Very short term arrhythmias during extreme exercise

[Robin999]

I am in my mid sixties, actively race on a bicycle, (generally races less than 30 mins) height 5ft 7in, weight 160 lbs, have a resting BP generally about 125/75 at 38 to 40 bpm. My pulse at full race pace is about 135 +or- 5bpm. Very vigorous hill climbing will normally get me to about 148-150 bpm before I crest the hill or "blow-up". That is I view 150 as my Max and 135 as my sustainable threshold associated with say about 210 watts +or- 10 watts according to fitness

Over the past few years I have noticed two quite different effects -

1 While riding moderately at say about 105 bpm - Sudden drops of about 20 bpm or so which last about 30 secs - These are almost always accompanied by that "lactic heavy-leg" feeling and these may re-occur randomly with 5 or 10 minutes between the re-occurences. These I can normally associate with "recovery" rides after a few days heavy training - Paradoxically if I push the riding and HR up on the ride the re-occurence disappears. This effect of short sudden drops does not worry me as I can associate it with overtraining and the cure is obvious.

2 On a small number of occasions while riding at slightly more than moderate pace and not necessarily at high power outputs, I have experienced periods of between 2 and 5 minutes when the HR has been elevated to 150 - 160 and sometimes beyond. On one occasion during a very vigorous hill climb interval session this was accompanied by an acute drop in power, sufficient to make me dismount and sit down, but mostly this is not so and there is no noticeable physiological effect. This may only happen once during an occasional training ride of 1 to 3 hours.  When I first noticed this a few years ago I put it down to measuring equipment malfunction but I have noticed it with different digital and analogue transmission equipment which although in itself is not conclusive has made me slightly concerned. I ride alone and do not believe there are spurious external signals causing this.
Again, apart from the extreme hill climb episode above it seems that when actually riding at full bore race pace the HR is much more disciplined.

Should I see my doctor or just stop worrying and enforce my own discipline as regards overtraining?

[Jerry_NJ]

Sounds like you are a very advanced athlete and would thus think it best to discuss with a doctor specializing in sports medicine.  Or, maybe a highly regarded sports (bike, I'd guess best) trainer. Does the UK medical system offer such specialists, or do you have to go "off network" and pay directly for such medical service.  A bit off topic, but as we're in the middle of legislative "discussions/debates" concerning more  government involvement in the provision of medical services in the USA, I wonder what others do.

You are way beyond anything I can relate to.  I am a few years old than you and was still a runner to the age 67, when my AFib got the best (worst) of me.  

[itdood]

Wow, you're in way better shape than I was in my 20s and I trained a lot back then.

FOr your age, your max is 155 bpm.  You're training zone should stay between 109-140.  At any age, staying around max predicted HR is a **** shoot, you can trigger just about any sort of arrythmia.

Given the odd declines and such, you could go see a cardilogist and get on an event monitor which will record your EKG while you train.  When you feel the blip, you hit a button and the event is recorded (2 minutes prior + time after the event).  You'll have to wear a 3 or 4 lead EKG, wired back to the EKG which communicates with a cell-phone like device that phones-home to send your data.  

The docs will see what's causing your arrythmia.  I would suspect some sort of block for when the drops occur.  FOr the high rate issues you experienced, the only thing that I can think of that would drop your ejection output to that extent would be lone afib.

Endurnace athletes are 5x more likely to develop arrythmias.

You can try the event monitor, whatever they catch probably isn't going to be all that treatable without some trade off side effects.  If it's what I'm completely guessing it is, a beta blocker could help prevent the lone afib (not sure), and for block I don't know what they do.  WIth the beta blocker your output is going to go down.  I think some blocks are ablatable.  I'm not sure...But yea I think you should get checked out.  

stress test, echo, holter.  If you're experiencing blood flow problems in your heart, like a midly clogged artery, you'd need a nuke stress test at the very least.  Even better would be a cardiac MRI.

[smconorm]

It sounds to me like there is definitely something going on with your heart and you should see a cardiologist.  Most arrhythmias are benign and you are no more at risk of sudden death than the general population.  However, sometimes an arrhythmia can be an indicator of an underlying structural problem with your heart.  

I am also a competitive cyclist in my upper 50's  with a lactate threshold of 157 and max HR of 180.  Last year, about this time, I experienced brief periods where my heart rate would shoot up to 220 and then recover to the 150's while going up a hill.  This was usually triggered by standing to generate more power.  The condition is referred to as "paroxysmal afib"  which means one recovers from afib naturally without needing a conversion.  During the 20 or 30 seconds of Afib, I would also loose power as you described.    I also experienced PVC's and other heart rate irregularities.  When this happens, you will see your heart rate monitor jump ---say from 125 to 155 and then back to 125.  This is the heart monitor averaging different rates of arrhythmia.    I wonder if your heart monitor is not able to record the faster frequency beats, or somehow filters them as noise, and is inadvertently indicating a lower heart rate when you see the sudden drops as you described?   The best way to sort this out is to wear a 24 hour Holter Monitor and try to replicate the conditions that bring on the symptoms.  The Holter accurately records all beats over 24 hours and you can review the output by time and events.  There are computer programs that interpret the data produced by these devices and you will get a lot of attention from data gathered during intense exercise--considerably beyond  the pre-programed range.

Arrhythmia conditions usually become worse over time.  In my case, I went through a number of tests to confirm there was nothing structurally wrong with my heart, I was on beta blockers for 6 months which drive you heart rate and blood pressure even lower and are difficult for an endurance athlete.  Last July I went through an ablation and to date I have had no ectopic beats since.  I have been riding as hard as ever without problems.  Incidentally, during my discharge from the hospital, I asked the head  EP if there was any problem with someone my age exercising at intense levels with a heart rate over 170 and was told to continue what I was doing.  Four of my cycling companions out of about 20 my age are dealing with arrhythmia conditions and three of us have had successful ablations. This condition doesn't seem fair do those of us who have lived a healthy lifestyle, but it is very common.