electrical testing of pacemaker

Msn Pavan Kumar,DM,NIMS.

Electrical Testing Of Pacemaker& Pacemaker Complications

Electrical Testing Of PacemakerPacemaker complications

Electrical Testing Of Pacemaker

Pacemaker components Battery Pacing impedance Pulse generator

1. Output circuit 2. Sensing circuit 3. Timing circuit4. Rate adaptive sensor5. Modes and mode switching

Battery :Lithium iodine battery

High energy density , Long shelf life , Predictable loss of

batteryBOL (vol) – 2.8v BOL (res) - <1komhs


Pacing impedance :Pacing impedance refers to the opposition to

current flow. Three sources contribute to pacing impedance:

1. Pacing lead conductor coil2. 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.


1. Pulse generator output circuit Capture threshold , Pacing threshold , stimulation

threshold Minimum amount of energy required to constantly

cause depolarization Volts and pulse duration


2.0 v 1.5 v 1 v


1. Pulse generator output circuit


1. Pulse generator output circuit

Site At implantation

Acute Chronic

Atrium <1.5mv 3-5 times threshold voltage

Twice theThreshold voltage

Ventricle

<1mv With PW 0.5ms

With PW of 0.5ms

1. Pulse generator output circuit High Pacemaker Output can

causeReduce longevity Diaphragmatic stimulationMuscle Sti. in Unipolar

pacemakersPatient may “feel” heart beat

Algorithm for checking pacemaker output threshold every beat and maintaining threshold just above it - Auto capture.



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)

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

3. Pulse generator timing circuit :a. Lower rate limit (LRL)b. Hysteresis ratec. Refractory and blanking periodsd. Ventricular safety pacing interval .e. Upper rate response .


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.


Condition LRL (beats/mt)

Infrequent pauses 40-50

Chronic persistent bradycardia 60-70

Relative bradycardia detrimental (long QT)

70-80

Detrimental fast heart rates (angina)

50-60

VVI 60-70

3. Pulse generator timing circuit :


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


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 – 150mspAVI – 200ms

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 gradientCRT – usually 80-120ms , for 100%ventricular pacing and

optimize COPhysiological response to faster heart rates can be answered



Refractory and blanking periods :

Refractory period – sensing present but no action

Blanking period - sensing absent and hence no action



Blanking periods :3. Pulse generator timing circuit :


Blanking period

Time Importance

Atrial blanking period

50-100ms Non programmable ,Avoid atrial sensing of its own paced beat

Post ventricular atrial blanking period

220ms Avoid sensing of ventricular beatLong PVAB decreases detection of AF,AFL

Ventricular blanking period

50-100ms Non programmable,Avoid ventricular sensing of its paced beat

Post atrial ventricular blanking period

28ms if the PAvB period is too long, R on T - ventricular tachyarrhythmia.

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 .





Ventricular safety pacing/ventricular triggered period/cross talk sensing window : Atrial pacing in DDD

Trigger ventricular sensing

PAVB - pAVI

False inhibition of ventricular pacing circuit

Asystole

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 ratesHRR 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 AVBChoosing URR : young patients (150b/mt) , old angina

(<110b/mt).Various sensors (activity , minute ventilation , QT)

4. Pulse generator rate responsive pacing:


4. Pulse generator rate responsive pacing:


Wenckebach

2:1 AVB

4. Pulse generator modes:


5. Pulse generator modes switching:


DDD / VDDAtrial tachyarrythmias

Sensed atrial events

Trigger fast ventricular rates

Palpitations. Dyspnoea. And Fatigue.

DDIR / VVIR

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.


Pacemaker follow up guidelines:Transtelephonic monitoring guidelinesMedicare

guidelinesSingle 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 guidelinesSingle 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

Electrical Testing Of PacemakerPacemaker complications

Pacemaker complications

Pocket complications

Pocket hematoma

Infection

Erosion

Wound pain

Allergic reactions


Lead dislodgement

Pneumothorax /air embolism

Cardiac perforation

Extracardiac stimulation

Venous thrombosis

Coronary sinus dissection

Twidller syndrome

Pacemaker malfunction

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.


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.


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.


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.



Device related infection :

2007;49;1851-1859 J. Am. Coll. Cardiol.

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


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)


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


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



Cardiac Perforation :

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.


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 ).


Twiddler syndrome:


Obese women with loose, fatty subcutaneous tissueSmall size of the implanted generator

with a large pocket Twisting of pulse generator in long axis

Lead dislodgement and lead fracture

Failure to capture

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

Twiddler syndrome:


Failure to captureFailure to outputSensing abnormalities(under and over

sensing)Specific mode complications

1. Pacemaker related tachycardia2. Pacemaker syndrome


Failure to capture:Pacing artifact present but no evoked potential .Causes

1. Lead dislodgement or perforation2. Lead maturation(inflammation/fibrosis)(exit block)3. Battery depletion4. Circuit failure(coil fracture , insulation defect)5. Capture management algorithm failure6. Inappropriate programming7. Pseudo malfunction8. Functional non capture9. Metabolic , drugs , cardiomyopathies


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

Failure to capture:


Failure to capture:


Pacing threshold

Normal Increased

Battery depletionFunctional non capture

Impedance

Normal DislodgementExit block

Decreased

Insulation failure/break

Increased Lead fracture Loose screw

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 depletion5. Recording artifact.


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.

Application of magnet

Failure to output:


Eliminates pauses

Pauses persistent

Impedance

Normal

Decreased

Insulation failure/break

Increased Lead fracture Loose screw

Battery depletion

Over sensingPseudo malfunction

Battery depletion :Elective replacement indicators (ERI)

1. Low voltage(2.1-2.4)2. Low pacing rate on magnet application3. Elevated battery impedance4. Increased pulse width duration5. Restricted programmability6. Change to simpler pacing mode

End of life (EOL)1. Low voltage(≤2.1vol)


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.



Pacemaker undersensing :

VVI pacemaker

Pacemaker over sensing :Present as failure to paceCauses

1. EMI 2. T , P , R over sensing .3. Cross talk4. Myopotential

(unipolar)5. Make break signals


Cross talk :

High atrial outputHigh ventricular

sensitivityLow VBP

Ventricular sensing of paced atrial impulse

Pts with Poor AV conduction – Ventricular Asystole

Electromagnetic interference :


Source Pacer damage

Inhibition

Rate increase

Asynchronous noise

Uni/bipolar

Cardioversion/Defibrillation

Y N N N U/B

Anit theft devices /Weapon detector

N Y N N U

Phone (cell/cordless)

N Y Y Y U/B

Ablation Y Y Y N U/B

Diathermy/lithotripsy

Y Y Y Y U/B

FM radioTV transmitter

N Y N Y U

MRI/PET Y Y(N) Y(N) Y(N) U/B

Pacemaker syndrome :Seen in 20% of PPI (5%

severe symptomatic)VVI/DDD/AAIPulsations 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


Pacemaker mediated tachycardia :


Dual chamberVPC , intact retrograde

conduction , PVARP<VA .Px , Rx :

1. PVARP > VA2. Long PVARP after VPC3. Absent atrial sensing

after VPC

Pacemaker Testing

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electrical testing of pacemaker

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