12.2 Transvenous Temporary Pacemaker
Key Takeaways
- Symptomatic bradycardia in the cath lab is managed per ACLS: atropine 1 mg IV first (repeat to 3 mg max), then transcutaneous pacing, then transvenous pacing if refractory.
- Emergency transvenous pacing uses central venous access—right internal jugular preferred, also subclavian or femoral vein—with a balloon-tipped pacing wire advanced to the RV apex.
- Initial temporary pacing settings are typically demand (VVI) mode at 60–80 bpm with output 5–10 mA (or 2× capture threshold) and sensitivity 1–2 mV.
- Capture is confirmed when each pacing spike is followed by a widened QRS complex; failure to capture requires increasing output or repositioning the lead under fluoroscopy.
- Complications include ventricular perforation, tamponade, pneumothorax, infection, and lead dislodgement—monitor hemodynamics continuously during insertion.
12.2 Transvenous Temporary Pacemaker
Transvenous temporary pacing provides short-term electrical stimulation when the heart rate or AV conduction is inadequate to maintain perfusion. In the cardiac catheterization laboratory, temporary pacing is required during high-degree AV block complicating PCI, post-valvular or structural procedures, transcatheter aortic valve replacement (TAVR) when conduction injury occurs, electrophysiology studies, and symptomatic bradycardia refractory to pharmacotherapy. The RCIS prepares equipment, assists with sterile insertion, operates fluoroscopy, monitors rhythm and hemodynamics, and verifies capture—often under extreme time pressure.
Indications and ACLS Bradycardia Pathway
Temporary pacing is indicated when bradycardia causes hypotension, altered mental status, chest pain, heart failure, or shock. Common cath-lab triggers include:
- Complete heart block or Mobitz type II second-degree AV block during or after PCI.
- Sinus arrest or severe sinus bradycardia unresponsive to atropine, especially after inferior MI (right coronary artery occlusion affecting the SA/AV nodes).
- Post-procedural conduction delay after TAVR, alcohol septal ablation, or septal defect closure.
- Overdrive pacing for torsades de pointes or certain reentrant arrhythmias (operator-directed).
The ACLS symptomatic bradycardia algorithm governs initial management:
- Atropine 1 mg IV, repeatable every 3–5 minutes to a maximum of 3 mg total. Atropine blocks vagal tone at the AV node and SA node. It is ineffective in denervated transplanted hearts and may fail in high-degree block below the AV node.
- If atropine fails, initiate transcutaneous pacing (TCP) with adhesive pads while preparing transvenous access. TCP is painful; ensure sedation/analgesia when possible.
- Transvenous pacing if TCP is ineffective, not tolerated, or prolonged pacing is anticipated.
- Dopamine 5–20 mcg/kg/min or epinephrine 2–10 mcg/min infusions as chronotropic support while pacing is established.
The RCIS activates the pacing tray, notifies the operator immediately when symptomatic bradycardia persists after the first atropine dose, and prepares fluoroscopy before the pacing wire is inserted.
Equipment Preparation
The temporary pacing tray typically contains:
- Balloon-tipped pacing wire (e.g., 5–6 Fr bipolar catheter such as Medtronic 10646 or equivalent)—the balloon floats with blood flow from the RA across the tricuspid valve into the RV when inflated with 1.5 mL air (never fluid, which is not compressible).
- Percutaneous introducer sheath (6–7 Fr) for venous access.
- External pulse generator (temporary pacemaker box) with rate, output (mA), and sensitivity controls.
- Sterile cables connecting the pacing wire to the generator.
- Syringe for balloon inflation, hemostatic valves, and guidewire if needed.
Confirm the generator is charged and set to demand (VVI) mode before the wire is connected. Have backup transcutaneous pads applied and ready.
Venous Access and Lead Advancement
Temporary pacing requires central venous access. Preferred sites in the cath lab:
| Access Site | Advantages | Disadvantages |
|---|---|---|
| Right internal jugular (RIJ) | Short, straight path to RA/RV; lower risk of pneumothorax than subclavian; preferred in emergencies | Carotid puncture risk if ultrasound not used |
| Subclavian vein | Familiar to cath-lab staff; stable sheath position | Pneumothorax risk; may conflict with future permanent device on same side |
| Femoral vein | Easy access in supine patient; no pneumothorax risk | Longer lead path; lead motion with leg movement; infection risk with prolonged use |
Ultrasound-guided venous cannulation is strongly preferred to avoid arterial puncture and improve first-pass success.
Fluoroscopic Advancement Technique
- Insert the introducer sheath and advance the deflated pacing wire to ~20 cm.
- Inflate the balloon with 1.0–1.5 mL air once the tip clears the sheath in the RA.
- Advance under fluoroscopy in LAO projection while monitoring the balloon float from RA → tricuspid valve → RV apex.
- Deflate the balloon once the wire is positioned at the RV apex to prevent perforation.
- Connect the wire to the external generator and begin pacing.
The RCIS operates the C-arm, keeps the field sterile, and calls out when the wire enters the RV or loops in the RA (failure to cross the tricuspid valve).
Pacing Parameters and Capture Verification
Initial settings for emergency temporary pacing:
- Mode: VVI (demand)—paces the ventricle when the native rate falls below the set rate; avoids competition with native rhythm.
- Rate: 60–80 bpm (increase to 80–90 if hemodynamically unstable).
- Output: Start at 5–10 mA (or 2× the capture threshold once determined).
- Sensitivity: 1–2 mV (adjust so the generator senses native R-waves without undersensing).
Confirming Capture
Electrical capture is present when each pacing spike on the monitor is immediately followed by a paced QRS complex (wide, left bundle branch block morphology because the RV is paced from the apex). Mechanical capture is confirmed by palpation of a pulse matching the paced rate or by arterial line waveform at each paced beat.
If capture is lost:
- Increase output in 2–5 mA increments.
- Reposition the wire under fluoroscopy (withdraw slightly or advance to re-engage the endocardium).
- Check cable connections and generator battery.
Failure to capture with a properly positioned wire at maximum output suggests metabolic derangement (hyperkalemia, acidosis), perforation, or generator malfunction.
Sensing
Proper sensing prevents competitive pacing (pacing during the vulnerable period of the T-wave, which can trigger ventricular fibrillation). If the generator senses native R-waves, the pacing indicator on the generator flashes in sync with native beats and pacing is inhibited. Undersensing causes fixed-rate pacing regardless of native rhythm; oversensing causes inappropriate inhibition (T-waves or muscle artifact counted as R-waves).
Securing the Lead and Post-Insertion Care
Once capture is stable:
- Suture the pacing wire to the skin at the insertion site to prevent dislodgement.
- Apply a sterile occlusive dressing over the sheath hub.
- Document insertion site, wire depth, capture threshold, output setting, and rhythm.
- Obtain a chest X-ray to confirm RV position and exclude pneumothorax.
- Restrict patient movement on the access side; femoral sheaths require strict bedrest.
Temporary wires are removed when native conduction returns or a permanent device is implanted. Never pull a pacing wire without inactivating the generator and deflating any balloon.
Complications and Emergency Response
| Complication | Mechanism | RCIS Response |
|---|---|---|
| Ventricular perforation | Stiff wire or inflated balloon at RV free wall | Sudden hypotension, loss of capture, possible tamponade—notify operator, prepare echo and pericardiocentesis tray |
| Cardiac tamponade | Perforation with hemopericardium | Beck's triad, pulsus paradoxus—fluid resuscitation, emergent pericardiocentesis |
| Pneumothorax | Subclavian venous access | Desaturation, absent breath sounds—stat chest X-ray, notify physician |
| Lead dislodgement | Patient movement, unsecured wire | Loss of capture—reposition under fluoro, increase output temporarily |
| Infection | Prolonged femoral access | Fever, erythema at site—culture, antibiotics, consider wire removal |
| Arrhythmias during insertion | Wire irritation of RV | VT or PVCs—notify operator, have defibrillator ready |
Transcutaneous Versus Transvenous Pacing
Transcutaneous pacing is a bridge, not a long-term solution. Pads are placed in anterior-posterior or anterior-lateral configuration. Set the generator to asynchronous (VOO) or demand (VVI) at maximum comfortable output until capture is achieved (often requires 50–100 mA). Confirm mechanical capture with pulse palpation—electrical capture on the monitor may not produce effective cardiac contraction at low outputs.
Transvenous pacing provides reliable, lower-energy capture and is preferred when pacing will be needed for more than a few hours. The RCIS should never delay transvenous access when TCP fails in a hemodynamically unstable patient.
Special Cath-Lab Scenarios
- Post-TAVR conduction injury: New LBBB or AV block may require temporary pacing for 24–72 hours; have a pacing wire ready before balloon valvuloplasty or valve deployment in high-risk conduction profiles.
- Alcohol septal ablation: Transient RBBB is common; complete heart block may require temporary pacing—RCIS monitors rhythm continuously during ethanol injection.
- Inferior STEMI: AV nodal ischemia causes bradycardia—atropine and temporary pacing are frequently needed before or during PCI.
Transvenous temporary pacing is a lifesaving cath-lab skill. Preparation, fluoro proficiency, and rapid capture verification separate controlled support from preventable deterioration.
An RCIS prepares for emergency transvenous pacemaker insertion in the cath lab. Which access site and target chamber are standard for temporary pacing?
Which initial temporary pacemaker settings are most appropriate for a hemodynamically unstable patient with complete heart block in the cath lab?
During transvenous pacing wire advancement, the balloon tip should be deflated once the wire reaches the RV apex. What is the primary reason?