Tuesday, October 09, 2007

Blaming It All on Mitral Valve Prolapse

Chicago is still reeling from the aftermath of the Chicago Marathon as they struggle to ascertain why Chad Schieber, an otherwise healthy 35 year old police officer, could die during the event. Certainly, everyone’s heart goes out to the grieving family, and at times like this, we all search for “the cause” – why should an otherwise fit individual die?

The coroner’s report that described “mitral valve prolapse” as the cause. But for those of us in the cardiac field, we wonder, how the heck can the presence of mitral valve prolapse cause death?

Mitral valve prolapse is caused by a redundancy of the mitral valve that causes the mitral valve (which separates the left atrium from the main pumping chamber of the heart, the left ventricle) to bow, or prolapse, into the left atrium. The leaflets are prevented from bowing too far back into the left atrium during systole by strong strands of tissue (called chordae) that act to tether the leaflets to the left ventricular chamber (think of the lines attached to a parachute that serve to hold air inside the parachute). Some patients have some leakage of the valve from the left ventricle backward into the left atrium caused by the bowing leaflets. Tons of folks live just fine with a minor leakage. But if the leakage gets too severe, or if one of the chordae ruptures, the flow of blood backward into the lungs can be so severe that the lungs fill abruptly with fluid, and respiratory collapse and perhaps death, occurs.

We are given limited information in the coroner’s report if a chordal rupture occurred in Mr. Stokes, only that he had “mitral valve prolapse.” So if he did NOT have chordal rupture, then we are left to wonder, would the mitral valve prolapse in and of itself, have killed him? Likely not. So if not, what other causes might explain his untimely demise?

First, let me say, I doubt we will ever know. But much more common in marathoners running on a hot day is the presence of heat stroke and electrolyte abnormalities. Given the hype about the need for water and the experience of this runner, it’s hard to imagine that heat stroke would be the most likely cause here, but it can’t be excluded. Electrolyte abnormalities, on the other hand, may have played a significant role.

There are two main “electrolytes of life,” as I like to call them: sodium and potassium. Sodium is the major electrolyte outside of cells, and potassium is the main electrolyte inside of cells. Sweat is important cooling mechanism for the body, since evaporative heat loss is a very effective way to lose heat. But with sweat goes sodium and a small amount of potassium, too. And so the marathoner drinks water – lots of water – but often, does not replace any of the sodium lost with sweating.

And the results for the heart can be catastrophic. An important study was recently reported in the New England Journal of Medicine regarding hyponatremia (low sodium levels) in marathon runners in the Boston Marathon. This weekend, I had a chance to see this first-hand on Sunday when a marathon runner presented to our ER with hyperventilation, confusion and muscle fasciculations (diffuse fine twitching) and positive cardiac markers. Here were his lab studies:

Sodium 125 (ref: 133-145 meq/L)
Potassium 3.4 (ref: 3.5-5.3meq/L)
Chloride: 90 (ref:98-108 meq/L)
CO2 17 (ref: 23-32 meq/L)

Myoglobin: 1453 (ref: 21-98)
CK-MB 62.5 (ref:0.6-6.3)
Troponin-I 0.31 (ref: 0.0-0.06)

His EKG was normal.

What was striking were his confusion and muscle fasciculations. If effect, his sodium was so low that it was affecting all of the excitable tissues: his neurons and muscles. Fortunately for this individual, he did not have any skipped heart beats.

But throw a few extra heart beats into a heart exposed to that low sodium (which certainly could happen in the setting of mitral valve prolapse) and fatal cardiac arrhythmias can occur abruptly and irreversibly, resulting in sudden death.

So could this have been the real cause of death for this young man? Perhaps. Perhaps not. But blaming it all on mitral valve prolapse sends the wrong message to the thousands of patients living with this common heart valve anomaly.

-Wes

9 comments:

Gary said...

I think it's bad enough that MVP is so overdiagnosed... now everyone is going to start thinking that it's going to kill them!

The Independent Urologist said...

I certainly am suspicious of the report and believe that the coroner had motives to state that the cause of death was the MVP, not the heat or the conditions in which the marathon took place. One has to wonder whether any political pressure came down on him and wonder from where that pressure came, ie the Mayor's office and the corporate sponsors. At the risk of seeming like a conspiracy theorist, I will now sign off.

DrRich said...

Wes,

Thanks for this post. It reinforces very graphically what I wrote about yesterday on the same topic on my About.com heart disease site (http://heartdisease.about.com). Accordingly, I wrote a follow-up post today, linking to yours.

Best,

Rich

Uncle_Anesthesia said...

At this time, without knowing Mr. Schieber's electrolyte panels, we don't know much about his hydration status. I agree with Dr. Wes that overhydration is potentially very dangerous to a marathoner (especially one with MVP). However, dehydration still remains an equally large threat. And while electrolytes are lost in sweat, sweat is itself markedly hypotonic, with the typical result of unreplaced sweating being a hypertonic hypovolemia.

The normal reflexive tachycardia and increased contractility that accompany hypovolemia could be potentially dangerous for an individual with MVP, and could contribute to chordal rupture that Dr. Wes mentioned. In addition, a person with MVP would be more likely to experience a drop in cardiac output secondary to inadequate preload, which coupled with the extreme oxygen demands of marathoning could also contribute to an arrhythmia in the absence of hyponatremia.

It is ultimately the responsibility of the runners to be aware of their health problems, as well as to hydrate in a proper manner (neither inadequately or excessively). However, when the event sponsors state that fluids will be available at certain points along the course, it is their responsibility to make that happen to allow the runners have the opportunity to make their own hydration choices.

BN said...

Hi Dr. Wes,

I came across this post after doing some googling on "MVP", which I was diagosed with two years ago. I applaud you for making your expert opinions so accessible, not only by posting in such a public realm but by writing in a plain language style people like myself can understand.

I'm writing because I want to offer a "rebuttal" of sorts. But first...

My Background: I'm a male in my mid-20's. Over the last 2.5 years, I've been in a fast-paced career where I am working 45-60 hours a week, getting little sleep (5 hrs/night avg.), eating poorly (+20% BMI over this period), and take sizeable doses of Adderall almost daily etc.

My Issue: I experience regular mild-to-moderate heart arthymias and twitching in my left leg. Symptoms usually appear in the afternoon of every work day and persist until I go to sleep, for a total of about 5-8 hours daily. On a few occassions where I have really stretched myself with sleep deprivation/nutrition/Adderall, I've had scary moments where the symptoms escalated from slow, steady palpatations to rapid, painful episodes.

The Bigger Point: I think there is a flip-side to mainstream medical opinion "blaming it all" on MVP after a sudden death where the person was found to have the condition. It seems when there is a living patient with MVP, doctors can be too dismissive of disease. For example, during the consultation after being diagnosed, my own cardiologist seemed almost apprehensive about how someone my age would let a "non-fatal" condition like MVP worry them. Beyond a very basic spiel about getting more sleep, etc., he was so unconcerned that he didn't even bother advising me on the long-term risks of heart infection, the need for antiobiotics prior to dental/surgical procedues, or any of the other seemingly serious MVP-related issues I've later learned about on my own accord.

While your post only addresses lack of evidence for MVP's direct causality in sudden death cases, I think the tone of your post title and some of the comments above indicate some degree of skepticism about MVP as a serious condition. While the condition may not *in itself* be a huge danger, given the prevalence of overstressed lifestyles like mine (as in my case), I worry that it could easily be a killer.

I'd be interested to hear any thoughts you may have. Thanks again for your great blog.

-BN

DrWes said...

BN-

Determining the cause of death can be a particularly perplexing challenge for health professionals. The presence of pathology does not necessarily imply causality. My point in this post is (1) that mitral valve prolapse is common, (2) we do not know the severity or other confounding reasons why the coroner determined MVP as the cause of death in this man, and (3) there are other issues in marathon runners other than the mitral valve finding that could easily have caused his demise. While I agree some doctors might not appreciate that MVP can be a serious condition, I was attempting to explain that its presence alone is unlikely to kill people unless some other issue was wrong with the mitral valve or the valve leakage was particularly severe.

Often, media reports things without the persective of the implications to the many, many people with this disorder. I was merely trying to lend some objectivity to the discussion.

The issue of the need for antibiotic prophylaxis should be discussed with your physician - not all patients require it (according to the new guidelines recently published).

BN said...

Developing a theory of causality for any event seems to be more of an artform than a science, even within actual scientific fields like medicine. I hope I didn't imply that I automatically subscribe to the notion that MVP was the exclusive cause of the jogger's death. I think the alternative explanations you provided seemed logical enough from this layman's point of view. On the other hand, while you pointed out electrolyte loss was a compelling potential cause, you seemed to focus in your post only on how it could cause death, not why it was more likely to induce the death than MVP complications. In fact, in the single example provided of a confirmed case of electrolyte loss, the patient apparently survived.

Going strictly on the varying theories you named and the support you provided for each, it seems that "a few extra [MVP-induced] heart beats into a heart exposed to that low sodium" is the most plausible explanation. You seemed comfortable with "combination explanation" yourself, but I think is my view that you can still "blame it all on mitral valve prolapse" practically speaking.

My view is this: MVP is a lifelong condition that, when aggravated by certain temporary stressors (e.g., electrolyte loss, or "pulling an all nighter on Adderall" in my case), can apparently be fatal. Because an people who do not have MVP are seemingly much more likely to survive these stressors than those who do, I think in all practicality it's fair to call MVP the underlying "cause." A cliche, but I think otherwise good analogy to draw here is AIDS: We say only that a person "died of AIDS", when in fact other pathogens (e.g. pneumonia) usually contribute to the death, don't we? (While I'm sure there are some physicians that may dispute even that claim, this sort of approach strikes me as too reductionistic....)

Anonymous said...

Dear Dr,
I was diagnosed with MVPS few years back. I on/off have symptoms (may or may not) associated with MVPS. Recently I went to a cardiologist who gave his opinion as "Your MVPS size(I don't know what he refers too may be the prolapse size!)is not at all appreciable as per the cardiologist in United States(I am living in India)and its a less moderate form of MVPS and you can engage in all type of activites except lifting heavy weights". Your article drives me crazy whether to have a strenous work out or not". I have a strange feeling of tachycardia when raising from bed suddenly and resolve itself recently and he says that MVPS are slimmers and this body type makes them aware their heart is beating too fast and refused to put on any drugs other than a life style as that of a person having a normal healthy heart. I need your expert opinion in this regard.

Angie said...

Although this is an old article I would like to provide BN and Anonymous a couple of resources that have greatly helped me understand our condition a little better. Thank you for this article Dr. Wes, it was an interesting read.
Here are the links:http://www.google.com/url?sa=t&rct=j&q=mitral%20valve%20prolapse%20syndrome&source=web&cd=1&cad=rja&sqi=2&ved=0CC0QFjAA&url=http%3A%2F%2Fwww.mitralvalveprolapse.com%2F&ei=9mjIUIiSKMjnrAGipYHoDg&usg=AFQjCNFMY7AzI_fQFWbIZlnG8ydFSgt0yw&sig2=v9w2mO2YpbcMKT5EPxEeYw&bvm=bv.1354675689,d.b2U

and this book provided Great insight!: http://www.amazon.com/gp/product/0446394076/ref=oh_details_o00_s00_i00

I'll check back periodically to see if either of you respond. Knowledge is power!