Inserting temporary pacemakers

What are temporary pacemakers?

Temporary cardiac pacing provides electrical stimulation to a heart that is compromised by disturbances in the conduction system, resulting in haemodynamic instability.

A temporary pacemaker to treat a bradydysrhythmia is used when the condition is temporary and when a permanent pacemaker is either not necessary or is not immediately available.

Temporary transvenous pacing

• Temporary transvenous pacing involves two components - obtaining central venous access and intracardiac placement of the pacing wire.

• The preferred route of access for temporary transvenous pacing is a percutaneous approach of the subclavian vein, the cephalic vein or, rarely, the axillary vein, the internal jugular vein or the femoral vein.¹

• Although right- or left-sided veins can be used, the right side is traditionally preferred as it is technically easier, and the left side is usually reserved for permanent systems.²

• The use of antibiotics should be considered for all wire insertions.³ Fluoroscopy is the preferred imaging technique but this is often not available, so ultrasound is an acceptable alternative.²

Complications of temporary pacing¹

A 2022 paper suggested that complications were more likely to be related to the length of hospital stay (such as urinary tract infection and pneumonia) rather than complications associated with device insertion.⁴

• An American review suggested a maximum complication rate of 12.6% with considerable variation between studies. Complication rates have certainly improved over time due to technological improvement and increasing operator experience. The most frequent complications are failure to secure venous access, failure to place the lead correctly, infection, thromboembolism, puncture of arteries, lung or myocardium, and life-threatening arrhythmias.

• A 2021 Japanese series found an adverse event rate of 35%.⁵

• In one review, 2-18% of patients developed sepsis after temporary pacemaker insertion. Consensus guidelines recommend that temporary pacemaker insertion should be avoided if there is a high probability that permanent pacing will eventually be required.⁶

• Temporary pacemakers must be checked by competent staff at least once daily for pacing thresholds, evidence of infections around venous access sites, integrity of connections, and battery status of the external generator.

• The underlying rhythm should also be assessed and recorded at these checks.

Indications for temporary transvenous cardiac pacing

All the indications for permanent pacing are also suitable for temporary pacing. They include:⁷

• Emergency or acute:
  

  • Acute myocardial infarction with:
    

    • Asystole.

    • Symptomatic bradycardia (sinus bradycardia with hypotension and type I second-degree atrioventricular (AV) block with hypotension not responsive to atropine).

    • Bilateral bundle branch block (BBB).

    • New or indeterminate-age bifascicular block with first-degree AV block.

    • Third-degree AV block.

  • Bradycardia not associated with acute myocardial infarction:
    

    • Asystole.

    • Second-degree or third-degree AV block with haemodynamic compromise or syncope at rest.

    • Ventricular tachyarrhythmias secondary to bradycardia.

• Elective:
  

  • Support for procedures that may promote bradycardia.

  • General anaesthesia with:
    

    • Second-degree or third-degree AV block.

    • Intermittent AV block.

    • First-degree AV block with bifascicular block.⁸

    • First-degree AV block and left bundle branch block (LBBB).

  • Cardiac surgery:
    

    • Aortic surgery.

    • Tricuspid surgery.

    • Ventricular septal defect closure.

    • Ostium primum repair.

  • Rarely considered for coronary angioplasty (usually to the right coronary artery) but may be required for angioplasty-induced bradycardia.⁹

• Overdrive suppression of tachyarrhythmias.

Inserting pacing wire

Temporary pacing wires should only be inserted by experienced practitioners. There is evidence that specialist practitioners have a much lower rate of complications than trainees and generalists.¹⁰

• Preparation:
  

  • Ensure that a defibrillator and other resuscitation equipment are immediately accessible.

  • The procedure requires strict aseptic technique, using a mask, gown and gloves.

  • ECG monitoring is required but the ECG leads should be off the chest.

• Cannulate the appropriate vein, using Seldinger's technique of guidewire and dilators to place a sheath of the correct size to allow passage of the pacing wire. Femoral or subclavian veins are often used but the median cubital vein has also been suggested as a safe alternative route.¹¹

• Mould the tip of the electrode to give a 20-30° curve for correct positioning in the heart.

• Advance the electrode under ultrasound or fluoroscopic guidance until it lies vertically in the right atrium with its tip pointing towards the free wall on the right side.

• Rotate the wire between the index finger and thumb such that it points towards the patient's left side; advance the wire steadily through the tricuspid valve and along the floor of the right ventricle to the apex.

• Common problems:
  

  • The wire does not cross the tricuspid valve: continue advancing the wire into the right atrium until it catches on the wall and forms a large loop. If it passes into the inferior vena cava or superior vena cava, pull back and push forward again until it does catch. With a large loop in place, rotate the wire until its tip flips through into the ventricle.

  • A wire appears to be in correct position but will not capture ventricle at acceptable output: fluoroscopy shows electrode tip is directed upwards towards the left shoulder and directed posteriorly rather than anteriorly.

  • Cannot obtain satisfactory pacing; withdraw the wire into the right atrium and repeat the attempt to cross the tricuspid valve.

  • Difficulty in positioning the wire at the apex of the right ventricle: pass the tip of the wire into the right ventricular outflow tract and gently withdraw while rotating between the index finger and thumb. When the tip is at a downwards angle, advance towards the apex.

Setting the pacemaker¹²¹³

• Set to 70/min or 10/min above the patient's ventricular rate.

• Set a pulse of 3 V (or follow the manufacturer's instructions); at this voltage, should capture ventricle so that each pacing spike is followed by a QRS complex. Determine the voltage threshold by gradually turning down the voltage until capture is lost (usually 0.7-1.0 V) and usually set the pacemaker to deliver a pulse of at least twice threshold.

• Check sensing by setting the pacemaker rate at 10-20/min <spontaneous ventricular rate and check ECG and pulse generator for pacing inhibition.

• Normally set sensitivity to maximum.

• Common problems:
  

  • No spikes seen and no output: usually due to failure of the battery or generator or a loose connection. Otherwise, oversensing is cured by reducing sensitivity or going to fixed rate pacing.

  • Spikes seen but no capture: often a loose connection but may be due to exit block causing a high threshold. Check the position of the pacing wire and consider repositioning.

Finishing off

• With the pacing wire positioned correctly and pacing established, remove the introducer sheath carefully.

• Suture the wire to the skin close to the point of insertion and cover with a dressing.

• Arrange a CXR to confirm a satisfactory position of the wire and to exclude a pneumothorax.

External pacemakers¹⁴

An external cardiac pacemaker is a medical device with electrodes that regulates myocardial contractility to maintain adequate heart rate and cardiac output. This emergency treatment is life-saving, but it cannot be relied upon for an extended period of time. A permanent method should replace this temporary bridge as soon as possible to maintain hemodynamic stability.

Pacing pads are placed on the patient's chest in either anterolateral or anteroposterior position. Many other different pacer pad placements are equally effective. The rate should be set between 60 to 90 beats per minute with the electrical output, (or 'the current'), set to its lowest setting. The rate should slowly increase until a pacer spike is seen on the monitor. The rate should gradually be increased until a QRS complex follows each spike which indicates electrical capture. Feeling for a pulse will confirm there is an output or this can also be confirmed by using ultrasound to observe ventricular contraction. This method of cardiac pacing is uncomfortable so a conscious patient will appreciate some sedation.