE
LRL THRESHOLD
Start activity
23

28. Activity Sensors
Disadvantages:
• 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. Minute Ventilation
Minute Ventilation Sensor
• Should this man’s heart rate be the same for both levels
of activity?
25

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. 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. Minute Ventilation
Minute Ventilation Transthoracic
Impedance Measurements
Ohm’s Law R=V/I Indifferent Electrode
28

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 Rate
10 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. There is a BIG difference
in how sensors work
Example: Patient Playing
Golf
30

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. Let’s look at a simple example
1. 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. Small difference in HR means a big
difference in CO
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

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. Is 53% more Oxygen
a big deal?
50% More O2
Denver
Houston
18,000 feet Sea Level
34

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.
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43. Questions
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