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Implantable cardiac devices

Cardiac pacing uses implantable devices for a number of different reasons. Devices used include: event recorders, which help diagnose cardiac arrhythmias; pacemakers, which help in the monitoring and treatment of bradyarrhythmias (slow heart rhythms); and defibrillators, which help in the monitoring and treatment of tachyarrhythmias (fast heart rhythms).

What is meant by implantable cardiac pacing devices?

An event recorder (also known as a loop recorder) is a small monitoring device - the size of a USB stick or smaller - that is implanted under the skin and used to diagnose arrhythmias by recording the cardiac events associated with them.

A pacemaker is an approximately matchbox-sized device that is used to monitor and treat bradyarrhythmias (slow heart rhythms).

A defibrillator is used to monitor and treat tachyarrhythmias (fast heart rhythms), and also provides protection against sudden cardiac death.

Development of implantable cardiac pacing devices

On 8 October 1958, Arne Larsson became the first patient to be fitted with a fully-implantable pacemaker. The procedure was carried out by Rune Elmqvist, an engineer working at Siemens-Elema, and Åke Senning, a Swedish cardiologist.

On 4 February 1980, the first successful implantation of an automatic defibrillator was carried out at the Johns Hopkins Hospital in Baltimore. The procedure was performed by the American cardiologist Michel Mirowski. Following this event, the automatic implantable defibrillator - and later the automatic implantable cardioverter defibrillator (ICD) - became one of the most successful therapeutic devices used within the field of cardiology.

What conditions are treated using implantable cardiac pacing devices?

How can implantable pacing devices help?

The implantation of an event recorder beneath the patient's skin is advisable if the patient experiences recurrent syncope (fainting spells) with complete loss of muscle tone, which remains unexplained despite a thorough investigation using a wide range of diagnostic techniques. The device can be used to record data on relevant cardiac events for a duration of approximately 3 years. What is even more important, though, is that the device also offers the option of patient-activated event recording, which can aid diagnosis by establishing the type of correlation that exists between the patient's heart rhythm and symptoms. In more than 90% of cases, further follow-up investigations will allow the physician to establish with certainty whether the patient's symptoms are caused by cardiac events. In certain cases, this diagnostic strategy may also be combined with home monitoring (the remote monitoring of recorded data).

If a patient is diagnosed with a type of bradyarrythmia (slow heart rhythm) that fulfills certain criteria, the implantation of a pacemaker may become necessary. The decision as to whether the patient receives a pacemaker with one, two or three leads will depend on the nature of the patient's underlying disease and heart rhythm. The implantation of the control unit is performed under local anesthesia, and involves a small incision approximately 5cm in length being made below the collar bone on either the left or right side. The leads (with electrodes at their tips), which connect the pacemaker to the heart, enable it to measure and analyze the heart's electrical activity and, if required, deliver localized electrical impulses to stimulate the heart muscle, thus ensuring that the heart continues to beat.

The use of defibrillators is recommended primarily in patients with heart failure, in order to prevent sudden cardiac death as a result of dangerously fast tachyarrhythmias (LVEF ≤ 35%).

The implantation procedure is similar to that used with pacemakers. Defibrillators continuously monitor the patient's heart rate and, if necessary, are able to terminate an episode of tachyarrhythmia (a dangerously fast and irregular heart rate) by either delivering quick electrical impulses that stimulate the heart muscle (known as fast pacing or antitachycardia pacing) or by delivering an electric shock. Many defibrillators can also measure and record additional parameters, such as patient-activated recordings, other types of arrhythmias, intrathoracic impedance (resistance) through the lungs and, where appropriate, details of any action taken by the device. Combined with home monitoring (remote monitoring), this can help to improve the patient's cardiac rhythm management. The effectiveness of individualized cardiac rhythm management depends on the quality of individualized programming and device management, which can help to ensure that potential problems are detected early and addressed without delay.

Treatment step-by-step

Where can I find out more about the implantation of cardiac pacing devices?

Deutsche Gesellschaft für Kardiologie (German Cardiac Society)
dgk.org

Deutsche Herzstiftung e.V. (German Heart Foundation)
herzstiftung.de

Defibrillator Deutschland e.V. [ICD self-help group]

defibrillator-deutschland.de

Articles on implantable cardiac pacing devices

Seifert M, Schau T, Moeller V, Neuss M, Meyhoefer J, Butter C:
Influence of pacing configurations, body mass index, and position of coronary sinus lead on frequency of phrenic nerve stimulation and pacing thresholds under cardiac resynchronization therapy. Europace. 2010 Jul;12(7):961-7. Epub 2010 May 5

Seifert M, Hoffmann J, Meyhöfer J, Butter C:
[Improving left ventricular contractility by stimulation during the absolute refractory period - cardiac contractility modulation (CCM)]. Herzschrittmacherther Elektrophysiol. 2008 Dec;19 Suppl 1:69-76. German

M. Seifert, M. Schlegl, W. Hoersch, E. Fleck, A. Doelger, C. Butter:
Functional capacity and Changes of the Neurohormonal and Cytokine Status after Long-term Cardiac Resynchronization Therapy in CHF Patients. Int J Cardiol. 2007 Jun 19

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