Could heat/humidity cause this?

I'm a newbie. Have Got 100% AV block. Got my PM 4 weeks ago and had a check this week. Dr said I could start to resume normal activities, so Thurs I went for a short outside walk in Tucson AZ (warm and very humid for us right now). Before PM I used to do this walk with no problem. First part is up hill. Felt winded and like walking in sand, flats seemed OK then downhill to house. Checked my HR: in the 60's. I would have expected 100's then settling to 80's. Repeated the same walk the next day but took pulse monitor with. HR in 110's to start, then fell into upper 60's going up hill. Was winded and sluggish. Finished walk in low 60's. When I went back into the house HR went up: 70's, 80's, 90's, then settled to mid 80's (seems to be my normal). So this morning I just got on my exercise bike and went from free wheeling to gradually increasing the resistance. HR increased to 120's then settled down when I decreased resistance or stopped. Seemed normal to me.

Really interesting part was I then went out to the garage to pump up my car tires (hot and humid). Felt sluggish but wasn't doing enough to get winded. Back in the house again and HR was 68, then after a few minutes increased to 90 and then settled to 80's.

By the way I am a retired engineer. Maybe over analyzing this?

Anyone had anything like this happen? Seems so consistant even though the experiment only has a few data points so far. I previously posted my first part and a couple of people suggested the rate response and I have to find out what my settings are next week.

I don't understand why my HR would drop when I'm out in the heat/humidity and stay up in the AC'd house. Any thoughts would be appreciated.

5 Comments

Finally, Another...

by donr - 2013-07-13 02:07:22

...Engineer in the mix. And from the Great American Desert, no less.
Important question - WHAT kind of engineer?

Over analyzing - at this point, no. What you have is data that describes the problem. But - Question - WHAT kind of pulse monitor? Some of them are not reliable when used in conjunction w/ PM.

I agree w/ you that HR does NOT match your load. Based on your description, I'd predict low HR as you walk out front door; increasing HR as you climb hill, reaching either a steady state or a max as you top the hill; decreasing to another, lower steady state as you walk the flat area & body has a chance to get over the deficits from the climb; followed by a decrease as you go downhill (Depending on steepness of slope, HR may go up if you need a lot of effort to keep from going too fast).

The warm/humid should only increase load over experience when it is hot & dry.

Another question - does the way you FEEL match the data points? IF you record a low HR & you feel like you are dragging along in diver's boots when you really expect it to be a higher HR, you have a match & the HR is probably correct.

Since you report that your HR seems low, it sounds like an RR problem. Is the RR function turned on. Do you know what MODE your PM is functioning in? It'll be 4 letters, like DDDR. ( 1st letter - how many chambers PACED; 2nd letter - how many chambers being monitored; 3rd letter - how many chambers inhibited; R - tells you if the RR function is turned ON.)

I see by your profile that you are in BLOCK 100% of the time.

One other alternative answer - IF you have a total block (100% of the time) your ventricles depend totally on your PM, which should be following your Atria. You did not say anything about the status of your Atria. Are they totally reliable? Any diagnosed SSS (Sick Sinus Syndrome) that could be the root cause of the problems now? You did not say & I did not look up what kind of PM you have. Is it a dual chamber job so that it can cover the Atria in the event they fail?

As far as your last question about HR inside vs outside - have you considered the reliability of your HR monitor based on your activity level - perhaps it does not respond well when you are outside walking.

Interesting questions.

Don

Great comments

by KAG - 2013-07-13 05:07:02

I appreciate your inputs, since I'm new to this they will help a lot when I ask questions next week. So much to learn and it takes so much time. To bad you can't go to a class/seminar and learn the basics vs researching yourself. Thank goodness I found this site.

First my degree is a BSEE but I worked as a Systems Engineer for 24 yrs.

My pulse monitor is a finger type, pulse oximeter, model CMS-50DL. Is there a site you can find out compatability with PMs?

I'd say that I feel like what the HR is. Walking uphill with low HR and feel winded and like walking in sand. Based on that the monitor is probably OK, but maybe there is a better one?

I have a dual chamber (2 wires) PM. I did ask what happens if my sinus node fails and they said the PM would take over. No mention of sick sinus, but I was wondering if something is going on there or if the PM is conflicting with the heart? I did have a few events they called either atrial tachycardia or A-fib, but didn't know which they were. They said they'd monitor for now.

I will be calling my cardio office Monday and start asing about my settings. I think they said RR was ON but can't swear to it. I asked for a printout when they did the initial check but then forgot about it, so will try to get a copy.

Hopefully will get this figured out so I can ramp up the exercise without feeling bad.

Thanks again
Kathy

Questions - Answers

by donr - 2013-07-13 07:07:32

Kathy: The finger type pulse -oxymeter is the best type - it works off the color of the blood under the fingernail for O2 levels & the pulse. Note that your pulse jumps around a lot sometimes from pulse to pulse. That's because it measures elapsed time for each individual pulse & converts that into a BPM. This device will serve you in good stead.

Your response to the walking uphill, if it correlates w/ your pulse numbers is an accurate reflection of what your pulse really is. so don't concern yourself w/ the correctness of that number.

I suspected that you had a dual chamber device - that's common for your problem. If you have to put one in, why not the one w/ the greatest capability?

Ah, so you had some atrial Tachy or A-Fib. That could cause you some problems. If one of those gets too high for the PM to drive the Ventricles, you have a lack of coordination & perhaps the symptoms you describe. Your PM specifically monitors the ventricles for electrical activity; if it does not come on time, it sends the command for them to contract. Since you have a complete block, it never sees what it is looking for, so it paces the ventricles. There are limits as to how fast the ventricles can function - a function of mass of muscle that must be moved & mass of blood that must be pumped, so it's possible for the Atria to out run the ventricles. At that point, the ventricles do not completely fill & you get a lack of O2 to the body.

You did not tell us what your lower & upper limits are. That is critical to understanding one particular answer to your questions. The lower limit (or base rate) is the rate below your PM will not let your heart go. (Actually, it calculates a time for a single beat based on the desired rate & stores that time; any individual beat that takes longer to occur than expected is replaced by a command by the PM.) They set TWO upper rates. The one you are interested in is the UTR (Upper Tracking Rate). At that point, the PM STOPS trying to track the atria & goes into what is called a 2:1 pacing - it only sends a signal to pace for EVERY OTHER BEAT. The symptoms are essentially what you describe. Looking at the pulse rate numbers you list. sounds like you may well be going into that mode. That is a setting issue - they need to raise the UTR. Sounds like your UTR is set at about 120 BPM from the numbers you report. Cardios are notorious for setting this one too low.

Do you ever sense the Atrial high rates? Some people can, others cannot. They are much weaker than the ventricular contractions. Be sure to pursue this issue w/. the cardio when you see him/her.

Be sure to get that download printout - understanding that is the key to understanding your PM & what it is or is not doing for you.

This is all just a start point for you to consider. You can check out the 2:1 business & the UTR by checking your pulse more frequently as you load your system & your HR goes up. It will SUDDENLY drop like a Uranium brick when you go over the UTR. That's your first real clue as to this being the case.

Good luck w/ your system analysis.

Don

Fantastic comments

by KAG - 2013-07-14 12:07:58

So good to connect with people going through similar things and gaining from their experiences and exchanging ideas.

Sally- I agree with your comments on seminars or tutorials. Maybe someday they'll realise that educating people who want the info is actually helpful in recovering and living with the devices. I think we're just a head of them. My dogs are rescues that I adopted about 11 yrs ago. They love to walk around the neighborhood. I live in a suburb. I'm looking forward to getting back to it but don't want to take them out until I understand what's happening when I go up hills. Since I leash walk them I don't worry to much about snakes but they could come in my yard. I haven't done any training but they do offer training in rattlesnake avoidance here. Basically they put a shock collar on the dog and have a live defanged snake. When the dog approaches the snake they zap them. I guess it only takes a time or two until the dogs understand.

I'm just 4 weeks out and healed up. Starting to cautiously move my arm more. I think that once I get a handle on this I'll reduce my monitoring too. I agree that if you do to much you can drive yourself nuts.

They told me that my limits are 60 and 140, but I do need to get that printout. What Don described would explain what I experience under load conditions, except I dropped to low 60's. Maybe that was the monitor accuracy though. Interesting that I didn't experience it when I was on my exercise bike in the house. I guess the added heat humidity outside could have stressed and put more load on my system. I may try upping the resistance on my bike and see if I can duplicate it. Understanding what's going on sure helps calm the anxiety for me.

Interesting experience doing lab testing on yourself too.

Thanks again for the responses and I look forward to exchanging more info.
Take Care
Kathy

2:1 Pacing at UTR

by donr - 2013-07-16 11:07:21

You commented that your lower HR after you MAY have topped out & slipped into 2:1 pacing - realize that when things get to that point that your heart may NOT be running exactly at your UTR or some othher HR. It may be extremely erratic, so that when the PM starts pacing only at every other beat it will not be regular, either & your P-O may well not be giving you accurate numbers for what you expect. If you get into that situation again, notice if the P-O gives you numbers all over the map - but ROUGHLY half the UTR.

Don

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So, my advice is to go about your daily routine and forget that you have a pacemaker implanted in your body.