PACEMAKERS

DR.MAYURI

What are they?

• ICD (or Implantable Cardioverter Defibrillator):– a small battery powered device implanted into a patient– detects an arrhythmia it delivers a shock to “restart” the heart, and

restore a sinus rhythm.

• Pacemaker:– A small battery powered device, implanted into a patient – Paces the heart when normal rhythm is slow, when there is a heart

block not allowing the ventricles to contract when the SA node fires, or any arrhythmia causing a slow rate.

INDICATIONS-

• Sinoatrial (SA) node—sick sinus syndrome, tachy-brady arrhythmia.

• bradycardia, hypersensitive carotid sinus syndrome, or vasovagal syncope

• Atrioventricular (AV) node—second-degree block or third-degree AV block

• Trifascicular block or bifascicular block.• Right bundle branch block (RBBB) and left

anterior or posterior hemiblock.

• congenital long Q-T syndrome .• Cardiomyopathy—patients with medically

refractory hypertrophic obstructive cardiomyopathy or

• decompensated heart failure in patients with dilated cardiomyopathy despite optimal medical.

• Alternating left bundle branch block (LBBB) and RBBB

Three-letter and five-letter identification codes of (NASPE)(BPEG)

LETTER I LETTER II LETTER III LETTER IV LETTER V

CHAMBER PACED(S)

CHAMBER SENSED(S)

MODE OF RESPONSE

Programmability & rate modulation

Antitaccyarrhythmia function

O= NONE O=NONE O=NONE O=NONE O=none

A= ATRIUM A=ATRIUM T=TRIGGERED S=single programmable

P=pacing

V=VENTRICLE V=VENTRICLE I=INHIBITTED M=multiple programmable

S=shock

D= DUAL(A+V) D=DUAL(A+V) D=DUAL(I+T) C=CommunicatingR = Ratemodulation

D=dual(P+S)

• In the 1970s, the Intersociety Commission for HeartDisease Resources (ICHD) suggested a classification code,

which is now widely accepted.• The original nomenclature involved a three-letter identi

fication code, as shown in the first three columns of Table.

• In 1980, this code was extended to five letters; the last two letters can be deleted when not applicable.

• In 1987, the NASPE (now known as the Heart Rhythm Society) and BPEG adopted a new five-letter code to describe the operation of implantable pacemakers.

What are the modes of pacing?

• Asynchronous pacing.

• Single-chamber demand pacing.

• Dual-chamber atrioventricular (AV) sequential demand pacing.

ASYNCHRONOUS PACING.

• Asynchronous or fixed-rate (e.g., AOO, VOO, DOO) modes pace at a preset rate independent of the inherent heart rate. They can be atrial, ventricular, or dual chamber.

• Complications- Competition and ventricular fibrillation (VF).

• VF occurs when the pacing spike is delivered during ventricular repolarization, very rare.

SINGLE CHAMBER DEMAND PACING

• Single-chamber demand pacing (e.g., AAI, VVI) paces at a preset rate only when the spontaneous heart rate drops below the preset rate.

• The ventricular-inhibited pacer is the most popular type and is suppressed by normal electrical activity of the QRS complex.

• For example, if patient's device is programmed to VVI 70/min, the device would pace in the ventricle only when the native ventricular rate fall below 70/min.

• Once the native ventricular rate resumed above 70 /min, the device would sense this activity and inhibit further pacing.

• Single-chamber demand pacing in the atrium functions in a similar way but is rarely used alone in the United States.

DUAL CHAMBER AV-SEQUENTAIL PACING• It requires two pacemaker leads, one in the right atrium and one in the right

ventricle. • The atrium is stimulated to contract first then after an adjustable PR interval

the ventricle is stimulated to contract.

if device is programmed to DDD 70/min with a PR interval (AKA: AV delay) of 200 ms,

1st the atrium is paced if the intrinsic heart rate falls below 70/min.

the device will wait for 200 ms to sense intrinsic ventricular activity.

If it does not see intrinsic activity within 200 ms, it will then pace in the ventricle as well.

• DDD pacemakers can also pace in the ventricle in response to intrinsic atrial activity.

• Ex- if the intrinsic atrial rate is 80/min

the device would inhibit pacing in the atrium because the base rate is set to 70/min

As the device is capable of sensing and pacing in both chambers

wait 200 ms from the time of the intrinsic atrial activity and watch for intrinsic ventricular activity

If there is no intrinsic ventricular activity occurring within 200 ms from the intrinsic atrial activity,

pace in the ventricle.

What are the parts of a pacemaker?

A Pacemaker System consists of a Pulse Generator plus Lead (s)

components

• Pulse generator- power source or battery

• Leads

• Cathode (negative electrode)

• Anode (positive electrode)

• Body tissue

1

3

2

4

Pulse generator

• Contains a battery that provides the energy for sending electrical impulses to the heart

• Houses the circuitry that controls pacemaker operations

• Casing (can)– Titanium.

• Connector (header)– Leads plug into ports

• Components– Diodes, resistors, oscillator, microchips

• Battery– The largest single component inside the pulse

generator– Lithium iodide

leads

• Deliver electrical impulses from the pulse generator to the heart

• Sense cardiac depolarisation

• Position within the heart– Endocardial or transvenous leads– Epicardial leads

• Fixation mechanism– Active/Screw-in– Passive/Tined

• Shape– Straight– J-shaped used in the atrium

• Polarity– Unipolar– Bipolar

• Insulator– Silicone– Polyurethane

• Passive fixation

– The tines become lodged in the trabeculae

• Active Fixation

– The helix (or screw) extends into the endocardial tissue

• Epicardial are Leads applied directly to the heart

• Cathode:-An electrode that is in contact with the heart

• Negatively charged

• Anode:-receives the electrical impulse after depolarization of cardiac tissue

• Positively charged when electrical current is flowing

Unipolar pacing

• Flows through the tip electrode (cathode)

• Stimulates the heart• Returns through body fluid

and tissue to the PG (anode) • Patient serves as the

grounding source• Electromagnetic

interference occurs more often in unipolar leads

anode

cathod

Bipolar pacing.Contains a lead with 2 electrodes in the heart

• Flows through the tip electrode located at the end of the lead wire.

• Stimulates the heart.• Returns to the ring electrode above

the lead tip.• Provides a built-in ground lead.• Circuit is completed within the heart• Provides more contact with the

endocardium; needs lower current to pace

• Less chance for cautery interference

Anode

Cathode

Rate response pacing

• Various activity-detecting systems have been developed in years past to create a reliable rate-responsive pacemaker.

• muscle movement, respiratory rate, minute ventilation, central venous temperature, QT interval, myocardial contractility ,oxygen saturation and pH in mixed venous blood, and ventricular depolarization gradient.

• Ex. patients who are subjected to mechanical hyperventilation (e.g., neurosurgery) can experience an increase in the rate of pacing.

• As a result, most device manufacturers recommend disabling the rate-responsive features before surgery.

• If reprogramming the device is not readily available, a magnet may be placed over the pacemaker site to temporarily convert it to asynchronous pacing.

How to detect of type of pacing.• In atrial pacing, an electrical spike appears before

the P wave and the QRS complex is usually normal.

• In ventricular pacing, the electrical spike is followed immediately by a widened QRS complex.

• In AV sequential pacing, there are two spikes, one before the P wave and another preceding the QRS Complex.

• The maximum pulse amplitude- 7.5 volts (V).• The maximum pulse width -1.5 msec

• Fluctuations in the pacing threshold in the first few weeks after a pacing lead has been implanted.

• There is a sharp rise in the pacing threshold - the first 2 weeks because of tissue reaction around the tip of the electrode despite the presence of steroid embedded at the tip.

• Then it falls to two to three times after the scar formation. So the pacing output be at least two times the threshold value or three times the pulse width of the threshold value.

• The most modern day PPM have preset sensitivity settings approximately 2.0 to 3.0 mV.

• Impedance between 250 and 1,300 ohms.

biventricular permanent pacemaker (PPM) or cardiacresynchronization therapy (CRT) device

• These devices are capable of pacing both the left ventricular septum (through a pacemakerlead in the right ventricle) and the left ventricular lateral free wall simultaneously (through a pacemaker lead in the coronary sinus), therefore allowing for activation of the entire left ventricle at the same time.

• INDICATIONS-• severe cardiomyopathy (EF< = 35%), • LBBB with New York Heart Association (NYHA) class III

or class IV symptoms despite optimal medical therapy

LIFE SPAN OF PPM AND ICD

• 5 to 10 years - dual-chamber pacing • 7 to 12 years -single-chamber pacing. • The silver-vanadium oxide batteries used in

ICDs typically last for 5 to 8 years

What is an ICD?• An ICD system consists of a pulse generator and leads for

tachyarrhythmia detection and therapy.• ICDs provide-• antitachycardia and antibradycardia pacing;• synchronized (cardioversion) or nonsynchronized (defibrillation)

shocks • the pulse generator is a self-powered computer within sealed

titanium casing (can).• One or two (in series) 3.2 V lithium–silver vanadium oxide

batteries with high power density are used to power the pulse generator, ci rcuitry, and aluminum electrolytic storage capacitors.

• defibrillatory shocks of 850 V -modern day devices.

• Modern ICDs use transvenous lead systems for sensing, pacing, and shocks. Epicardial leads are still used in infants and small children.

• Current ICDs have many programmable features, but essentially they measure each cardiac R-R interval and categorize the rate as normal, too fast (short R-R interval) or too slow.

How does it work?• The internal computer decide between antitachycardia

pacing and shock.• If shock is chosen, an internal capacitor is charged which

takes 5 to 13 seconds. • It reconfirms ventricular tachycardia (VT) or ventricular

fibrillation (VF) after charging to prevent inappropriate shock therapy.

• Typically, ICDs deliver no more than six shocks per episode. • Once a shock is delivered, the ICD will redetect to

determine whether or not the shock successfully terminated the arrhythmia.

• A tachycardia episode is considered terminated when sinus rhythm has been restored.

INDICATIONS OF ICD• Cardiac arrest resulting from VT/VF• Spontaneous sustained VT with structural heart disease• Syncope of undetermined origin.• Ischemic cardiomyopathy (EF ≤30%) without a recent myocardial infarction

(within the last 4 weeks) or revascularization in the past 3 months.• Ischemic or nonischemic dilated cardiomyopathy (EF ≤35%) with New York

Heart Association (NYHA) class II or III heart failure symptoms stable for the past 9 months.

• Brugada syndrome—right bundle branch block (RBBB) and ST segment elevation leads V1 to V3

• Arrhythmogenic right ventricular dysplasia• Long and short Q-T syndrome• Hypertrophic obstructive cardiomyopathy

PRE-OP EVALUATION OF A PT WITH PACEMAKER

• Routine systemic workup, paying particular attention to cardiovascular disorders.

• Special attention should be paid to the history • Symptoms, and signs of myocardial infarction

(MI), congestive heart failure, and arrhythmia.• Serum electrolytes, especially potassium level,

must be in the normal range.

Patient with acardiac rhythm management device (CRMD)

• Establish whether a patient has a CRMD• Define the type of CRMD• Determine dependency on pacing function of

the CRMD• Determine CRMD function.

• To Determine a patient has a CRMD-(a) patient interview, medical records review, review of

available chest x-ray films ,electrocardiogram, or any available monitor or rhythm strip information

(b) Physical examination (checking for scars, palpating for device).

• To Define the type of device (a) obtaining the manufacturer's identification card fromthe patient or other source, (b) chest x-ray studies if no other data are available, or (c)referring to supplemental resources e.g., manufacturers'

databases, pacemaker clinic records, consultation with a cardiologist.

Other information

(a) battery life(b) programmed pacing mode such as VVIR, DDDR,(c)pacemaker dependency (d) intrinsic rhythm,(e) magnet rate and rhythm (f) prior recorded arrhythmic events (g) pacemaker lead parameters (including pacing

threshold, ability to sense intrinsic activity, and lead impedance.

Evaluate if the pacemaker or ICD is working

• Slowing the intrinsic heart rate to a rate below that of the pacemaker by carotid massage or a Valsalva maneuver.

• Carotid massage to slow the heart rate should be used cautiously because it could result in an arteriosclerotic plaque embolizing to the cerebral circulation.

• If the rate does not slow down enough for the pacemaker to take over the ventricle, device can be tested by placing a magnet over it to convert it to a fixed-rate pacing mode.

• The rate at which the pacemaker will pace in the presence of a magnet varies among device manufacturers and is dependent on the battery life.

Pre-op preparation • Determining whether electromagnetic interference (EMI) is likely to

occur during the planned procedure;• Determining whether reprogramming the cardiac rhythm management

device (CRMD) pacemaking function to an asynchronous pacing mode or disabling any special algorithms is needed;

• Suspending antitachyarrhythmia functions if present;• Advising the surgeon performing the procedure to consider use of a

bipolar electrocautery system or ultrasonic (harmonic) scalpel to minimize potential adverse effects of EMI on the pulse generator or leads;

• Assuring the availability of temporary pacing and defibrillation equipment; and

• Evaluating the possible effects of anesthetic techniques on CRMD function and patient-CRMD interactions.

• reprogramming the device to asynchronous pacing mode before surgery as electrocautery during surgery may inhibit pacing function

INTRAOPERATIVE MANAGEMENT

monitors

• continuous electrocardiogram (ECG) • continuous peripheral pulse monitorings-1. palpation of the pulse,2. auscultation of heart sounds, 3. pulse plethysmography or oximetry,4. a tracing of arterial wave form,5. or ultrasound peripheral pulse monitoring.• Arterial line and central venous pressure or pulmonary artery

pressure monitoring may be used only if the patient has poor ventricular function.

• The “artifact filter” on the ECG monitor should be disabled in order to detect the pacing spikes.

• The ECG monitor should be set in diagnostic mode instead of monitoring mode.

• A complete array of drugs and equipment must be immediately available for cardiopulmonary resuscitation.

• The minimal requirements include, electrocardiograph (ECG) monitor,

• a transcutaneous external pacing and• DC defibrillator, and the usual drugs for

resuscitation.

• The electrodes should be placed as far (more than 6 in. or 15 cm) from a cardiac rhythm management device (CRMD) as possible.

• The electrodes are positioned perpendicular to the CRMD system.

• There are three recommended electrode placements:

Anteroposterior placement. The right arm (RA) electrode placed under the left scapula and the left leg (LL) electrode at apex of the heart

• Apex-anterior placement. The RA electrode placed under the right clavicle and the LL electrode at the apex of the heart

• Apex-posterior placement. The RA electrode placed over the right scapula and the LL electrode at the apex of the heart

A: Apex—anterior placement with bothpads placed anteriorly. B and C: Apex—posterior placement are shown with the device inthe left prepectoral region (B) and the right pectoral region (C).

Electromagnetic interference• During electrocautery, the electrocardiogram is frequently

useless because of interference. • The best monitor available to determine if inhibition is

taking place is a hand on the pulse.• The precordial or esophageal stethoscope, pulse oximeter,

or blood pressure is also acceptable. • The responses of pacemakers to electrocautery or other

electromagnetic interference • Inhibition of pacing• Asynchronous pacing• Reset to Backup mode• Myocardial burns, rare• Ventricular fibrillation (VF),

prevention

• precautions should be taken to minimize the effects of electrocautery:

• Place the cautery grounding plate as close to the operative site and as far from the cardiac rhythm management device (CRMD)

• For some cases, the grounding plate might need to be placed contralateral to the CRMD generator.

• Cautery should not be used within 15 cm of the pacemaker.• Limit cautery use to 1-second bursts every 10 seconds to

prevent repetitive asystolic periods.• If the pacemaker is inhibited by the cautery, place a high-

powered magnet over pacemaker to convert it to fixed-rate mode.

• Using bipolar electrocautery forceps or ultrasonic (harmonic) scalpel reduces electromagnetic interference.

SPECIAL CONSIDERATIONS• ESWL-ESWL is no longer contraindicated for patients with

pacemakers. The only exception to this general statement is the abdominally placed

pacemaker generators. Because these generators are in the blast path of the shock wave, such patients should not be treated with ESWL.

However, most transvenous pacemaker generators are placed in a pectoral location that is at a safe distance from the blast path.

• Consider preoperative disabling of atrial pacing if the lithotripsy system triggers on the R wave.

• Although most pacemakers are not affected by ESWL, sometimes it may cause pacemaker malfunctions-

• Pacing irregularity• Oversensing of asynchronous shocks• Damage to rate-sensing piezoelectric crystal• Intermittent inhibition of ventricular output in dual-chamber

pacemaker.

• There may be a rate increase in a rate-response (adaptive) pacemaker after ESWL shocks. Therefore,special precautions should be taken preoperatively

• an alternative means of pacing, suchas transcutaneous pacing, should also be available in case the pacemaker becomes permanently damaged.

• Low-energy shock waves (< 16 kV) should be used initiall y; then the energy level is gradually increased while pacemaker function is monitored carefully.

• It is best to disable tachycardia detection of an ICD during ESWL and to thoroughly test the ICD following the procedure.

ECT

• ECT appears safe for patients with pacemakers because little current flows within the heart due to the high impedance of body tissues.

• However, the seizure and succinylcholine fasciculations may generate sufficient myopotentials for pacemaker inhibition (unipolar devices) or ventricular tracking (adaptiverate devices).

• So it is advisable to program the pacemaker to (asynchronous) mode for pacemaker-dependent patients.

• An external pacemaker should also be available.• ICDs-tachycardia detection is disabled before ECT and

reprogrammed to its original programmed parameters afterwards.

MRI• MRI is generally contraindicated in patients with a CRMD.• If MRI must be performed, consultation with the ordering physician,

the patient's cardiologist, the diagnostic radiologist and the CRMD manufacturer.

• MRI can cause rapid pacing, inhibition, resetting of DDD pacemakers, and transient reed switch malfunction with asynchronous pacing.

• Serious malfunction with no output or rapid pacing may occur because pulsed energy from MRI can enter the lead by capacitive coupling and cause rapid ventricular pacing

• When an MRI is considered absolutely essential, it is reasonable to program the pacemaker to its lowest voltage and pulse width or to OOO mode, provided the patient has an adequate underlying rhythm.

• The pulse waveform should be closely monitored in pacemaker-dependent patients and an external pacemaker and defibrillator should be available.

• Device function must be checked after MRI.

POST-OP CONSIDERATIONS

• Cardiac rate and rhythm should be continuously monitored throughout the immediate postoperative.

• Backup pacing capability and cardioversion-defibrillation equipment should be immediately available at all times

PROBLEMS DUE TO PACEMAKERS

UNDERSENSING

• Pacer fails to detect an intrinsic rhythm• Paces unnecessarily• Patient may feel “extra beats”• If an unneeded pacer spike falls in the latter

portion of T wave, dangerous tachyarrhythmias or V fib may occur (R on T)

TX: Increase sensitivity of pacer.

UndersensingPacemaker doesn’t sense patient’s own beat

and fires

OVERSENSING

• Pacer interprets noncardiac electrical signals as originating in the heart

• Detects extraneous signals such as those produced by electrical equipment or the activity of skeletal muscles (tensing, flexing of chest muscles, SUX)

• Inhibits itself from pacing• On ECG: pauses longer than the normal pacing

interval are present• Often, electrical artifact is seen• Deprived of pacing, the patient suffers CO, feels

dizzy/light-headed• Most often due to sensitivity being programmed too

highTX: Reduce sensitivity

OversensingPacemaker senses heart beat even though it isn’t beating. Note the long

pauses.

NON-CAPTURE

• Pacer’s electrical stimulus (pacing) fails to depolarize (capture) the heart

• There is no “failure to pace”• Pacing is simply unsuccessful at stimulating a

contraction• ECG shows pacer spikes but no cardiac

response• CO occursTX: threshold/output strength or duration

PACER FAILURE

A.Earlyelectrode displacement/breakage

B. Failure > 6 monthsPremature battery depletionFaulty pulse generator

PACEMAKER MALFUNCTIONS

1. Vertigo/Syncope*Worsens with exercise

2. Unusual fatigue3. Low B/P/ peripheral pulses4. Cyanosis5. Jugular vein distention6. Oliguria7. Dyspnea/Orthopnea8. Altered mental status

THANKYOU…..