Just got checked for a PFO

[dreamdive]

Here are a few things to know about echos to assess for PFO:

Typically, a TransTHORACIC echo is sufficient for most people except for the obese (there it might become a technical difficult study) and women who have massive breast tissue (again, technical difficulty). For a transthoracic echo, no probe needs to be swallowed and no anesthesia needed.

A Trans ESOPHAGEAL echo is performed by inserted a probe in the esophagus. This is done when a TTE is not possible and typically requires some anesthesia unless you have no gag reflex.

Saline bubble studies are sufficient in most, but contrast studies are more sensitive.

There is a disturbing study I read in which divers got retested for PFO's years later and found that they had "new" PFO's or larger ones. Only very few had non when they previously were tested positive for one. This suggests (Ajduplessis did already in his post) that PFO's may occur later in live and are not just a birth "defects". It also suggests they can close spontaneously (smaller ones).

Although there is a lot of discussion and worries about PFO's being responsible for undeserved hits, those without them are not necessary save from RIGHT TO LEFT shunts! We have another recent study that demonstrates that INTRAPULMONARY shunts are responsible for RIGHT TO LEFT shunts, as well. Some people are more susceptible than others in having them open up.

I will post a summary on that in the next month on the Add Helium website, but in the meantime for those interested in reading articles on the subject matter, you can find the references here: Add Helium - The Rebreather Epicenter. This link will take you to the Reference Library. Look under "PFO/Intrapulmonary Shunts" for the references.

 

[chillyinCanada]

I think I'm going to continue to run with denial and ignorance.

 

[DaleC]

Thanks for the reply Drew.

I asked because this subject came up when we did a chamber tour with the head of hyperbaric medicine at VGH. His view was not to get tested for several reasons. PFO's are quite common yet the incidence of DCI is quite low suggesting the risk related to PFO's is not as great as the risk of corrective surgery, which he said was significant seeing as it was open heart surgery. He also asked who would actually stop diving because they knew they had a PFO or who would simply modify their behavior. Most would modify so he suggested simply doing so regardless as it was good practice.

Dive conservatively and don't worry about PFO's was the take home from him, unless of course it became an acute issue. I'm not saying which idea is right (to each their own) but I thought it was interesting coming from a medical doctor. I would have thought he would be more corrective in perspective.

 

[kathydee]

Congrats! I relate. It was a great feeling to get back negative results on the PFO test I took before considering going towards tech .

 

[TSandM]

Actually, the placement of an occluding device for closure of a PFO is not open heart surgery. It is done via catheter. It's still not a procedure without risks, but it's not as bad as surgery.

 

[Patoux01]

Actually, the placement of an occluding device for closure of a PFO is not open heart surgery. It is done via catheter. It's still not a procedure without risks, but it's not as bad as surgery.

Still scary stuff!

https://www.youtube.com/watch?v=A3bvyyIYAVc

Way too scary for me.

 

[dreamdive]

Thanks for the reply Drew.

I asked because this subject came up when we did a chamber tour with the head of hyperbaric medicine at VGH. His view was not to get tested for several reasons. PFO's are quite common yet the incidence of DCI is quite low suggesting the risk related to PFO's is not as great as the risk of corrective surgery, which he said was significant seeing as it was open heart surgery. He also asked who would actually stop diving because they knew they had a PFO or who would simply modify their behavior. Most would modify so he suggested simply doing so regardless as it was good practice.

Dive conservatively and don't worry about PFO's was the take home from him, unless of course it became an acute issue. I'm not saying which idea is right (to each their own) but I thought it was interesting coming from a medical doctor. I would have thought he would be more corrective in perspective.

Like anything else, this is not "cut and dry", either.

I agree that routine Echo to R/O PFO's for the recreational diver is not warranted. Those going tech however, might want to consider it. Those aspiring tech divers who then turn out to have a PFO can re-evaluate their decision.
Divers who have strange symptoms and "undeserved" hits, might want to consider getting checked. If they have it, they can decide what to do with it.

The remedy of "diving conservative" by lowering your lower number on your GF is highly questionable! What does diving conservative actually mean? I bet we get 10 or more different answers on that one and some of those answers are not even good remedies for this.

Recreational dive computers are already set up "conservatively". I have yet to read a good recommendation on how to dive with a PFO. Yes, diving with Nitrox instead of air is one, but I don't know of a study that verified that or other "recommendations".

It's a personal choice for sure. The risk of getting DCS is low when diving common profiles and the risk of DCS with a PFO are only a bit higher. That is why the medical diving community is not recommending 1. everybody getting checked and 2. everybody getting their PFO fixed.

Besides, some of us are more susceptible of getting bend than others regardless of PFO or intrapulmonary shunting.

 

[lowviz]

I don't disagree with anything above with respect to either content or concept. I have a "first order" view of a patent shunt and I would appreciate your view on this.

Could a shunt be modeled as nothing more than simple inefficient scrubbing in the lungs? Yes, I understand that a shunt can be opened under stress and wildly complicate calculations, but let's assume everyone had a patent shunt that didn't change size.

So if we all had such a shunt, wouldn't there just be a different set of algorithms/tables?

 

[dreamdive]

I don't disagree with anything above with respect to either content or concept. I have a "first order" view of a patent shunt and I would appreciate your view on this.

Could a shunt be modeled as nothing more than simple inefficient scrubbing in the lungs? Yes, I understand that a shunt can be opened under stress and wildly complicate calculations, but let's assume everyone had a patent shunt that didn't change size.

So if we all had such a shunt, wouldn't there just be a different set of algorithms/tables?

You know, after I read the article "Exercise after SCUBA diving increases the incidence of arterial gas embolism" and knowing that I don't have a PFO, I have made a few changes. However the pathology and pathophysiology of DCS from either PFO or intrapulmonary shunting appears to be different.

In a PFO you can induce a shunt if the pressure from the right atria becomes greater than the left. Usually, the left side of the heart has higher pressures. So what would change the pressure relationship: Bearing down such as during a valsalva or straining while climbing up a ladder.

We know that just because you have bubbles on echo in the left side of the heart, does not guarantee you from getting a hit. One of our instructors had unknowingly been diving with a big PFO for years doing helium and long deco dives until he finally got a Type II hit. This and other examples and studies has scientist rethink the role of the bubble in DCS. There appears to be a paradigm shift in which the bubble no longer serves as a primary but rather a cofounder of DCS.

This being said (and we know that even if you do everything "right" during deco, you can still get DCS), deco algorithms still attempt to control the bubble. As long as we don't know and be able to manipulate the cofounders of DCS, that is pretty much all we can do at this point. But, we have to remind ourselves that this is less than perfect. More confusing and frustrating is determining WHAT algorithm to dive. We know that one size does not fit all and dives vary as do divers, yet most divers will dive the same GF or algorithm regardless because they don't know when and how to adjust. What do I mean:

I see divers use the same GF setting when they dive a 200 ft, 300 ft, 500 ft dive over 20, 50, longer duration. They dive it and ascend regardless if they are cold or warm, had high workloads.....the computer does not know if you ongased more because you worked harder at depth or if you offgas less because you are cold. The diver does but typically makes no adjustments. Most divers don't understand tissue loading and which tissues need to be managed primarily on a given dive and thus they don't adjust GF's.

So my answer to your question is a long one but to summarize: It ain't that simple. Let's not forget that our algorithms are THEORETICAL and not FACTUAL. And, that our susceptibility changes daily and there is big variability between divers.

The most useful thing a diver can do is to become a "thinking diver" rather being a automaton following a dive computer.

I am still learning and at this rate, always will.

 

[DaleC]

Thanks Lynne. I can't remember exactly how he phrased the procedure. For conservatism he discussed setting computers or diving tables more conservatively, doing 5 minute instead of 3 minute SS's, longer SI's, more conservative repetitive dives and breathing a rich mix after the dive. That last one he chuckled about because, as a doctor, he has pretty easy access to O2 which he keeps on his boat.

This is actually a good argument for adopting min deco procedures. Doing a slow ascent to reduce bubble growth would seem to be a better overall strategy than bend and mend.

We also discussed an interesting fact about one of our most popular local sites, Whytecliff Park. Post dive almost all divers drive immediately back to Vancouver via the upper levels hwy. Within 5 minutes you make an elevation gain of 300m right from sea level and back down again. He suggested sitting around and talking for a while afterwards.

The difference between recreational and technical is a good one. We discussed all this from a recreational perspective.