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Monday, 15 September 2008

Implantable Cardioverter Defibrillator

Here's  a picture showing an ICD like mine installed under the skin, just below the collar bone. In my case, there is one lead from the ICD to my heart.

My ICD is a Vitality2 made by Boston Scientific (previously known as Guidant) The unit has the following parts:
  • Sensors that can detect my heart rate 
  • Microprocessor that controls it
  • RAM for storing data it collects 
  • Capacitors for bulding and applying the shock (this is the reason why an ICD is larger than a pacemaker)
  • Telemetry module that communicates with an external computer for programing
  • Batteries - battery life is 5-8 years, depending how much use I make of it. When the battery is exhausted, the whole thing has to be replaced. 

The ICD has three functions:
1. Defibrillation - this will provide a shock to stop Ventricular Fibrillation (VF).

2. Cardioversion - this will control Tachycardia by providing a smaller shock.

3. Pacing - if my heart rate drops below 40bpm the unit will provide pacing pulses to raise my pulse to 60 bpm.

Function 1 is the main reason I have the unit, since I have gone into VF once before, which very nearly killed me. If the unit ever shocks me it will almost certainly be saving my life in doing so.

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