What is it

Cardiac pacing is the use of a small electrical current to artificially produce a heartbeat. A pacing box at the bedside creates a current and a specialised wire on the inside or outside surface of the heart delivers the electrical stimulation to the heart. Temporary pacing systems are used for a short period of time (days or weeks) and the pacing wire is put in at the bedside (no surgery is required). Treatment of certain long-term heart rhythm problems requires insertion of a small pacing box inside the body. This is attached to a pacing wire that sits in the heart (surgery is needed).

How does a normal heartbeat occur?

	The heart has a “built in” electrical conduction system made up of specialised tissue called nodes and fibres. Each heartbeat follows the movement of a single small electrical current (impulse) through all the heart muscle. Each electrical impulse usually begins in the sinoatrial node (SA node) and travels through the right and left atria causing them to contract and push blood through to the lower sections of the heart (ventricles).
This image was source from the Carle Heart Center
Electrical impulses then reach the atrioventricular node (AV node) and pass down through the conduction fibres lying both between and around the ventricles. This causes the ventricles to contract and blood to be pushed out of the heart to the rest of the body. Normally the adult heart beats in a regular rhythm at a rate of about 60 to 100 beats per minute. Effective contractions at an adequate heart rate are essential for delivering oxygen and nutrients to the organs and tissue of the body.

What can go wrong with the Heart Rhythm?

There are many types of abnormal heart rhythms (arrhythmias). Any area of the conduction system can fail to work properly. This can result in the heart beating too fast (tachycardia) or too slow (bradycardia). The electrical impulse can begin in the wrong place, such as the atrioventricular node (AV node) or the ventricles instead of the SA node at the top of the heart. This means that atrial pumping is not co-ordinated with ventricular pumping, and the heart will pump less blood around the body with each heartbeat.

The heartbeat rhythm of heart can be irregular. The atria and ventricles can beat independently if there is no electrical conduction through the atrioventricular node. In this case the atria beat at a normal rate but the ventricles beat very slowly (complete heart block). Temporary cardiac pacing is commonly used in complete heart block to speed up the rate at which the ventricles beat.

What is done.

An electrode (the wire tip) is placed in contact with either the internal or external surface of the heart. The electrode is placed in position in one of the following ways: A long narrow tube (catheter) with an electrode at the tip is threaded into a large blood vessel, usually in the groin or neck, until it reaches the inside of the heart. This is done with the aid of x-ray screening to see the exact position of the catheter During heart surgery the exposed ends of insulated pacing wires are attached to the outside surface of the heart and then brought through the front of the chest.

This image was sourced from Medtronic

A battery powered pacing box (see figure above) is attached by cables to the pacing wires. An electrical pathway is set up between the pacing box and the heart.

Why is it done?

Temporary cardiac pacing is used to maintain a normal heart rate in patients whose own heart rate is not pumping enough blood around the body. This may be in slow heart rhythms (bradycardia or heart blocks), fast rhythms (atrial fibrillation or ventricular tachycardia or when the heart fails to beat (sick sinus syndrome). Temporary cardiac pacing may be used when:

• Following a heart attack (acute myocardial infarction);
• Following cardiac surgery;
• Awaiting insertion of a permanent pacemaker;
• When the heart stops beating (cardiac arrest).
• It can also be used to make the heartbeat faster in order to over ride an undesirable rhythm.

What are the risks?

In patients where temporary cardiac pacing has been established by placing a catheter into the heart via a large blood vessel complications may include:

• Bleeding at the insertion site (an occasional problem);
• Infection (more likely if the wire is left in place for several days);
• Pacing wire may pierce the blood vessel or the heart wall and cause bleeding (a rare complication);
• Puncture and collapse of the lung if the wire is mis-directed (very uncommon); or
• Hiccough – due to contraction of the diaphragm (large muscle between the chest and the abdomen) indirectly as the electrical impulse spreads from the heart to the diaphragm.

Additionally in post cardiac surgery patients who have temporary cardiac pacing [via wires attached to the heart] there is also a low risk of infection and hiccough occurring. These patients must also be observed for a rare complication of bleeding following removal of the pacing wires. This bleeding can cause pressure around the heart and cause the patient to feel unwell. If there is a large amount of blood the patient will need further surgery to drain the blood.

In either method of temporary cardiac pacing methods described above, the pacemaker may fail to work properly (malfunction). In this case the pacemaker battery, connections and cables need to be checked for faults and the settings should be reassessed.

All Intensive Care interventions and procedures carry a degree of potential risk even when performed by skilled and experienced staff.

Publication

Temporary Cardiac Pacing Version 1

Published February 2008

Author Deirdre Moran CNS RNSH

The information contained on this page is general in nature and therefore cannot reflect individual patient variation.  In addition it reflects Australian intensive care practice which may differ from other countries. It is meant as a back up to specific information which will be discussed with you by the Doctors and Nurses caring for your loved one.  ICCMU attests to the accuracy of the information contained here BUT takes no responsibility for how it may apply to an individual patient.  Please refer to the full disclaimer.