do you need to be afraid of pacemakers &...

West Herts Cardiology

Do you need to be afraid of Pacemakers & ICDs?

East Midland Conference Centre, Nottingham

10th November 2011

Dr John Bayliss

Consultant Cardiologist, West Hertfordshire NHS Trust

Arrhythmia lead, Beds & Herts Heart & Stroke Network


Devices intro

Pacemaker types

Brady

CRT

ICD

Unipolar v Bipolar

Effects of Diathermy

How to avoid problems

Be safe, not sorry: Knowledge + Confidence

Do you need to be afraid of Pacemakers & ICDs?


Device Therapy

Pacemakers

Cardiac Resynchronisation Therapy (CRT, Biventricular pacing)

Implantable Cardioverter Defibrillators (ICD)

Gastric Vagal stimulator


Variable device implant rates in UK !

Numbers of devices will increase +++ in future

Patients will be older (+ more co-morbidities)


Conduction system : Indications for devices

Brady Pacing

Sick Sinus

syndrome

Atrio-

Ventricular

Block

+

Conduction

disease

ICD

VT / VF

CRT

CHF

+LBBB


Indications for device therapy

1. Pacing for Bradycardias

AV Block: 3° or 2 ° (even if asymptomatic)

Sinus Node Disease (“Sick Sinus Syndrome”)

AVB + SND

AVB + AF (“Slow AF”)

Vasovagal Syndromes (cardioinhibitory = asystole)

2. Pacing in HCM to “desynchronise” LV septum

3. Pacing in CHF Biventricular pacing for Cardiac Resynchronisation Therapy (CRT) to “resynchronise” LV

4. Anti-tachy pacing → ICD


Device Therapy: Bradycardia

Pacemakers

for slow rhythms: bradycardia

to prevent/terminate fast rhythms: anti-tachycardia


Permanent Pacing Codes

Paced Chamber Sensed Chamber Action if sensed

A Atrium A Atrium I Inhibit pacing

V Ventricle V Ventricle T Trigger pacing

D Dual (A+V) D Dual (A+V) D Dual (I+T)

O None O None

-R Rate responsive = pacing rate ↑ with exercise VOO Ventricular pacing (asynchronous) = Fixed rate VVI Ventricular “demand” pacing VVI-R Ventricular “demand” pacing, rate responsive DDD Dual chamber, AV sequential, “physiological” DDD-R Dual chamber pacing, rate responsive


I *

Ventricular

lead

• sensed intrinsic QRS

Inhibits ventricular pacing

• Ventricular pacing

• Ventricular sensing

VVI

Vs Vs Vp Vp Vs Vp Vp


T / I

*

* Atrial

lead

Ventricular

Lead

• Pacing in both the atrium

and ventricle (Dual)

• Sensing in both the atrium

and ventricle (Dual)

• i • intrinsic P wave or intrinsic

QRS can Inhibit pacing

• Intrinsic P Wave can

“Trigger” a paced QRS

I

DDD

Dual

AsVs ApVs ApVp ApVp AsVp AsVp


Device Therapy: CRT

Cardiac Resynchronisation Therapy

in Heart Failure with LBBB (usually in SR)

(CRT, “Biventricular pacing”)

Leads to RA+RV+LV (CRT-P) : 3 leads

may include ICD capability (CRT-D) : ?thicker ICD lead

RA

RV

LV


Device Therapy: CRT

Cardiac Resynchronisation Therapy


Device Therapy: ICD

Implantable Cardioverter Defibrillator: ICD – 1 lead

Brady pacing

Anti-Tachy therapies

VT: anti-tachy pacing

VF: DC Shock(s)

Note thicker shock coil lead

compared to simple pacing lead


Device Therapy: ICD

Implantable Cardioverter Defibrillator: CRT-D

Brady pacing

Anti-Tachy therapies

VT: anti-tachy pacing

VF: DC Shock(s)

Note thicker shock coil lead

compared to simple pacing lead


ICD function

VT termination by ramp pacing

VT sense

Tachy pace →SR


ICD function

VT terminated by single shock

VT sense

Charge→Shock→SR


ICD function

VF terminated by single 34J shock

VF sense

Charge→Shock →SR


Pacing ± ICD Systems: Summary

Single Dual Biventricular

chamber chamber

1 lead 2 leads 3 leads

Usually RV RA+RV RA+RV+LV

(might be RA)


Current from the device

flows down the lead to the

tip electrode (cathode)

Stimulates the heart

Returns through body fluid

and tissue to the device

(anode)

Sensing can be poor

Cathode

Anode

-

+

Unipolar Pacing lead

Pacing System: Unipolar


Pacing System: Bipolar

Current from the device

flows down the lead to the

tip electrode (cathode)

Stimulates the heart

Returns to the device via

the ring electrode (anode)

above the lead tip and

back up the lead

Coaxial Bipolar Pacing lead

Anode

Cathode


Diathermy System

Monopolar

Wide spread of

electrical “noise”

towards plate

Bipolar

Small area of electrical

“noise” between

forceps


Effects of diathermy on Cardiac Devices

Effect of sensing the diathermy current

Effect of current / energy transmitted via lead(s)

Effect of current / energy on device



Effect of sensing the diathermy current Inhibition of pacing

(= Asystole if pacemaker dependent)

Triggering heart rate increase

ICD interpreting as VT/VF → ICD function

(tachy pace or ICD Shock, may cause VF !)

Effect of current / energy transmitted via lead(s)

Effect of current / energy on device


Inhibition of pacing during diathermy

Diathermy

Pacing No pacing



Effect of sensing the diathermy current Inhibition of pacing

(= Asystole if pacemaker dependent)

Triggering heart rate increase

ICD interpreting as VT/VF → ICD function

(tachy pace or ICD Shock, may cause VF !)

Effect of current / energy transmitted via lead(s) Damage to endocardium → fibrosis

= impaired pacing / sensing functions

Effect of current / energy on device Battery failure

Damage to electronics

Reprogramming settings


Worse if pacemaker dependent or battery nearly depleted

Diathermy may cause

Endocardial damage at pacing lead tip

= Elevated pacing capture threshold…

Sudden further loss of battery power

Intermittent failure to capture = Asystole

Pacing failure after diathermy

No pacing = asystole


Is a magnet over the pacemaker useful ?

To disable sensing, so pacemaker ignores electrical

“noise”, or any spontaneous beats

= makes pacemaker pace


“Magnet Mode” of pacemakers

Unpredictable

? Dangerous

DO NOT USE


Inappropriate effect of Magnet mode

Magnet mode causing fixed rate asynchronous pacing

Intrinsic beat in vulnerable period → VF

Salukhe T V et al. Br. J. Anaesth. 2004;93:95-104


Risk of not treating Risk of treating

Benefit of not treating Benefit of treating

Risks v Benefits


MHRA guidelines - 2006

www.mhra.gov.uk

http://www.mhra.gov.uk/



Caution

Using surgical diathermy / electrocautery on patients with an

implantable pacemaker or implantable cardioverter defibrillator

(ICD) can present additional risk of electrical interference and

appropriate precautions need to be considered.

Manufacturers either contraindicate or give strong warnings

against its use, particularly the monopolar mode.

Where the risk/benefit analysis favours the use of surgical

diathermy/electrocautery - particularly in emergency situations,

the use of bipolar operating mode should first be considered.

However, it should be noted that interference remains a

possibility with bipolar mode.



Notes

Interference generated by monopolar surgical diathermy

(electrocautery) is more severe than bipolar and can be sufficient

to temporarily inhibit pacemaker output, give rise to a temporary

increase in pacing, or cause a loss of programmed settings.

For ICDs there is a possibility that noise/interference may be

misinterpreted as ventricular tachycardia or ventricular fibrillation

causing inappropriate initiation of therapy.

Where the implant’s internal power source is low, device

operation may be uncertain during or after the application of

monopolar surgical diathermy/electrocautery.


Guidance for peri-op management of devices

All patients

All practitioners who assess a patient who may need

diathermy, shortwave, microwave or ultrasound diathermy

should ask the patient (and if necessary their relatives)

about possible device implants before planning to use such

techniques. (Note also that MRI is contraindicated in such patients).

Radiofrequency (short wave), microwave or ultrasound

diathermy therapy should NEVER be used in any patient

with a device / lead(s). (Note that Leads may remain implanted even after the device box is removed).

Diathermy / electrocautery should be avoided whenever

possible in all patients with a pacemaker or ICD.

1



All cases, including emergency cases - 1 Staff must hold ILS accreditation, and be prepared to resuscitate .

There must be an external defibrillator with external pacing capability

within the operating room.

The patient must be attached to an ECG monitor and to the external

pacing defibrillator during the procedure.

(beware ECG monitor “paced” mode misinterpreting asystole)

Do NOT place a ring magnet over the device hoping that this will

somehow avoid problems, unless advised to do so by a Cardiac

Physiologist/Cardiologist.

In the event that the patient becomes asystolic, has a ventricular

arrhythmia, or any pulseless electrical activity during a surgical

procedure, resuscitation and medical intervention should take place

without delay in the usual manner of managing a cardiac arrest –

irrespective of the patient’s device.

2



All cases, including emergency cases - 2 Electrocautery diathermy should NEVER be used near a pacemaker / ICD

If electrocautery diathermy must be used in any other area away from the

pacemaker/ICD:

Use Bipolar diathermy if possible (eg diathermy forceps)

If Monopolar diathermy is essential, apply the indifferent plate/pad to

leg opposite pacemaker/ICD to minimise generated electrical circuit

near device (eg if pacemaker/ICD is in upper left chest, then place pad on right thigh).

Use diathermy for short bursts, 1 second or less,

with ECG monitoring to observe the effect on the rhythm.

In a patient with a pacemaker, allow 3 second delay between each

1 second burst of diathermy to allow recovery from any asystole that

occurs during the diathermy.

In a patient with an ICD, allow 10 second delay between each

1 second burst of diathermy to reduce the possibility of triggering a

shock, and to dissipate energy conduction through the ICD lead.

3



All cases, including emergency cases - 3 If serious arrhythmia develops during diathermy,

treat the arrhythmia as usual, stop using diathermy, complete the

operation as safely as possible and contact a Device Physiologist.

A 12-lead ECG must be performed immediately after surgery.

If the heart rate is below 50bpm on the 12-lead ECG there may be a

problem with the device and a Device Physiologist should be contacted.

A pacemaker/ICD check should be performed post-operatively as an

inpatient prior to discharge.

4



Planned procedures - 1 Patients with implanted devices or leads (even if box has been removed),

can be identified at routine pre-admission screening.

When a patient is identified as having an implanted device this should be

recorded in the notes and the key clinical and surgical staff informed.

The Hospital responsible for device follow-up (may not be the hospital in

which surgery is planned…), device manufacturer and model number,

and reason for implant (e.g. heart block etc) should be recorded.

The Cardiology/Device team responsible for the patient should be

contacted for advice, following a local protocol.

If diathermy is essential, discuss with the Device team well in advance,

so arrangements can be made for them to review the patient to make any

adjustments that might be necessary to facilitate use of diathermy.

5



Planned procedures - 2 Each patient’s case should be risk assessed individually by the Device

team. At least 2 weeks’ notice between referral and operation date is

usually required to allow time for this.

The patient may not need to be seen in the Pacing Clinic,

if a pacemaker has been checked within the past 12 months,

or an ICD checked within 6 months.

It is important to determine and be aware :

If the patient is pacemaker dependent ?

= patient at risk of asystole if the device malfunctions.

If the device battery is near to depletion ?

= device may cease to function if affected by diathermy.

What the “magnet mode” is programmed to?

= What effect placing a magnet over the pacemaker may have.

What ICD settings are programmed to detect and treat VT/VF

6



Planned procedures - 3 If the patient has an ICD, the Device Physiologist will probably

program the device to a no-shock mode for the duration of the op.

The Physiologist will need to be available on the day of the operation to

turn the device therapies off pre-procedure and turn them back on

immediately post- procedure.

During the time the device shock mode is turned off, the surgical/theatre

team must be ready to provide immediate resuscitation.

Any Beta Blocker or anti-arrhythmic therapy should usually be continued

pre-, peri- and post operatively, and not withheld.

If the patient is at high cardiovascular risk and is due to have major

surgery, and is not on a Beta Blocker, consideration should be given to

planned initiation of the Beta Blocker pre-operatively, as this reduces

cardiovascular complications.

7

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