3rd Degree Heart Block

I had an interesting strip the other day. We were called to a physician's office for an abnormal ECG. The EMD dispatch sent us "hot." But the prearrival instructions indicated no immediate emergency. Patient was alert talking with good color, no pain and no shortness of breath. And as it usually turns out at a doctor's office, the patient was there for a scheduled appointment, rather than an emergency appointment.

We found a fit 86 year-old female who it turns out had had a syncopal episode several days before while working for several hours ( and more strenuously than usual) in her garden. Other than that, she had no complaint. She was fit, drove a car, walked without a cane, and could carry on quite a conversation.

Her blood pressure was 120/60. Her pulse was 32. She was on a beta blocker, but had been for decades.

The doctor showed me the ECG. No ST abnormalities. A 12-lead from two months ago showed a sinus at 64.

I studied my monitor for a moment, but couldn't make a snap call on the rhythm. It was regular. The Ps seemed to have a relation to the QRS, yet there looked to be a second P emerging from the T. There were no dropped beats.






It wasn't until I ran out a long strip that I was able to see it more clearly. It was a 3rd degree block. The QRSs were all equal and the Ps were all equal. There was, in fact, no traditional relationship between the Ps and QRSs. Where it was tricky was the atrial(Ps) rate was 63, where the ventricular (QRS) rate was 33/34. In other words the P rate was not quite double the QRS, so it took awhile for P/QRS separation to become visible. (Only on the 4th strip can I see it.)

I saw the woman later in the ER and was had a long chat as she lay there, waiting to be taken upstairs to get a pacemaker, her heart still beating strong at 34, a standby pacer attached if her rate should suddenly drop.