Atrial fibrillation - page 3

by Soliloquy

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What are people with Atrial fibrillation at risk for? Acute MI or Pulmonary Embolus?... Read More


  1. 0
    Doesn't afib lead to strokes more than a PE? PE would result from DVT or right side of heart? Correct? Left side would lead to brain?
  2. 0
    Quote from Stoogesfan
    Doesn't afib lead to strokes more than a PE? PE would result from DVT or right side of heart? Correct? Left side would lead to brain?
    Definitely!
  3. 1
    It's a lousy question, but it wants to know if you know your anatomy and cardiac conduction. PE is a better answer than MI, although both are theoretically possible because the coronary arteries originate....where???

    For extra credit, explain to your classmates here why DVT does not lead to stroke in a person with an otherwise normal heart (the vast majority of persons). You will be astonished at how many nurses believe that's the most compelling reason for worrying about DVT. It isn't.
    psu_213 likes this.
  4. 0
    Quote from GrnTea
    You will be astonished at how many nurses believe that's the most compelling reason for worrying about DVT. It isn't.
    We even had an instructor try to explained how the DVT would lead to stroke....I felt pretty bad for her as she was trying to talk her way through it.
  5. 0
    The only way in which this would be possible would be a cardiac malformation that allowed venous blood to go directly into the arterial circulation. These do exist (think single ventricle, Tetralogy of Fallot, and others), and are sometimes occult, but even in the case of an unsuspected ASD or VSD, you would also have to have higher pressure in the venous side than the arterial side to carry a clot over there. It does happen, but uncommonly. Regular old stuff, not so much. The pulmonary capillary bed is designed to be a strainer for all sorts of little clots that you develop normally; they dissolve harmlessly if they aren't too big, having been prevented by the size of the capillaries from getting over to the arterial side. Good engineering.
  6. 0
    Embolic strokes that originate in the venous circulation or in the right heart are not all that exceedingly rare. The most common right to left shunt; a PFO, occurs in 25% of the population, hardly all that rare. Of patients with a stroke of unknown cause, PFO's are far more prevalent, occurring in 40% of those patients, suggesting that PFO's are responsible for a significant (as opposed to very rare) number of strokes. The L>R pressure gradient that occurs in systole does help prevent R to L flow during systole, however in diastole the pressure differences are essentially the same which allows intermittent pressure increases in the R heart (such as due to a cough or deep breath) to cause R to L flow.
  7. 0
    Having a PFO is not the same thing as having a right-to-left shunt; saying that 25% of the population has a PFO may be true, but it doesn't mean that they all have a right-to-left shunt by any stretch of the imagination, and it certainly doesn't mean that 25% of all strokes are attributable to this.

    It is physiologically impossible for a right-to-left shunt to exist in the presence of PFO unless the right heart pressure exceeds the left heart pressure, as you note. I will grant you that this does occur-- the heart and soul of the Patriots' offensive line, Tedy Bruschi, suffered such a stroke at a young age, had his hitherto-unappreciated PFO repair done, and was back playing by the end of the season, stroke fortunately resolved. He probably exceeded his left sided pressure with a big Valsalva maneuver at the bottom of a pile. If a stroke occurs in an otherwise healthy young person without other risk factors, this is where they look first.

    However, this actually goes to illustrate my point, which is that actual embolic strokes from venous clots are, in fact, rare. Else we would see many more of them in younger people. Sure, we see a few, but ask yourself-- of all the embolic CVAs you saw in your unit in the last year, how many were, say, in people without atrial fibrillation or single ventricle who were under forty? Under fifty? Under sixty? Not too darn many.
  8. 0
    Quote from GrnTea
    Having a PFO is not the same thing as having a right-to-left shunt; saying that 25% of the population has a PFO may be true, but it doesn't mean that they all have a right-to-left shunt by any stretch of the imagination, and it certainly doesn't mean that 25% of all strokes are attributable to this.

    It is physiologically impossible for a right-to-left shunt to exist in the presence of PFO unless the right heart pressure exceeds the left heart pressure, as you note. I will grant you that this does occur-- the heart and soul of the Patriots' offensive line, Tedy Bruschi, suffered such a stroke at a young age, had his hitherto-unappreciated PFO repair done, and was back playing by the end of the season, stroke fortunately resolved. He probably exceeded his left sided pressure with a big Valsalva maneuver at the bottom of a pile. If a stroke occurs in an otherwise healthy young person without other risk factors, this is where they look first.

    However, this actually goes to illustrate my point, which is that actual embolic strokes from venous clots are, in fact, rare. Else we would see many more of them in younger people. Sure, we see a few, but ask yourself-- of all the embolic CVAs you saw in your unit in the last year, how many were, say, in people without atrial fibrillation or single ventricle who were under forty? Under fifty? Under sixty? Not too darn many.
    Not to change the subject from afib but I think that CHDs are incredibly interesting topic as more kids with them survive and end up managed in primary care.

    I have a primary care pt that I manage with a know PFO, and we discuss risks quite frequently. The last meta-analysis I read listed PFO associated with ~5% of all embolic strokes. 25% is way off.
  9. 0
    Quote from GrnTea
    Having a PFO is not the same thing as having a right-to-left shunt;

    It is actually the same thing. PFO is the most common form of right-to-left circulatory shunt (RLS).

    By definition, a diagnosed PFO is a proven right to left shunt. Other than a few studies that determine PFO prevalence by autopsy, the most common method is by echo bubble study. Of course a bubble study finds a PFO only when a right to left shunt is demonstrated. So by definition, of those diagnosed with PFO by echo, ALL of them demonstrated a right to left shunt, and not only in rare circumstances, the bubbles are injected and are only in the right atrium for a few seconds.

    Quote from GrnTea
    saying that 25% of the population has a PFO may be true, but it doesn't mean that they all have a right-to-left shunt by any stretch of the imagination, and it certainly doesn't mean that 25% of all strokes are attributable to this.
    I've read and re-read my post and I have no idea where you got that 25% of strokes are attributable to PFO's.

    Quote from GrnTea
    It is physiologically impossible for a right-to-left shunt to exist in the presence of PFO unless the right heart pressure exceeds the left heart pressure, as you note. I will grant you that this does occur-- the heart and soul of the Patriots' offensive line, Tedy Bruschi, suffered such a stroke at a young age, had his hitherto-unappreciated PFO repair done, and was back playing by the end of the season, stroke fortunately resolved. He probably exceeded his left sided pressure with a big Valsalva maneuver at the bottom of a pile. If a stroke occurs in an otherwise healthy young person without other risk factors, this is where they look first.

    However, this actually goes to illustrate my point, which is that actual embolic strokes from venous clots are, in fact, rare. Else we would see many more of them in younger people. Sure, we see a few, but ask yourself-- of all the embolic CVAs you saw in your unit in the last year, how many were, say, in people without atrial fibrillation or single ventricle who were under forty? Under fifty? Under sixty? Not too darn many.
    Again, when diagnosed by echo, you're only looking to see if a right to left shunt exists in a window of time lasting a few seconds, you're not waiting hours or even minutes for shunting to occur.

    Rare in medical terms is usually described in terms of occurrence per 1000, or 10,000, etc. If PFO's contribute to 5% of strokes, that's hardly rare, that's 1 in 20. The vast majority of strokes occur in patient's over 50, so considering that of all stroke patients (the majority being older) the prevalence of PFO is 60% higher than in the general population, PFO's would appear to play a role even in the older patient population. All of the stroke patients I've seen with a potentially culprit PFO have been over 50 years old.
  10. 0
    The paper you quote is from Sweden and may have suffered from translation problems. it says, "When septae fail to fuse, how*ever, the PFO is a potential tunnel that can be opened by reversal of the interatrial pressure gradient. PFO is the most common form of right-to-left circulatory shunt (RLS)."


    I think we agree that a PFO is a potential cause of right-to-left shunt, but since many PFOs are discovered incidentally on autopsy for people who have never suffered any sort of CVA, it's a stretch to say a PFO *is* an RLS. It IS the most common finding associated with RLS, but that's different.

    The CVA patients you've seen with a potential culprit PFO are all over 50. Since they have had their PFOs since birth (actually, before birth) (barring exceptional circumstances), it is clear that the mere existence of a PFO does not inevitably cause stroke. But I think we're probably done explaining this now .


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