Friday, October 9, 2015

Atrial Bleeping Fibrillation, Part III: P-Waves From Heaven

On Monday night, I went for a quick, easy run while the kids were at Karate.  I was definitely in atrial fibrillation when I started.  So I started off with what appeared to be the "new normal," a heart rate limited slog at roughly 50 miler pace.  But I just kept going, pushing a little harder from time to time to see how it felt.  By the last hill, I felt pretty good, but didn't think anything of it, even afterwards.

But as I would discover later, my heart had snapped back into regular rhythm.

With a quick study of the .gpx file from the run on Trainingpeaks, I think I can guess to within a minute when I converted back to Normal Sinus Rhythm by looking at how efficiently I run.  The metric of "Efficiency Factor" (EF) is computed by dividing running speed (normalized for grade) in yards per minute by average heart rate.  Note the overall EF of 1.43 in the first frame:

Frame 2 highlights a roughly 2 minute segment 12-13 minutes into the run, with EF of 1.28.  This is typical of what I've seen during my week of Afib, and is far from the EF of 1.5-1.6 that I usually see.  A 10-20% loss of high end cardiac output, and therefore efficiency, is what is expected for Afib.  Not a literal killer, but certainly a killer of any chance of qualifying for the Ironman World Championships, which has been a perennial goal of mine for the last 3 years. 

And in the final frame, the EF is suddenly back to normal values:

 Later that evening, I checked my pulse, expecting it to be irregularly irregular again.  But it was surprisingly constant.  I didn't want to believe it, but it remaines so five minutes later.   And in the morning, I hooked myself up to a monitor at work:

GE.  We bring good things to life.  Like NSR.

P-waves! Glorious P-waves! And they've remained there since.  With the exception of a couple of skipped beats that scared the holy hell out of me, they've remained.

The next morning, I felt as if someone had slipped me an (extra) quad espresso.  I was walking on air, and my swim felt supercharged.

Unfortunately, speaking of espresso, I'm still going to pursue the prudent course and keep ratcheting down caffeine.  I'm grieving.  I love me some stimulating beverage.  It's basically my only remaining vice.

The leading theory for how it happened to me remains the altitude tent, or at the very least, the simulated height to which I pushed it and how soon I did it (increasing 500-1,000 "feet"/week, sleeping nightly (and often poorly) at 10,000 "feet."  This article (Thanks to Ted Rasoumoff) would suggest that pulmonary artery pressures go up substantially, even in asymptomatic residents of high altitude.  Between this and three 20 hour weeks of training, plus work, plus family time and duties...I know, but there are just so many awesome things in my life that it's easy to want to do it all...there was just too much stress and not enough recovery going on.  But I'll say it one last time: As someone who grew up at 7300 feet, I would've thought this was going to be pure gravy.

I had felt some sense of strain and for lack of a better word, bogginess, in my chest for the week or two before recognizing the irregular heartbeats and Afib, and it was starting to feel a little difficult and uncomfortable to lay flat and sleep in the tent.  I wrote some of this off to the small enclosure itself (it's just a hood that covers the head of the bed, and can be mildly uncomfortable), but clearly there was more to it than that.  It makes mechanistic sense that increased right-sided heart pressures led to stretching of the right atrium and the corresponding cardiac conduction pathway, which is how you get arrhythmias like atrial fibrillation.  It also follows that quitting the tent would allow pulmonary pressures, then right-sided heart pressures, to decrease.  Then the atrial conduction pathways would shrink back to normal length (as this was not yet permanent cardiac remodeling).  Then the aberrant conduction would go away when the normal course of electrical impulses through the atrium overrode it and took back over.

Responses of this sort to an altitude tent have not been reported with any great frequency.  But obviously, that's irrelevant to me.  The altitude tent experiment is certainly over.  Look for it on Ebay.

Since I'm feeling like a cool million, I'm going to slowly and cautiously start ramping up the mileage again in preparation for Ironman Arizona.  Assuming my working hypothesis is right, this shouldn't be a problem.  But I guess we'll see.  Say a prayer to Our Lady of Regular Heartbeats for me.


Monday, October 5, 2015

Atrial Bleeping Fibrillation, Part II--Gathering Info and Planning

Larry was most helpful.  No surprise there!!

Main points:
1) Afib likely to be recurrent.  (Again, I actually think I might have had it back in '99 after I ran my first marathon.  I seem to recall "funny heartbeats" for awhile after it, but they went away.)
2) Cardioversion and antiarrhythmic drugs are hit-or-miss.  They may or may not keep me in normal sinus rhythm (NSR).  In triathlon terms, NSR means that the atria squeeze in a coordinated manner before the ventricles, and I get to keep that 10-20% of top-end cardiac output, which is pretty important in a race).
3) As I suspected, anticoagulation (coumadin) is not necessary for me personally to decrease stroke risk.  With the exception of Afib, I just don't have any risk factors.  Asprin every day is enough.  Endurance athletes are just not likely to have the risk factors to justify coumadin (big gun blood thinner).  Plus, a hard bike crash on coumadin would not be good.
4) Catheter ablation is more reliable, but not 100% either.  This will likely be the solution if it recurs.
5) I will not just drop dead from afib (I was 99.94572% sure this was the case; it was my wife's question).
6) Having used an altitude tent for the last several weeks was a likely contributor of cardiac stress, but not a known cause of Afib.
7) Dudes and chicks over 40 have a 1 in 4 lifetime risk of afib.

What to make of it all? I'm almost undoubtedly still doing IMAZ.  I may not have the day I want, but that's just a little more out of my hands than it was a couple weeks ago.  We'll see what happens.  Still gonna be an endurance geek, still gonna give KQing a shot when it's feasible.  No more altitude tent.  No reason to try that experiment again.  I will be cardioverted this week, and we'll see if it sticks.  Modifiable risk factors for most people are alcohol intake (none here), caffeine intake (way too much, already tapering), and overall health--you know, like regular exercise...

I'd felt fairly knocked on my ass for the last few days, but I'm starting to get my emotional if not cardiac mojo back.  If the AFib thing still lingers, it's going to be ablation time, probably sooner rather than later.  I'm going to walk through the standard treatment algorithm of cardioversion--> antiarrhythmics--> ablation a whole lot quicker than most people would.  Color me impatient, but I don't see any benefit to putzing around with non-solutions.

Interestingly, Larry has also been putting in for the Norseman lottery...


Atrial Bleeping Fibrillation, Part I

The last three weeks of Ironman Arizona preparation have been of the "build" variety, meaning a whole ton of time and miles.  Week #2 was 22 hours, with 15 on the bike.  By the end of this third and most recent week, I was predictably feeling burnt.  This was not surprising. 

I recovered pretty quickly with a few days off, with the notable exception of my heartbeat still feeling slow and irregular, which it has for about a week.  I hadn't given it much thought other than it being PVCs/dropped beats, which is not much of a problem, but it occurred to me that it might be atrial fibrillation, which would be.  But atrial fibrillation usually correlates with a faster heart rate.  Yesterday morning, I ran before work--a slow, short, recovery style run.  It felt easy for the most part, but with periods of wanting to stop for no good reason.  When I got to work Saturday, I figured I'd put it to bed one way or another.  So I hooked myself up to one of the monitors in an empty OR:

It's slow, irregular, and lacking the "P" waves associated with a Normal Sinus Rhythm.  So I got myself seen in the ER while working, like a typical bad patient doctor would.  The official EKG showed the same thing: Atrial fibrillation.  As in, atrial bleeping fibrillation, as in, full stop on IMAZ prep and perhaps other things, as in, I'm likely to get cardioverted (shocked) in the next couple days and put on meds to anticoagulate and maintain rhythm.

Educational moment--In the diagram to the right, the EKG waveform for atrial fibrillation is shown on top.  The purple arrow on the lower tracing points to a "P" wave, which indicates normal atrial contraction.  There are no identifiable "P" waves in atrial fibrillation, and a corresponding loss of cardiac power with ineffective atrial contraction.

In hindsight, this was probably not the first episode I've had. When I ran my first marathon back in '99, a trail run near Santa Cruz, I remember feeling funny heartbeats towards the end of the race, and for awhile thereafter.  Soon after that, I remember getting on a treadmill with a heart rate meter (a novelty back then, as far as I remembered), and pushing my heart rate up to almost 190. This may not seem high to some, but currently, my threshold HR is in the mid to high 150s, and my "barf number" is in the low to mid 160s. Relative to the astronomical number I pushed at age 32, I thought my current HR must have been the aberration, a product of subsequent medical school and residency deconditioning or stress. More likely, the earlier, higher number was the anomaly.

I'm not sure where this is all leading, both in the short run and long.  The cardiac possibilities run from cardioversion (low voltage shock) and being basically done with it, to needing ongoing meds and even a catheter ablation procedure if it keeps coming back.  The lifestyle implications are that I need to get off my typical industrial doses of caffeine.  Crap.  I'm a big fan of caffeine.  But I'm a big fan of cardiac output too.  The endurance possibilities run from just having a long taper into IMAZ to having to become basically a recreational athlete.  This actually wouldn't be the end of the world.  But being a non-athlete is a non-option as far as I'm concerned.

I'm reading up and talking to people I know to make sure it's handled the best possible way.  Tonight I'm going to have a phone chat with Larry Creswell, Cardiac surgeon and endurance athlete.