Cardiac pacing: types and indications

Cardiac pacing is a treatment for heart rhythm disorders in which a miniature device (pacemaker) delivers weak electrical impulses to the heart muscle, thereby maintaining the heart rate within safe limits. Doctors use it when the heart's own electrical circuitry is malfunctioning, such as with severe bradycardia, pauses, conduction blocks, or recurrent syncope associated with a slow pulse. Current guidelines consider pacing the standard for a wide range of conditions, from atrioventricular blocks to the aftereffects of certain valve procedures. [1]

The key is accurate recognition of the problem. Sometimes cardiac pacing is prescribed for life (for example, in the case of permanent complete block), sometimes after conduction system injury or cardiac intervention, when the heart rate becomes too low and threatens syncope. A separate approach is the prevention of "pacing-induced cardiomyopathy," when prolonged single-ventricle pacing can compromise the synchrony of contractions: in this case, more "physiological" pacing sites are selected. [2]

It's important to understand that cardiac pacing doesn't "cure" the underlying cause permanently, but rather compensates for its consequences. However, with the right parameters and regular monitoring, people can return to their normal lives, including work, travel, and physical activity. Modern devices support remote monitoring and allow the doctor to see how you're feeling without frequent clinic visits. [3]

In recent years, the field of rhythmology has undergone a "renewal": the advent of electrodeless, caseless pacemakers, physiological stimulation of the cardiac conduction system (the His bundle and the left leg area), and expanded capabilities of magnetic resonance imaging in patients with implanted systems. This makes therapy more precise and safer. [4]

When is cardiac pacing really necessary?

Classic indications are symptomatic bradycardia and acquired high-grade atrioventricular blocks: when a slow pulse causes weakness, dizziness, syncope, or threatens circulatory arrest. In these situations, pacing restores a safe heart rate and reduces the risk of injury from syncope. The decision is based on electrocardiograms, Holter monitoring, and provocative testing, as well as evidence-based guidelines. [5]

There are specific scenarios. After aortic valve implantation or replacement, some patients experience new conduction blocks—in this case, pacing often becomes a "safety net." In patients with sick sinus syndrome, pacing allows the use of effective antitachycardia medications without the risk of dangerous bradycardia. And in neuromediated syncope with long pauses, pacing reduces the frequency of episodes in carefully selected patients. [6]

For patients with heart failure and widespread depolarization, a special type of therapy called resynchronization therapy is used: this is not "regular" cardiac pacing, but rather the coordinated operation of electrodes, which restores synchronicity between the heart chambers. Recent recommendations also include the tactic of "physiological stimulation" of the conduction system to avoid the undesirable effects of prolonged right ventricular pacing. [7]

Pediatric patients and people with infiltrative myocardial diseases are considered separately: the indications and settings here are more precise, and the decision is made in specialized centers by an experienced multidisciplinary team. [8]

How a pacemaker works

A standard pacemaker consists of a housing (generator) and thin insulated wires (electrodes) that are implanted in the desired areas of the heart. The generator contains a battery, a microprocessor, and amplifiers for sensing its own signals and delivering impulses. The device can recognize when the heart is beating naturally and only "pick up" the rhythm when needed—this saves battery life and supports the heart's natural rhythm. [9]

Motion and breathing sensors help activate what's known as an "exertion-dependent rhythm": when you walk up stairs, your heart rate increases, ensuring adequate blood flow. The doctor programs the sensitivity thresholds, lower and upper heart rate limits, atrial-ventricular delays, and other parameters, then adjusts them during follow-up visits or via remote monitoring. [10]

Implantation is performed under local anesthesia through a small incision under the collarbone. Electrodes are inserted through a vein under X-ray guidance, secured in place, and connected to a generator placed in a subcutaneous "pocket." At the end of the procedure, stimulation thresholds and signal reliability are checked, and the patient is then instructed on the procedures for the first few weeks. [11]

Battery life is measured in years and depends on stimulation frequency and settings. When the battery is running low, the device will notify you in advance during a scheduled visit or via a remote monitoring system, after which the generator is routinely replaced (usually without replacing the electrodes if they are in good condition). [12]

Types of devices and modes: from classic to "physiological"

Single-chamber pacemakers operate in either the atrium or ventricle and are suitable for simple scenarios. Dual-chamber pacemakers coordinate the atrium and ventricle, maintaining a physiological contraction sequence—this reduces fatigue and improves exercise tolerance. Three-chamber devices with resynchronization are used for certain applications. [13]

Unframed pacemakers are mini-capsules that are implanted directly into the heart cavity via a catheter, meaning there's no subcutaneous pocket or intravascular electrodes. Previously, they were only single-chamber, but dual-chamber systems are now available: two capsules in the atrium and ventricle "communicate" with each other and synchronize their activity wirelessly. This is especially valuable in patients with a high risk of infection or venous complications. [14]

A separate approach is "physiological" stimulation of the conduction system: either at the level of the His bundle or in the region of the left leg. This approach is closer to the natural propagation of the impulse along the conduction fibers and reduces the risk of synchrony disturbances. In new guidelines, it has been assigned recommendation classes in situations where a large proportion of ventricular stimulation is expected. [15]

Almost all new devices are "magnetic resonance imaging compatible" if protocol is followed. This means that examinations can be performed if the MRI team and cardiologists have agreed on the parameters and safety regimen. Previously, MRI was considered a contraindication; now, with proper preparation, the examinations are safe and informative. [16]

How does implantation occur and the first weeks?

Preparation includes an assessment of indications, analysis of comorbidities, selection of device type, and an access plan. Infection prophylaxis is often added, and the pocket location is selected based on body type and hand dominance. The patient is informed in advance about post-implantation care to ensure proper electrode placement. [17]

During the surgery, cardiac function is monitored and stimulation and sensitivity thresholds are immediately tested. If everything is stable, the wound is sutured with absorbable sutures, a bandage is applied, and the patient is transferred from the operating room after a few hours. In standard cases, discharge is possible the following day. [18]

During the first 1-2 weeks, it's important to protect the arm on the implanted side: avoid lifting it too high, avoid carrying heavy objects, and ensure proper dressing care. If any signs of infection (redness, pain, discharge, fever) occur, contact the clinic immediately—early treatment prevents serious complications. At the same time, the patient receives a "device passport" with the model and parameters. [19]

Next come scheduled checkups. Modern pacemakers transmit data via a home transmitter: the doctor can see the percentage of time the device stimulated, whether there were any arrhythmia episodes, and how the battery is performing. This saves visits and allows for prompt adjustments if the condition changes. [20]

Living with a Stimulator: Limitations, Compatibility, and Safety

Daily activity is usually relatively unrestricted: walking, swimming, cycling, and moderate exercise are all permitted. Strength training and contact sports are discussed individually to avoid damaging the pocket area. When traveling, it is important to carry the device passport and clinic contact information. [21]

Magnetic resonance imaging (MRI) has become easier: with compatible systems, examinations are performed according to an agreed-upon protocol under specialist supervision. This opens up access to comprehensive diagnostics of the brain, joints, and other organs without increased risk. [22]

Electromagnetic safety rules boil down to common sense: keep powerful magnets and industrial field sources at a distance, don't carry your smartphone in your breast pocket above the device, and don't linger near anti-theft devices in stores. Current recommendations replicate the "six-inch rule" for consumer electronics and accessories with magnets. If you work near sources of strong fields, consult with your doctor and occupational safety officials. [23]

Airports and security checks: metal detectors are safe to pass through without stopping, but it's best not to hold handheld scanners directly over your pocket—show the device's identification and inform the officer about the stimulator. Home appliances, induction cooktops, headphones, and speaker interference are generally safe if kept at a reasonable distance and avoid prolonged contact with magnets. [24]

Risks and how to reduce them

Like any procedure, implantation carries risks: bleeding, hematoma, electrode displacement, pneumothorax, and infection of the pocket or the entire system. Most complications are rare and well-managed with early treatment. Risk is reduced by careful planning, infection prevention, and careful implantation technique. [25]

Long-term risks include battery wear, electrode failure or increased stimulation threshold, and rare episodes of electromagnetic interference. In practice, these issues are addressed through routine checkups and remote monitoring, which highlights problems long before symptoms occur. [26]

If an infection is detected, complete removal of the system and subsequent reimplantation are sometimes required. In patients with a high risk of infection, problematic venous access, or previous complications, a caseless stimulator may be an alternative, as it reduces the number of potential weak points. [27]

If a significant proportion of stimulation of the right ventricle leads to deterioration of function, a transition to “physiological” stimulation of the conduction system or to resynchronization is considered - the decision is made individually at a consultation. [28]

New technologies and the near future

Dual-chamber, caseless systems have already been approved and are in use: mini-capsules in the atrium and ventricle exchange data, coordinating their operation without wires or pockets. This expands the indications for caseless technology and is particularly useful for people with problematic veins or a high risk of infection. Extended observational programs and the accumulation of real-world data are underway. [29]

Physiological pacing (His bundle and left bundle branch block) is rapidly becoming the new norm where a high proportion of ventricular pacing is expected: it is closer to natural myocardial activation and helps maintain synchrony. Guidelines have already formalized indications and selection algorithms. [30]

Remote monitoring has evolved from an "add-on" to a core component of monitoring: devices automatically transmit rhythm data, arrhythmia episodes, stimulation thresholds, and battery status to the doctor. This speeds up problem detection and allows for more precise adjustments to your activity and symptoms. [31]

Finally, the issue of compatibility with magnetic resonance imaging is practically resolved: if protocols are followed, even complex patient categories can be safely examined. For you, this means fewer compromises between treatment and high-quality diagnostics. [32]