Procedure

Indications and positioning of temporary pacing wires

Department of Cardiothoracic Surgery, John Radcliffe Hospital, Oxford, UK

^* Corresponding author: ^* Professor of Cardiovascular Surgery (University of Oxford), Consultant Cardiac Surgeon, Department of Cardiothoracic Surgery, John Radcliffe Hospital, Oxford, OX3 9DU, UK. Tel.: +44-1865-221121; fax: +44-1865-220244. E-mail: david.taggart@orh.nhs.uk

	Summary

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Atrial and/or ventricular pacing wires are frequently inserted at the end of a cardiac surgical procedure. Their main use is to improve haemodynamic function in the presence of arrhythmias as well as to suppress atrial and ventricular tachyarrhythmias. Their use is generally safe and simple, but infrequent, and rarely catastrophic, complications have been reported.

Key Words: Atrial pacing • Epicardial pacing • Pacing wires • Ventricular pacing

	Introduction

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Temporary epicardial pacing wires have been routinely employed in cardiac surgery since 1960 for therapeutic as well as diagnostic purposes [1]. The pacing electrodes are implanted during surgery and are used for atrial or ventricular, as well as atrioventricular pacing in the post-operative period. They can be also used for suppressing both atrial and ventricular tachyarrhythmias [2].

Indications for temporary epicardial pacing
The main indication for insertion of epicardial pacing wires is perioperative arrhythmias that may result in significant haemodynamic compromise. In the presence of epicardial pacing wires ventricular and/or atrial pacing can be readily commenced in the operating room as well as in the cardiac ITU to optimise cardiac function by maintaining an adequate heart rate and, therefore, augmenting cardiac output. The most important arrhythmias necessitating pacing include bradycardia, nodal or junctional arrhythmias and atrioventricular block. Many surgeons choose to insert ventricular or atrial and ventricular pacing wires routinely at the conclusion of cardiopulmonary bypass. Others only insert temporary pacing wires in patients with significant pre- and peri-operative arrhythmias that may be at risk of post-operative rhythm disturbances and resulting haemodynamic compromise. Insertion of pacing wires can be especially helpful in patients undergoing open cardiac procedures or after surgery for congenital heart disease where the incidence of arrhythmias and heart block is significantly increased [3]. Patients with myocardial impairment may benefit from the atrioventricular synchrony that pacing provides [4,5].

A recent study reported the infrequent use of temporary epicardial pacing following routine coronary artery bypass grafting. Multivariate analysis identified three risk factors that were significantly associated with pacing: previous history of arrhythmia, pacing required to come off CPB and diabetes mellitus [6]. Puskas and colleagues suggested that routine use of pacing wires following CABG may be unnecessary and that the need for pacing prior to chest closure identifies those who are likely to need postoperative pacing [7]. They also suggest that off-pump coronary surgery may be associated with a lesser requirement for temporary epicardial pacing wire insertion.

	Surgical technique

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At the end of the cardiac procedure being performed and with the heart exposed atrial and/or ventricular pacing wires are placed.

Insertion of atrial pacing wires
Atrial pacing wires are sutured to the right atrial appendage or the body of the right atrium (Video 1).

Click on image to view video Video 1 Insertion of atrial pacing wires. Two pacing wires are sutured onto the right atrial appendage using the attached needle. The wires are passed percutaneously to the right of the midline and secured.

Insertion of ventricular pacing wires
Ventricular pacing wires are placed on the anterior or diaphragmatic surface of the right ventricle. Wires should be inserted into the bare muscular portion of the ventricle to ensure adequate myocardial contact (Video 2).

Click on image to view video Video 2 Insertion of ventricular pacing wires. The distal ends of the pacing wires are passed percutaneously to the left of the midline. Pacing wires (MMCTSLink 96) are inserted into the bare muscular portion of the anterior surface of the right ventricle using the attached needle.

View larger version (82K): [in this window] [in a new window]   Photo 1 Insertion of right ventricular pacing wires.

The position of the left ventricular lead has an important effect on biventricular pacing in patients with heart failure and left bundle brunch block [9]. The midlateral region of the left ventricular wall is thought to be the most effective position to obtain the best haemodynamic effect with pacing. However, Dekker and colleagues, using a temporary epicardial electrode for biventricular pacing at various sites on the left ventricle, argued that the optimal left ventricle epicardial pace site varies widely among patients with a failing heart in whom biventricular stimulation is attempted [9]. It is generally accepted that in patients with heart failure, the left ventricular lead should be placed in the midlateral or posterior wall of the left ventriclar wall as this may provide early excitation in the region with greatest baseline delay in activation in addition to limiting mitral regurgitation by prestimulating the papillary muscle [10,11].

It must be noted that in patients undergoing CABG, special attention should be paid to the site of lead placement — behind rather than in front of saphenous vein grafts — to avoid the potential complications relating to graft compression and/or injury.

While unipolar pacing wires are most frequently used, bipolar wires are also available and are thought to have better pacing and sensing functions compared to unipolar leads. Insertion of the former may be less time consuming as only one lead is inserted instead of two. However, in practice, choice is generally dictated by the surgeon's preference, cost and availability.

For pacing patients with peri-operative bradycardia, the rate is usually set to 70–90 bpm. The threshold is checked following insertion and the output is set a few mA higher than the trigger threshold. This should be repeated at regular intervals to ensure satisfactory pacing until removal of pacing wires to avoid loss of capture that may result from the increase in pacing threshold that occurs in the post-operative period.

Removal of pacing wires
Pacing wires are usually removed on the fourth postoperative day. If longer term pacing is required, consideration should be given to permanent pacemaker insertion. Prior to removal, a coagulation screen should be checked. Wires are removed with gentle transcutaneous retraction. Some surgeons choose to divide the atrial wires flush with the skin and allowing them to retract owing to the potential for tearing and subsequent haemorrhage from a thin-walled right atrium following forceful retraction. The patient's vital signs should be monitored following wire removal to allow early identification of the rare but well-documented potential complications.

	Complications

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Infrequent but serious complications have been described in association with temporary epicardial pacing wires use. Rare catastrophic complications have also been reported.

Complications associated with insertion
Bleeding from the site of insertion can occur necessitating insertion of additional sutures.

Complications during use
There is an increase in atrial and ventricular threshold when pacing is continued beyond a few days postoperatively. Their function has been shown to deteriorate on a daily basis [12]. This may lead to failed sensing or capture. Dislodgement and fracture of pacing wires can also occur and infection may complicate prolonged use. Atrial and ventricular pacing wires could also cause phrenic nerve irritation and diaphragmatic stimulation and careful choice of the site of pacing wire insertion should limit these problems.

Complications associated with wire removal
Patients are at risk of ventricular arrhythmias during epicardial pacing wire removal necessitating electrocardiographic monitoring [13]. More important but rarer complications include haemorrhage and tamponade from atrial and ventricular lacerations [14], injuries to saphenous vein grafts [15], retained wire and bronchial foreign body [16]. Anticoagulated patients are at higher risk of haemorrhagic complications.

	Results

Top Summary Introduction Surgical technique Complications Results Conclusion References

 
The use of temporary epicardial pacing wires in cardiac surgery is associated with low morbidity and mortality. This is mainly associated with the complications occurring during wire removal (see above). A review of the routine use of temporary pacing wires reported an incidence of major complications of 0.04% [11]. Premature ventricular contractions and nonsustained ventricular tachycardia during ventricular wire removal have an incidence of 66% and 7%, respectively [10]. Repeat cardiac surgery and a history of heart failure are independent predictors of such tachyarrhythmias thus increasing the risk associated with temporary epicardial pacing. In addition, anticoagulated patients can experience a prolonged hospital stay due to the delay in discharge awaiting wire removal, with an incremental increase in cost.

	Conclusion

Top Summary Introduction Surgical technique Complications Results Conclusion References

 
Temporary epicardial pacing can be used postoperatively for prevention as well as suppression of arrhythmias. They should not be used routinely as certain factors predict the likelihood for post-operative pacing requirement. Investigations and monitoring allows early identification of the rare but potentially catastrophic complications.

	References

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