What type of pacer from a 12-lead?

[Cohiba]

For background, I'm a RN in the ED of a level 1 trauma center (CEN/CCRN/TCRN plus some other stuff that doesn't make it on my signature block) but have a question that none of our docs can answer and there isn't a cardiologist in the department right now whose brain I can pick. Given that, I'm wondering if a patient has a pacemaker, in the absence of ANY INFORMATION AT ALL beyond a 12-lead EKG (i.e. a demented/unconscious/very ill-informed patient with no ID or a wallet with a pacemaker info card) is there any way to tell what chambers are sensed and what chambers are paced? I'd think that if there was a P-wave followed by a pacer spike than a QRS one could assume the pacer is atrial-sensed/ventricular paced or if there was a pacer spike/P-wave then pacer spike/QRS then the pacemaker is dual-sensed/dual-paced, etc. though if I'm wrong on that, I'm open to learning how I'm wrong...

[Cowboyardee]

I'd think that if there was a P-wave followed by a pacer spike than a QRS one could assume the pacer is atrial-sensed/ventricular paced or if there was a pacer spike/P-wave then pacer spike/QRS then the pacemaker is dual-sensed/dual-paced, etc. though if I'm wrong on that, I'm open to learning how I'm wrong...

Unfortunately, it's trickier than that, but also a little hard to explain. When you see a pacer spike initiating a QRS complex, you know the patient is ventricular paced. When you see a pacer spike before a P wave, you know the patient is atrial paced. So far, so easy. It gets tougher. Let's take your examples...

1) If there was a P wave, followed by a pacer spike and a QRS wave, you know he's ventricular paced. But you don't know whether he's atrial paced, atrial sensed, or ventricular sensed. The pacer could be sensing his P waves and pacing his ventricles based on that (DDI or DDD settings); the pacer could be paying no attention to the P waves and merely pacing his ventricles, either with sensing for innate QRS complexes (VVI setting) or without (VOO setting).

2) You see pacer spikes before both P waves and QRS complexes. Here, you do know that the patient has a dual chambered pacer and that both chambers are paced. But you don't know for certain which chambers are sensed. You might have DOO, where neither chamber is sensed; you might have DVI where intrinsic P waves are ignored by intrinsic QRS complexes are sensed; you might have DDI, where both chambers are sensed, but the patient's intrinsic PR interval isn't used to determine whether to pace the ventricles; or you might have DDD where both chambers are sensed and the patient's PR interval determines whether to fire a ventricular spike.

In any of the above, sometimes you might see either chamber both pacing and not pacing, and in these cases you can say that the patient is both sensed and paced in that chamber.

Basically, if you can spot a pacer both pacing and sensing in a chamber, then you know it does both. But if you don't spot it pacing and sensing in a chamber, it's tricky to say with certainty that the pacer is unable to do so without interrogating it.

[Pheebz777, BSN, RN]

You can't go wrong with wanting to know the Ins and Outs of how things work. I'm sure if you get a hold of a cardiologist and ask your question, you might get a perplexed look from him. It's just as significant as wanting to know what coronary artery was stented without performing a heart cath without any prior data or history.