4. Electrical Testing Of Pacemaker
Battery :
Lithium iodine battery
High energy density ,
Long shelf life ,
Predictable loss of battery
BOL (vol) – 2.8v
BOL (res) - <1komhs
5. Electrical Testing Of Pacemaker
Pacing impedance :
Pacing impedance refers to the opposition to current flow. Three
sources contribute to pacing impedance:
1. Pacing lead conductor coil
2. Electrode-tissue interface
Electrode resistance
Polarization
Normal lead impedance vary from 250-1200ohms.
Single impedance value may be of little use with out previous values
for comparison.
6. Electrical Testing Of Pacemaker
1.Pulse generator output circuit
Capture threshold , Pacing threshold , stimulation threshold
Minimum amount of energy required to constantly cause
depolarization
Volts and pulse duration
8. Electrical Testing Of Pacemaker
1. Pulse generator output circuit
Site At implantation Acute Chronic
Atrium <1.5mv 3-5 times Twice the
threshold Threshold voltage
voltage
Ventricle <1mv With PW 0.5ms With PW of 0.5ms
9. Electrical Testing Of Pacemaker
1.Pulse generator output circuit
High Pacemaker Output can cause
Reduce longevity
Diaphragmatic stimulation
Muscle Sti. in Unipolar pacemakers
Patient may “feel” heart beat
Algorithm for checking pacemaker
output threshold every beat and
maintaining threshold just above it -
Auto capture.
10. Electrical Testing Of Pacemaker
2.Pulse generator sensing circuit :
Ability of the device to detect intrinsic beat of the heart
Measured - peak to peak magnitude (mv) & slew rate(mv/ms)
11. Electrical Testing Of Pacemaker
2. Pulse generator sensing circuit :
Reduce Lower Rate below intrinsic rate to inhibit pacing and ensure
intrinsic activity
Increase sensitivity setting while observing EGM. The sensitivity
value at which sensing is lost on the EGM is the sensing threshold.
Sensitivity threshold safety is twice the attained valve.
Sensitivity Slew rate
Atrium 1-2mv(0.5mv) > 0.5 v/s
ventricle 2-3mv > 0.75 v/s
12. Electrical Testing Of Pacemaker
3. Pulse generator timing circuit :
a. Lower rate limit (LRL)
b. Hysteresis rate
c. Refractory and blanking periods
d. Ventricular safety pacing interval .
e. Upper rate response .
13. Electrical Testing Of Pacemaker
3.Pulse generator timing circuit :
Lower rate interval - lowest rate that the pacemaker will pace .
A paced or non-refractory sensed event restarts the rate timer at
the programmed rate.
15. Electrical Testing Of Pacemaker
3. Pulse generator timing circuit :
Hysteresis :
Hysteresis allows the rate to drop below the programmed pacing LRL.
Advantages of hysteresis :
1. Encourages native rhythm – maintain AV sync in VVI , prolong
battery life
2. Prevent retrograde conduction – avoids pacemaker syndrome
16. Electrical Testing Of Pacemaker
3. Pulse generator timing circuit :
AV delay (AVI) – pacemaker equivalent of PR interval.
Sensed vs paced AVI – paced AVI is programmed at 125-200ms ,
sensed AV interval is programmed at 20-50ms shorter than paced.
Dynamic AV delay allow pacemaker to respond to exercise
sAVI – 150ms
pAVI – 200ms
17. Electrical Testing Of Pacemaker
3. Pulse generator timing circuit :
AV delay (AVI)
Longer AVI :
Good AV conduction – maintains AV synchrony , long battery life
Achieved by following methods :Programming longer AVI ,
managed ventricular pacing , AV delay hysteresis .
Shorter AVI:
HOCM – RV apical pacing decreases HOCM gradient
CRT – usually 80-120ms , for 100%ventricular pacing and optimize CO
Physiological response to faster heart rates can be answered
18. Electrical Testing Of Pacemaker
3. Pulse generator timing circuit :
Refractory and
blanking periods :
Refractory period –
sensing present but no
action
Blanking period -
sensing absent and
hence no action
19. Electrical Testing Of Pacemaker
3. Pulse generator timing circuit : Blanking periods :
Blanking period Time Importance
Atrial blanking period 50-100ms Non programmable ,
Avoid atrial sensing of its own paced
beat
Post ventricular atrial 220ms Avoid sensing of ventricular beat
blanking period Long PVAB decreases detection of
AF,AFL
Ventricular blanking 50-100ms Non programmable,
period Avoid ventricular sensing of its paced
beat
Post atrial ventricular 28ms if the PAvB period is too long, R on T -
blanking period ventricular tachyarrhythmia.
20. Electrical Testing Of Pacemaker
3. Pulse generator timing circuit : Refractory period:
Refractory period Importance
Ventricular refractory period (VRP) Prevent sensing of T wave .
Atrial refractory period (ARP) AVI (120-200ms) .
Post ventricular atrial refractory period Avoid sensing retrograde P waves
(PMT) , far field R waves .
22. Electrical Testing Of Pacemaker
4. Pulse generator rate responsive pacing:
Rate responsive pacing refer to ability of pacemaker to increase its
lower rate in response to physiological stimulus
Sinus node dysfunction , AF patients – fail to increase heart rates
HRR should start with in 10s of exercise , peak at 90 – 120s and
should return to baseline with in 60 – 120s after exercise.
Fastest rate at which pacemaker will pace upper rate response.
If intrinsic atrial rate exceeds URR then wenckebach or 2:1 AVB
Choosing URR : young patients (150b/mt) , old angina (<110b/mt).
Various sensors (activity , minute ventilation , QT)
25. Electrical Testing Of Pacemaker
5. Pulse generator modes switching:
DDD / VDD
Atrial tachyarrythmias
Sensed atrial events
DDIR /
Trigger fast ventricular rates VVIR
Palpitations. Dyspnoea. And Fatigue.
26. Electrical Testing Of Pacemaker
5. Pulse generator modes switching:
Programming mode switching Mode switching occurs when
the sensed atrial rate exceeds a programmed atrial tachycardia
detection rate. By definition, this value must be faster than the URL
(maximum tracking rate). Atrial tachycardia detection is typically
programmed to 175-l88bpm or thereabouts.AMS base rate is higher
than LRI.
27. Electrical Testing Of Pacemaker
Pacemaker follow up guidelines: Transtelephonic monitoring guidelines
Medicare guidelines
Single chambered pacing Dual chambered pacing
1st month q 2 week 1st month q 2 weeks
2nd -48th month q 12 week 2nd – 30th month q 12weeks
49th – 72nd month q 8 week 31st – 48th month q 8 weeks
73rd month and later q 4 weeks 49th month and later q 4week
NASPE guidelines
Single or dual pacing
1st visit 6 – 8 week post implant , if symptomatic prior to this
5th month
From 6th month q 3month
Battery wear present q 1month
30. Pacemaker complications
Pocket hematoma :
The risk of haematoma is increased in patients taking antithrombotic
or anticoagulant drugs (Goldstein et al., 1998).
Most small hematomas can be managed conservatively with cold
compress and withdrawal of antiplatelet or antithrombotic agents.
Occasionally, large hematomas that compromise the suture line or
skin integrity may have to be surgically evacuated.
Needle aspiration increases risk of infection and should not be done.
31. Pacemaker complications
Pocket hematoma :
In patients requiring oral anticoagulants (warfarin), to take INR of
about 2.0 at the time of implantation is safe (Belott & Reynolds, 2000).
Unfractionated heparin or low-molecular-weight heparin are always
discontinued prior to device implant and ideally avoided for a
minimum of 24 hours post implantation.
Administration of anticoagulants can be resumed within 48-72 h after
implantation if there is no evidence of substantial hematoma formation.
32. Pacemaker complications
Device-related infections :
The reported incidence of pacemaker-related infection ranges from
0.5% to 6% in early series
The use of prophylactic antibiotics and pocket irrigation with antibiotic
solutions has decreased the rate of acute infections following pacemaker
implantations to <1 to 2 percent in most series
The mortality of persistent infection when infected leads are not
removed can be as high as 66%.
DM, malignancy, operator inexperience, advanced age, corticosteroid
use, anticoagulation, recent device manipulation, CRF, and bacteremia
from a distant focus of infection.
33. Pacemaker complications
Device related infection :
Device infection is defined as either:
(a) deep infection - infection involving the generator pocket
and/or the intravenous portion of the leads, with bacteremia,
requiring device extraction or
(b) superficial infection - characterized by local inflammation,
involving the skin but not the generator pocket, and treated with
oral antibiotics.
37. Pacemaker complications
Wound pain :
Infection , Pacemaker implanted too superficially , Pacemaker
implanted too laterally , Pacemaker allergy .
Skin erosion :
Incidence has been estimated around 0.8% .Old age , infection.
Surgical revision of pocket and reimplantation .
Allergic reactions :
Always rule out infection before coming to diagnosis of allergy
38. Pacemaker complications
Lead dislodgement:
Relatively common – 5-10% of
patients(ICD database 2001)
Atrial more common than
ventricular(2-3% vs. 1%)
Micro dislodgement , macro
dislodgement
Increased pacing threshold , failure
to pace and sense
Active fixation (decreases risk)
39. Pacemaker complications
Pneumothorax , :
Uncommon complication – 1.6-2.6%
During or 48 hrs after procedure
Inadvent puncture and laceration of
subclavian vein , artery or lung
Related to operator experience and
underlying anatomy
Avoided by
1. Venogram – flouroscpic puncture
2. Axillary venous access (Martin etal’96)
3. One way mechanism sheath
40. Pacemaker complications
Cardiac Perforation :
Uncommon but potentially serious complication - lower than 1%.
Acute (<5 days) , subacute(5d-1month) , chronic (>1month)
Increasing stimulation threshold , RBBB pattern for RV pacing,
intercostal muscle or diaphragmatic contraction, friction rub, and
pericarditis, pericardial effusion, or cardiac tamponade.
CXR , ECHO , CT
Lead withdrawal and repositioning ; surgical back up
42. Pacemaker complications
Extracardiac stimulation
The diaphragm or pectoral or intercostal muscles
Diaphragmatic stimulation - direct stimulation of the diaphragm (left)
or stimulation of the phrenic nerve (right).
Early postimplantation period , dislodgment of the pacing lead.
MC in patients with LV coronary vein branch lead placement for CRT
Output pacing importance (testing and treatment)
Pectoral stimulation - incorrect orientation of the pacemaker or a
current leak from a lead insulation failure or exposed connector.
43. Pacemaker complications
Venous thrombosis :
Venous thrombosis occurs in 30% to 50% of patients and only 1-3%
of patients become symptomatic.
Manifestations vary from usually asymptomatic, acute symptomatic
thrombosis, and even SVCS .
Early or late after pacemaker implantation.
Predictors of severe stenosis are multiple pacemaker leads , previous
pacing , double coils , hormone therapy .
Asymptomatic (no treatment) , symptomatic (anticoagulants –
endovascular stents – surgical correction ).
44. Pacemaker complications
Twiddler syndrome:
Obese women with loose, fatty subcutaneous tissue
Small size of the implanted generator with a large pocket
Twisting of pulse generator in long axis
Lead dislodgement and lead fracture
Failure to capture
45. Pacemaker complications
Twiddler syndrome:
The prevelance of this syndrome is
0.07% (Gungor et al., 2009)
Rotated along the transverse axis it is
referred by us as the reel syndrome.
Pocket should be revised.
Avoid by
Limit the pocket size,
Suture the device to the fascia
The patients not to manipulate
their device pocket
46. Pacemaker malfunction
Failure to capture
Failure to output
Sensing abnormalities(under and over sensing)
Specific mode complications
1. Pacemaker related tachycardia
2. Pacemaker syndrome
47. Pacemaker malfunction
Failure to capture:
Pacing artifact present but no evoked potential .
Causes
1. Lead dislodgement or perforation
2. Lead maturation(inflammation/fibrosis)(exit block)
3. Battery depletion
4. Circuit failure(coil fracture , insulation defect)
5. Capture management algorithm failure
6. Inappropriate programming
7. Pseudo malfunction
8. Functional non capture
9. Metabolic , drugs , cardiomyopathies
48. Pacemaker malfunction
Failure to capture:
Electrocardiographic tracing from a patient with a DDDR pacemaker. All ventricular
pacing artifacts but one failed to result in ventricular depolarization—
that is, failure to capture
49. Pacemaker malfunction
Failure to capture:
Pacing threshold
Normal Increased
Dislodgement
Normal Exit block
Battery depletion
Functional non capture
Impedance Insulation
Decreased failure/break
Lead fracture
Increased Loose screw
50. Pacemaker malfunction
Failure to output:
Absence of pacing stimuli and hence no capture .
Causes
1. Pseudo malfunction - hysteresis , PMT termination , sleep rate
2. Over sensing - EMI ; T P R over sensing ;
Myopotential/diaphragmatic ; Cross talk ; Make break signals
3. Open circuit - lead fracture , loose screw , air in the pocket ,
incompatible lead .
4. Battery depletion
5. Recording artifact.
51. Pacemaker malfunction
Failure to output:
VVIR pacemaker This patient had a pacemaker programmed to a unipolar
sensing configuration. The sensing of myopotentials led to symptomatic
pauses, and reprogramming the pacemaker to a bipolar sensing configuration
prevented subsequent myopotential over sensing.
52. Pacemaker malfunction
Failure to
output:
Application of magnet
Eliminates pauses Pauses persistent
Over sensing Normal Battery
depletion
Pseudo malfunction
Impedance Insulation
Decreased failure/break
Lead fracture
Increased Loose screw
53. Pacemaker malfunction
Battery depletion :
Elective replacement indicators (ERI)
1. Low voltage(2.1-2.4)
2. Low pacing rate on magnet application
3. Elevated battery impedance
4. Increased pulse width duration
5. Restricted programmability
6. Change to simpler pacing mode
End of life (EOL)
1. Low voltage(≤2.1vol)
54. Pacemaker malfunction
Pacemaker undersensing :
Pacing artifact present but no sensing(sensed beat doesn’t reset cycle)
Causes are
1. Defect in signal production – scar /fibrosis , BBB , ectopic ,
cardioversion , defibrillation , metabolic.
2. Defect in signal transmission – lead fracture /dislodgement ,
insulation failure , partial open circuit.
3. Defect in pacemaker – battery depletion , sensing circuit
abnormalities , committed DVI.
56. Pacemaker malfunction
Pacemaker over sensing :
Cross talk :
Present as failure to pace
High atrial output
Causes
High ventricular sensitivity
1. EMI Low VBP
2. T , P , R over sensing .
3. Cross talk Ventricular sensing of
4. Myopotential (unipolar) paced atrial impulse
5. Make break signals
Pts with Poor AV conduction
– Ventricular Asystole
57. Pacemaker malfunction
Electromagnetic interference :
Source Pacer Inhibition Rate Asynchronous Uni/
damage increase noise bipolar
Cardioversion/ Y N N N U/B
Defibrillation
Anit theft devices / N Y N N U
Weapon detector
Phone (cell/cordless) N Y Y Y U/B
Ablation Y Y Y N U/B
Diathermy/ Y Y Y Y U/B
lithotripsy
FM radio N Y N Y U
TV transmitter
MRI/PET Y Y(N) Y(N) Y(N) U/B
58. Pacemaker malfunction
Pacemaker syndrome :
Seen in 20% of PPI (5% severe
symptomatic)
VVI/DDD/AAI
Pulsations in neck , fatigue ,
cough ,chest fullness , headache ,
chocking sensation , PND ,
confusion , syncope , pulmonary
edema.
Rx : VVI – program hysteresis ,
or change to DDD ; DDD –atrial
lead reprogrammed or changed
59. Pacemaker malfunction
Pacemaker mediated tachycardia :
Dual chamber
VPC , intact retrograde
conduction , PVARP<VA .
Px , Rx :
1. PVARP > VA
2. Long PVARP after VPC
3. Absent atrial sensing after VPC