The pacemaker is a small device that sends electrical pulses to the heart with the aim to keep it beating regularly. The pacemaker may improve the quality of life of patients with specific heart problems. The device consists of a pulse generator, which has a battery, an electrical computer circuit, and one or more pacing leads. The generator produces an electrical impulse through the pacing leads to the heart.
Almost all modern pacemakers work according to the patient’s demand. They usually sense the presence of a misses beat or if the heart is beating too slow sending signals with the aim to keep the standard heart rate.
Indications of Pacemaker Insertion
The electrical system of the heart is responsible for the contraction of this specific muscle. An electrical signal is sent every time the heart beats and after that the heart muscle contracts pumping blood through the heart chambers and the aorta.
The electrical signals that trigger the heart contractions are generated by a group of specialized cells located in specific areas of the heart. The sinus node is the natural pacemaker of the heart because it physiologically generates electrical impulses at regular intervals of time. These electrical impulses are propagated to a group of cells in the atrioventricular node. The atrioventricular node then transmits the pulse to the ventricles, the lower chambers of the heart. When something disrupts this natural process leading to an abnormal heartbeat, a pacemaker or implantable cardioverter defibrillator (ICD) will be needed.
This system can be disrupted for several reasons, leading to severe heart conditions, such as:
- Severe bradycardia. This condition is characterized by an abnormally slow heartbeat.
- Tachycardia. An unusually fast heartbeat determines this condition.
Other causes are
- Sick sinus syndrome. This syndrome is characterized by the inappropriate function of the sinus node described by the presence of bradycardia sometimes combined with tachycardia. Different studies have proved that some types of medication can generate the syndrome such as calcium channel blockers and beta blockers.
- Atrial fibrillation. An irregular and fast heart rhythm characterizes this arrhythmia. It is usually treated with anti-arrhythmic medication, but sometimes the condition is not manageable with pharmacological therapy alone as not all patients respond the same way. Patients with atrial fibrillation can experience brady-arrhythmia. In these cases, a pacemaker is recommended according to the European Society Of Cardiology and the American Heart Association.
- Heart block. Patients affected by this type of heart rhythm disorder are common. The propagation of the electrical impulse is blocked at some point between the sinus node and the atrioventricular node
- Cardiac arrest. The cardiac arrest is a likely deadly condition where the electrical activity becomes so disturbed that the heart stops beating. An implantable cardioverter defibrillator (ICD), is used to prevent and treat cardiac arrest and potential deadly arrhythmias.
Types of implantable pacemakers
There are several different types of pacemaker. The main categories are:
- single-chamber pacemaker: they have a single lead which is placed either in the right ventricle or in the right atrium of the heart.
- dual-chamber pacemaker: they have two leads, one for each chamber (atria or ventricles) of the right side of the heart.
- biventricular pacemaker: they have three leads, one placed in the right atrium, one in the right ventricle and one in the left ventricle
Pacemaker Insertion Procedure
The implantation of a pacemaker is an easy minimally invasive procedure where complications are uncommon. Usually, it is a procedure performed under local anesthesia. The generator is placed under the skin near the clavicle on the left side or the right side of the chest. The generator is attached to leads and is guided through a blood vessel to the heart. The time of surgery is about 60 minutes.
There are different types of techniques to implant a pacemaker.
- The Transvenous implantation is the most common method to implant a pacemaker or an implantable cardioverter defibrillator. During this procedure, the cardiologist will make a 5 to 6cm incision just below the clavicle, on the left or right side of the chest, and insert the pacing leads into a vein. The pacing leads are conducted along the vein into the right chamber of the heart using X-ray scans for guidance. The other ends of the leads are connected to the pacemaker, which is fitted into a small pocket created by the cardiologist between the skin of the upper chest and the pectoral muscle. This procedure is performed with local anaesthesia and it usually takes about 60 minutes.
- Epicardial implantation. This type of implantation is an alternative and less widely used method of fitting a pacemaker. In this procedure, the pacing lead or leads are attached to the outer surface of the heart through a cut in the abdomen, just below the chest. It is usually used in children and people who have heart surgery at the same time as pacemaker implantation. It’s carried out under general anaesthesia, which means you’ll be asleep throughout the procedure. The procedure usually requires between 60 and 120 minutes. The recovery following epicardial implantation is usually longer than after transvenous implantation.
- Subcutaneous implantation. This type of implantation is performed with general anaesthesia or with local anaesthesia and sedation. During the procedure, a pocket will be created on the left side of the chest where the cardioverter will be positioned. The pacing lead and electrodes are also placed under the skin along the breastbone and are connected to the device. After the incisions have been closed, the sensing, pacing and recording functions of the ICD will be tested and adjusted. Fitting an ICD can take 1 to 3 hours depending on the type of device.
The patient can return to the usual daily living activities soon after surgery. Physical activity should be avoided for at least four weeks.
Although extremely unlikely to malfunction, the patient should follow some precautions as directed by his treating physician when using electrical devices such as: power-generating equipment, other medical electrical equipment (MRI, radiation therapy, electrocautery, …), security systems, cellphones, …
Safety of Pacemaker Insertion Surgery
Having a pacemaker implanted is usually a safe procedure with a low risk of complications.
The biggest concern is the pacemaker losing its ability to control the heartbeat, either because it malfunctions, or because the lead moves from the correct position.
It’s sometimes possible to reprogram the pacemaker to fix a malfunction using wireless signals, but further surgery may be needed when there’s an incorrect positiong.
Complications of Pacemaker Implantation
The procedure carries some risks, although low. Some of the possible complications are:
- Blood clots. Sometime anticoagulants are necessary
- Pacemaker infection. A pacemaker infection is usually treated using a combination of antibiotics and surgery to remove and then replace the pacemaker.
- Punctured lung. This complication happens when the lung is punctured during the procedure. This means air can leak from the affected lung into the chest area. This problem is known as pneumothorax.
Possible issues with the pacemaker
As with any electronic device, there’s a small chance that the pacemaker could stop working correctly. This is known as a pacemaker malfunction. A pacemaker can stop working properly if:
- the lead gets pulled out of position
- the battery of the pulse generator fails (it usually lasts between 5-15 years)
- the circuits that control the pacemaker are damaged after being exposed to strong magnetic fields
- the pacemaker hasn’t been properly programmed
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