🫀 Temporary Cardiac Pacing in Perioperative Care: TCP and TTVP for Unstable Bradycardia

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♦️ Introduction

In perioperative settings, bradyarrhythmias can arise suddenly during anesthetic induction or at any point intraoperatively. These events require prompt action, as bradycardia can quickly compromise hemodynamics.

Consider a scenario during emergency surgery in which a patient’s heart rate abruptly falls into the 30s and does not respond to atropine. In this situation, where bradycardia is hemodynamically unstable, external pacing is the fastest intervention. Immediate CPR may also be required. External pacing—which includes transcutaneous pacing (TCP) and temporary transvenous pacing (TTVP)—serves as essential bridge therapy until a permanent pacemaker can be placed, when indicated.

Observational studies show that a subset of patients with symptomatic bradycardia go on to require TTVP, although reported rates vary widely depending on patient characteristics and institutional practices. These patients represent a high-risk population with increased mortality and complication rates, and TTVP is considered the minimal necessary bridge until permanent pacemaker implantation.

This article offers a concise, exam-focused overview suited for anesthesiology board preparation in the US, Europe, and internationally. It covers classification of external pacing methods, indications, procedural steps, capture verification, threshold management, troubleshooting, and complication recognition.

♦️ Classification of External Pacing Modalities

🔷 Transcutaneous Pacing (TCP)

Transcutaneous pacing (TCP) is a non-invasive method that delivers electrical stimulation to the heart through electrode pads placed on the chest wall, though the stimulation itself can be painful. It requires no special procedural steps or sterile preparation and can be started within minutes, making it the first-line option in emergencies.

TCP is difficult to maintain for long durations, and pain and skin irritation must be considered. Each pacing stimulus typically causes noticeable chest wall muscle contractions. Its key advantage is speed, and it serves as bridge therapy until transition to TTVP or permanent pacemaker implantation. Because skeletal muscle contraction causes significant discomfort, prolonged use without sedation and analgesia is generally impractical.

🔷 Temporary Transvenous Pacing (TTVP)

Temporary transvenous pacing (TTVP) is an invasive method in which a pacing lead inserted through a central vein—most often via internal jugular vein puncture—is positioned directly in the right ventricle. Compared with TCP, TTVP provides stable capture and can be used for several days to weeks.

TTVP requires venous access and fluoroscopic placement, so it cannot be initiated as rapidly as TCP. However, its low, stable threshold allows comfortable pacing even in conscious patients. It is commonly used while waiting for permanent pacemaker implantation or during recovery from transient conduction disturbances.

🔷 Epicardial Pacing

Epicardial pacing uses wires sutured directly to the epicardium during cardiac surgery. It is common in postoperative management of open-heart surgery patients and carries lower infection and thrombosis risk because the wires do not contact blood directly.

Threshold checks are performed regularly in the early postoperative period. The wires are typically removed once intrinsic rhythm stabilizes, though bleeding or cardiac tamponade may occur during removal. Persistent conduction disturbances may require permanent pacemaker placement.

♦️ Indications—Defining Hemodynamic Instability

Understanding indications for external pacing requires recognizing hemodynamically unstable bradycardia. This clinical decision is central to the ACLS bradycardia algorithm.

🔷 Definition of Unstable Bradycardia

Unstable bradycardia refers to impaired organ perfusion caused by bradycardia, presenting harmful symptoms or signs. AHA guidelines emphasize the presence or absence of organ hypoperfusion in determining whether bradycardia is symptomatic, rather than the absolute heart rate value. Earlier guidelines specified HR <50/min, but current practice focuses on clinical manifestations.

Symptoms include dizziness, lightheadedness, altered mental status, ischemic chest discomfort, acute heart failure, hypotension, and syncope. Clinicians must also determine whether bradycardia is the primary cause or a consequence of other conditions (ischemia, hypoxia, electrolyte imbalance, acidosis, hypothermia).

If altered consciousness, chest pain, acute heart failure, or shock signs are present, intervention may be necessary even at slightly higher heart rates.

🔷 Judgment When Atropine is Ineffective

Atropine is first-line medication for bradycardia, but it is often ineffective in high-degree AV block or sick sinus syndrome. When atropine fails to improve hemodynamics, pacing should be initiated promptly. International guidelines reinforce the need for early pacing in symptomatic bradycardia unresponsive to medication.

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♦️ TCP Procedure and Settings

TCP is the fastest method in emergencies, so understanding its steps is essential.

🔷 Pad Placement

Pads may be placed in anterior–posterior (AP) or anterior–lateral (AL) positions. AP placement is associated with lower capture thresholds.

• AP: Anterior pad at left sternal border; posterior pad below left scapula.
• AL: Easier in supine patients but generally requires higher current.

🔷 Rate and Current Settings

Pacing rate is set first, typically 60–80/min. Current is started low and increased until capture occurs.

Once capture is confirmed, output is set at 1.5–2× the capture threshold. Excessively high output increases pain and burn risk.

🔷 Capture Verification

• Electrical capture: Wide QRS after pacing spike, often with ST–T changes.
• Mechanical capture: Confirm via arterial pulse, pulse oximetry waveform, arterial pressure, or improved perfusion.

Both must be present to consider pacing successful.

♦️ Sedation and Analgesia for TCP

TCP stimulates both myocardium and chest wall skeletal muscles, making it uncomfortable for conscious patients. Sedation and analgesia are therefore important.

🔷 Why TCP Causes Significant Pain

Electrical current activates chest wall muscles, causing repeated contractions and persistent discomfort. Pain may worsen hemodynamics through sympathetic activation.

🔷 Sedation and Opioid Combination

For pain management during TCP, benzodiazepine sedatives such as midazolam are often used. Opioids may also be used, but this should be carefully considered depending on the patient’s condition. Sedation should balance comfort with hemodynamic and airway safety. In emergencies, pacing stabilization takes priority, followed by sedation adjustments. In the operating room, anesthesia often covers analgesic needs. Prolonged TCP or transition to TTVP may require deeper sedation.

Recent emergency medicine reviews emphasize that transcutaneous pacing should almost always be paired with appropriate analgesia and sedation in conscious patients, whenever the clinical situation allows. Tailoring the regimen to each patient’s hemodynamic status and airway risk can significantly improve tolerance without compromising safety.

♦️ TTVP—Technique and Access

TTVP provides stable long-term pacing and is typically what clinicians mean by “temporary pacing.”

🔷 Vascular Access

The right internal jugular vein is most commonly used and recommended because of its straight path to the right ventricle.

Subclavian and femoral routes are alternatives but have higher risks or lower stability.

🔷 Lead Advancement and Positioning

Leads are advanced to the right ventricular apex, ideally under fluoroscopy. In emergencies, ECG guidance is used. Contact with the myocardium appears as ST elevation.

Stable capture at low threshold indicates correct positioning. Leads must be secured and thresholds checked regularly.

🔷 Initial Settings

Settings include pacing rate, output, and sensitivity.

Sensitivity uses an inverse scale:

🔷 Understanding Demand Pacing

Demand pacing inhibits output when intrinsic beats are sensed, preventing competition and reducing risk of dangerous arrhythmias such as ventricular fibrillation.

♦️ Pacing Modes—Understanding the NBG Code

🔗 Pacemakers 101 for Residents & Perioperative Staff

🔷 Three-Letter Code Basics

• 1st letter: chamber paced (V/A/D)
• 2nd letter: chamber sensed
• 3rd letter: response to sensing (I/T/D/O)

🔷 Major Pacing Modes

• VOO: Fixed-rate ventricular pacing without sensing; useful during EMI or sensing failure.
• VVI: Ventricular demand pacing; most common temporary mode.
• DDD: Paces/senses both atrium and ventricle; physiologic but requires two leads.

♦️ Troubleshooting—Failure to Capture and Sensing Issues

🔷 Causes of Capture Failure

Thresholds can change from patient condition, electrolytes, hypoxemia, medications, or even posture. Regular threshold checks and maintaining 1.5–2× safety margin are fundamental.

🔷 Sensing Abnormalities

🔷 Management

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♦️ Complications and Limitations

🔷 TCP Complications

Skin burns are the most serious risk, especially with prolonged high-output pacing. Severe cases can reach third-degree burns. Skin should be checked every 30 minutes; transition to TTVP should be early. Pain, motion artifacts, incomplete capture, and psychological distress may also occur.

🔷 TTVP Complications

Large database analysis reports cardiac tamponade incidence of approximately 0.6%, pneumothorax approximately 0.9%, and bleeding approximately 2.4%. Additional issues include hematoma, arterial puncture, ventricular arrhythmias, infection, and thrombosis. Infection risk increases with duration, so removal should be timely.

Large registry studies suggest that serious complications from temporary transvenous pacing are relatively uncommon overall, but their impact can be substantial when they occur. These analyses highlight that procedural experience, careful imaging guidance, and standardized protocols are key factors in keeping complication rates low across institutions.

🔷 Electromagnetic Interference

External pacemakers may malfunction near EMI sources. MRI is contraindicated. Electrocautery use may require mode changes (e.g., asynchronous pacing).

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📝 Summary: Take Home Messages

External pacing is essential bridge therapy for hemodynamically unstable bradycardia. A solid understanding of capture verification, troubleshooting, and complication management is important for both specialist examinations and clinical practice.

🔑 Key Points

🔗 Related articles

📚 References & Further reading

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