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Monday, July 11, 2022

Atrial Fibrulation

This is a transcript of a talk given by Dr Andria Coley, CardioThorasic surgeon from the University of Texas, Cardiology Institute.  It deals with the present knowledge of Atrial Fibrillation as of 2022.  

Here is the URL if you prefer to watch the Video.
The transcript can serve as a useful check list.

1/ For decades the medical profession have had the impression that A-Fib is really not that serious.  You have an episode, get over it and carry on.
 
2/ From studies, following up on people with A-Fib it  became clear that A-Fib is a serious problem and it is becoming more and more common.  Recently a great deal of research has been carried out on A-fib, on its prognosis and how to treat it.
 
3/ People with A-Fib have a 5 times greater chance of a stroke, three times greater chance of heart failure and twice the chance of early cardiac caused death.
 
4/ A 5 year study of a group of patients who had A-fib for the first time, which was serious enough for them to be hospitalized, showed a huge increase in a whole range of conditions over the following years.  These included a high rate of heart failure, high rates of stroke, heart attacks, bleeding problems from being on blood thinners, and most serious, just under half of these patients passed away within the 5 year study period.
 
5/ A-Fib is 2 to 3 times as prevalent in the USAas in other 'western' countries.   She puts this down to the American diet, way of life and other medical problems that are common in America.
 
6/ There are a number of new options for sorting out A-Fib.
 
7/ In the healthy heart, the Sinus Node at the top of the Left Atrium starts the pulse.  The pulse is picked up by the AV node which sends it to the Ventricles.
 
Note: the blood enters the Atriums which pumps it to the ventricals which pumps it to the body (0ne side of the heart) or to the lungs (the other side).
 
8/ When a group of rogue cells 'decides' to send a false signal, it causes the Atrium to fibrillate - a little like the twitch you get in your eye sometimes.
 
9/ If this rogue signal hits the AV node it causes Rapid Ventricular Response.  ie.  The heart speeds up.  This is when people typically feel A-Fib.  When the Atrium is in A-fib, it can happen without the person being aware.  What we feel consciously is the ventricle pulsing away at a rapid rate. The complications (see below) from A-Fib occur even when only the Atrium is involved (even without the rapid Ventricular pulsing).

The Pathopysiology of A-fib

1/ AF is refractory (hard to treat).
 
2/ AF can cause heart scarring.  Electrical signals are transmited through muscle, not through scar tissue.  Scar tissue can disrupt normal signal transmission but can also be used by a surgeon to stop abnormal signal transmission.
 
3/ AF can cause the heart to stretch, further disrupting normal signalling leading to more A-Fib, leading to more stretching (and scarring).  A really bad cycle.
 
4/ Early A-Fib is called paroxysmal (comes and goes), usually from one wee cluster of cells that has gone rogue.  Usually this is on the back of the left  Atrium where the veins from the lungs enter the Atrium.
 
5/ About 6 months after this first stage, if it hasn't been taken care of, things change. Scarring and stretching begins to occur, messing up the signaling and starting what the Electro-Physiologists call a rotor.  This causes non-paroxysmal, or prolonged AF.  At this stage the new treatments that are coming on line, are useful. The old methods can't cure A-Fib at this stage in the progress of the disease.
 
6/ AF is responsible for a fifth of the strokes in the USA.
 
7/ The Atrial Appendix is one spot particularly indicated in forming clots since the blood tends to pool there, especially in someone who has AF and hence does not have a completely one-way flow of blood.
 
Note: The Atrial Appendix is a wee pocket in the wall of the heart of no known use.  A surgeon can put a plug in it if he is inside the heart or a clamp, if outside the heart.  This gets rid of the main source of blood clots. If a clamp is used, the wee pocket dies and ceases to be a problem.
 
8/ Of particular concern,  as the heart stretches, it pulls the sides of the vales apart and the valve can no longer close completely.  This allows back flow of blood and increases the chance of a clot forming and hence stroke.
  
9/ This whole process of stretching and scarring leading to more AF is a vicious downward cycle.


What can be done (in increasing order of intervention)

1/ As has been done for some time, anticoagulants are taken to avoid stroke.  Much better choices than Aspirin are available these days. Aspirin only affects the platelets and stops them clotting.  The medicine must be taken continually since one can not tell when one is in A-Fib if it doesn't trigger off the AV node, (causing the Ventricle to speed up).  Clots can form within 5 minutes of A-fib starting.
 
2/  Some people can not tolerate being on thinners.  For these folks a surgeon will often either block off or pinch off the Atrial Appendage/appendix since this is where 95% of the clots are created.  The AA isn't needed for proper heart function.
 
3/ Beta blockers are meant to stop the Ventricle from racing but they don't stop A-Fib or the complications that come with it.
 
4/  Other medications such as Amiodarone HCl are sometimes tried to re-establish normal cardiac rhythm but If AF continues, they can make one feel pretty bad.  These medicines can also affect the liver.
 
5/ Resetting the heart with a shock.  If you already have an advanced AF, the reset from a shock, likely won't last.  Shock is more effective in the very early stages of AF.
 
6/ Ablation(1), using scar tissue to stop bad signals.  Done by an Electro-Physiologist with a probe inserted through a  vein in the groin. This is for the paroxysmal (early) AF in which the rogue signal is being generated where the veins enter the Atrium from the lungs.  If AF is caught early,  it is highly effective.   When done for a later, more advanced case, success is only about 35%.

7/ Ablation (2) (when the surgeon is in your chest),  She scars a maize over your heart which only allows the good signals to propagate. Even for the really difficult cases, this technique is effective in 85 - 90% of cases.
 
8/ The best system - the Hybrid maze.
Cardio-surgeon goes in through a small incision just below the breast bone, and with a probe goes up to the heart and scars the appropriate part of the outside of the heart.  A few days later the electropysiologist goes in through a vein in the groin and finishes the job from inside.  Success is around 80%.


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