VSD and caves

[wetvet]

Hi Dr. Deco (and all you budding bubble docs):

I've got a potential problem, and am interested in opinions on my "condition".
I am booked to go to Florida in Nov to do a week long course that will give me cavern, intro to cave and full cave certs. I already have a bunch of certifications (including adv. nitrox and decompression proceedures), and have done over 150 dives and 15 or 20 decompression dives uneventfully. I feel that I am prepared for the course.

My problem arises from the fact that I have an Interventricular Septal Defect (VSD). Simply put, I have a hole the size of a nickel (Canadian nickel ) between the big chambers of my heart. I am concerned that I will have trouble from the instructor when I do the cave course (have sent email, awaiting response). I feel that I understand the physiology quite well, and feel that the VSD is no increase for DCS, and since my heart is strong enough for me to play competetive hockey and numerous other sports, it shouldn't be a problem. Even with the hole, I am more aerobically fit than many of my diving compatriots or students. Let me know if you forsee a problem that I've missed.

 

[Diver0001]

wetvet once bubbled...
Hi Dr. Deco (and all you budding bubble docs):

I've got a potential problem, and am interested in opinions on my "condition".
I am booked to go to Florida in Nov to do a week long course that will give me cavern, intro to cave and full cave certs. I already have a bunch of certifications (including adv. nitrox and decompression proceedures), and have done over 150 dives and 15 or 20 decompression dives uneventfully. I feel that I am prepared for the course.

My problem arises from the fact that I have an Interventricular Septal Defect (VSD). Simply put, I have a hole the size of a nickel (Canadian nickel ) between the big chambers of my heart. I am concerned that I will have trouble from the instructor when I do the cave course (have sent email, awaiting response). I feel that I understand the physiology quite well, and feel that the VSD is no increase for DCS, and since my heart is strong enough for me to play competetive hockey and numerous other sports, it shouldn't be a problem. Even with the hole, I am more aerobically fit than many of my diving compatriots or students. Let me know if you forsee a problem that I've missed.

EEeuuwww!! Why don't you get that fiiiiuxed????

Sorry, couldn't resist

(how can you tell Rob worked WAY too many hours this week..... :mouth: )

R..

 

[Air_Miser]

Hey WetVet, I'm very interested to hear what comes of your question.

I'm a new diver, and completely in love with the sport. I can't wait for my kids to be old enough to experience it, but- My 4-year-old son has a VSD (a tiny one compared to yours, but still there), and I have no idea what this will mean in terms of do's & don'ts for sports. So for he shows zero symptoms, and the doc's

What happened when you got your original certification, did you have to get a full physical and "ok" from a doctor to take the course?

Hope you don't mind the quizzing....

Matt.

 

[Saturation]

VSD, ASD or PFO are all at risk for paradoxical emboli or emboli from bubbles.

The risk of emboli is proportionate to the size of the opening and when the right sided pressures exceed the left sided pressures. When such reverse of pressure differences exist is luckily rarer in VSD over a PFO.

The critical diameter for a PFO is about 5mm, about half that of a dime. Its unclear what the size of a VSD should be but lacking information, must consider a PFO's size with some similarity.

With an opening, a risk for embolization is high to make technical level dives very risky, at the very least to the buddy who dives with the patient.

http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=11527606&dopt=Abstract

The risk of bubbling increases as the deco obligation rises, its probably highest in substantial deco.

Dr. Paul Thomas, who generously details his PFO incident on this scubaboard, miraculously survived his embolization, which occured after diving without issue for decades, albeit not in decompression [Paul, correct me if I'm in error.]

Unlike open water, an injured diver can be brought to surface anywhere with a controlled ascent by his buddy. In a cave system, the buddy must swim said buddy all the way to safety.

A grand traverse at Peacock has an outbound swim of almost 1 hour, ~ 4500 feet, round trip. Any risk of rescue will rest heavily with assumed normal buddy. In systems with restrictions and high silt risk, additional problems loom.

Screening for atrial defects is unwarranted because of the cost and risk associated with testing for it. VSD however, can be seen adequately by standard echocardiography. However, the situation is different if there is a known defect beforehand. If the size and nature of the defect was discovered in childhood, chances are some changes have occurred since then, it could have shrunk or closed, considering the level of fitness described.

To pursue a passion for advanced diving, it would be prudent to insure a VSD has closed. Depending on the type of VSD, there may be other associated defects in the heart or valves that could be an added issue.

http://www.nlm.nih.gov/medlineplus/ency/article/001099.htm

 

[wetvet]

Saturation,

thanks for the response......please tell me where I am confused. Due to the much larger muscle mass and pressure differential in ventricles (as compared to atria), the risk of right to left shunts is very small, unless I am in heart failure which results in excessive myocardial development on the right side (which I do not have....so far). The size of the hole was actually measured a few years ago, so it hasn't changed much. My understanding of right-left shunts in the atria is due to the lower pressure differential, and lower total pressure. I assume that even a severe valsalva maneuver would overcome this pressure. The 100mmHg that the ventricles produce (and 40mmHg difference between right and left) would be impossible to reverse (again assuming I am not in heart failure). I actually felt that I was safer than the average joe, because I had had enough heart work to be confident that I did not have a PFO, which many people do have, and are unaware of.
If you could explain how a Right to Left shift can happen thru a VSD, I would be very interested. Thanks.

Wetvet

P.S Air_Miser, your little one should have almost no clinical signs of VSD. Even with the one I have, I have to run a long way, and overcome my aerobic capacity before I become dizzy (I'm talking a few miles). You can feel this coming on, and if you slow down the exercise a little, it goes away (kinda like being narced). Encourage him to do what he wants, and not worry about it.

 

[pufferfish]

wetvet once bubbled...
Saturation,

thanks for the response......please tell me where I am confused. Due to the much larger muscle mass and pressure differential in ventricles (as compared to atria), the risk of right to left shunts is very small, unless I am in heart failure which results in excessive myocardial development on the right side (which I do not have....so far). The size of the hole was actually measured a few years ago, so it hasn't changed much. My understanding of right-left shunts in the atria is due to the lower pressure differential, and lower total pressure. I assume that even a severe valsalva maneuver would overcome this pressure. The 100mmHg that the ventricles produce (and 40mmHg difference between right and left) would be impossible to reverse (again assuming I am not in heart failure). I actually felt that I was safer than the average joe, because I had had enough heart work to be confident that I did not have a PFO, which many people do have, and are unaware of.
If you could explain how a Right to Left shift can happen thru a VSD, I would be very interested. Thanks.

Wetvet

That is a very interesting question Wetvet and one where good data does not seem to exist. It seems though that the risk of a right to left shunt of venous bubbles does exist with a VSD particularly in diastole when during the cardiac cycle the heart is relaxed.

The pressure differential between the left and right ventricles during systole as you point out above would be unlikely to allow the shunting of blood from the right to left heart. However during diastole the pressure differential is far less and the risk of a right to left shunt through a VSD might be much greater. A valsalva maneuver might be one mechanism allowing bubbles to pass from the right to left ventricles. Immersion in and of itself might increase right sided heart pressures and 'prime the pump' for such a scenerio.

Here are some pressures listed for diastole in the ventricles.

Right Ventricular End Diastolic pressure 2-8 mm Hg
Left Ventricular End Diastolic pressure 3-12 mm Hg

As these pressure approximate those seen in the atria and an increased risk does exist for DCS in persons with a PFO one might assume a similar but unknown risk for DCS exists during diastole in a person with a significant VSD.

If that is the case, diving in a overhead environment such as a cave would not seem prudent with a VSD not only for yourself but for your buddy or instructor who may not be prepared to assume the slight increase in absolute risk for neurological DCS. Dr. Paul Thomas's story from last fall just highlights this issue of PFO risk and buddy responsibility.

Of course I am not expert in these matters but what you might do is email Dr. Bove the cardiologist who did some of the studies on the risk of PFO and DCS and see what he has to say. I have emailed him a few times and he has answered my questions.
His site is www.scubamed.com
You might check his new book on diving medicine due to come out next month.

 

[Saturation]

wetvet once bubbled...
Saturation,

thanks for the response......please tell me where I am confused. Due to the much larger muscle mass and pressure differential in ventricles (as compared to atria), the risk of right to left shunts is very small, unless I am in heart failure which results in excessive myocardial development on the right side (which I do not have....so far). The size of the hole was actually measured a few years ago, so it hasn't changed much. My understanding of right-left shunts in the atria is due to the lower pressure differential, and lower total pressure. I assume that even a severe valsalva maneuver would overcome this pressure. The 100mmHg that the ventricles produce (and 40mmHg difference between right and left) would be impossible to reverse (again assuming I am not in heart failure). I actually felt that I was safer than the average joe, because I had had enough heart work to be confident that I did not have a PFO, which many people do have, and are unaware of.
If you could explain how a Right to Left shift can happen thru a VSD, I would be very interested. Thanks.
Wetvet

My pleasure WV. I hope you don't mind the technical talk.

Unfortunately, the difference between right and left ventricle pressures at diastole can be, worse case, zero.


http://www.merck.com/pubs/mmanual/tables/198tb5.htm

An asymptomatic VSD is not a contraindication to no-stop diving, however in technical diving, unanswered questions loom.

Since there is always a risk for "paradoxic" emboli in VSD without closure, it follows such a risk exists for gas emboli in decompression dives. Standing recommendations exist for prophylaxis if thrombi exists in a setting of VSD. What prophylaxis can be done against gas emboli from deco in a setting of VSD? Sadly, the best prophylaxis is no deco, limited deco, or conservative profiles. Generally full cave requires moderately lengthy deco profiles.

http://www.ccs.ca/society/conferences/archives/1996/1996part-03.asp

Can bubbles tranverse the ventricles spontaneously as no gradient can exist across a VSD?

Change in intrathoracic pressure usually affects the heart equally, but if not, it may provide a gradient to aide a traverse. A rise in intrathoracic pressure can occur while breathing with heavy tank loads climbing out of a cavern zone.

As a diver ages, conditions with the VSD may change, and will need follow up. Will change in a VSD aide an emboli during a dive, that occurs undetected between physician visits?

These are questions difficult to answer, and given that, how would one respond to it when the nearest surface for aide will require a 30min to 1 hour continuous swim? Many cave locations are in remote areas, and cave teams rely on each other for help.

To know the situation with one's heart as it stands now puts a risk analysis in a better light. With good exercise tolerance and no recommendation by physicians to consider VSD closure, then the pulmonary to system shunt ratio is under 2.0 and the VSD must therefore be small and insignificant. I presume that there are no signs of RV enlargement, pulmonic hypertension or valvular dysfunction. I presume there is no trace of polcythemia.

Concrete answers to these general insights are best with the case facts and with a diving physician-cardiologist in person.

 

[Saturation]

Nice post, Pufferfish! Without any reservation, Dr. Bove is THE authority in diving cardiology, and possibly diving medicine in general.

 

[Dr Deco]

Dear wetvet:

Ouch

On this question, I must say that I am speaking virtually entirely from what I have read; I do not have research experience in Ventral Septal Defects (VSD). "Saturation" has already given the viewpoint from a medical doctor, and indicated that he did not really believe that decompression diving with this problem is without risk.

Research Scientist

My views are not any different that Saturation’s. I might add some comments, however. Your viewpoint that the normal L-R ventricular gradient is large is correct. A scan of PubMed reveled one study (see below for reference) with dogs that indicated that the L-R gradient was maintained throughout the cardiac cycle with various preloads. This is not what is found with atrial wall problems, and it could well be an important difference. The study was with open chest dogs and did not have a strong Valsalva component. How the preloads were changed, I do not know. They probably were not large.

If you experienced a large bubble load in the venous return, you might just as well suffer from a problem of pulmonary artery hypertension, secondary to pulmonary capillary blockade, and find that bubbles arterialized through pulmonary shunts.

Legal aspect :boom:

You can well imagine that, if you were to mind a medical complication and death resulted, the insurers would attempt to mitigate their losses. Gas bubbles are always found in the arterial system of divers returned to the surface from depths. You can be sure that it will be argued that you dove knowing that this could be a problem. While certainly not wishing to be gory about this, one would be naive to think that an insurance company would not attempt to shift a large portion of the blame to you. It is logical.

Dr Deco :doctor:

Please note the next class in Decompression Physiology :grad:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

Reference

Geiran O, Thorvaldson J, Molaug M, Ilebekk A. Changes in cardiac dynamics by opening an interventricular shunt in dogs. J Surg Res. 1990 Jan; 48 (1): 6-12.

 

[wetvet]

Thanks for all your information....I am going to attempt to contact Dr. Bove, and see what he says....Thanks to Pufferfish and Saturation for the reference. I hadn't considered diastole as a source for regurge or shunt, and will have to look into it. I still don't think that ventricular problems are comparable to atrial defects, but I am very interested in defining my risks. I will also contact my cardiologist to pin down all my pertinant info at this time. My interpretation of his advice before was that I could get it fixed if I insisted, and maybe this will give me the incentive to do so. I will keep you posted as to what I find out.

Thanks again.

Wetvet