Pacing

Often trainees describe being mystified by the use of epicardial pacing in cardiac surgery. The basics are really quite straightforward and this section seeks to address fears and increase knowledge levels and hopefully makes you feel calmer about dealing with the patient being paced

Virtually all patients undergoing CPB have wires sewn to the surface (epicardium) of the heart. In Southampton by convention we use 2 blue wires for the ventricle and 2 white wires for the atrium. It’s important to secure the wires to the correct terminal. Toptip: In the OR look at the heart! You’ll notice blue wires secured to anterior surface of the large pumping chamber (RV) these go in the V + and – terminals. The white wires are sewn to the right atrial appendage and attached to the A + and – terminals.

Separation from CPB needs to occur with a tidy rhythm with the anaesthetist in control of the circulation. This is often done with DDD or AAI pacing. The nomenclature stands for paced, sensed, response in that order. Therefore if the patient is in a slow nodal rhythm with a long PR interval a mode like DDD would suit. If the patient has perfect sinus rhythm at a rate of 50 the AAI at 90 bpm would also be reasonable. As a guide if the patient has had a CABG and there is no issue with AV conduction AAI is a completely reasonable mode. Some clinicians advocate its use over DDD as it gives rise to a more physiological pattern of conduction. If however there has been AV or MV surgery which often causes trauma to conducting pathways a mode such as DDD might be a better option.

In the OR there are multiple potentials that interfere with pacing e.g. diathermy. Occasionally you might see the sensitivity threshold turned up high or off altogether (DOO pacing). It is important this is reset to standard settings when brought down to CICU as it can give rise to R on T phenomenon if left unattended.