Atrial Histogram

After reading a copy of my Pacemaker phone in report, I see that my Atrial Histogram chart shows my BPM is between 60-70 for 76% of the time. On either side of that Bar it is almost flat. I believe the chart should read more like a bell curve (Mountain shaped) instead of one Bar. What has to happen to achieve that Bell curve?? Or doesn't it really matter??
Clarencio

4 Comments

Histogram

by golden_snitch - 2014-07-10 03:07:59

Hi!

No, it must not. If you have a job that requires sitting in front of a PC most of the time, you sit in the office 7-8 hours per day. Add the 6-8 hours of sleep plus the time that you spend in front of the TV, in your car, reading, speaking on the phone etc. - most people spend 70-80% or more of their day not moving. For all the mentioned activities you do not need a heart rate faster than 60-70 beats per minute. So, it's normal that you have 76% pacing at 60-70bpm. There are still 24% left, scattered over higher rates. Also, keep in mind that the histogram shows you an average that's calculated from several weeks or even months of data. It does not fully reflect what happens on every single day. You might have days, for instance when you exercise, when the histogram looks differently. But still, on average over several weeks/months, you get the 76% at 60-70bpm.

Don't worry about the data, what matters is how you feel. If you are feeling fine, then that histogram is just right for you :-)

Inga

Statistics & Histograms

by donr - 2014-07-12 08:07:05

Clarencio: There is a mathematical reason why it cannot be bell-shaped as you would like to see it.

The Bell-shape (Gaussian distribution to statisticians) Is created by a special set of conditions for the data.

First, & foremost, the data must be capable of being randomly distributed across some range of values. HR's cannot, especially when you have a PM.

The PM has a lower limit that cuts off the ability for the heart to drop below some rate - like 60 BPM. You therefore have a hard constraint on lower limit.

The upper limit on HR is highly dependent on WHY you have the PM. For some people it is not influenced at all. for others there are influences because the PM will not support rates beyond a fixed HR, leading to all sorts of non-random rates existing at the upper end.

Secondly, the HR is influenced by your daily activity patterns, so again, HR is NOT randomly distributed across the range of rates you COULD sustain. Inga analyzed that very well for your situation. Considering your age - somewhere in the 80's - I'd suspect that you do not get up & go out to plow the south forty w/ a mule pulled plow all day, so it makes sense that your HR stays relatively low.

Third - consider the fineness of the cells the data is categorized into - bands of 10 BPM. That significantly affects the shape of the curve. If your normal HR varies only between 60 BPM & 100 BPM, intervals of 10 BPM does NOT give you much variation along the horizontal line of your HR histogram. Let's go to the extreme & say that the PM uses intervals of 40 BPM. Then ALL of the HR samples would fall into the same interval & your histogram would look like a flat topped box w/ 100% of the beats being in it!!!!!

Supposing that the intervals were only 3 BPM along the horizontal line. You histogram would have a lot more tall, skinny bars & a significantly different shape to it - DEPENDING on your activity levels during the day, week, month, etc, as Inga said. We could also throw in there the Accuracy of your sinus node at causing your heart to beat. IF the SA node is not nice & regular above the base rate, your HR will not be regular & the histogram will be ragged. That's the reason that 10 BPM intervals are used along the horizontal axis for the histogram. Make that interval too short & the natural variation in SA rate starts to make the data look scary & bad. That natural variation is about 1-2 BPM. You will see it registered on an ER monitor where the HR is calculated based on elapsed time between beats for every beat.

If you want to see an interesting Histogram, since I've fallen on unusual times (for ME) , my histogram mirrors yours for the last year or so due to forced inactivity during waking hours.

Previously I'd get up & my day would be filled w/ constant activity, all day long till late evening. I only slept 5-6 hours, so I did NOT have a really significant period of inactivity - hence low HR & the vertical bar at my base rate was less than 50%. I had a second bar out at about 100-100 BPM that was about 30% & all the rest of the 20% was scattered between the two tall bars & a few % to the right of the 100-110 bar.

That's called a Bi-Modal distribution & it freaked out one Medtronic Tech who looked at my histogram. My cardio was not excited by it - that was normal for me - he knew my living pattern.

So- mathematically, don't get excited by your histogram - there's a reason it has that shape. Consider what it would be for a person paralyzed & bed-ridden. Not much variation at all.

Donr.

Atrail thingy

by clarencio - 2014-07-13 02:07:40

Thanks Inga and Donr.
Donr, your diagnosis of my condition is really hitting the nail on the head. I am almost 83 years young. I watch the news fom about 5 to 7 AM. Eat breakfast then go to work around the house and my boat shed with duties and hobbies which include lots of steps up/down and flat ground. Then I eat lunch and read. Then I have a drink (or so) and snooze. Eat dinner, watch the early news, read some more and go to bed. Since you have explained it so well to me I can now relate to that BAR on my chart. By the way I am enrolling at "Harvard" so that I may understand some of your more technical explanations.
clarencio

Read both comments.....

by donr - 2014-07-13 06:07:12

....together.

All I added was a description of WHY HR histograms cannot be bell shaped. Inga told you why you should not worry about it & justified the reason for your particular histogram. Both are necessary to understand your situation.

When I looked up your history & saw your age, Inga's discussion was right on the spot - which you verified.

Don

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At age 20, I will be getting a pacemaker in few weeks along with an SA node ablation. This opportunity may change a five year prognosis into a normal life span! I look forward to being a little old lady with a wicked cane!