Pacemaker settings and modes

The medical device that maintains the heart rhythm is a complex device made of inert medical titanium alloy. The device is a kind of mini computer that regulates the work of the heart.

The pacemaker setup, i.e. the choice of the optimal mode for stimulating the heart, depends on the indications for its installation. Programming is performed during implantation. Further check of the pacemaker setup is performed at each scheduled visit to the cardiologist. If necessary, the doctor changes the functional mode of the device.

Pacemaker modes

There are several types of medical devices that maintain heart rhythm:

• Single-chamber – stimulation of the ventricle or atrium.
• Dual chamber – stimulation of the ventricle and atrium.
• Three-chamber – stimulation of both ventricles and the right atrium.
• Four-chamber – impact on all chambers of the organ.

There are also wireless artificial heart rhythm drivers and cardioverter-defibrillators. All of them operate in different stimulation modes, ensuring normal functioning of the heart muscle.

In 1974, a special system of codes was developed that described the functions of the ECS. Later, the coding began to be used to indicate the operating mode of the device and consisted of 3-5 letters.

1. The first symbol is the heart chamber for stimulation:

• A - atria.
• V – ventricles.
• D – two-chamber systems affecting the atria and ventricles.

2. The second symbol indicates the chamber that is analyzed by the ECS (device sensitivity function). If the device has the letter O, it indicates that the implant does not work in this mode.
3. The third symbol is the pacemaker's response to spontaneous cardiac chamber activity.

• I – inhibition, that is, the generation of an impulse is inhibited by a certain event.
• T – pulse generation is triggered as a response to an event.
• D – Ventricular activity inhibits the device impulse, and atrial activity initiates ventricular stimulation.
• O – no response to the event, i.e. the pacemaker operates in the asynchronous stimulation mode with a fixed frequency.

4. The fourth letter is frequency adaptation, the answer. R is used if the mechanism has the function of adapting the stimulation frequency to the physiological needs of the body. Some pacemakers have sensors that monitor physical activity and breathing.
5. The fifth symbol is multifocal stimulation of the heart muscle.

• O – absence of this function in the device.
• A, V, D – presence of a second atrial or ventricular electrode.

Let's consider the most common modes of implant operation:

• VVI – single-chamber ventricular demand pacing.
• VVIR – single-chamber ventricular pacing on demand with rate adaptation.
• AAI – single-chamber atrial on-demand pacing.
• AAIR – single-chamber atrial pacing on demand with rate adaptation;
• DDD – dual-chamber atrioventricular biocontrolled stimulation.
• DDDR – dual-chamber atrioventricular biocontrolled stimulation with rate adaptation.

The choice of adequate stimulation mode depends on the indications for the device installation. With low physical activity and no need for constant functioning of the pacemaker, the VVI mode is selected. VVI and VVIR are used in the diagnosis of chronic atrial fibrillation. DDD and DDDR are optimal for AV blocks, left ventricular dysfunction.

Ddd pacemaker mode

The pacemaker operating in DDD mode indicates dual-chamber atrioventricular biocontrolled stimulation. That is, the pacemaker is fully automatic and has a frequency adaptation function.

Indications for the DDD regimen:

• AV block.
• Sinus bradycardia.
• Stopping the sinus node.
• Sinoatrial block.
• Pacemaker syndrome.
• Tachycardia with a circular motion mechanism.
• Atrial or ventricular extrasystole.

The device electrodes are located in the atrial and ventricular chambers. Due to this, effective correction of all conduction disturbances occurs, provided there is no constant arrhythmia. This mode is not set in the case of constant atrial fibrillation or flutter, as well as in case of slow retrograde.

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Vvi pacemaker mode

If the artificial pacemaker operates in VVI mode, this indicates single-chamber ventricular stimulation on demand. This set of functions is typical primarily for single-chamber pacemakers, but other modern pacemaker models can also operate in VVI mode.

Indications for VVI:

• Persistent atrial fibrillation.
• AV block of II and III degree in patients with cerebral pathologies or locomotor function disorders.
• Attacks of bradycardia.

VVI starts working when spontaneous depolarization is registered, the frequency of which exceeds the programmed one. In the absence of spontaneous ventricular activity, the implant is in the "on demand" mode.

Pacemaker rhythm

The heart rhythm is completely dependent on the impulses generated in the sinus node. The sinus node is the main driver of the heart rhythm and the sections of the conduction system. Normally, it generates impulses with a frequency of 60-100 beats per minute. Contractions occur at equal intervals.

If there is a violation of the time intervals between individual contractions, this leads to a shortening of systole (contraction) or a decrease in diastole (relaxation). The processes of stimulation of the heart rhythm are regulated by hormones of the endocrine system and the autonomic nervous system.

To eliminate problems with serious heart rhythm disturbances, which may have congenital causes or arise due to certain diseases, patients undergo surgery to install an ECS. The pacemaker rhythm maintains the physiological work of the heart, preventing various failures. The frequency of contractions is set using the device mode, as a rule, within the normal range for a healthy person.

Pacemaker battery

An artificial cardiac pacemaker is a complex device with many different functions. Its main task is to maintain normal heart function. The duration of the pacemaker's operation largely depends on the power source. The battery for the pacemaker is a miniature but capacious accumulator, the charge of which lasts for 3-10 years.

Most devices operate on the basis of a lithium-ion battery. Some modern models use a solid-type electrolyte based on titanium, platinum or lithium thiophosphate as a power source. Batteries are made of materials that are safe for health and life.

If the battery fails, the entire device is replaced. It should also be noted that before the pacemaker is implanted, the battery is tested for defects. This reduces the need for premature replacement of the device, i.e., a repeat operation.

Replacing the battery in a pacemaker

The time it takes to replace the battery in the pacemaker depends on the model of the artificial pacemaker, its functionality and the set stimulation mode.

On average, the device's service life is 5-10 years. But if the patient's own heart rhythm is preserved and the pacemaker is turned on from time to time, it can work without interruption for 10-13 years.

If the battery fails, the patient undergoes surgery to remove the old pacemaker and install a new device. During surgery, only the case or the case and electrodes may be replaced.

How to charge a pacemaker?

An artificial heart rhythm driver is a kind of mini computer. It consists of a strong case, electrodes and, of course, a battery. The life of the device depends on the capacity of the power source.

• The pacemaker is implanted under the skin in the collarbone area and connected to the heart muscle with wires. It is impossible to connect a cord and recharge a pacemaker that is already implanted.
• Miniature dimensions and optimal operating mode allow the device to operate without interruption for 5-10 years.
• The signal that the battery charge is running low is a violation of the established stimulation mode. The process of replacing the battery is carried out together with the removal of the device case and sewing in a new one.

That is, today there is no possibility of wireless recharging of the pacemaker. But in the 1960s, several models were created that had a power source based on a radioactive isotope - plutonium. The half-life of this element is about 87 years.

The idea of producing pacemakers with such a battery was quickly abandoned. This is due to the high toxicity of plutonium and the need to extract the device after the death of the patient, which entailed the problem of further disposal of the isotope. Another obvious reason for the lack of an eternal battery is the wear of the electrodes and the body itself.

Pacemaker malfunction

Most often, failures in the artificial pacemaker are associated with the recognition of impulses or stimulation of the organ chambers. The malfunction of the pacemaker occurs due to the following reasons:

• Battery drain.
• Displacement of the device electrode.
• Violation of the integrity of the electrode.
• Fibrous changes around the end of the electrode.
• Myocardial perforation by electrode.
• High stimulation threshold.
• Impact of external factors: electromagnetic and magnetic radiation, mechanical trauma.

Problems with the pacemaker are detected with a pulse artifact without capture or with no artifacts with severe bradycardia. Changes in the stimulation frequency and disruption of the synchronization function are observed. An increase in the refractory period of the pacemaker is possible.

To restore normal operation of the pacemaker, a comprehensive diagnosis of its condition and reprogramming is carried out. In some cases, the device is replaced with a new one.