Are you able to reliably tell apart a pacing device from an implantable cardiac defibrillator on radiograph? Let’s go over some imaging pearls for cardiac devices. For starters, let’s go over some pacemaker anatomy. The battery pack, or CAN, is typically embedded in the chest wall. The leads run into the central veins into the heart, and the lead tip is typically embedded in the myocardial wall.

So how do we tell apart a pacing lead from an implantable defibrillator lead? The key is looking at the thickness of the lead. See here on this pacing lead, it’s thin throughout its entire course. But notice on this defibrillator lead, this thickened part towards the tip, that’s actually where the coiling for the defibrillator is housed.

To understand proper lead placement, first we need to understand the orientation of the heart on radiograph. Remember that the right ventricle is anterior to the left ventricle, and that the coronary vein drains into the coronary sinus wrapped around the posterior aspect of the left ventricle behind the heart.

Dual lead pacemakers have one lead embedded in the right atrium and another in the right ventricle. Three lead pacemakers add an additional lead that runs through the coronary sinus into the coronary vein to pace the left ventricle posteriorly. Three lead ICDs combine two pacing leads, one in the right atrium and another going into the coronary sinus, with a third implantable defibrillator lead embedded in the right ventricle.

Too much to remember? Don’t worry, there’s a lot of apps that can help you identify which device your patient has for the electrophysiology team.

Full Byte

Pacemakers: Part 1

Pacemakers & ICDs: Part 2 Reading Room

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