A cardiac pacemaker is an electronic therapeutic device implanted in the body, which delivers electrical pulses powered by a battery through a pulse generator and stimulates the heart muscle contacted by the electrodes through the conduction of the wires, causing the heart to excite and contract, thus achieving the purpose of treating heart dysfunction due to certain cardiac arrhythmias. Since the first pacemaker was implanted in the human body in 1958, the pacemaker manufacturing technology and techniques have developed rapidly and their functions have become more and more perfect. While the application of pacemakers has successfully treated slow arrhythmias and saved the lives of thousands of patients, pacemakers have also begun to be applied to tachyarrhythmias and non-cardiac diseases, such as the prevention of paroxysmal atrial tachyarrhythmias, carotid sinus syncope, and biventricular synchronization for drug-refractory congestive heart failure.
Artificial cardiac pacing systems consist of two main components: the pulse generator and the electrode leads. The pulse generator is often referred to as the pacemaker alone. In addition to the above-mentioned pacing function, the pacing system also has a sensing function to transmit the heart’s own ECG activity back to the pulse generator.
The pacemaker consists mainly of a power source (i.e., a battery, nowadays mainly lithium-iodine batteries) and an electronic process that generates and outputs electrical pulses.
The electrode lead is a conductive metal wire wrapped with an insulating layer, whose function is to transmit the electrical impulses from the pacemaker to the heart and to transmit the intracavitary ECG from the heart to the pacemaker’s perception line.
Indications for permanent cardiac pacing
With the refinement of pacing engineering, the indications for pacing therapy have gradually expanded. In the early years, the main purpose of pacemaker implantation was to save the patient’s life, but now it also includes restoring the patient’s work capacity and quality of life. In 2012, the American College of Cardiology/American Heart Association/American Heart Rhythm Association reformulated guidelines for pacemaker implantation.
Rational choice of pacemaker
The choice of pacemaker for a specific patient is a question that clinicians often have to face. The principles are as follows.
1. In the presence of chronic persistent atrial fibrillation or in the presence of atrial stasis, choose VVI(R).
2. Choose AAI(R) if there is no AV block or if the predicted probability of near-term AV block is low in those with sinus node insufficiency; otherwise, choose DDD(R).
3.People with atrioventricular block such as:
① Presence of persistent atrial tachyarrhythmia, choose VVI(R);
②Sinus syndrome, choose DDD(R);
(iii) VDD or DDD for normal sinus node function or low probability of expected sinus node insufficiency.
Single ventricular pacing is no longer recommended, and dual-chamber pacing increases survival-corrected quality of life at a price that is generally considered acceptable. The choice between AAI or DDD pacing, although DDD is more expensive, should be considered in the context of the patient’s potential to develop atrioventricular block.
It is also important to consider the patient’s age, cardiac disease and co-morbidities, financial status, and overall general condition of the patient.
Artificial pacing system implantation methods
Temporary cardiac pacing
There are five methods: percutaneous pacing, transesophageal pacing, transthoracic puncture pacing, open-chest epicardial pacing, and transvenous pacing. At present, the latter is mostly chosen.
Temporary pacing leads are usually delivered by puncture through the femoral, subclavian or internal jugular veins. Displacement of the electrode leads is more common than with permanent pacing. Postoperative ECG monitoring should be intensified, including early increases in pacing threshold, changes in sensory sensitivity, and electrode lead dislocation, especially in pacemaker-dependent patients. In addition, since the electrode lead is connected to the outside world through the puncture point, care should be taken to avoid local cleanliness and infection, especially in those who have been placed for a long time. In addition, after temporary pacing via the femoral vein, the patient should remain in a flat position with the lower extremity on the side of the venous puncture restrained.
Permanent cardiac pacing
The majority of endocardial electrode leads are currently used. Technical points include vein selection, electrode fixation of the lead and pacemaker placement.
The veins that can be inserted with electrode leads are: superficial veins are cephalic veins and external jugular veins, deep veins are subclavian veins, axillary veins and internal jugular veins. Usually the cephalic vein or subclavian vein on the opposite side of the customary hand is preferred, and then the internal or external jugular vein is selected if it is unsuccessful.
2.Placement of the electrode leads is done according to the need to place the electrode leads into the heart chambers to be paced, usually with passive fixation, but also with active fixation of the electrode leads.
3.Pacemaker placement The pacemaker is usually buried under the skin of the chest on the same side of the electrode lead. The electrode lead is connected to the pulse generator, and the excess lead is placed in the subcutaneous pocket near the muscle surface and the pacemaker near the skin.
In brief, the method is that the electrode lead is inserted through a vein in the arm or below the clavicle and, under X-ray fluoroscopy, is inserted into the intended cardiac pacing position, secured and detected. A pacemaker connected to the electrode lead is then buried in the chest, the skin is sutured, and the procedure is completed.
Unlike other cardiac interventions, the successful implantation of a pacemaker is only a relatively simple first step, but the big but important task is the long-term follow-up of the patient after the procedure. The follow-up begins on the day of implantation and continues throughout the patient’s life.
After the operation, the patient is taught to take his or her own pulse, as pulse checks are an easy and effective way to monitor the work of the pacemaker. Make sure to monitor the pulse in the same physical state every day, e.g., when waking up early in the morning or after 15 mim of meditation.
In the early stages of pacemaker placement, the pacing threshold is often unstable and needs to be adjusted in time. Therefore, regular check-ups are required, usually every 2 weeks for 1 month and once a month for 3 months after the procedure (depending on the patient). In addition to the electrode position, sleep deprivation, full meals, anti-arrhythmic drugs, and high blood pressure may have an effect on the threshold. Therefore, postoperative patients should maintain a good mood, ensure a regular life and resting system, and avoid all possible adverse factors. The follow-up period and content of follow-up should be tight at both ends and loose in the middle.
Many patients are worried about the installation of pacemakers, but in fact, it is very safe. Although there are many pacemaker complications and failures, the overall incidence is only about 1%. In patients who are eligible for pacemaker implantation, the benefits far outweigh the disadvantages if they are treated regularly and followed up regularly.