A pacemaker is a device capable of stimulating, pacing the electrical activity of the heart when it is too slow.
A pacemaker is a small device composed of two parts – a generator and leads (electrodes) – that is placed under the skin in your chest to help you control your heart rate. People may need a pacemaker for a variety of reasons, mainly due to a group of conditions called intracardiac conduction disturbances, in which the heart rate is abnormal. Normal ageing of the heart can disrupt your heart rate, making it beat too slowly. Another common cause of heart rhythm disturbances is damage to the heart muscle as a result of a heart attack. Certain medications can also affect your heart rate. For some people, genetic illnesses cause an abnormal heart rate. Regardless of the underlying cause of an abnormal heart rate, a pacemaker can correct it. A pacemaker can often be implanted in the chest during a minor surgical procedure. You may need to take certain precautions in your daily life after the pacemaker has been implanted.
Different types of pacemaker
Pacemakers are implanted to help control your heart rate. They may be implanted temporarily to treat a slow heart rate after a heart attack, a surgical procedure or a drug overdose. Pacemakers can also be implanted permanently to correct a slow heart rate (bradycardia) or, in some cases, to help treat heart failure. Smaller pacemakers the size of pills have been developed and are currently undergoing clinical trials. This new lead-free device can be implanted directly in the heart, where it emits an electrical pulse to control the heart rate. Since no leads are required, this device can reduce the risk of infection and speed up recovery time.
How the heart beats (physiology of the heart)
To understand how a pacemaker works, it helps to know how the heart beats. The heart is a fist-sized muscular pump with four chambers, two on the left and two on the right. The upper chambers are the atria (right and left). The lower chambers are the right and left ventricles. In order for your heart to function properly, the chambers of the heart must work in coordination. Your heart must also beat at an appropriate rate – normally between 60 and 100 beats per minute in a resting adult. If your heart beats too quickly or too slowly, the blood doesn’t circulate sufficiently around your body, leading to fatigue, fainting, shortness of breath, confusion and other signs and symptoms. Your heart’s electrical system controls the pumping action of the chambers. A normal heart rhythm begins in your right atrium, in the sinus node. This group of cells – your natural pacemaker – acts like a spark plug, generating regular electrical pulses that spread through specialised muscle fibres. When an electrical pulse reaches the right and the left atria, they contract and inject blood into the ventricles. After a fraction of a second’s delay to allow the ventricles to refill, the pulse reaches the ventricles, causing them to contract and pump blood to the rest of your body.
What is a pacemaker?
An implanted electronic pacemaker mimics the action of your natural pacemaker. An implanted pacemaker consists of two parts:
- The pulse generator
This small metal container contains a battery and the electrical circuit that regulates the rate of electrical pulses sent to your heart.
- The leads (electrodes)
One to three flexible, insulated wires are placed in one or more chambers of your heart and emit electrical pulses to adjust your heart rate. Pacemakers monitor your heart rhythm and, if it is too slow, the pacemaker accelerates your heart rate by sending electrical signals to your heart. In addition, most pacemakers are equipped with sensors that detect movements of the body or breathing rate, which tells the pacemaker to increase your heart rate during exercise in order to meet your body’s increased need for blood and oxygen.
- Single-chamber pacemaker
This type of pacemaker generally transmits electrical pulses from the pulse generator to your heart’s right ventricle.A dual-chamber pacemaker transmits electrical pulses from the pulse generator to your heart’s right ventricle and right atrium. The pulses help to control the synchronisation of contractions between the two chambers.
- Biventricular pacemaker
A biventricular pacemaker is a treatment option for patients suffering from heart failure when the heart’s electrical systems have been damaged. Unlike an ordinary pacemaker, a biventricular pacemaker stimulates the two lower chambers of the heart (right and left ventricles) in order to make them beat more efficiently. A biventricular pacemaker stimulates the two ventricles so that all or part of the ventricular muscle contracts in synchrony. This allows your heart to pump blood more efficiently. Because this treatment restarts the ventricular pumping mechanism, it is also known as cardiac resynchronization therapy (CRT).
The risks of pacemaker implantation
The complications associated with surgery to implant your pacemaker are rare, but may include:
- Infection at the operating site
- Allergic reaction to the iodinated contrast agents or anaesthetic products used during your procedures
- Swelling, bruising or bleeding at the site of the pulse generator, especially if you are taking anticoagulants
- Damage to the blood vessels or nerves near the pacemaker
- Collapsed lung
- Life-threatening complications of pacemaker implantation are very rare.
How to prepare for the procedure
Before your doctor decides if you need a pacemaker, you’ll have several tests done to find the cause of your irregular heartbeat. These could include:
- Electrocardiogram (ECG)
In this non-invasive test, electrodes are placed on your chest and sometimes on your limbs to measure your heart’s electrical impulses. Your heart rhythm may give an indication of the type of disorder you have.
- 24-hours loop recorder
A loop recorder monitor your heart rythm over a period of 24 hours. The electrode wires on the chest are routed to a battery-powered recorder placed in your pocket or on your belt or a strap. While wearing the monitor, you will keep a log of your activities and symptoms. Your doctor will compare the log with the electrical recordings to try to find out the cause of your symptoms.
This non-invasive test uses harmless sound waves that allow your doctor to see your heart without making an incision. During the procedure, a small instrument called a transducer is placed on your chest. It collects the reflected sound waves (echoes) from your heart and transmits them to a machine that uses the sound wave pattern to compose images of your beating heart on a monitor. These images show how your heart is working, and the images recorded allow your doctor to measure the size and thickness of your heart muscle.
- Stress test
Some heart problems only occur during exercise. For a stress test, an electrocardiogram is taken before and immediately after walking on a treadmill or an riding an exercise bike. In some cases, an echocardiogram or nuclear imaging may be carried out.
What to expect from the procedure
- Before the procedure
The surgery to implant the pacemaker is generally done while you are awake and usually takes a few hours. Before the procedure, you will be taken to a special room (called a preparation room or waiting area). Most pacemaker implantations are done using local anaesthesia to numb the incision area. You may be given additional medications intravenously to help you relax. The implantation will be carried out in a room equipped with special x-ray equipment. Your chest will be cleaned with an antibacterial soap and an infusion will be given through your arm.
- During the procedure
During the surgery, one or more leads will be inserted into a major vein under or near your collarbone and guided to your heart using x-ray images. One end of each wire is fixed to the appropriate position in your heart, while the other end is attached to the pulse generator, which is usually implanted under the skin beneath your collarbone. The intervention lasts between fifteen and thirty minutes for single-chamber and dual-chamber pacemakers.
- After the procedure
You will usually stay in hospital for a day after having the pacemaker implanted. Before you leave, your pacemaker will be programmed to respond to your specific pacing needs. A further visit is often scheduled to check that your pacemaker settings are correct. After your pacemaker has been implanted, your doctor may recommend that you avoid vigorous exercise or heavy lifting for about a month. You may have some pain in the area where the pacemaker was implanted. Common painkillers are sufficient to relieve pain during the days following the procedure.
It’s unlikely that your pacemaker would stop working properly as a result of electrical interference.
Still, you should take a few precautions.
- Mobile phones.
It is safe to talk on a mobile phone, but avoid putting your phone directly over the pacemaker implantation site when the phone is switched on. Although this is unlikely, your pacemaker could interpret the mobile phone signal as a heartbeat and stop the stimulation, producing symptoms such as fatigue or dizziness.
- Security gates.
Passing through an airport metal detector won’t interfere with your pacemaker, although the metal in it could make the alarm go off. But avoid lingering near a metal-detection system. If security staff insist on using a hand-held metal detector, ask them not to place the device near your pacemaker for longer than necessary, or request another form of personal search. To avoid potential problems, carry an ID card stating that you have a pacemaker.
- Medical equipment.
If a doctor is considering a medical procedure involving intensive exposure to electromagnetic energy, tell them that you have a pacemaker. These procedures include magnetic resonance imaging (MRI), cancer radiation treatment and shock wave lithotripsy, which uses shock waves to break up large kidney stones or gallstones. If you have surgery, a procedure to control bleeding (electrocautery) could also interfere with the functioning of your pacemaker.
- Power-generating equipment.
Stand at least 20 inches away from welding equipment, high-voltage transformers or motor-generator systems. If you work around such equipment, your doctor may arrange to test your workplace to determine whether the equipment affects your pacemaker.
Once implanted, your pacemaker’s battery should last five to 15 years. When the battery wears out, the pulse generator will be replaced. The leads of your pacemaker can be left in place – although they will need to be replaced eventually – and the procedure to change your pacemaker’s battery is often quicker and requires less recovery time than the initial procedure to implant your pacemaker. Pacemakers are a standard treatment for a number of illnesses involving the heart’s electrical system. By preventing a slow heart rate, pacemakers can treat symptoms such as fatigue, dizziness and fainting. Because most pacemakers nowadays automatically adjust your heart rate depending on your level of physical activity, they can allow you to resume a more active lifestyle.