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Old 07-10-2006, 06:51 AM   #16
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Re: Angina threshold - why does it change?

Quote:
Originally Posted by Ken289

We got a little off the topic of the thread with my digression into unstable angina (although the discussion was very useful). What about the "angina threshold" question??

Thanks.
So I guess the topic is what makes angina more or less likely?
The best definition of stable angina is that it is an angina that is chest discomfort and shorness of breath that is "relatively easy to predict given a certain activity." Outside that realm, angina becomes more and more unstable...never know when, where or from what.
So the "angina threshold" becomes a useful topic ONLY for stagble angina...this is almost a truism.

Good heart muscle contraction depends on a good flow of well oxygenated blood with a good supply of acetyl Co-A (yep, FAT, not glucose.) It must be delivered through unimpeded pathways to all of the active heart muscle and in enough quantity that no cramping occurs from shortage of nutrients. Anything interefering with this flow this like a dietary vasoconstrictor will bring on the angina. The amount of cardiac nourishment needed depends on the amount of work the heart must do and that is dependent on the needs of the muscles. Ultimately, the only load that the heart sees is the head of pressure that it must pump against, the BLOOD PRESSURE.
I think the greatest variable in understanding STABLE angina's pain threshold is the instantaneous blood pressure...not the average over 30 days or the resting BP but the BP of the moment. Thus a squirt of a pressor agent either from the pituitary or the adrenals can make an otherwise pain free workout quite painful. Example, pleasant day on the elliptical walker at a rate that never hurts and FNN says on the cute plasma monitor: "Hey bro, all your stocks have tanked." ADRENALINE>>> up with the BP>>> ANGINA. <owww>
And a day where one is reataining more water will make this pressure head higher at all levels of exertion...so the amount of salt the day before can be a factor.

Again, this kind of thinking is really only applicable to stable angina by definition.

Last edited by Lenin; 07-10-2006 at 06:56 AM.

 
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Old 07-10-2006, 10:03 AM   #17
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Re: Angina threshold - why does it change?

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Originally Posted by Ken289
Kenkeith--the more I talk the more I sound like I know what I am saying---but probably not.

What are the causes of spasm (yes of short duration) right at the entrance to the stent? That mechanical entrapment of platlets occurs (or can occur) seems somewhat obvious, no matter how slippery they are from the plavix. A not insignificant related question is: if they are mechanically trapped there, how would they cause irritation leading to constricting chemical release? Seems hard to imagine. Perhaps the mechanical edges of the stent, "poking" into the wall of the artery, not unlike someone poking a stick in your side, is enough to irritate nearby cells and they protest by pouring out these vasoconstrictors. This in turn spasms the artery wall.

How's that for a theory.
Make sense?
How does the stent area being inflexible and the other area away from the stent maintains its elasticity properties fit into your theory? Is the artery flexing against an inflexible stent causing a lesion (poking)?

 
Old 07-10-2006, 11:12 AM   #18
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Re: Angina threshold - why does it change?

The cardiac nurses showed me an actual stent, floating in a test tube of water. It looked fragile as heck, but I did not touch it. My only data point is a cath xray in one of the papers which showed a 90% narrowing of the artery right before the stent. The stent area was wide open (looked like a rectangle) while the artery itself necked down severely right in front of the rectangular zone. I admit some contradiction between looking fragile and "stick poking" yet how else to explain the picture I saw?

All guesswork.

 
Old 07-11-2006, 05:26 AM   #19
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Re: Angina threshold - why does it change?

Quote:
Originally Posted by Ken289
yet how else to explain the picture I saw?

.
Perhaps by seeing the narrowing as caused by thickening of the intima of the artery wall with plaque. What makes you think it was narrowed by spasm instead?

Last edited by Lenin; 07-11-2006 at 05:27 AM.

 
Old 07-11-2006, 08:22 AM   #20
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Re: Angina threshold - why does it change?

QUOTE: "The stent area was wide open (looked like a rectangle) while the artery itself necked down severely right in front of the rectangular zone."

Sounds like putting a square stent in a round hole. Necked down indicates to me an oversized stent.

 
Old 07-11-2006, 11:03 AM   #21
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Re: Angina threshold - why does it change?

The diameter of the stent area was the same (approx) as the upstream diameter of the native artery, except for the necked down area. If I can find the pix I'll post a url. Oversized?? Not hardly.

 
Old 07-11-2006, 11:19 AM   #22
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Re: Angina threshold - why does it change?

Lenin: can you develop plaque in weeks or days instead of months or years? I have had in mind that plaque development takes a while to proceed.

Say, I just received stats this morning from the last hospital stay. LDL = 59!! a new all time low. The plaque has got to be melting off the walls as we speak. HDL continues at abysmal low levels, this time 25, also a new all time low. These last numbers were before starting Niaspan and were without exercise. Hopefully the HDL number will come up a little. Do you have any experience or reading on what percent gains in HDL are reasonable to expect?

Thanks.

 
Old 07-12-2006, 10:08 AM   #23
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Re: Angina threshold - why does it change?

Quote:
Originally Posted by Ken289
Lenin: can you develop plaque in weeks or days instead of months or years? I have had in mind that plaque development takes a while to proceed.

Say, I just received stats this morning from the last hospital stay. LDL = 59!! a new all time low. The plaque has got to be melting off the walls as we speak. HDL continues at abysmal low levels, this time 25, also a new all time low. These last numbers were before starting Niaspan and were without exercise. Hopefully the HDL number will come up a little. Do you have any experience or reading on what percent gains in HDL are reasonable to expect?

Thanks.
You may want to start a new thread with your own "interesting" guestions about cholesterol. Generally, it will help maintain a better archive and not contaminate someone else's interests. If you do a search on LDL on this forum, you may find the subject more enlightening and informative. There a few threads that come to mind on the subject.

 
Old 07-12-2006, 10:18 AM   #24
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Re: Angina threshold - why does it change?

Quote:
Originally Posted by Ken289
The diameter of the stent area was the same (approx) as the upstream diameter of the native artery, except for the necked down area. If I can find the pix I'll post a url. Oversized?? Not hardly.
Arteries and all vessels for that matter can be tortuous and irregular. One has to view the broader area of the stent placement to make a determination
if the stent is of proper size post procedure. Not uncommon to have an incorrect sized stent! "Necked down" image representation is not a spasm!

 
Old 07-12-2006, 11:19 AM   #25
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Re: Angina threshold - why does it change?

Well, this is what I have found out about my angina and exercise.
I execise daily for short terms on a stepper (5-10min, 3 or 4 times, intense) and then later on a treadmill. The treadmill is the main exercise and I do sessions of 500m up to about 2.5km once or twice a day.

On the stepper I get virtually no angina (pressure or pain). I find the stepper really useful as I can exercise as much as I like without worrying about the angina barrier. (I think one problem with angina and exercise is that angina can stop a person getting a enough exercise to be really useful - so any recovery becomes a very slow process.)
My Dr says I could also take nitrate while I exercise, but I refuse to do that.

On the treadmill I get pressure (builds gradually), and sometimes pain as well. Of course I stop when I feel it's too risky to continue. My Dr. says to be careful and never to try to break through the angina barrier. Sometimes I reckon I do that - maybe foolishly - I don't know. I often feel the chest pressure in slow waves - peaking and then dropping away. Naively perhaps, I interpret this as blood building, bursting through the artery, then slowing again. I try to stop and avoid that situation but sometimes it happens nevertheless.
If I exercise on the stepper I can now get a good treadmill performance - 2 to 3 km - including about half of that uphill. And I sometimes stop when I want - not just because of the angina pressure. The 2-3km treadmill performance is quite reproducible provided I don't have a break (eg stopping for more than a day). The success on the treadmill carries over to my other activities - by that I mean later in the day I can walk up hills without angina - even 6 or 8 hours after being on the treadmill. As I have said before I interpret that as a dilation of the arteries that lasts at least for several hours. In fact I now know it even lasts overnight (ie a good treadmill performance in the afternoon carries over to the next morning and I can again get 2 or 3 km on the treadmill then.)
But I do have a problem - I play sport on 2 or 3 evenings in the week. This is light aerobic exercise for 2 or 3 hours and I come home quite exhausted. Sometimes I get chest pressure doing it. Well, the day after that my exercise capacity is gone. Yep, I am back to the sort of angina I started with months ago. Treadmill performance has gone and I get angina almost from the start and have to stop at a 200 -500m. That has really got me tossed. I exercise harder and it stuffs me up. And it lasts the whole day - in the evening I am still useless on the treadmill. It could be I am just overdoing it. Or maybe it's my blood chemistry I just don't know. My DR is puzzled too. In spite of all this the very next day (ie after the one bad day) I can again get on the 'mill and run 2 or 3 km.
Exercise helps but if you overdo it - it works against you.
Someone here may have an answer to this.
(My Dr has suggested Monudur isosorbide mononitrate 60mg - this is a sustained release nitrate.)
Thanks for reading this long post.
Beafsteak.

 
Old 07-14-2006, 01:01 PM   #26
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Re: Angina threshold - why does it change?

I don't know how to reconcile your specific exercise routine as it is somewhat inconsistent to what I have read and understand (limited) of exercise physiology.

There are two muscle fiber groups for skeletal tissue called fast twitch and slow twitch muscle fiber. At one time in a person's age the group is 50% each. As one ages there almost always is a loss of fast twitch muscle fibers (no steriods.)

Exercise and molecular science in relation to muscle fibers recognize slow twitch is more efficient in using one's energy reserve of ATP (chemical produced from food energy), and can fuel repeated and extended muscle contractions economically.

As fast twitch fibers decline there is more demand and an ineffcient use of oxygen that calls for rapid firing of the muscle fibers..

I would say the angina threshold is not changed, but the demand for oxygen changes depending on the exercise. It is reasonable to say walking up stairs, inclined treadmill, riding a bicycle, sprinting will meet the threshold quicker than walking a fast pace and possibly running at an even pace. It is the inefficiency utilizing the fast twitch group that makes the difference. As an example, I can walk 5 METs without a problem, but a slower walking pace and add the incline to make 5 METs will fatigue my leg muscles. Someone else may get angina.

 
Old 07-15-2006, 07:47 AM   #27
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Re: Angina threshold - why does it change?

Quote:
Originally Posted by Beefsteak
On the stepper I get virtually no angina (pressure or pain). I find the stepper really useful as I can exercise as much as I like without worrying about the angina barrier.
Beefsteak: thanks for sharing all the details...there are a number of points to talk about. I am surprised about the above comment, at least on the surface. I have found more rigorous exercise on the stepper than on the treadmill. I can get to higher BPMs faster on the stepper. So your experience is hard to explain....until, I have thought more about the question I have been researching about resistance training in cardiac rehab.

The crew in charge of my rehab says no for now and recommends against it; looking on line finds the same recommendations although some general comments are being made that says it is ok. The basic reason I can discern from the writing is that resistance training raises blood pressure without necessarily a proportional increase in heart rate. Aerobic training seems to raise heat rate without a proportional increase in blood pressure.

Does this sound reasonable? Perhaps the stepper is more like resistance training and raises your blood pressure but not your heart rate (proportionally)?? Since you are data driven, have you compared corresponding heart rates from stepper vs treadmill (at equivalent time periods)? Might be interesting.

I just saw kenkeith's response and this sounds pretty good and might explain some of the general reluctance to include resistance training in cardiac rehab.

Regading your comment about taking the sustained release nitrate...I am taking that and have discovered conflicting knowledge in the technical community. I experienced TREMENDOUS headaches when I first started on the isosorbide, almost debillitating. This has gradually gone away as my body has "normalized" to the presence of nitrates. I asked if the fact that my headaches have decreased means that the coronary artery dilation has also decreased. RNs in the cardiac rehab program said definitely NO, that the head arteries respond differently to the nitrates than the coronary arteries, and the coronaries are receiving essentially the same dilation. The cardiologist however said the opposite: that decreased headaches meant that the coronary arteries were being dilated less. I tend to believe the cardio.

 
Old 07-15-2006, 09:42 AM   #28
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Re: Angina threshold - why does it change?

Quote: "The basic reason I can discern from the writing is that resistance training raises blood pressure without necessarily a proportional increase in heart rate. Aerobic training seems to raise heat rate without a proportional increase in blood pressure."

I agree the scenario of more comfort doing steps than a less stress routine is very unusual. I'm not going to say it is conundrum...but close.

A ratio change of higher BP to heartbeats maybe true, but the post's query references threshold changes. I postulated the threshold does'nt change, but the method reaching the threshold changes. My example refers to my stress test of fast pace walking measured by METs did not meet any threshold, but the same METs with walking combined with an incline met my threshold.

 
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