Thursday, October 1, 2015

Tachycardia and Misdirection

On August 1st I started my seventh consecutive ride of the Mt Tam double century - the only double I have completed every year since I started riding doubles in 2009. This would be my third year doing it on the recumbent and I was hoping for a PR as my training had gone well so far. Little did I know that it would result in a two month excursion into the world of cardiology.

I went to bed early on the Friday evening as I had to be up at 3:00am for the drive to San Rafael. I woke up at about 1:00 with night sweats, which was perhaps a bit ominous, but I felt fine. Drank a cup of coffee on the drive up after my usual pre-ride breakfast of oatmeal and banana. The ride started at 5:00am in pleasant temperatures and was easy going for the first couple of hours to the first rest stop. I almost certainly hadn't drunk enough, a common failing in early morning rides in cool weather, and I had added another cup of coffee to my usual Perpetuem drink mix. I hadn't filled my Camelbak at the start, but did so now for the long climb ahead. The weather was typical summer morning weather, overcast and foggy and by the time I had climbed from Alpine Dam at 600' to the start of the Ridgeway I was in the cloud. There are seven big rollers on the Ridgeway with some 12% grades before the turn off on the East Peak road at around 2000'. As often is the case, shortly after the turn I climbed out of the cloud into very dry and warm air. Mt Tam is a double peak and I was closing in on the first summit, heart rate about 140, at about 2300' when I started to lose the feeling in my legs. Never felt anything similar on the bike. I got off and next I hear a beep from the Garmin notifying me that my heart rate was too high at 163. Since I'm just standing by the bike this is odd and even more that it is still climbing. At 175, which is close to my max, it finally peaked and started to come down but slowly. At this point I elected to walk a bit and when the heart rate got a bit lower I tried to ride again, but the rate just started climbing right back up. Although I didn't have any chest pain, I was quite concerned that I might have a serious problem as this was all very unfamiliar and I knew of several riding friends who had heart attacks or heart issues on a bike ride.

When I reached the first summit I cruised down to the saddle and then walked up to the top having asked several passing riders to alert the volunteers at the top that I needed medical attention. Despite walking very slowly my HR stayed unexpectedly high. I had already decided that I was done for the day and wanted to get checked out properly. By the time the paramedics arrived I was basically back to normal but feeling a bit shaken. The paramedics didn't find any problems on the EKG but took me into Marin General ER for a complete checkup. The tests showed no indications of a heart attack but they were puzzled by the loss of sensation in my legs. I was discharged with a diagnosis of Super Ventricular Tachycardia (PSVT) and told to follow up with my doctor, which I duly did on the Monday. He got me a referral with an Electro-Cardiologist but the first appointment was not for two weeks.

Meanwhile I got on the web to find out more about TachyCardia and learned that (a) the condition is quite common, but comes in a whole variety of forms, some a lot more nasty than others and (b) that endurance athletes seem more prone to developing the condition. For example, this rather timely article in VeloNews made rather scary reading. At this point my hope was that it was an isolated event caused by dehydration and too much caffeine as these are both known triggers. Indeed I had been advised on the discharge instructions to cut out caffeine. On Monday I did a recovery ride that went fine. Tuesday I started one of the moderate 60 minute training rides that I had been doing regularly and at around 30 minutes my heart rate started to climb with no corresponding increase in effort. I had by this time learned about the Valsalver maneuver that stimulates the Vagal nerve and lowers the heart rate, and I managed to bring the rate down but abandoned the session. So not a one-off. Since I was supposed to be doing the Raid Pyrenean in early September and leaving on August 28th I was getting concerned. So I did the squeaky wheel thing and messaged my doctor. He upgraded my referral with the cardiologist and I was able to get an appointment for Thursday. Wednesday is my usual day to go into the office which is on the third floor and, of course, I took the six flights of stairs. By the time I reached the final flight I was struggling and my heart was pounding. Needless to say this did nothing to improve my mental state. The visit with the cardiologist wasn't very helpful as he wanted data from a two week heart rate monitor that wouldn't produce any results before I left for Europe. I was scheduled for a stress test and heart ultrasound the following Thursday and fitting of the monitor. On Friday morning my heart rate spiked during our gentle early morning dog walk. I decided to be a squeaky wheel again and called the cardiologist's nurse to see if I could get the monitor fitted sooner. They said they could do it today and when I went in I asked if I could have a 48hr monitor, on the grounds that I really wanted to get an early diagnosis so I could make an informed decision about the bike tour.

So I left the clinic wired up with a 48hr Halter monitor, which is like a continuous EKG. I did several rides on the trainer and had an attack each time, so the data was there. I even printed off a portion of the graph from TrainerRoad showing the heart rate spike:

The results came back early in the week but they only showed Sinus Tachycardia which basically means increased heart rate but no abnormal rthymn. While this was good news, there was still no explanation for it.

The stress test was interesting. I had had two previous tests, several years earlier, mandated before I could take my "miracle cure" Migraine drug. This time was a bit different owing to the ultrasound component. Before the test I was given the ultrasound at rest, which involved holding my breath, as the lungs evidently get in the way. Then I did the test, which went fine and at the end had to very quickly get back on the table for a second ultrasound with the heart pumping hard. Needless to say trying to hold your breath in that state is virtually impossible, but evidently they got the data. After the test I was fitted with the two week Zio monitor, which was much less invasive than the Halter monitor, but couldn't be immersed in water, so no swimming or hot tubs.

At this stage I was feeling much more upbeat and thinking I could do the Raid Pyrenean. On the Saturday I did a moderate, 1 hour, ride on the trainer. While I did have one heart rate spike midway, I got the rate down with a Valsalver maneuver and was able to finish the session with no further incidents. A couple more lighter sessions went well also.

On the Tuesday I had a follow up with the cardiologist. He didn't have much input and was waiting for the results from the Zio. Basically if that didn't show any abnormalities, he said he would pass me on to someone else.

So I decided the time had come for a real test. I hadn't actually been out on the road since the Mt Tam event so I decided to get my travel bike (Lightning P38) set up and go climb a hill or two. The warmup was going well on a route that I have ridden many times, up Alpine road to Portola Valley. The grade picks up slowly and never gets more than 5%. My heart rate was about 130 when suddenly, for no apparent reason, it started to climb. When it got to 150, a rate I would normally expect on, say, an 8% grade, I dismounted and did the Valsalver maneuver. It fairly quickly came back into the 120's but it was clear I had failed the test as I hadn't even got to the real hill. So I turned around and headed home. It was an easy cruise back down the 2-3% grade to Foothill followed by a short 3% grade which I know is actually the last uphill before home.

But that slight grade caused yet another spike, which really surprised me. I decided to ride it out as I knew the section was short and it would flatten soon. However I abandoned that plan when the rate went through 150 and kept climbing. By the time I got off the bike it had reached 165 and the Valsalver maneuvers weren't working. As soon as I stopped the maneuver the HR started climbing again. After a while another cyclist stopped to ask if I was ok and I said I wasn't sure, so he stayed with me. In an incredible coincidence this cyclist had also been on the Mt Tam double! Eventually with my HR still high I decided I should lie down. Of course that attracted a lot of attention. A car stopped and a young couple, one of whom had been a cardiology nurse stopped and also stayed. My HR was still about 120 at this point. Someone must have phoned 911 as then a police car showed up. I assured him that I would be fine and that I had called my wife to collect me and the bike, but he really wanted to summon the paramedics (I was only about a mile from Stanford Hospital), so I acquiesced. They did the EKG test (fine) and when I told them I was seeing a cardiologist they didn't push the ER option, which I knew would be a waste of time and money. By this time my HR was below 100. Shortly afterwards my wife arrived and we loaded the bike into the car and went home.

I duly cancelled the Raid Pyrenean trip. Of course, being stupid, I hadn't taken out cancellation insurance. I briefly considered going along as a tourist but decided I would likely be miserable not being able to ride. Fortunately I was within the 50% refund period, but I lost the money spent on the expensive RyanAir flights (pre-paid bike case). A lesson learned - stuff happens.

I didn't ride the bike for a week, but did one final easy spin on the day before we left. Shouldn't have. HR spike after 10 minutes from 120 to 150 and again, couldn't get it down. Lay down for 20 minutes and it eventually passed.

And so to England and two weeks vacation consisting of visiting friends and family and not riding, but doing some walking. To this point I had never had an attack unless riding or walking, but woke up on the plane around midnight with a full blown attack. Breathed my way through it, but was a quivering wreck for 20 minutes.

Midway through the first week I got a message from that a new test result was available. I knew that this would be the Zio patch data, but I decided not to look at it. If it was bad news it would spoil the vacation and, anyway, the data almost certainly needed to be interpreted by the cardiologist who I would be seeing the day after I returned. So it sat there in my mailbox tempting me, but I held firm. No attacks for over a week but then a mild one while solo walking my sister-in-law's dog, climbing a hill. I was getting quite good at breathing through the symptoms, but I still found the whole experience unpleasant. It's also so darn random. The following day I did a solo 6 mile walk on Dartmoor, involving a few steep climbs without any events.

By now I'd read everything I could find on Tachycardia and was still searching for the cause of the original event. Given that the Halter monitor didn't show any abnormalities, I'm pretty sure that the Zio patch won't either and, indeed, that is what the cardiologist tells me when I meet him.

So, what really happened? While talking it over with my wife Jenny and friends and family on the trip, I concluded that all the attacks except the first were basically anxiety attacks. I was focusing on my heart rate and if my legs felt slightly odd or the rate ticked up a bit, my mind decided the original event was happening again; cue the adrenaline and a vicious cycle ensued with a rising heart rate guaranteed. But that doesn't explain the first attack. Eventually the penny dropped. I had just bonked (hit the wall), or to give it the technical term: hypoglycemia. I didn't know this before, but hypoglycemia releases adrenaline to force the liver to make glucose in a hurry, which explains the rapid heart rate rise, plus the anxiety I was feeling from my losing feeling in my legs fed the vicious cycle. I had never bonked before so I really didn't have a clear sense of what it felt like. Evidently it can manifest in many forms, one of which is a complete loss of function in the legs.

Ok, so why did I bonk so early in the ride, having never bonked before? I'm guessing muscle glycogen depletion, given that it was my legs that went out. Everybody talks about "carbo-loading" before an athletic event, and what this really means is trying to load your muscles up with as much glycogen as possible. You will still run out on a long endurance ride, especially if your effort level takes you into the anaerobic level, but the more you start with, the longer it takes to deplete. Plus, provided you keep topping up with sports drinks and high-carb food, you should be ok. Now, for the past couple of years I have been on a lower-carb diet, basically cutting out most sugar and junk carbs, and in the weeks prior to the ride I had dropped my carb intake a bit more. So I'm pretty sure I went into the ride without a full load of glycogen, which I then compounded by not eating or drinking enough in the early going. And the Mt Tam climb is long, with quite a few steep pitches, so it is quite plausible that I bonked near the summit.

What is slightly depressing is that neither the paramedics nor the ER doctor suggested this as a cause; the ER doc even consulted a neurologist about the loss of feeling in my legs. Several times when explaining the event, I wished I could relive those few moments; loss of feeling is how I remember it, but it was very fast and it stopped as soon as I got off the bike. Nevertheless, everbody, including me, was focused on the PSVT diagnosis. Now, as my cardiologist explained to me, PSVT is technically a correct diagnosis, as Sinus Tachycardia is one form of PSVT.

I learned a lot during this process. I know know a lot more about heart arrhythmias (way more than I need to). I also learned a lot about proper breathing techniques having discovered that I had a rather shallow (chest) breathing habit, rather then deep diaphragm breathing. Most important for endurance cycling I now understand a lot more about the way the body metabolizes energy and the benefits of keeping carbohydrate intake down even while exercising in order to keep insulin levels low and maximize fat burning. I can highly recommend this website for lots of information on the subject.

A fellow endurance rider recommended the Metabolic Efficiency/Lactate test at the UC Davis Sports Medicine department. Last week I did the test and was very pleased to learn that I am above average and my carb/fat burn ratio is 25%/75% at typical riding levels, whereas this ratio is reversed in most people. The not so good news was that my heart rate training zones were very compressed which is another way of saying that my heart rate is high even at low efforts. So some of those spikes that I thought might have been anxiety might just have been my HR rising to the level it needed to be. Of course, this is new, as my HR used to be extremely stable and closely correlated in a linear fashion to my power output. The sports medicine doctor suggested getting a Ferritin test as low levels can cause an increased HR, but that came back normal. At which point both my primary care physician and the cardiologist had no further suggestions.

Anyway to cap it off, I'm back in base training, monitoring my heart rate (invisibly to avoid any anxiety spikes). It still seems a little high but the trend is down, which is good. I have yet to do a sustained climb, but I'll get there soon.

1 comment:

  1. Very, very interesting blog, Mick....I think panic / anxiety attacks are much more common than we realise. Glad to hear you're better physically and you've got your head around it - which is just as important.