From: Iqwal Mangat
It looks like the patient has an underlying atrial tachycardia (likely atrial
fibrillation) which is suppressing the pacemaker.
Once a magnet is applied, the pacemaker fires asynchronously on top of the
patient's own underlying rhythm at a rate of 75(?72) PPM.
The pacemaker is likely functioning well.
Response:
This patient probably has a supraventricular tachycardia at a rate of about
140/min. The rhythm is very regular and would make atrial fibrillation unlikely.
It is probably SVT as the QRS in sinus rhythm at the end of the last tracing
has the same shape as that of the tachycardia.
It is interesting that the pacemaker induced QRS complexes do not seem very
wide either.
In any case the pacer is sensing well, with the magnet is pacing at 71.4/min.
(upper right hand part of the first strip) which indicates the battery is
still good and paces when it is possible to capture the ventricle.
From:
"Andy O'Grady"
I am a GP in New Zealand.
I don't do telemetry of ECGs from my office so the use of a magnet is new
to me.
I assume that the magnet starts the pacemaker? I think that the first trace
shows a SVT and that the pacemaker is not responding. The second trace shows
pacing spikes and a slight slowing of the SVT.
I am not sure what this indicates but think the pacemaker is faulty and
needs replacing. Thanks for a really interesting site.
Response:
Dear Andy, the magnet response of different pacemaker models often differ.
You are correct as the magnet turns off the sensing circuit and places the
pacer in a VOO mode.
This allows one to verify pacer output when non is apparent because the
patient's rhythm is faster than the rate set for the pacer.
Yes the patient probably has an SVT, which may have been terminated by the
competitive pacing of the pacemaker. This could be what is called underdrive
pacing to terminate an arrhythmia.
The pacer spikes at 71.4 /min., some of which capture the ventricle, indicate
that the pacer is working just fine.
From: clubmidi@synapse.net ,Fri,
04 Oct 1996
Atrial fibrillation. The pace is functioning normally
Response:
The rhythm would seem to be too regular to be atrial fibrillation. Also
if the arrhythmia was terminated by the pacemaker this would also argue
against atrial fibrillation.
The pacer is working well.
From Stephen Ruble
It seems that the pacer is working too well.
The rate is around 150, which is twice what it should be.
When the magnet was applied, there appeared to be two separate QRS complexes,
as if there were two pacing areas.
Am I even close??
Response:
Dear Stephen, An interesting idea but in fact the pacer is not pacing at
150/min.
Note the change in QRS morphology with the capture beats at the end of the
second strip.
Another clue is that the EKG receiver measured the pacer rate at 71.4 (upper
right hand corner) and suggests that the pacer is not pacing at 150/min.
From: Dr.Hygriv Rao gbpant@giasdl01.vsnl.net.in ,G B Pant Hospital,
New Delhi
Answer to the ECG puzzler questions:-
1. Patient's rhythm: Supraventricular junctional at a rate of 150 /min.
2. Pacemaker function: Loss of capture.
Response:
Dear Hygriv. Yes this is probably an SVT but at 140/min. Note that the QRS
complexes are separated by more than two large squares on the ECG paper
(two squares are 150/min.)
This rate difference is important, as a rate of 150/min. should "ring
a bell" and make you think of atrial flutter with 2:1 block.
The pacer is working well, and the lack of capture reflects an attempt to
pace the heart during the ventricular refractory period.
Captures are seen at the end of the second strip when the SVT terminates.
From: Gi-Byoung Nam
The patient's rhythm is junctional tachycardia.
The pacemaker is functioning well.
Response:
Dear Gi-Byoung Nam,
Yes this is very possibly a junctional tachycardia, but it is a little slow.
Also the pacer seems to have broken up the SVT rather easily and might suggest
that this is an patient with a concealed accessory A/V pathway with a slowing
in the A/V node to explain the slow rate.
A/V reentry tends to be easier to terminate with pacing as opposed to AVNRT.
Dr. Michael Rosengarten