Need help reading remote report

A friend who originally got a pacemaker because of vaso-vagal syncope asked me for help interpreting the following:

Scheduled remote reviewed. Normal device function.  
18 new VHR events logged 31 seconds to 12 minutes 25 seconds w/ rates 150's bpm; EGMs suggest SVT
AF burden <1%; longest 1 to 3 hours; V rate histogram shows ~90% binned >110 bpm; available EGM suggest SVT
Next remote 91 days. HB

Q. V rate histogram shows ~90% binned > 110bpm

    What is "histogram"?

    What is "binned"

Q. How serious is SVT at this frequency of occurance?

Q. What is EMG?



I'll try to help

by crustyg - 2022-03-24 12:27:23

Histogram - proper name for a bar-chart.

The 'binned' bit: not entirely sure but in the context of V rate histogram I suggest that it means that more than 90% of the events were allocated into bar chart for >110BPM (i.e. allocated to the counting bin for >110 BPM that defines the height of the bar at that position).

ElectroMyoGram: technically what our devices record isn't an ECG/EKG but an electromyogram.  Differences being that the usual values for heights of peaks/troughs don't apply here, AND the device is recording from two different locations 'inside' the heart at once.  This is very useful, as it's normally possible to see which lead (A or V) shows the tachy-event first, as you can see the electrical peak on A and then fractionally later on V (or vice versa).  Although sometimes the lead which is coming first changes during a tachy-event, it should be possible to use this timing relationship to determine which part of the heart (A or V) is causing the tachy-event.  Which lead shows the last of the tachy-event is also potentially useful (first to finish is the cause). So the report is suggesting that these events are arising in the Atria somewhere.

Does it matter: yes, I think it does. 18 episodes of (presumed) SVT in 3months (implied - you don't state this) - quite a lot.  At least one event 12.5min long - that's going to have had an impact on cardiac output/BP.

Intermittent SVTs can often progress to more frequent and prolonged events and eventually become established, perhaps as AFlut or AFib.  High rate SVT with ventricular response much over 170BPM rapidly leads to heart failure, even in young patients (we used to see this in patients with untreated WPW), due to lack of blood supply to the heart muscle.

I suspect that a session in the cardiac suite is looming for your friend.

My understanding

by Gemita - 2022-03-24 15:18:41

Hello Gotrhythm,

You are testing us.  For me a Histogram is a stored pacemaker report giving details of the number of atrial and ventricular events that have occurred during a given period.  A "Rate" Histogram Report in particular shows heart rate data in three categories: atrial, ventricular, and ventricular rate during atrial tachyarrhythmias like Flutter, AT, AF, SVT. 

My understanding here of binned is that the Ventricular Rate Histogram showed about 90% of the recorded "Ventricular Rate events" were above 110 bpm and these were allocated (binned) to the category of >110 bpm.  The EGM (pacemaker stored electrogram or intracardiac electrogram) suggests the cause for the high ventricular rate was SVT.

The significance of 18 SVT episodes depends on the number of episodes your friend had at the higher duration compared to the lower.  If the majority of episodes were short in and out episodes of half a minute, they may have gone unnoticed, but an atrial tachyarrhythmia lasting 12 and a half minutes at high speeds could quickly lead to instability and chest discomfort even in those without a heart condition, as I well know.  As they have only "suggested" your friend had 18 episodes of SVT from Rate Histograms and stored EGM/AEGM (electrograms and/or atrial electrograms), they may recommend a surface ECG (or external longer term monitoring) to verify the arrhythmia present. That is what they did for me when they reported 1:1 SVT which then became Multifocal Atrial Tachycardia on closer surface ECG inspection.  Coincidentally it was reported on one occasion that I had had 18 SVT episodes over a 24 hour period, together with 1 episode of non sustained VT and episodes of AF with a rapid ventricular rate.  I was very unstable at the time.

EGM = Electrogram:  pacemaker stored electrical recordings made from within the heart as opposed to a surface ECG (Electrocardiogram)

Does that help? 


by Gemita - 2022-03-24 21:58:07

I believe Gotrhythm is talking about an EGM (electrogram) not EMG (electromyogram) but please correct me if I am mistaken.  I think Gotrhythm made a typing error at the end of her message since she clearly refers to EGMs earlier on

Fair point

by crustyg - 2022-03-25 03:53:36

But even allowing for my mistake we're talking about the same thing.  What our devices record isn't strictly an ECG/EKG - but it's the same idea, just the details of collection and interpretation are slightly different.

The -myo- in question doesn't have to be striated skeletal muscle for recording - it can be cardiac muscle.


by Gotrhythm - 2022-03-25 12:49:34

My friend sends her thanks to you both.

It is always comforting to know that I can turn here for answers when the limitations of my pacemaker understanding get exposed.

You're right, Gemita. EMG was a typo. [wry face] The limitations to my proofreading are also exposed.

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