Types of pacemakers

There are several types of medical devices for maintaining heart rhythm. All of them perform the main function - maintaining the physiological work of the heart. Each of the pacemakers has its own operating features. In case of heart rhythm disturbance, the device sends an electric charge to the muscle, which restores the required heart rate. If the organ works normally, the pacemaker controls it, but in case of any disturbances it immediately works, correcting the pathological condition.

Let's look at the main types of pacemakers:

• Temporary – used when urgent correction of heart rhythm is required (acute myocardial infarction, bradycardia, tachyarrhythmia). Necessary for diagnosing heart function, as well as in the preoperative period.
• External – refers to temporary, used to correct cardiac rhythm according to various indications. The design of this device consists of volumetric electrodes that are applied to the chest and the cardiac projection area (between the spine and the left shoulder blade). Suitable for diagnosing a painful condition and for preventive purposes.
• Implantable – a miniature device with a titanium or any other body-inert alloy shell. It is implanted in the subclavian region under the pectoralis major muscle. The operation is performed under local anesthesia, and the electrodes are brought to the heart chambers through the subclavian vein.
• Single-chamber – one of the most common types of pacemakers with one electrode in the heart ventricle. The first models worked only at a given heart rate. While modern devices are designed to change the heart rhythm if necessary.
• Dual-chamber – consists of two electrodes that are placed in the ventricle and atrium. This creates a physiological synchronous contraction of the heart chambers. This type of pacemaker is considered the most comfortable for patients, compared to single-chamber.
• Three- and four-chamber – stimulate a given sequence of heart chambers. Provide physiological intracardiac hemodynamics and eliminate desynchrony of heart chambers in severe pathologies.

In addition to the classification described above, devices are divided by functionality:

• Pacemakers – set the correct rhythm for the heart.
• Cardioverter defibrillators set the rhythm, stop arrhythmia attacks and perform ventricular fibrillation.

The devices also differ in their cost. The more modern the model, the higher its price. The following price categories are distinguished:

• Imported models with many functions, usually three- and four-chamber, wireless. Provide a full lifestyle. But due to increased energy consumption, they have a shorter service life.
• The best option in terms of price-quality. Most often, these are two-chamber and the latest versions of single-chamber ECT.
• Outdated models – are distinguished by their reliability and relatively low cost. They are inferior in functionality, ease of use and appearance.

The doctor and the patient work together to choose the best pacemaker option. The doctor selects the device models based not only on medical indications, but also on the patient's capabilities and wishes.

Single chamber pacemaker

An artificial pacemaker with an active electrode that stimulates only one chamber of the organ (ventricle or atrium) is a single-chamber pacemaker. The device is quite simple and has several varieties:

• Frequency-adaptive – automatically increases frequency during physical activity.
• Without frequency adaptation – stimulation is carried out at a constantly set frequency.

The main disadvantage of this device is that the atrium maintains its rhythm, while the contractions of the ventricle and atrium may not coincide. Because of this, blood from the ventricle is thrown into the atrium and blood vessels. That is, the device does not ensure coordinated work of the ventricle and atrium.

The main indication for installing the mechanism is stimulation of the right ventricle:

• Permanent form of atrial fibrillation.
• Sick sinus syndrome.

During implantation, the electrode can be installed in either the left or right ventricle. However, single-chamber devices are currently limited in use, as there are more modern models with expanded functionality.

In addition, even the simplest dual-chamber pacemakers can operate in single-chamber stimulation mode. As for the cost of a single-chamber device, the simplest model will cost about $200, and more modern ones from $500.

Dual chamber pacemaker

A device that senses and stimulates both chambers of the heart with and without frequency-adaptive adaptation is a dual-chamber pacemaker. One electrode is inserted into the atrium cavity, and the second into the right ventricle. This stimulates all blood pumping links, ensuring coordinated work and proper blood flow in the heart.

Bifocal cardiac pacing comes in the following types:

• Atrioventricular - endocardial electrodes are placed in the right atrium and right ventricle.
• Biatrial - one electrode is inserted into the right atrial appendage, and the second is needed for synchronized electrical stimulation of the left atrium, in the coronary sinus.

The main difference between a two-chamber device and its predecessor, a single-chamber device, is that when the contractions of the atrium and ventricle coincide, blood flow into the atrium and blood vessels is excluded. The pacemaker coordinates and controls the atrial and ventricular rhythms, setting the natural rhythm of contractions - first the atria, then the ventricles.

It should also be taken into account that the device operates in DDDR or DDR mode. That is, the device changes not only the frequency of rhythm control, but also the duration of the delay of AV contractions. The ECS ensures full filling of blood vessels even if the conductive functions of the organ are impaired.

Main indications for dual chamber pacemaker:

• Bradycardia with a pulse rate below 40 beats per minute.
• Morgagni-Adam-Stokes syndrome.
• AV blocks of 2nd and 3rd degree.
• Incomplete blockades.
• Carotid sinus syndrome.
• Severe disturbances of myocardial contractile function during physical activity.
• Pathologies with slowing and quickening of heart rate.
• Chronotropic incompetence (insufficient increase in heart rate during exercise and excessive contraction at rest).

In addition to the above indications, the device is implanted when additional functions are needed, for example, recording electrocardiography. The device allows you to lead a full active lifestyle with a minimum of contraindications. But it should be taken into account that an additional set of functions leads to a rapid discharge of the ECS battery. The device is 1.5-2 times more expensive than a single-chamber device.

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Three-chamber pacemakers

The latest generation of pacemakers that stimulate three chambers of the heart in a certain sequence are three-chamber pacemakers. The device ensures physiological movement of blood through the chambers of the organ.

The device consists of three electrodes, one is attached to the atrium, and the other two to the left and right ventricles. This causes cardiac resynchronization, which creates normal blood flow throughout all parts of the heart. The device can operate in single- and dual-chamber stimulation modes.

Indications for use:

• Disruption (resynchronization) of cardiac activity.
• Dyssynchrony of cardiac chambers in bradyarrhythmia or severe bradycardia.
• Rigid sinus rhythm caused by depletion of organ reserves.

As a rule, three-chamber devices have a sensor and partial adaptation functions. The sensors collect information about the respiratory rate, activity of the nervous system and body temperature. Analysis of the received data allows you to select the optimal operating mode of the device. The cost of the device depends on its manufacturer and functionality. Compared to previous generations of ECS, three-chamber mechanisms have the highest price.

Temporary pacemaker

One of the treatment and preventive methods that prevents cases of death due to heart rhythm disturbances is wearing a temporary pacemaker. An external artificial pacemaker is installed by a resuscitator in the following cases:

• Arrhythmia.
• Absolute blockade.
• Slow heart rate associated with fainting.
• Myocardial infarction.
• Ventricular tachycardia against the background of bradycardia and other life-threatening pathologies.

Temporary stimulation of cardiac rhythm is not performed in the absence of good venous access, with hemorrhagic diathesis and anticoagulant therapy.

The device is installed in an ambulance or in intensive care. During the introduction of a temporary pacemaker, the doctor inserts a catheter into a peripheral vein, providing conditions for monitoring cardiopulmonary resuscitation. The electrode is inserted through the internal jugular or subclavian vein.

After the patient's condition returns to normal, a comprehensive examination of the body is carried out and, if indicated, a permanent pacemaker is implanted.

Pacemaker defibrillator

An ECS with the function of detecting and eliminating ventricular fibrillation is an implantable pacemaker defibrillator (ICD).

The main indications for the use of ICD:

• Life-threatening arrhythmia.
• Heart attacks that damage the heart's electrical system.
• History of sudden cardiac arrest and risk of recurrence.
• Congenital heart defects.
• Long QT syndrome.
• Brugada syndrome.

The device saves lives, since in 5% of cases ventricular fibrillation without electropulse treatment leads to death. That is, the device restarts the heart when it stops and normalizes the heart rhythm.

How a pacemaker defibrillator works

The peculiarity of the work of an artificial pacemaker with defibrillator functions is that the device monitors heart contractions and normalizes them if necessary. The pacemaker has wires with electrodes that are inserted into the heart chambers. The device gives electrical signals that allow you to track the heart rhythm.

If arrhythmia is detected, low-energy discharges occur, normalizing the organ's function. The rhythm is restored and the device operates in monitoring mode. High-energy impulses can cause painful sensations.

External pacemaker

An external device designed to prevent fatalities is an external pacemaker. The device is installed when the heart stops beating or when the heart rate slows to a life-threatening level.

The device is necessary for temporary blockages, acute myocardial infarction with transient disturbances of cardiac rhythm and conduction, as well as in case of drug overdose.

External pacemaker has high-resistance volumetric electrodes. They are applied to the anterior and posterior chest wall. The device produces long-lasting high-amplitude pulses – 20-40 ms up to 200 mA. This cardiac stimulation procedure is quite painful compared to endocardial, but allows avoiding infectious complications, thrombosis and bleeding, pneumothorax or cardiac perforation.

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Wireless pacemaker

In 2016, the FDA (American Federal Administration for Supervision of Quality of Food and Drugs) approved serial production of the world's first wireless pacemaker Micra. The device was developed by Medtronic and is a real breakthrough in the management of patients with heart disease.

An artificial heart rhythm driver allows you to control any disturbances. The mechanism is placed directly in the heart, but without any additional wires. Implantation is carried out through the femoral artery into the right ventricle of the organ. The operation to install Micra takes about 30 minutes, and the battery is replaced without surgical intervention.

Indications for installation of the device:

• Atrial fibrillation.
• Atrial fibrillation.
• Bradycardia-tachycardia syndrome.

The device is absolutely safe for patients, but nevertheless there is a risk of complications: displacement of the pacemaker, heart attack, deep vein thrombosis of the lower extremities, pulmonary embolism, etc. These complications occurred in 7% of patients and required hospitalization for further treatment.

Despite all the advantages of this device, there are contraindications for its installation. A wireless pacemaker is not implanted if there are other devices in the body that can affect the operation of the device. The device is not installed if the patient's veins cannot accommodate a 7.8-mm guide carter. Contraindications include obesity, individual intolerance to heparin anticoagulants and the materials from which the device body is made.