Pacemaker

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A group of cells that produce neural or endocrine activity in order to produce a rhythmical biological activity. It may be replaced by an artificial electrical device. Where the organ is not specified this is invariably the heart, but some regard the interstitial cells of Cajal as pacemakers within the gastrointestinal system.

Contents

Cardiac pacemakers

Chest radiograph showing outline of pacemaker. Most pacemakers are normally sited on the left.

History

The first successful implantable pacemaker, designed by Wilson Greatbatch, was fitted in 1960 in the veterans hospital in Buffalo. A previous effort in 1958 at the Karolinska Institute had failed quickly.[1]

Physiological

Pathophysiology

Temporary Pacing

  • Percussion pacing

Permanent Pacemaker

Types

The main types practically are

  • Single lead - as in the classic relatively cheap and cheerful VVI pacemaker often adequate option to treat complete heart block
  • Dual lead - necessary for synchrony of atrial and ventricular contraction which increases cardiac output and allows more physiological cardiac function. This can be important in heart failure.
  • Leadless - under development aiming for a lower complication rate than conventional permanent pacemakers
  • Defibrillators - Will also have potential pacemaking functionality.

Codes

Pacemaker Codes (NASPE/North American Society of Pacing and Electrophysiology/BPEG/British Pacing and Electrophysiology Group)
Cardiac chamber

paced

Cardiac chamber

sensed

Mode of

response

Programmable

functions

Anti-arrhythmia

functions

V≡ventricle V≡ventricle T≡triggered C≡communicating P≡paced
A≡atria A≡atria I≡inhibited R≡rate modulated S≡shock
D≡dual A & V D≡dual A & V D≡dual triggered/inhibited M≡multiprogrammable D≡dual paced & shock
O≡off O≡off O≡off P≡simple programmable O≡off
S≡Special(see note) S≡Special(see note) O≡off
Primary function

S designation is only valid in manufacturers description of a pacemaker that can use either an atrial or ventricular lead. Once the lead is attached the code becomes A or V.

Secondary function

S designation is only valid in manufacturers description of a pacemaker that can sense using either an atrial or ventricular lead. Once the lead is attached the code becomes A or V.

Magnet application usually temporarily turns off sensing function into an asynchronous mode such as AOO, VOO, DOO. The rare T mode is used to observe the location of sensing of intrinsic events and can be very useful Only R mode is usually specified as other modes are implicate. P mode is limited to single chamber pacemakers. M mode has usually rate, sensing, output, refractory periods, hysteresis and mode options Most bradycardia devices are assumed to be ????O devices and a fifth code position is only commonly used in defibrillators

Complications

The complication rate of lead permanent implantable pacemakers approaches 10%. Complications include infection, cardiac perforation, venous occlusion, tricuspid regurgitation. Leads can dislodge, fracture and fail. Pulse generators can erode and provide long term sources of infection. The complication rate of leadless pacemakers may be lower[2][3][4].

Post-mortem Removal

Removal is mandatory before cremation as batteries may explode at the temperatures reached.[5] This may damage the crematorium equipment. Usually in the subcutaneous space in right infra-clavicular area, but few may be epigastric. The devices can also migrate laterally or inferiorly.[6]

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Current BMA advice is that medical practitioners may set their own fee for doing the removal of a pacemaker. In the UK, statute suggests you can charge for it, though it appears the commissioner of the healthcare may be liable rather than next of kin so it is possible that an NHS medical practitioner may not get specific compensation if the bill is challenged and found to be routinely commissioned as could be the case if the deceased was their pre-existing patient[7]. Be careful.

This task may often be performed by the anatomical pathology technicians (colloquially known as the mortuary technicians). If the patient dies at home a GP may be asked by the undertaker to remove the device. Undertakers may be trained to remove pacemakers.

To remove, simply make an incision over the device. Remove the device, cutting the wires to leave them in situ. A GP was on one occasion criticised for using a pocket-knife to do this, which may represent a confusion with operating on the living, but there is clearly scope for upset. Beware the possibility of an implanted defibrillator, which requires switching off by a wireless control box to avoid risk to operators from electric shock.


References

  1. Obit: Telegraph: http://www.telegraph.co.uk/news/obituaries/medicine-obituaries/8794961/Wilson-Greatbatch.html</a>
  2. Knops RE, Tjong FV, Neuzil P, Sperzel J, Miller MA, Petru J, Simon J, Sediva L, de Groot JR, Dukkipati SR, Koruth JS, Wilde AA, Kautzner J, Reddy VY. Chronic performance of a leadless cardiac pacemaker: 1-year follow-up of the LEADLESS trial. Journal of the American College of Cardiology. 2015 Apr 21; 65(15):1497-504.(Link to article – subscription may be required.)
  3. Ritter P, Duray GZ, Steinwender C, Soejima K, Omar R, Mont L, Boersma LV, Knops RE, Chinitz L, Zhang S, Narasimhan C, Hummel J, Lloyd M, Simmers TA, Voigt A, Laager V, Stromberg K, Bonner MD, Sheldon TJ, Reynolds D. Early performance of a miniaturized leadless cardiac pacemaker: the Micra Transcatheter Pacing Study. European heart journal. 2015 Jun 4.(Epub ahead of print) (Link to article – subscription may be required.)
  4. Reddy VY, Exner DV, Cantillon DJ, Doshi R, Bunch TJ, Tomassoni GF, Friedman PA, Estes NA, Ip J, Niazi I, Plunkitt K, Banker R, Porterfield J, Ip JE, Dukkipati SR. Percutaneous Implantation of an Entirely Intracardiac Leadless Pacemaker. The New England journal of medicine. 2015 Sep 17; 373(12):1125-35.(Link to article – subscription may be required.)
  5. Gale CP, Mulley GP. Pacemaker explosions in crematoria: problems and possible solutions. Journal of the Royal Society of Medicine. 2002 Jul; 95(7):353-5.
  6. Gale CP, Mulley GP. A migrating pacemaker. Postgraduate medical journal. 2005 Mar; 81(953):198-9.(Link to article – subscription may be required.)
  7. http://www.pulsetoday.co.uk/story.asp?storyCode=4001909&sectioncode=19>