Cardiac Pacing

Cardiac pacing for beginners

Resident Phattarasit

2008/F.ABUDAYAH 2

Clinical objectives

• Define pacemaker• Differentiate types of pacemaker• List function of pacemaker• Complication• management

First pacemaker

Arne Larsson

Class I Indications for Permanent Pacing in Adults (AHA/ACC)

1. Third-degree AV block at any anatomic level associated with any of the following

– Symptomatic bradycardia presumed secondary to AV block

– Symptomatic bradycardia secondary to drugs required for dysrhythmia management or other medical condition

– Documented periods of asystole lasting more than 3 seconds or an escape rate of less than 40 beats/min in an awake, asymptomatic patient


1. Third-degree AV block at any anatomic level associated with any of the following

– After catheter ablation of the AV node – Postoperative AV block that is not expected to

resolve – Neuromuscular disease with AV block (e.g., the

muscular dystrophies)


2. Symptomatic bradycardia resulting from second-degree AV block regardless of type or site of block


3. Chronic bifascicular or trifascicular block with intermittent third-degree AV block or type II second-degree AV block

LAFBFar LAD (-30 to -90)

qR qR

rS rS rS

LPFB + RBBB (bifascicular block)


4. After acute myocardial infarction with any of the following conditions:

– Persistent second-degree AV block at the His-Purkinje level with bilateral bundle branch block or third-degree AV block at the level of or below the His-Purkinje system

– Transient second- or third-degree infranodal AV block and associated bundle branch block

– Symptomatic, persistent second- or third-degree AV block


5. Sinus node dysfunction with symptomatic bradycardia (including sinus pauses) or chronotropic incompetence


6. Recurrent syncope caused by carotid sinus stimulation

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Clinical Indication

1. Symptomatic bradycardia2. Symptomatic heart block

– 2nd degree heart block – 3rd or complete heart block– Bifasicular or trifasicular bundle branch blocks.

3. Prophylaxis

Pacemaker Components

• Pulse Generator (battery)• Electronic Circuitry• Lead system

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Pulse Generator (battery)

• In permanent pacemaker is encapsulated in a metal can ,to protect the generator from electromagnetic interference

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PaPulse Generator (battery)cemaker Design

• Temporary pacing system generator is externally contained in a small box

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Pulse Generator (battery)

• Transcutanus external pacing system house the generator in a piece of equipment similar to portable ECG monitor.

Pulse Generator

• Lithium-iodine cell is the current standard battery

• Advantages:– Long life – 4 to 10 years– Output voltage decreases gradually with

time making sudden battery failure unlikely

Electronic Circuitry

• Determines the function of the pacemaker itself

• Utilizes a standard nomenclature for describing pacemakers

Pacemaker Terminology

I II III IV VChamber Paced

Chamber Sensed

Response to Sensing

Rate Modulation, Programmability

Anti-tachycardia Features

A=Atrium A=Atrium T=Triggered P=Simple P=Pacing

V=Ventricle V=Ventricle I=Inhibited M=Multi-programmable

S=Shock

D=Dual D=Dual D=Dual R=Rate Adaptive D=Dual

O=None O=None O=None C=Communicating

O=None

Common Permanent Pacemakers

Lead Systems

• Endocardial leads which are inserted using a subclavian vein approach

• Actively fixed to the endocardium using screws or tines

• Unipolar or bipolar leads

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Pacemaker function

1. Pacing function2. Sensing function3. Capture function

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Pacing function

Atrial pacing: stimulation of RT atrium produce spic on ECG

preceding P wave

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Pacing function

Ventricle pacing :stimulation of RT or LT ventricle produce a spic

on ECG preceding QRS complex.

Electrocardiogram During Cardiac Pacing

• VVI- senses intrinsic cardiac activity in the ventricle and when a preset interval of time with no ventricular activity occurs it depolarizes the right ventricle causing ventricular contraction

Pacer spike

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Pacing function

AVpacing:direct stimulation of RT atrium and either

ventricles mimic normal heart conduction

Atrial Spike Ventricular Spike

AV Pacing Ventricular Pacing

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Sensing function

Sensing :Ability of the cardiac pace maker to see

intrinsic cardiac activity when it occurs.

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Sensing function

Demand: • pacing stimulation delivered only if the heart

rate falls below the preset limit.Fixed:• no ability to sense. constantly delivers the

preset stimulus at preset rate.Triggered: delivers stimuli in response to

(sensing )cardiac event.

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Capture function

Capture: Ability of the pacemaker to generate a

response from the heart (contraction) after electrical stimulation.

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Capture function

1. Electrical capture : indicated by P or QRS following and

corresponding to a pacemaker spike.2. Mechanical capture: palpable pulse corresponding to the

electrical event.

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Pacing types

• Permanent• Temporary• biventricular

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Types of pacing

1. Permanent pacemaker• Used to treat chronic heart condition • Surgically placed transvenuosly under local

anesthesia• Pulse generator placed in a pocket

subcutaneously ,can be adjusted externally

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Permanent pacemaker

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2. Temporary pacemaker• Placed during emergencies• Indicated for pts’ high degree

heart block or unstable bradycardia

• Can be placed transvenosly, epicardially,transcutanusly or transthorasicly

Types of pacing

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3. Biventricular pacemaker• Used in sever heart failure• Utilize three leads in right atrium, right ventricle and left ventricle to coordinate ventricular coordination and improve cardiac out put

Types of pacing

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INSERTION SITES

• Left Subclavian (most reliable) • Internal jugular (lower incidence of

pneumothorax) • Femoral vein • Brachial vein

Complications of Implantation

Infections

• Pacemaker insertion is a surgical procedure:– 1% risk for bacteremia– 2% risk for wound or pocket infection

• Usually occur soon after pacer insertion• Presence of a foreign body complicates

management


Infection

• Cellulitis or pocket infection:– Tenderness and redness over the

pacemaker itself– Avoid performing a needle aspiration –

damage the pacer


Infection

• Bacteremia: – Staphylococcus aureus and Staphylococcus

epi 60-70% of the time– Empiric antibiotics should include

vancomycin pending culture


Infection

• Consult the pacemaker physician• Draw blood cultures• Give appropriate antibiotics• Frequently the pacer and lead system

need to be removed


Thrombophlebitis

• venous obstruction : 30% – 50%– axillary, subclavian, and innominate veins or the

superior vena cava (SVC).

• definitive diagnosis : duplex sonography, CT

• Tx : heparin with long term warfarin


The “Pacemaker Syndrome”

• new complaints or report a worsening of the symptoms

• syncope or near-syncope• orthostatic dizziness• fatigue• exercise intolerance• weakness



• lethargy• chest fullness or pain• cough• uncomfortable pulsations in the neck or

abdomen• right upper quadrant painother nonspecific

symptoms



• loss of AV synchrony (VVI)• If sinus node function is intact atrial contract

when the tricuspid and mitral valves are closed

• jugular and pulmonary venous pressures and may produce symptoms of congestive heart failure.

• Atrial distention can result Elevated levels of B-type natriuretic peptide (BNP)


Pacer spike

VVI

The “Pacemaker Syndrome” Complications of Implantation


• Consultation with a cardiologist • Change VVI to DDI


Magnet Placement• The EKG technician should perform a 12 lead

cardiogram and then a rhythm strip with a magnet over the pacer

• Does not inactivate the pacer as is commonly believed

• Activate a lead switch present in the pacemaker which converts the pacer to a asynchronous or fixed-rate pacing mode

• Inhibits the sensing function of a pacemaker• Magnets are usually manufacturer specific, as are

available external reprogramming devices

Pacemaker Malfunction

• Failure to capture• Undersensing • Oversensing• Inappropriate rate


Failure to capture

• Lead disconnection, break, or displacement • Exit block (failure of an adequate stimulus to

depolarize the paced chamber)• Battery depletion



Failure to capture

Failure to capture

• Exit block (failure of an adequate stimulus to depolarize the paced chamber)– ischemia or infarction of the endocardium – systemic hyperkalemia– class III antiarrhythmic drugs, such as amiodarone


Undersensing

• Lead displacement• Inadequate endocardial lead contact• Low-voltage intracardiac p waves and QRS

complexes• Lead fracture


UndersensingComplications of Implantation


Failure to capture

Oversensing

• Sensing extracardiac signals: myopotentials • T wave sensing • Electromagnetic interference

– digital cellular phone


OversensingComplications of Implantation

Inappropriate Pacemaker Rate

• Battery depletion • Ventriculoatrial conduction with pacemaker-

mediated tachycardia• 1:1 response to atrial dysrhythmias (atrial flutter)

• magnet application usually converts the pacemaker to a fixed rate in a competitive mode and terminates the tachyarrhythmia.


Management

• History & Physical Examination – pacemaker identification card– pacemaker malfunction present : syncope, near-

syncope, orthostatic dizziness, lightheadedness, dyspnea, or palpitations.

– wound infection or pocket infection typically arises with localized pain

– pacemaker syndrome

Management

• Chest Radiograph : PA, lateral– define pacing catheter tip position and to

determine the number of pacing leads

• 12-Lead Electrocardiogram

• Consult cariologist

Management

• Electrical defibrillation : safe distance (≥10 cm) from the pulse generator (≥8 cm ACLS 2010 )

• Immediate return of pacing (capture) may not occur after defibrillation

• Temporary transcutaneous pacing

Case 1

• 67 year old male presents to the emergency room 12 hours after insertion of a pacemaker complaining of left sided chest pain and shortness of breath

• PR 96 /min , RR 33 /min, BP 125/85, Oxygen saturation 88% RA

• CXR as shown

Pneumothorax

• Occurs during cannulation of the subclavian vien

• Incidence - ?? Cardiologist dependent• Treatment:

– Asymptomatic or small – observation– Symptomatic or large – tube thoracostomy

• Notify the pacemaker physician

Case 2

• 72 year old male presents to the emergency room after a fall, tripped over a bath mat, no LOC

• Shortened and rotated left leg• Past history – pacemaker, hypertension• Nurse does an routine pre-op CXR and EKG

Septal Perforation

• Usually identified at the time of pacer insertion but leads can displace after insertion

• Can occur with transvenous pacer insertion• Keys diagnosis are a RBBB pattern on EKG and

a pacer lead displaced to the apex of the heart on CXR

Septal Perforation

• Management:– Notify the pacer service– Pacer wire has to be removed but not

emergently– Small VSD which heals spontaneously

Conclusions

• Pacemakers are becoming more common everyday

• We need to understand basic pacing terminology and modes to treat patients effectively.

• Most pacer malfunctions are due to failure to sense, failure to capture, over-sensing, or in-appropriate rate

• Standard ACLS protocols apply to all unstable patients with pacemakers.

Thank you

Cardiac Pacing

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