Temporary pacing: technique, indications and complications
THE CONTEXT
Temporary pacing delivers an electrical impulse to initiate cardiac tissue depolarisation and trigger contraction. It can be delivered through an intracardiac electrode or through the skin.
Transvenous technique and ECG
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A bipolar electrode is introduced through the internal jugular, subclavian or femoral vein and usually positioned at the right ventricular (RV) apex under fluoroscopic imaging.
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The electrode connects to an external pacemaker with adjustable energy output and pacing rate.
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Right ventricular pacing produces regular broad QRS complexes with a left bundle branch block pattern, each immediately preceded by a pacing spike.
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The pacemaker operates only when the heart rate falls below a preset level. Temporary atrial or dual-chamber pacing is occasionally used.
Indications
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Temporary pacing is used for transient atrioventricular (AV) block and other arrhythmias complicating acute myocardial infarction (MI) or cardiac surgery.
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It can maintain rhythm during reversible bradycardia caused by metabolic disturbance or drug overdose, and can serve as a bridge to permanent pacing.
Complications and failure
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Complications include pneumothorax, cardiac tamponade, brachial plexus or subclavian artery injury, pericarditis, and local infection or sepsis, usually involving Staphylococcus aureus.
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Pacing failure may result from lead displacement or a progressive rise in threshold caused by tissue oedema, termed exit block.
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Complication rates increase with time, so a temporary pacing system should ideally be used for no more than 7 days.
Transcutaneous pacing
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Two large adhesive gel pad electrodes are placed over the apex and upper right sternal border, or over the anterior and posterior chest.
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Transcutaneous pacing is quick and easy to establish but causes discomfort through forceful pectoral and intercostal muscle contraction.
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Modern external defibrillators often incorporate transcutaneous pacing, which can be used until transvenous pacing is established.