Classification
Cardiac pacing is subdivided into several types depending on the duration of use and the chosen surgical approach.
By duration, the following are distinguished:
- Permanent pacing;
- Temporary pacing.
By surgical approach, they are distinguished:
- Myocardial (epicardial);
- Endocardial.
Myocardial pacing technique
The surgery requires an open approach. The patient is placed supine with the left side elevated. A left-sided anterior thoracotomy is performed in the 4th–5th intercostal space. The pericardium is opened with a longitudinal incision 8–10 cm long.
Stages of electrode implantation:
- Site selection: An area of the myocardium free of blood vessels and adipose tissue is found on the anterolateral surface of the left ventricle.
- Insertion: The myocardial wall is sutured using a spring-coil electrode with an atraumatic needle.
- Immersion: Pulling on the thread, the coiled end is immersed into the thickness of the myocardium.
- Fixation: A silicone rubber clamp is sutured to the myocardium with two ligatures.
- Removal of the guidewire: The plastic thread with the needle is extracted.
- Pair installation: Two electrodes are implanted at a distance of 1.5–2.0 cm from each other.
- Testing: Trial pacing is performed.
Completion of surgery: The electrodes are secured to the pericardium with interrupted nodal sutures and brought out of the pleural cavity through the 3rd–4th intercostal space. Then they are fixed to the pacemaker (PM) with slip-on Teflon nuts. A pocket is formed by blunt dissection within the thickness of the pectoralis major muscle. The pacemaker is placed between the electrodes to avoid tension of the sutures on the soft tissues. The surgery ends with drainage of the pleural cavity and wound closure.
Endocardial pacing
The procedure is performed under local anesthesia using fluoroscopic and ECG guidance. Access is achieved with a puncture needle via the external jugular, subclavian, or brachial vein.
Procedure specifics: Inside the coil electrode, there is a metallic stylet that dictates the shape and direction. The probe-electrode is introduced into the cavity of the right ventricle, passed through the tricuspid valve, and advanced 6–10 cm until firm contact with the endocardium of the apex is achieved.
Criteria for correct placement:
- Upward displacement of the ST segment on the intracavitary ECG.
- Pacing threshold: 2 ± 0.5 mA.
After placement, the puncture needle is removed, and the peripheral end is secured with a ligature.
- In temporary pacing (monopolar), the anode is inserted subcutaneously on the anterior chest wall. Its location must be changed every 2–3 days.
- In permanent pacing, the device itself is implanted into the subclavian fossa.
Briefly: answers to topical questions
What types of cardiac pacing are there?
Cardiac pacing is classified according to two criteria:
- By duration: permanent and temporary.
- By approach: myocardial (epicardial) and endocardial.
Which tissue layers are dissected layer by layer during a left-sided anterior thoracotomy?
During a lateral thoracotomy, the skin, parts of the pectoralis major and serratus anterior muscles, as well as the intercostal muscles, fascia, and pleura are dissected. The serratus anterior and pectoralis major muscles are dissected partially; the edge of the latissimus dorsi and the scapula are retracted posteriorly.
What anatomical landmarks are used for subclavian vein puncture?
Landmarks within the projection of the clavipectoral triangle (trigonum clavipectorale) are used for puncture and catheterization of the subclavian vein. The main anatomical landmarks are:
- Clavicle — referenced by its midpoint.
- Puncture site — located 1 cm medial to the midpoint of the clavicle.
Access to the vein can be achieved from a supraclavicular or infraclavicular point. Puncture is possible due to the constant patency of the vein lumen, as its walls are firmly fixed to the fascial sheath of the subclavius muscle and neck fascia.
What intraoperative complications are possible when advancing an endocardial electrode into the right ventricle?
The following complications are possible when advancing an endocardial electrode into the right ventricle:
- Life-threatening arrhythmias — usually associated with electrode instability or its position in the right ventricle.
- Perforation and death.
- Loss of capture (loss of capture) — 10–37%.
- Venous thrombosis and pulmonary embolism — with the femoral approach, their incidence is 18–85% and 50–60%, respectively.
Fluoroscopy is recommended to reduce risks.
Mnemonic for veins in the endocardial approach: "External Girlfriend Cries" (External jugular, Subclavian, Brachial veins).
Class and exam questions
What criteria confirm the correct placement of the endocardial lead?
Upward displacement of the ST segment on the intracavitary ECG and a pacing threshold equal to 2 ± 0.5 mA.
Where is the pacemaker pocket formed during the myocardial approach?
The pocket is created by blunt dissection within the thickness of the pectoralis major muscle. The device is placed between the electrodes.
What should the distance be between two myocardial leads?
The electrodes are implanted at a strictly distance of 1.5–2.0 cm from each other.
What else to study on this topic
- Topographic anatomy of the pectoralis major muscle (formation of the pocket)
- Surgical anatomy of the external jugular, subclavian, and brachial veins
- Specifics of interpreting the intracavitary ECG
- Rules for pleural cavity drainage after thoracotomy
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