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Author(s): Sandeep Hothi and David Sprigings

Temporary cardiac pacing is the electrical stimulation of the heart to induce contraction. It can be achieved via several routes: transvenous, epicardial, transoesophageal and external (transcutaneous). This chapter describes temporary transvenous and external cardiac pacing.

Temporary Transvenous Cardiac Pacing!!navigator!!

Indications, contraindications and potential complications of temporary transvenous pacing are summarized in Table 119.1.

Preparation

  1. Confirm the indications for the procedure. Check there is no major contraindication to central vein cannulation. Decide on the route of venous access. Choose the femoral vein in preference to the internal jugular vein if the patient is haemodynamically unstable (especially if you have limited experience, as placement of the lead via the femoral vein is usually easier) or has received thrombolysis. Ensure that a defibrillator and other resuscitation equipment are to hand.
  2. Explain the procedure to the patient, and obtain consent, unless the situation precludes this. Check that the bed is suitable for X-ray screening and that the screening equipment can obtain satisfactory access to the patient.
  3. Connect an ECG monitor (making sure the leads are off the chest, so that they are not confused with the pacing lead when screening) and put in a peripheral venous cannula. Give supplemental oxygen via nasal cannulae or a mask, with continuous monitoring of oxygen saturation by oximetry. If sedation is needed, give midazolam 2 mg (1 mg in the elderly) IV over 30s, followed after 2 min by increments of 0.5–1 mg if needed (usual range 2.5–5 mg).
  4. Put on mask, gown and gloves. Prepare the skin with chlorhexidine or povidone-iodine and apply drapes to a wide area. Unpack the pacing lead and check that it will pass down the central venous catheter.

Cannulation of a central vein

  1. See Chapter 116 for a detailed description of central vein cannulation.

Placement of the lead (Figures 119.1 and 119.2)

  1. Advance the lead into the right atrium and direct it towards the apex of the right ventricle (just medial to the lateral border of the cardiac silhouette): it may cross the tricuspid valve easily.
  2. If you have difficulty, form a loop of lead in the right atrium. With slight rotation and advancement of the lead, the loop should prolapse across the tricuspid valve.
  3. Manipulate the lead so that the tip curves downwards at the apex of the right ventricle and lies in a gentle S-shape within the right atrium and ventricle. Displacement of the lead may occur if there is too much or not enough slack.
  4. Ask your assistant to attach the terminal pins of the pacing lead to the connecting lead and pacing box.

Checking the threshold

  1. Set the box to ‘demand’ mode, with a pacing rate faster than the intrinsic heart rate. Set the output at 3V. This should result in a paced rhythm. If it does not, you need to find a better position. Before moving from a position that may have taken a long while to achieve, make sure the problem is not due to loose contacts: check these are all secure.
  2. Progressively reduce the output until there is failure to capture: the heart rate drops abruptly and pacing spikes are seen but not followed by paced beats. A threshold of <1V is ideal. A threshold a little above this is acceptable if the lead position is stable.
  3. Check the stability of the lead position. Set the box at a rate faster than the intrinsic heart rate, with an output of 1V (or just above threshold). Ask the patient to cough forcefully and breathe deeply. Watch the monitor for loss of capture.

Final points

  1. Set the output at more than three times the threshold or 3V, whichever is higher. Set the mode to ‘demand’. If the patient is now in sinus rhythm at a rate of >50/min, set a back-up rate of 50/min. If there is atrioventricular block or bradycardia, set at 70–80/min (90–100/min if there is cardiogenic shock).
  2. Remove the insertion sheath, with screening of the lead and counter-advancement if needed to prevent displacement. If the sheath has a haemostatic valve, it can be left in place.
  3. Suture the lead (or sheath if left in place) to the skin close to the point of insertion and cover it with a dressing. The rest of the lead should be looped and also sutured to the skin. An air and water occlusive dressing is then applied over the entry site to the skin.
  4. Clear up and dispose of sharps safely. Arrange a chest X-ray to confirm satisfactory lead position and exclude a pneumothorax.
  5. Document the procedure including: indications/access/threshold/final pacemaker box settings/any complications/post-procedure chest X-ray findings/plan of management.
  6. Establish continuous ECG monitoring. RV apical pacing should result in QRS complexes of left bundle branch block morphology with superior axis (positive in leads I and aVL).

Aftercare

  1. Check the pacing threshold daily. The threshold usually rises to 2–3 times its initial value over the first few days after insertion because of endocardial oedema. The commonest reason for failure to capture and/or sense after the procedure is lead displacement.
  2. If infection related to the lead is suspected, see p. 664.

Troubleshooting

The pacing lead cannot be advanced into the heart

This can happen if you have cannulated the carotid artery rather than the internal jugular vein: the pacing lead bounces off the aortic valve. Ask advice from a senior colleague or cardiologist. If inadvertent arterial cannulation is confirmed, withdraw the lead and sheath and apply pressure over the vessel to achieve haemostasis.

A pacing lead placed via the femoral vein will usually pass easily up the iliac veins and inferior vena cava, with a little manipulation, but may keep diving into other veins. Reducing the curve on the end of the lead may make this less likely to happen.

Tachyarrhythmias

Ventricular extrasystoles and non-sustained ventricular tachycardia are common as the lead crosses the tricuspid valve and do not require treatment. If there is sustained ventricular tachycardia, withdraw the pacing lead and it will usually terminate.

Ventricular fibrillation may occur with manipulation of the lead in the right ventricle, especially in patients with acute coronary syndromes, and requires defibrillation and other standard measures.

If ventricular tachycardia recurs after placement, check that the position of the lead is still satisfactory and that excess slack has not formed in the area of the tricuspid valve.

Failure to capture

Causes include:

  • Contacts not secure: check these.
  • Pacing lead not in right ventricle: it may be in the right atrium, in the coronary sinus (a lead in the coronary sinus points towards the left shoulder) or in the splenic vein (with femoral vein access). Ask advice from a senior colleague or cardiologist.
  • Pacing lead has perforated the right ventricle. This may cause pericardial chest pain and diaphragmatic pacing at low output (3V or less). Withdraw the lead and reposition it. Be aware that cardiac tamponade may occur following cardiac perforation but is rare.

External Cardiac Pacing!!navigator!!

Indications are as for transvenous pacing. Consider sedation if the patient is awake as the procedure is uncomfortable: it is therefore more appropriate as a backup prior to transvenous or permanent pacing.

Further Reading ⬆

The Task Force on cardiac pacing and resynchronization therapy of the European Society of Cardiology (ESC) (2013) 2013 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy. European Heart Journal 34, 2281–2329.