Complex Pacemaker Devices

Internal Cardiac Defibrillator (ICD)

An ICD monitors the heart rhythm continuously. If a dangerous, rapid heart rhythm disturbance should develop,  the ICD will try to correct it by pacing the heart more rapidly than normal. If this is not successful, or in the event of VF, an ICD is programmed to deliver a high shock (cardiovert) which will, in most cases, restore the heart rhythm to normal. 

ICDs are generally fitted to patients who have heart conditions that put them at risk of sudden death as a result of arrhythmias or unstable heart rhythms. Many trials since the 1980s have established that they can save lives.

Cardiac Resynchronisation Therapy

Cardiac Resynchronisation Therapy or CRT is a relatively new form of treatment that involves a sophisticated pacemaker being inserted in order to improve the coordination and overal function of the heart.

There are several types:

CRT-Pacing (CRT-P) - This is a device that paces the right ventricle and the left ventricle in synchrony so has a wire or pacing lead that is positioned to stimulate both- in most cases stimulating the lateral wall of the left ventricle involves passing the lead up one of the veins that drains this part of the heart via the coronary sinus.

CRT-Defibrillator (CRT-D) - This has the function of both a CRT-P and ICD. It paces both left and right ventricle but can also deliver a shock in the event of dangerous arrhythmia.

Cardiac 'dyssynchrony' occurs in patients when the heart's contraction is uncoordinated. This is usually secondary to cardiac failure,commonly in the presence of left bundle branch block (LBBB). It can also occur due to prolonged use of a simpler pacemaker. In these cases, various regions of the heart are stimulated at different times. As a result the heart's contraction is no longer uniform and is less effective. When cardiac dyssynchrony is corrected with this type of pacemaker, the heart's function and importantly many patients' symptoms improve can improve.

What does the procedure involve?

Insertion of a pacemaker is normally performed with a local anaesthetic and is nowadays increasingly done on a day-case basis. The whole procedure usually takes several hours depending on the complexity of the case. An area of skin, normally below the left collar-bone if you are right-handed, is cleaned with antiseptic. The skin and muscle are then infiltrated with local anaesthetic where a small incision (usually about 5cm) is made. Following this a vein (usually the subclavian or cephalic) is identified and the pacemaker leads are inserted into their optimal positions. When this has been achieved, and checks have been performed to verify this, the pacemaker itself is screwed onto the leads.  Finally the pacemaker is placed under the skin and the incision is sutured.