A Cardiac Pacemaker is an electronic device implanted in the body to correct heart’s rhythm and transmission system disorders.
The heart is the most vital organ for our lives. Circulation of the blood in our body through the blood vessels supplying the tissues depends on the systematic work of the heart. The heart is composed of muscular tissues, about the size of a fist and weighs around half of a kilo. It has four chambers. As seen in the Figure 1, two upper chambers are the right and left atria while the two lower chambers are the right and left ventricles. There is a tricuspid valve between the right atrium and the right ventricle. Major superior and inferior veins (vena cava) open to the right atrium. Pulmonary artery arises from the right ventricle.
Pulmonary valve is located at the inlet of pulmonary artery. The mitral valve is located between the left atrium and the left ventricle. Four veins (pulmonary veins) from the lungs open to the left atrium. The aorta arises from the left ventricle. The aortic valve is between the left ventricle and the aorta. The arteries supply the body with oxygenated blood.
The pulmonary artery carries the venous blood returned from the body to the lungs to be oxygenated. The oxygenated blood by the lungs is returned to the left atrium and left ventricle through pulmonary veins. The blood pumped out from the left ventricle to the aorta and its branches travels the whole body to supply the tissues.
The blood circulates through the body by heart’s regular contraction and relaxation. During contraction of the heart (systole), the blood in the heart is pumped out to the arteries. Following contraction, the heart relaxes and dilates (diastole) in which the blood is returned to the heart through veins. The pulse is the contraction of the heart which pumps the blood to the vessels.
The heart contracts 60 to 80 times a minute to pump a volume of 5-6 L blood to the vessels and allows blood to constantly circulate inside the veins by contracting and relaxing. The circulation rate is determined by the heart depending on the needs of our body.
The heart muscle needs a stimulus to perform its functions, i.e., to contract and relax. This stimulus is provided by the heart’s specific transmission (electric) system. This system produces electricity which is distributed over the heart by particular pathways. The heart muscle that receives the stimulus contracts and relaxes to perform its functions.
The cardiac stimulus is initiated by the Sinoatrial Node in the right ventricle. This node is the natural generator of our heart. The electricity produced by this node is initially distributed to the right atrium then to the left atrium by special transmission tissue (transmission wires) and reaches to a second node between the atria and ventricles. This node is called Atrio-Ventricular node. Then it is transmitted to the bundle of His’, right left anterior and left posterior branches and special fibers called Purkinje, to the ventricles i.e. heart muscle. The atria are contracted when electrical stimulus is spread over them, and pumps the blood to the ventricles. The stimulus is then spread over the ventricles and this time the ventricles are contracted. This order continues without a stop to keep us alive. This special transmission system has also diseases.
The diseases affecting the heart’s transmission system include coronary artery disease, heart attack, hypertension, aortic and mitral valve diseases, postoperative open heart surgery, some medicines, and old-age. Sometimes the cause is not known.
The diseases of the heart’s transmission system include the followings:
A disease of the sinoatrial nodeThe sinoatrial node normally produces 60-80 stimuli a minute. It can be 140-160/min. with the increased activity. The sick sinus occurs when the sinoatrial node fails to function.
A – Sinusal Arrest occurs when sinoatrial node does not produce stimulus.
B –Sinusal Bradycardia occurs when less stimuli are produced than normal; stimulus is less than 50/min.
C – Sinusal Tachycardia occurs when the number of stimuli from sinoatrial node is greater than normal; greater than 90-100/min.
The disease of atrio-ventricular node.It is categorized by stimulus transmitted by this node;
A – First Degree A-V Block: Sinusal stimulus is delayed to pass the A-V node.
B – Second Degree A-V Block: Some part of sinusal stimulus passes through the A-V node and the other part is blocked. There are two types, Type I and Type II.
Sinusal stimulus cannot pass through the A-V node in any way. The stimulus is completely interrupted at this node. So, another focus under the A-V node produces a stimulus in an attempt to maintain the life. Otherwise it is highly likely for the heart to come to a complete stop. All heart cells are able to produce stimulus in addition to the transmission system. However, such rhythms are sick rhythms and impair the regular function of the heart.
A disorder of transmission pathways, i.e., interruptions and pauses of electrical system, results in dysfunction of the heart. The number of heart beats is reduced or increased, resulting in BRADYCARDIA or TACHYCARDIA. Bradycardia is the most common condition that requires a cardiac pacemaker. In tachycardia, a device called INTRACARDIAC DEFIBRILLATOR (ICD) is implanted to regulate the cardiac rhythm.
Symptoms of Bradycardia
These symptoms may be severe or mild depending on the number of heart beats. A bradycardia-related syncope is sometime difficult to differ from other syncope associated with other causes especially neurology-related syncope. With a bradycardia-related syncope, the patient will abruptly fall down on the floor or their head will tilt to one side while sittin because of the lack of supply of blood to the brain. No pulse is palpated at that moment. The event lasts short. A death may occur when lasting longer than 5-6 seconds. Fainted person will regain consciousness in 2-3 seconds. If they haven’t hit somewhere when they fainted, they will stand up and continue what they were doing.
Pulse Generator: the part producing stimulus
Lead or Electrode: The part transmitting
Pulse generator consists of a battery and electronic circuit. Battery is usually lithium. Electronic circuit is a miniature computer with various programs installed in. The programs can be changed when required by a magnet. The power from the battery is converted to small electronic pulses and transmitted to the heart by lead. The electronic circuit controls the timing and intensity of electric stimuli transmitted to the heart.
Lead (electrode) provides the transmission between the heart and the pulse generator. It is usually an insulated wire from polyurethane.
A pacemaker has two important functions:
A – Stimulation: Producing a stimulus at a required rate when the heart doesn’t produce one or when it is slow,
B – Detection or Sensation: Detecting and monitoring the heart’s natural activity; producing a stimulus when required. So, a pulse generator will not produce a stimulus when the heart has its rhythm.
There are two types of a cardiac pacemaker.
1- Temporary Cardiac Pacemaker : In some cases, temporary blocks or bradycardia may occur in the heart. Such cases will naturally recover. However, a temporary cardiac pacemaker is implanted to maintain patient rhythm and life until it get backs to normal.
It consists of a pacemaker box and special lead. The lead is placed inside the heart through a vascular access (from neck, arm or groin). The other end of the wire is connected to the pacemaker box. Such pacemakers implanted temporarily are easy to remove when the patient recovers.
2- Permanent Pacemaker: Implanted in the body permanently.
There are two methods of implantation:
A – Endocardial method: The electrode is guided through a blood vessel to be placed in the heart. The procedure required local anesthesia.
B – Epicardial method: The electrode is directly stitched on the heart muscle. This procedure requires general anesthesia. It is rare in cases where it is impossible to perform endocardial method.
This procedure is performed in a special catheter lab with a radioscopy device and under full sterilization, administering local anesthesia. During the procedure, the surgeon and assisting staff will wear a sterile dress, bonnet, and mask as in the operating theatre. The front side of the chest is cleaned with a special solution and covered with a sterile blanket. The pacemakeris usually implanted in the left chest (may be in the right side) below the clavicula.
The site is incised in 8-10 cm. Depending on the type of the pacemaker implanted 1-2-3 leads are guided through the vessels exposed by incision to be placed in the required cavity of the heart. Measurements we call threshold measuring are performed to see the state of the lead to detect and produce a stimulus. The leads are then attached to tissues and vessel at the site of incision. The other end of the lead is connected to the pulse generator which is placed in the pocket specially prepared under the skin, and the skin is sutured.
Depending on the condition of the heart, the heart chamber to be stimulated must be priorly determined by the operator.
One-chamber stimulation: The right atrium and the right ventricle are selected for this stimulation. Only one lead is used.
Two-chamber stimulation: Both the right atrium and the right ventricle of the heart are stimulated. Two leads are placed in the right atrium and right ventricle.
Three-chamber Bi-Ventricular stimulation: A special type of stimulation used in heart failure. Three leads are placed in the right atrium, right ventricle, and coronary sinus. In this case, the right atrium, right ventricle and left ventricle will be stimulated.
The procedure usually takes 1-2 hours for implantation of a permanent pacemaker. In implantation of three-chamber pacemakers, it may take time to find the coronary sinus and implant the lead, resulting in prolonged time for the procedure around 3-4 hours.
Implantation of a pacemaker is a surgical procedure. Some adverse events we call complication may arise during the procedure. Our hospital is highly experienced in this field. Since 1989, over 5000 patients have been successfully implanted a cardiac pacemaker. The rate of complications is scarcely any.
The rate of major vital complications is low. It is 1-5%. Such complications include pericardial tamponade, pneumothorax and vascular injuries.
Pericardial tamponade: Occurs during placing a lead especially a twisted lead. The electrode damages and perforates the cardiac tissue and is inserted in the pericardium. In the meantime, the blood is accumulated between the pericardial leaflets. The heart dysfunctions depending on the volume of accumulated fluid. The blood inside the pericardium must be drained by a puncture or a surgical procedure. A cardiac perforation is very rare during placement of an electrode. It often occurs in a heart failure where cardiac tissue becomes very thin.
Pneumothorax: The pleura are perforated and the lung tissue deflates during trying to find a vessel for electrode to enter the heart. In this case, the pleura are filled with air. The air may need to be discharged by connecting an outside tube. The volume of the air filled in the pleura is highly little in minor injuries, and is spontaneously sucked without any interventions. Pneumothorax usually occurs with COPD and Amphysema, and chest deformities.
Vascular injury: Occurs with injury of coronary sinus during implantation of a three-chamber pacemaker in heart failure. Sometimes, coronary sinus or its branches may be perforated resulting in accumulation of blood around the heart, and also a pericardial tamponade may develop.
Other than these major complications, there may be minor complications including rhythm disturbances, swelling of pacemaker pocket, pain, and hemorrhage which are easy to correct.
In case of failure to find a vessel to pass the electrode (the vessel may be obstructed or very thin, or absent congenitally), the procedure may be repeated on the other side.
If the vessel is impossible to find, the electrode is surgically placed using epicardial method.
The electrode is likely to dislocate where it was implanted in the heart in the first three months. It needs re-correction.
The heart produces abnormal rhythms in cardiovascular diseases and myocardial diseases in particular. These rhythms are too fast and may be fatal if left uncorrected. These life-threatening rhythms are called Ventricular Tachycardia and Ventricular Fibrillation. The myocardium fails to contract and relax because of these fast rhythms. They, ventricular fibrillation in particular, are only corrected by electrical shock. The ICD or defibrillator is implanted in the heart to correct these rhythms. Their generators are somewhat more complex and electrodes are specially designed. This device is slightly larger than normal pacemakers and implanted in the body as permanent pacemakers. It also functions as a pacemaker.
In heart failure, delay of electrical transmission in the heart occurs in the Left Branch Block. The heart’s right and left atria are unable to work synchronously at the same time due to this electrical delay in seconds. The heart gradually fails and heart failure becomes severe. To correct this, electrodes are placed in the heart’s right and sol ventricles. These electrodes allow either side of the heart to work synchronously.
Refer to “Heart Failure” section to have further information about this device.
A pacemaker is an electronic device. There is a magnetic field around the devices that are operated with electricity and involve a magnet. This field is usually weak and does not affect your pacemaker. However, a strong electromagnetic field produces an electromagnetic interaction. This may temporarily affect the functions of your pacemaker. It may cause you problem even it is temporary.
The detectors at an airport and entry of some buildings have a strong electromagnetic field. You must tell the officer there you have a pacemaker (showing your card) and not pass through such areas.
Some surgeries and the devices used in surgeries may affect the pacemaker.
Radiography, computed tomography, and dental procedures do not affect your pacemaker; however you should tell the technician you have a pacemaker.
Diagnostic ultrasound devices should be kept away from the pacemaker. A transducer will not cause a problem unless it is on the pacemaker pocket.
A transducer in the therapeutic ultrasound devices should be kept at a distance of minimum 15 cm from the pacemaker.
The applicator of an electrolysis device should be kept away 15-20 cm.
A number of interventions are not recommended under normal circumstances. Only the physician who will perform the procedure and monitor you should take precautions depending on the severity of the procedure and permit performing such procedures. They are electrocautery, diathermy, radiotherapy, external defibrillation, lipotrophy, radiofrequency ablation, lipotropsi, transcutaneous electrical nerve stimulation (TENS), and some hearing aids producing digital signals using a magnetic field.
A number of interventions and use of some devices are strongly not recommended.
Some domestic devices do not affect the pacemaker.
The telephones or cordless telephones do not pose a risk. Mobile telephones and radio telephones are recommended to keep at a distance of 15 cm from the pacemaker and on the other side if possible. The receiver of standard telephones should be kept away from pacemaker pocket.
Pacemakers have internal safety feature. This safety feature can protect your pacemaker from domestic appliances. Your pacemaker should be at a distance of 10 cm from such appliances which include washing machines, electrical blankets, vacuum cleaners, irons, cordless knifes, treadmills, hair driers, microwaves, electric ovens, televisions, radios, and kitchen robots.
The devices which should be operated at a distance of 15-20 cm from the pacemaker include electrical cable hair driers, pagers, sewing machines, overlock machines, musical speakers with large magnets.
Care should be taken when using such devices and you should not be alone when using them. The electrical devices must be plugged into a socket that is grounded. Any possible electric leakages must be controlled.