Beta blockers and exercise

[nspower]

I had ischemic heart attack in 2007 from 100% occluded LCx and 95% LAD. My LAD was stented but LCx was left blocked (distal) and is retrogradly filled through RCA. The RCA is without any blockage. My EF is 30-35%.

Other than regular heart medicines and low fat diet, I have been advised regular 30 minutes slow walk. slow walk due to low EF.

I was told that the walk was necessary for development of collaterals. I take 25 mg Carvidilol (betablocker) daily. Since MI my resting pulse rate has gradually reduced, from being in 80s after MI to 60s during last 5-6 months.

Earlier my pulse rate used to rise above 100 bpm during the walk. In last few months I have noticed that my pulse rate do not rise much after 30 minutes walk. At best it is around 80 bpm.

My question is "with low pulse rate will it be possible to develop/maintain collaterals". Or do I need to walk faster to raise my pulse rate to 100+ despite low EF?

Or should I reduce the dose of beta blocker?

[ed34]

There have been cases where people have formed collaterals quite quickly, even during an MI. So variant pressures in the coronary artery network don't really require a high blood pressure, it's simply the differences in pressure across the arteries. When having an MI, you won't be exercising through it, so even at rest this natural bypass system kicks in. However, it doesn't seem to work with everyone, unfortunately. I met a guy in hospital who had a 99% blockage in his LAD, and he had formed no collaterals. Maybe your ability is down to genes. I had a totally blocked LAD at the top, but the bottom was collateral fed, not enough for exertion, but certainly enough to keep me and the muscle alive. It was very strange to see on the angiogram, blood was flowing UP my LAD instead of DOWN. It worked, so that's all that matters I suppose.

[nspower]

ed34,
Thanks for the advise. What I understand from your post is that walk provides short term pressure gradiant for maintaining flow through collaterals. Most of us with heart disease are on ACE-Inihibitors which keeps the bp lower than normal and therefore by walking for 30-40 minutes we increase bp which is helpful for collaterals.  I will  keep the walking schedule as much away from timing of betablocker/ACE-I dose and see if it helps in maintaining higher pulse without additional exertion? Of course I will also try to walk faster to maintain 100 bpm pulse. But I am not sure how it will impact EF?

jrbon,
Thanks for your comments. In my case due to low EF, emphesis was on keeping the pulse below 100-110. Subsequently they implanted an ICD (six months from MI). I was advised to walk not more than 30-40 minutes.

Yes, my pulse rate reduced gradually. Initially I was put on higher dose of beta blocker (35+ mg daily) and high dose of ACE-I (12.5 mg daily) but this did not help reducing the pulse rate. In last one and a half year, after I consulted another cardiologist, my beta-blocker and ACE-I dose were reduced (25 mg carvidilol and 2.5-5 mg remipril). It is when the doses were reduced that the pulse started reducing. But in last 5-6 months I have noticed substantial change and stability in pulse rate.

In my cardiologist's words selection of individual specific betablocker and ACE-I doses is an art rather than science. In my case he appears to be right, so far.

[jrbon]

Your recommendation, does not match mine.

The first month after MI, I was told to walk slowly ... but after  8 weeks of cardiac rehabilitation we were asked to walk 6 KM in an hour, which is not slow at all.

When I left the rehabilitation and after an stress test, they fixed me a training HR where I have to be between 30-40 minutes every day, to achieve it I need a good slope in addition to walk as fast as I can.

By the way, they never mention that this will enhance angiogenesis. Just better muscle performance that will need less oxygen for the same effort, reducing that way the risk of anginas.

The other point that sounds strange from your post is that, if I understand correctly, you have been on medication for about 3 years and it is in the last 6 months when your HR decreases from 80 to 60??

How does your dr. explain this?

My HR was dropping while I was increasing my meds doses (about 2 month after MI) and stay very very stable since.

Jesus

[ed34]

If you reduce your beta blocker, you will certainly regret it. It is likely you will start to feel angina at rest. Also if someone makes you angry, it will feel like someone has thrown a spear through your chest. Beta blockers are very important for keeping your heart from over reacting. There is obviously some improvement going on because you are achieving the same results with a much lower heart rate now. So, as you say, where do you go from here?
I visited my cardiologist last week to discuss opening the blockages in my distal LAD. I asked him about my collaterals, because I was concerned they may close now my proximal LAD has been opened, giving a better flow. I was worried this could make matters worse. He explained that collaterals are all to do with pressure variances. If blood is not able to get through my blockages in the distal LAD then the collaterals will remain open. The more blood that gets past the blockages, the more the collaterals will shrink, so if he opens those blockages, I will lose the collaterals, but rightly so. I believe this is correct because ECP develops collaterals using cuffs, to force more blood under more pressure into the coronary arteries, exaggerating any existing problems. Over time, in many patients, the collaterals shrink, because the pressure increase was false and they can't be fooled for too long. So, top up ECP is required.
I don't think it is necessarily how much work you are doing, it's all down to the pressure gradients across your coronary artery network. Even at rest, I would have thought some collateral development would be possible, if the conditions were right.
When was your EF last checked?
If your gentle walk was producing a pulse of 100+, then surely there's no problem with increasing your speed or adding some gentle inclines to achieve this again? perhaps limit it to 100. I remember I used to walk on a flat with a pulse of 75 and I could go on forever. It felt like I wasn't really achieving anything. However, adding a gentle incline soon woke me up. I had to walk less than half speed then and stop a few times.