Transcript of Live Chat with Dr. Petar Denoble from DAN on the topic PFO

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Here is the transcript from the live chat hosted here on ScubaBoard with Dr. Petar Denoble from Diver's Alert Network (DAN). The topic of the chat was patent foramen ovale (PFO). For the sake of transparency, there were a few links added by Dr. Denoble after the chat, for people to find more information with regards to some of his answers. Thanks to DAN, and Dr. Denoble for joining us here on SB for this event.

2012-11-08 17:58:31 HowardE -> Welcome to the chat. I am the moderator, and will post the questions one at a time for our guest speaker... Dr. Petar Denoble from DAN.

2012-11-08 18:00:10 HowardE -> After Dr. Denoble's opening statements, I will post the first questions.

2012-11-08 18:01:00 petarjd -> Glad to be here. I suppose, most of participants are familiar with PFO, but I could provide more details as needed. Patent foramen ovale (PFO) is a relatively benign cardiac defect that leaves a passage in a wall that normally separates the left and right upper chambers of the heart. A number of retrospective studies have established that the incidence of PFO is 2 to 6 times greater in divers who experience a neurological DCS hit. We will discuss the relationship of PFO and DCS and I am ready to answer your questions.

2012-11-08 18:01:03 JTemple -> Hi. I got skin bends in Indo in’08. Later diagnosed with a PFO which is now closed. I was wondering if there are any statistics pointing to whether or not DCS hits, and specifically skin bends, with confirmation of PFO, is more common in women or men? Also, is there any data or reports of subsequent DCS after PFO closure?

2012-11-08 18:03:16 petarjd -> Skin bends seem to be quite often associated with PFO. I am not aware of any statistics but based on our experienced at DAN, we think that women may be more likely to experience skin bends. This is just an impression and the data we have could not prove or disprove it because we do not see the other side of the Moon. Some statistics indicate that women more often get bend but this may be specific for a particular geographic region and its demographics.
Regarding a subsequent DCS after PFO closure, preliminary data from our ongoing study revealed a few cases of DCS after PFO closure. However, some divers claim that they do not get any DCS symptoms after the closure despite diving in a similar was as before the closure. It is too early in the study to make any conclusions.

2012-11-08 18:03:38 DesertRatExpeditions -> I recently found out I have a PFO by way of Echo with Bubble study. I had a follow up TEE which I get the results for in about 30 mins. I have had migraines as well as verbal neurologic issues on one occasion. I have worked in the dive industry off and on and am a certified Adv Trimix diver and divemaster. Do you think that I would be indicated for a PFO fix?

2012-11-08 18:06:07 petarjd -> The PFO closure is a personal choice based on risk/benefit analysis. If you have a large PFO, a history of repeated DCS, and if you must continue diving, than you should consider the closure. However, you have to discuss with your cardiologist the risks of the closure itself. If your PFO is small, no history of DCS, then you should probably modify your dive to reduce the risk of bubbles and thus the risk of DCS.

2012-11-08 18:06:30 JTemple -> Thanks. As a follow-up, I have a personal theory about women and skin bends, that women with a higher BMI (more body fat, overweight, especially in the middle) might be more susceptible to skin bends especially if they have a PFO. Is there any data pointing to a correlation between higher BMI and skin bends?

2012-11-08 18:08:26 petarjd -> I am not aware of data supporting your idea. There are some indications that skin bend is associated with more subcutaneous fat, but it may be that women are more prone to report skin changes than men. It would take a prospective study to answer your question with confidence.

2012-11-08 18:09:07 DesertRatExpeditions -> Follow up to question already asked: I have also had other diving issues relating to loss of breath underwater (not being able to take a breath) and a sudden drop in blood pressure back on boat, and separately a “panic" event where my resp rate increased and heart rate shot through the roof without provocation. Do you think this might be related?

2012-11-08 18:11:33 petarjd -> The symptoms you describe may be a due to atherosclerotic changes in the vessels of your heart and brain. I am not sure if that is related to the PFO. More likely, it is related to age. You need a thorough work up and evaluation before you decide to dive again.

2012-11-08 18:12:46 petarjd -> DesertRatExpeditions, I would be glad to discuss in more details your concerns, by the phone, tomorrow morning.

2012-11-08 18:12:54 JTemple -> My theory is certainly not based on any scientific data, just an observation from what I have seen posted by other women divers, and my own experience. But it would seem reasonable that higher subcutaneous fat would affect the rate at which blood flows through tissues. So the bubbles, in effect, would get trapped.

2012-11-08 18:14:17 petarjd -> Your guess is as good as any other at this stage of our knowledge. I prefer to look for evidence before adopting any explanation. It is easier for me that way.

2012-11-08 18:14:39 DesertRatExpeditions -> That would be great. for reference. I am 32 (incident was when I was 29) 6' and 185lbs.

2012-11-08 18:14:42 DesertRatExpeditions -> I have to leave to go to my Dr's appointment now, but if you PM me the info to contact you then I will. Thank you for your time..

2012-11-08 18:15:50 DiverDAN -> DesertRatExpeditions, please give us a call tomorrow at 919-684-2948. Our medics or Petar will be happy to answer your questions in greater detail.

2012-11-08 18:19:06 petarjd -> I would like to mention that although there seem to be a statistical association between PFO and DCS, it is not necessary causal relationship. The stats indicate that divers suffering DCS are more likely to be confirmed positive with PFO than divers who never experienced DCS. However, there may be some referral bias or some other unknown bias which brings up more often divers with PFO. To be sure that the relationship exists, we would have to use a prospective data, meaning, get divers enrolled in study upfront and then follow them for certain number of years and see who gets more DCS, divers with PFO or divers without PFO. One such study is underway in Europe and we hope to learn about its findings in a few years.

2012-11-08 18:19:10 ddeborahdelamar -> I am a hyperbaric tender at a tourist destination. We have had three patients over the last year or so with severe type 2 DCI whose dive profiles (one was a snuba participant with max depth 25fsw for 20 min.), histories and medical tests revealed nothing about why they became ill. We treated with standard tables (USN TT6, TT5, TT9) and all patients had full resolution of symptoms. In private discussions amongst the medical staff, PFO as possible cause was mentioned in all three cases, but this was not discussed with the patient. All of the patients were advised to see their regular medical providers for checkups when they returned home. My question is, in such cases, should they tell people like this to get checked for PFOs?

2012-11-08 18:21:08 NetDoc -> PFOs have always concerned me. I don't believe that I have any symptoms as I don't even know what they are. What would be a good indication that you HAVE a PFO, other than getting bent? In other words, when should you be concerned enough to go to a doctor for testing?

2012-11-08 18:23:19 petarjd -> The dive profile you mentioned seem mild, but they are not risk free and divers without PFO may get DCS. PFO is more likely to contribute to DCS in dives that result with lot of bubbles. Regarding your question test or not for PFO, I would suggest that divers consult their diving physician. There are many factors to take into consideration for that decision. I think that divers with repeated cerebral DCS, skin or vestibular DCS should consider testing for PFO, but this is not a standard practice.

2012-11-08 18:25:58 petarjd -> To NetDoc: the PFO is present in about 25% of people. It does not cause any symptoms per se. It was suspected at one point that it contributes to a stroke but clinical trials did not show that the PFO closure protects patients at risk for stroke. Another study was conducted with patients with migraine, but it resulted with the rejection of migraine as indication for PFO closure. So, you do not need to be concerned about it.

2012-11-08 18:26:24 JTemple -> Did you have a chance to read the RESPECT study that was just recently published? I haven't read it yet, myself, but the comments about it on one of the PFO Facebook pages have been very interesting. If you have read it, any comments about the results?

2012-11-08 18:27:07 JTemple -> In response to NetDoc's post, I had no doubt I had a PFO before the tests even came back. Long time sufferer of migraines with aura, some post-dive symptoms which in retrospect were most likely very mild cases of skin bends. When I suffered a serious case in Indonesia (3 rides in the chamber), I knew.

2012-11-08 18:27:51 petarjd -> I do not recollect enough about that study to be able to discuss it. Sorry. ( I looked up the study after the chat. The report can be found here: RESPECT 10-25 Final.ashx. The group of patients was specially selected. The closure seems to reduce the risk of repeated stroke for about 50%. The unwanted side effect rate was considered acceptable in reference to the risk of stroke. However, if you judge the side effects rate in reference to the risk of DCS which is very small, then there is no obvious benefit for divers.)

2012-11-08 18:29:03 ddeborahdelamar -> Thanks for the "a lot of bubbles" and repetitive incidents -- that info helps.

2012-11-08 18:30:50 petarjd -> jTemple, the migraine with aura may be associated with PFO as an coincidence, but the closure of PFO does not solve the migraine in all patients. (Some ongoing studies about migraine and PFO can be found here: Comorbidities Associated With Migraine and Patent Foramen Ovale (CAMP) - Full Text View -, PRIMA PFO Migraine Trial - Full Text View - I agree with you, divers who had a repeated instances of skin bend, or any bend, should in the first place revise their dive practice and, if everything is OK by professional standards, consider testing for PFO.

2012-11-08 18:34:52 petarjd -> ddeborah: let me add some explanations. The PFO is not open all the time. For PFO to let blood (and possibly bubbles) from right heart into the left heart, it takes also to raise pressure in the right atrium above the pressure in the left atrium. This occurs after Valsalva or similar maneuvers. A lot of bubbles in circulation may also change pressure difference and help to open right-to-left path. A few bubbles may not act in this way, or at least, it is less likely. Bubbles can also pass to the left side in people who do not have PFO.

2012-11-08 18:35:11 JTemple -> Yes, I agree about the closure not necessarily solving the migraine problem. In my case, I was migraine free for about 4 months post-closure. I was thrilled. Then all of a sudden, I had a series of about 5 migraines in 2 weeks. Scary. So I went in for an Echo to be sure no clots were forming on the device. Then I was migraine free for many months, thrilled again. But now they have come back again, about 1 every 6 weeks or so. So I am unfortunately not one of the lucky ones reporting to be migraine free post-closure. Yet in my opinion, if one has severe migraines and a PFO, from my own personal experience I would recommend closure -- after discussing everything with one's own doctor, of course.

2012-11-08 18:37:19 petarjd -> JTemple, thank you for sharing your experience. By the way, do you participate in our PFO study? We are following about 60 divers at this time, all with PFO, some with closure other without closure. We hope to be able to answer more questions about the risk-benefit of closure for diving. At this time we are not close to the answer.

2012-11-08 18:39:44 petarjd -> Is there anybody out there who tested negative for PFO?

2012-11-08 18:39:51 DiverDAN -> JTemple, if you are interested in participating in the study here's some more details:

2012-11-08 18:39:56 kathydee -> I did

2012-11-08 18:40:10 ddeborahdelamar -> I think I understand it. And I know that the studies have not been done. But it seems to me that these patients might have more rapid progression or largers changes of symptoms than other patients would have. Could that be what happened in the chamber during the first tx's for all 3 I'm referring to.

2012-11-08 18:40:13 kathydee -> ucla testing

2012-11-08 18:40:27 petarjd -> kathydee, why did you decided to undergo testing?

2012-11-08 18:41:37 petarjd -> ddeborahdelmar, did you suggest that divers with DCS and PFO respond faster to recompression treatment and recover

2012-11-08 18:41:48 JTemple -> No, I am not currently a participant. I actually have all the paperwork in a folder here on my desk at work. I didn't sign up as I didn't feel I could accurately complete all the paperwork. It's rather extensive! ;-)

2012-11-08 18:42:35 DiverDAN -> JTemple, if you have any questions about the paperwork, we'd be happy to assist you. You can email

2012-11-08 18:42:43 kathydee -> learned about PFO's in our training and since I eventually would like to tech dive, thought testing a reasonable thing to do.

2012-11-08 18:43:18 petarjd -> JTemple, if you tried the clinical trial for migraine and PFO, that would have been an extensive documentation!

2012-11-08 18:43:50 kathydee -> Especially since UCLA offers free testing as part of an ongoing study

2012-11-08 18:45:35 petarjd -> Kathydee, please, remember that about 25% of divers have the PFO and only 1% of divers gets DCS. Some of divers with DCS have PFO, other do not. So, the most important safety aspect of diving is to follow safe diving practices.

2012-11-08 18:45:52 ddeborahdelamar -> No. I witnessed rapid changes in symptoms during 1st recompression -- not necessarily for the better. More rapid than most of the patients I see.

2012-11-08 18:46:44 petarjd -> kathydee, it is noble to support scientific studies.

2012-11-08 18:47:45 petarjd -> ddeborah, I would like to learn more about that case. maybe you could send me a brief description of the case and its evolution under treatment?

2012-11-08 18:47:56 JTemple -> Haha! No trials. I was very lucky to get the head cardiologist at Kaiser in SF, who is a diver, and who understood that my quality of life would be affected if I had to stop diving. ;-) So he pushed thru the surgery, and I had my closure done at UCSF Pediatric Cath lab, by the chief there! I was a lucky girl! I'll review the paperwork again for the DAN study. I actually feel badly that I am not participating.

2012-11-08 18:49:14 ddeborahdelamar -> Privately if records are available, yes.

2012-11-08 18:49:49 petarjd -> jTemple, the participation in our study is painless; just some paper work and periodic reporting about diving and dive outcomes

2012-11-08 18:50:37 kathydee -> Of course, a negative test did not change the way I dive. I still dive conservatively.

2012-11-08 18:52:38 petarjd -> One of the studies that came out recently indicated that the risks associated with PFO closure outweigh potential benefits for divers. The study suffered some methodological issues and we consider that we have to continue with our study, especially because we do not expose anybody to any additional risk.

2012-11-08 18:53:18 JTemple -> I can say that since my closure, I have been on about 4 dive vacations each 1 or 2 weeks long and I have not had any symptoms and have felt great compared to how I would feel after a dive pre-closure. But I have changed how I dive. I don't do the 4-5 dives a day thing now, typically only 2 or 3 day. And I only dive Nitrox with my computer set to air profiles (with a 2nd computer set to nitrox to monitor O2 and nitrogen build up).

2012-11-08 18:56:35 petarjd -> JTemple, that is a good approach. Maybe, you would be equally safe with these modifications of your dive style even without the closure of PFO. That is why we advise divers with a history of DCS to consult with a diving physician before they make any decision for testing or even for closure. A thorough review of dive practice and proper modifications may provide needed safety and enable DCS free diving.

2012-11-08 18:56:36 JTemple -> Do the divers in your study who have had their PFOs closed report that they have changed how they dive compared to pre-closure/pre-DCS?

2012-11-08 18:58:14 petarjd -> We are trying to document dives before and after testing positive and before and after closure. It is normal that people become more conservative once they learn they may be at risk.

2012-11-08 18:58:59 JTemple -> Yes, it is entirely possible. And of course we don't know that the PFO actually caused my hit, either. But given the migraines, and the fact that I was having subtle symptoms pre-closure even after very easy, non-repetitive diving, this seemed like the right path for me.

2012-11-08 18:59:17 HowardE -> At this point... as we approach the end of the chat, we'll have some final comments from Dr. Denoble

2012-11-08 19:03:17 petarjd -> To test or not test? Divers who have repeated DCS of cerebral, spinal or cutaneous forms despite proper risk control in their dive practice, should probably consider themselves susceptible to DCS and opt out from diving or further reduce their dive exposure. The probability they would test positive for PFO is about 80 percent and thus makes testing unnecessary unless they are considering the PFO closure. The PFO closure eliminates only RLS through the PFO but does not prevent other possible shunts. In other words, even if there is a causal relationship between the RLS and DCS, the closure of PFO is not a complete solution. In addition, the closure itself is associated with hazards and risks, which may be higher than the risk of DCS. We need more studies and you are welcome to consider participation in our study.

2012-11-08 19:03:35 HowardE -> Let me personally thank everyone who came to the chat. Thanks to DAN and Dr. Denoble for offering to provide this informative session. The questions were great, and we look forward to hosting another live chat with DAN in the near future.

2012-11-08 19:04:15 DiverDAN -> Thank you for the opportunity! We look forward to future chats and would love to hear what other topics you'd like to discuss!
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hi dr

---------- Post Merged at 01:19 PM ---------- Previous Post was at 01:16 PM ----------

could u please explain me the principle of rdp,for example at 10m 45min pg is h, who they calculate it.

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