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Cardiac pacing.

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VOL: 102, ISSUE: 19, PAGE NO: 21

What is it?


What is it?
- Cardiac pacing involves the fitting of a pacemaker to regulate the heart rate.



- A pacemaker is a small, battery-operated device that enables the heart to maintain a regular rhythm.



- Some pacemakers are permanent (internal) and some are temporary (external).



- The battery in a permanent pacemaker should last 5-15 years.



- Temporary pacemakers can be used to regulate the heart rate post surgery or in emergencies.



How does it work?
- Single-chamber pacing involves inserting an electrode (wire) into either the right ventricle or right atrium, whereas dual chamber pacing involves placing an electrode into both the right atrium and right ventricle (Pudner, 2000).



- The electrode is attached to either an external or internal pacemaker.



- It is then possible to stimulate the heart into depolarising and contracting by generating an electric impulse in the pacemaker, which passes along the electrode into the heart.



- Most pacemakers are demand pacemakers. These have a sensor that turns them off when the heartbeat rises above a certain level and reactivates when the heartbeat is too slow.



- The electrode is placed in the heart after an introducer has first been passed into the subclavian or cephalic vein.



- Once one end of the electrode has been placed in the heart the other end is attached to the permanent or temporary pacemaker.



- Permanent pacemakers are surgically implanted below the clavicle or within the abdominal wall.



- Temporary pacemakers are worn outside the body but connected to the heart via a vein in the neck or leg or through the chest wall.



- Temporary and permanent pacemakers are both introduced under local anaesthetic.



- Heart rhythm problems can occur when the sinoatrial node, the small mass of specialised cells at the top of the right atrium that produces electrical impulses, becomes defective. This can cause the heartbeat to become too fast, too slow or irregular.



- Rhythm problems can occur because of ablockage of the heart’s electrical pathways.



- There are a variety of conditions that may require a temporary or permanent pacemaker. These include (Pudner, 2006):



- Bradycardia: slow heartbeat resulting in symptoms including fatigue and dizziness. It may be caused by the wear of ageing or conditions such as heart block;



- Atrial fibrillation: rhythm disorder where the atria beat too rapidly or too slowly and also irregularly. Drugs used to control atrial fibrillation may cause bradycardia which in turn would require a pacemaker;



- Heart failure: gradual failure of the heart to supply the required volume of blood to the rest of the body. Biventricular pacing or resynchronisation is where a special pacemaker is programmed to increase the strength of muscle contractions in the heart, increasing the supply of blood;



- Syncope: a condition where people faint when the heart rhythm becomes too slow. If fainting becomes frequent, a pacemaker may be fitted to increase the heart rate;



- Pacemakers can also be used to maintain the heart rhythm after cardiac surgery and for prophylaxis during general anaesthesia in patients with a slow heart rate (Pudner, 2000).

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