Presented at HRS Boston 2012

1. Present Solutions to the Problem of
Electromagnetic Interference: Are
They Good Enough?
Sergio L. Pinski, MD
Cleveland Clinic Florida
Weston, FL, USA

2. Presenter Disclosure Information
 BostonScientific, Medtronic, St
Jude: consultant, member of
speaker’s bureau

4. Pacemaker and ICD Responses to EMI
 Pacing inhibition
 Triggering of rapid or premature
pacing
 Spurious tachyarrhythmia detection
 Noise reversion mode
 Electric (power-on) reset
 Closure of the reed-switch
 Damage to the generator or the
electrode-myocardial interface

5. Pinski SL. PACE 2002;25:1367

12. Results
Episode Adjudication
5,248 Episodes
with Rhythm
Classification
3678 (70%)
1570 (30%) Estimated incidence
Appropriate
Inappropriate 1 year 5 year
(MVT / PVT /
(non-VT / VF) 6% 17%
VF)
820 (27.4%) 134 (2.6%)
Estimated incidence
Atrial Fib, SVT, Noise, Artifact,
1 year 5 year
sinus tach, or Oversensing
1.1% 1.8%
non-sustained
Page 12

13. Results
Episode Classification
Percent Percent of
of all NAO
Classification Episodes Patients Episodes Episodes
External noise / EMI 76 56 1.4% 56.7%
Lead / Connector 37 30 0.7% 27.6%
Muscle noise 11 11 0.2% 8.2%
Ventricular lead
7 3 0.1% 5.2%
oversensing of atrium
T wave oversensing 2 2 0.1% 1.5%
Other noise,
1 1 0.1% 0.7%
oversensing
Total 134 101 2.6% 100.0%
Page 13

14. Results
Incidence of NAO Resolution With Shock by Subtype
Category Episodes with Decrease in Noise
External noise / EMI 44 / 76 (58%)
Lead/Connector 13 / 37 (35%)
Muscle noise 3 / 11 (27%)
Other noise/oversensing 0 / 10 (0%)
Total 60 / 134 (45%)
P = .03 comparing External/EMI to Lead/Connector to Muscle – Fisher Exact test.
Example of Example with
noise reduction post shock no change post shock
Page 14

15. Santucci et al. NEJM
1998;339:1371

16. Mitigation of EMI
 Shielding
 Bipolar sensing (lower frequencies)
 Electronic filtering (passive and
active)
 Noise rejection algorithms
 Noise reversion mode

17. Design Constraints
• Need to sense very low level biological
signals
 More ICDs than PMs, more in the atrial than
ventricular channel
• Small size is highly desirable by patients
and physicians for comfort and appearance
but limits size and number of components
• Low power
 Power used to mitigate EMI reduces the life or
increases the battery size of the device

21. Passive Filter Attenuation vs. Frequency

22. EMI Filter
Installation
In order to function properly at high frequencies, the EMI filter must be
installed (laser welded) so that it forms an integral part of the overall EMI
shield:
Filtered Hermetic Seal
Titanium Can
(EMI Shield)

23. Example of Passive
EMI Filter Performance
Cardiac Sense Lead
without EMI filter with EMI filter
100 MHz to 10 GHz 100 MHz to 10 GHz

24. Noise rejection algorithm
Clinical example of DNA in action: Identical noise and 5 mV R-wave in both devices
Legacy Device COGNIS & TELIGEN
Legacy devices could have sensed this noise as a COGNIS-TELIGEN recognizes the low level signal as noise
physiologic signal and appropriately adjusts sensitivity

25. – DNA uses the characteristics of a noise signal—frequency and
energy—to identify a signal as noise
– When noise is present, DNA keeps the AGC floor above the noise
– DNA is automatically active on all three sensing channels: atrium,
right ventricle and left ventricle
Note the presence of
electroconvulsive therapy
noise on the ventricular
rate sensing channel and
on the shocking egram
channel. In this Case
Study, DNA keeps AGC
sensing floor above noise.
Note: DNA will not make the Boston Scientific devices immune from sensing all noise. The device could still sense EMI or other sources of high amplitude noise.
Page 25

27. Sorin Group Noise Management - Tachy
• Since 1996 Sorin Group/ELA has had a ventricular noise circuit in all
its ICDs
• Based on the premise that human beings cannot sustain intervals in
the 188-125 ms range. If intervals consistently in that range are
seen they are most likely the result of EMI (noise).
• After several retriggered windows Ventricular Sensitivity is
decreased by 0.2 mV on each retriggered window until not
retriggered. This process is done on a beat to beat basis
• The circuit is turned off for 15 cycles with an interval of
400 ms to 188 ms to assure arrhythmia detection
• On the 16th cycle, if there has not been an interval larger than 188
ms the noise circuit is turned on again
• Atrial noise circuit similar to Brady function

28. Sorin Group Noise Management - Tachy
R
P V
P
95 30
220 30
Figures show the addition of a 30 ms noise window to the 95 ms (sensed)
or the 220 ms (paced) absolute refractory

29. Sorin Group Noise Management - Tachy
AVD
95 ms
95 ms 95 ms
125 ms 125 ms
Noise level
0.2 mV steps
Sensitivity level Ventricular pacing can be inhibited
(parameter “V pacing on noise”)
Graphic representation of noise sensing to the point of decreasing V sensing
See example on the following slide
29

30. ICD Ventricular Noise Circuit Example
30
15 Cycles with noise circuit off after fast cycle
30

31. Noise Reversion Modes
Programmable
Manufacturer Noise detection window response Additional features
Boston Scientific XOO (nominal), Inhibit Non programmable
ICDs 40 ms retriggerable window pacing Dynamic Noise Algorithm
Programmed Non programmable
Medtronic PMs atrial/ventricular refractory asynchronous pacing
Medtronic ICDs Not available RV lead noise detection
Inhibit (nominal), pace Reduced sensitivity by 0.2
Sorin Paradym 125-188 ms asynchronous ms q 16 ms
St Jude PMs 30 Hz XOO (nomimal), off
XOO 50 BPM (nomimal),
St Jude ICDs 100 Hz off

32. Determinants of the Clinical
Consequences of EMI
 Intensity of the field
 Signal spectrum
 Distance and position of the patient
Duration of exposure
Nonprogrammable device characteristics
Lead configuration
Programmed parameters
Sensitivity
Mode (baseline, noise reversion, committed)
Patient characteristics
Pacemaker-dependency
Susceptibility to asynchronous pacing
Susceptibility to rapid pacing rates

33. ANSI/AAMI PC69 standards -2207
 Extensive guideline for in vitro
testing of pacemaker and ICDs
 Typical settings, (eg cellular
phone operating at 6 inches)
 Different frequencies
 Tests also to rule out damage to
the generator from electrocautery
and external defibrillation

34. AAMI PC9- Testing for low-frequency EMI via
injected current
6
ISO 14708-2/EN 45502-2-1 Connection of tissue equivalent interface
circuit (left) and multichannel bipolar cardiac pacemaker (right).

35. AAMI PC69- Testing for radiated EMI > 450 MHz

36.  “There are known knowns; there
are things we know we know. We
also know there are known
unknowns; that is to say we know
there are some things we do not
know. But there are also unknown
unknowns -- the ones we don't
know we don't know."
Donald Rumsfeld, US Secretary of Defense

37. Cell Phone EMI
• Cellular phone without amplification:
0.3 to 0.6 watts
• Cell phone with 3 watt after market
amplifier and 9 dB gain antenna:
23.8 watts

38. Garg et al. JICE 2002;7:181

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41. Beginning of oversensing
Furrer et al. NEJM 2004;350:1689

43. Wayar et al. PACE 2003;26:1292

44. Conclusions
 Full electromagnetic compatibility
has not been achieved yet (and
may never be)
 Multiple potential sources of EMI
exist in daily life, work and
medical environments

45. Conclusions
 Improvement in sensing circuits and
algorithms together with better
awareness of sources of
electromagnetic interference have
already reduced EMI
 Continous surveillance is needed as
new emitting sources are introduced

46. Conclusions
 Sources of further minimization
 Continuous improvements in
device engineering
 Awareness of manufacturers of
emitters
 Patient and public education