Supraventricular Tachycardia

This is an image of Bobby Julich, the most notable cyclist in the world to have been afflicted with supraventricular tachycardia. In 1996 Julich was in top racing form but suddenly withdrew from an Olympic Trial when his heartbeat reached an alarming level. He was treated with radiofrequency ablation and came back to pro racing to compete in that year's Vuelta a España. In 1998 he went on to finish third in the Tour de France.

Now we have an image of a not-so-notable cyclist:

That's me, crashing out in my first mountain bike race at Craighead Park. I don't share much with Bobby Julich, but I, too, am afflicted with supraventricular tachycardia.

In the spring of 2004 I was diagnosed with paroxysmal supraventricular tachycardia, but I have almost certainly had the condition much longer than that--perhaps for my entire life. What this seems to mean is that at unpredictable and irregular intervals the upper-chambers of my heart (the atria) speed up, putting them out-of-sync with the main pumping chambers (the ventricles). Usually, I don't notice this arrhythmia at all, but occasionally I can feel that my heart seems to be skipping beats or pounding irregularly.

In a normal heart, when the left atrium contracts, the mitral valve opens to allow blood into the left ventricle, which has just been emptied by its own contraction. In my heart the atrium apparently will sometimes contract at a time when the mitral valve is closed because the ventricle happens to be contracting at the same time. This causes the atrial blood to pound against the mitral valve and, over time, has caused me to develop mitral valve prolapse (a ballooning out of the valve). Interestingly, the "benefit" of mitral valve prolapse is that the sloppy valve acts as a shock absorber and makes the pounding of my heart less noticeable than it might be in someone with a normal heart.

The inefficient and asynchronous beating of my heart also means that sometimes the atria are not filled with blood when the ventricular valves open. Thus, the next ventricular heartbeat is "skipped." This causes an effective drop in blood pressure, and the body's feedback loop stimulates my ventricular heart-rate to increase in order to bring my blood pressure back up to its required level. So episodes of supraventricular tachycardia manifest themselves in an elevated and irregular heartbeat. If the heart-rate gets too high, the heart muscle does not have enough time to recover between beats. Contractions become weaker, resulting in exhaustion, dizziness, fainting, and (very rarely) death.

My desire to collect objective data about the functioning of my heart was a major factor in my decision to purchase a Garmin 305 GPS with heart-rate monitor. And after collecting several months of data during my time-trials, I have begun to have confidence in my understanding of my heart condition.

In the vast majority of my rides there is no evidence of any anomalous heart rhythm, but in a few there are episodes of arrhythmia of wildly varying length. In the first graph below I have superimposed the graph of my heart-rate on two rides of the same course at about the same average speed. During the "red" ride, my heart seems to have been beating normally throughout, with my maximum heart-rate peaking at about 158 at the tops of the steepest hills.

Comparison of Heart-rate During a Typical Ride and During One with Episodes of Arrhythmia
(Click on image to enlarge)

The "blue" ride, however, clearly has a section from mile 17 to mile 21 in which my heart-rate is about 15 beats-per-minute faster than expected. During this fifteen-minute period, my heart-rate spikes up to over 160 BPM (nearing, or slightly exceeding, the expected "maximum heart rate" for a person my age). I happened to glance at my heart-rate monitor during this section of the ride so I knew what was happening, but I felt perfectly fine. This is, of course, not particularly surprising. When my heart is in arrhythmia it is quite like having a four-cylinder car that is firing on only three cylinders. At low RPM's the engine runs sluggishly and may backfire; at high RPM's the engine seems to smooth out again.

Next we have a graph of my performance during my fastest-ever time trial on April 12th of this year. The green line shows the elevation, while the red line shows the associated heart-rate at that point. It was a cool day so there were no reliable heart data for the first three miles until I worked up a sweat and the chest-band was able to have good electrical conduction.

Data about Personal Record Ride
(Click on image to enlarge)

Note that from mile 3 until about mile 7 my heart-rate is consistently in the range of 140-150 BPM. This is consistent with a hard time-trial effort. Then, even though the route is descending and thus my heart-rate should be slowing because of the reduced effort, the data show a sudden upward blip of 15-20 BPM. For almost the whole rest of the ride my heart-rate stays above 150 BPM--greater than 95% of my maximal heart-rate by the standard calculation (Max HR = 220-age). Indeed, the average HR for the entire ride turned out to be 155 BPM -- an astonishing 95% to 98% of maximal HR, depending on one's method of calculation. Yet I felt solid, healthy, and energetic throughout the entire time trial. One can see in the data, by the way, that my heart occasionally tries to "reset" its rhythm. From mile 7 through 9, there are five separate downward blips of just the amount one might expect; and again at mile 27, in the midst of a fairly difficult little climb there is another downward blip of the right amount. In each case, however, there was so much adrenalin coursing through my system as I raced "the little demon" that my heart went right back into arrhythmia.

What can I conclude from all this? First, that I am blessed with a strong hemodynamic system so that minor cardiac inefficiency is not at all debilitating. Second, that if I can ever get out on a time trial on a really good day, and compete with the little demon without the handicap of arrhythmia, I should be able to shatter the record!

Update 7/29/2015

Today I came across a very useful and interesting article on cardiac arrhythmias in endurance athletes. If you have (or think you may have) such an arrhythmia, that article gives you a great dose of good guidance. As for me, I am still cycling 4,000 to 5,000 miles a year. This is enough to qualify me as a serious cyclist, but I'm not a competitive athlete. While I've completed a few centuries, my normal rides are in the 30-60 mile range (usually closer to 30).

For me, the best way to deal with SVT has been to completely avoid caffeine (coffee and tea, especially). That artificial surge of Adrenalin seems to have predisposed me to arrhythmia, and cutting it out entirely has really helped. I rarely have any problems at all (knock wood), but when something does knock my heatbeat off stride, I find that the Valsalva maneuver is pretty effective at restoring a normal rhythm. But the road ahead is never certain and contains different obstacles for everyone.

Update 1/28/2018

Here is another article that discusses the use of heart-rate monitors in athletes who suspect tachycardia. The gist of the article is that glitches in transmission of data tend to make athletic HRM devices unreliable in accurately detecting SVT. However, athletes with diagnosed SVT are advised to use these devices anyway. I guess the idea is that if you know you have SVT you should reduce exercise intensity whenever you see an exceptionally high heart rate. Better safe than sorry.

A more recent study suggests that newer HRM's are useful in detecting paroxysmal supraventricular tachycardia, but it was based on fewer subjects with fewer devices (Apple, Samsung, and Fitbit) during instances of induced SVT. It seemed a little less rigorous to me.

Matney Mountain and Push Mountain

Today Sue and I drove around to the south side of the lake in order to ride up Matney Mountain and Push Mountain in the Ozark National Forest. This is one of the prettiest and safest rides in the area with two big mountains (big for the Ozarks), lots of little hills, and lovely views across the valley. Here is the profile from my Garmin (click on the image to enlarge it):

The most intriguing part of the adventure occurred, however, before we even began the ride. On the drive to the base of Matney Mountain, we stopped off to watch the water overflowing the top of Norfork Dam:

Crunching the Numbers

For Christmas this year I bought myself a Garmin 305 Forerunner, the latest element in my number-crunching approach to cycling. I wasn't always a number cruncher. For many years I just rode my bike--usually a 30-pound mountain bike--wherever the road or trail took me. Those were the years, back in the late 80s or 90s, when I made my first circuit of Trout Lake on a mountain bike. It was a 27-mile ride, and I thought I had nearly circumnavigated the globe. Now my ordinary ride is 31.2 miles. About that same time I started doing a few rides here in Hand Cove; it was a big accomplishment for me the first time I was able to ride up Cemetery Hill without stopping--or feeling that my hammering heart was going to immediately put me in the small hilltop cemetery. Now I cycle up that brute during every time trial.

I guess I didn't really get serious about cycling until the spring of 2002 when my son David began to hike the Appalachian Trail. This was also the year in which Lance Armstrong was being hyped to win his third consecutive Tour de France (equaling three-time winner Greg Lemond). It occurred to me that I could share both of these efforts vicariously by logging as many miles on my bike each week as David would be hiking. Of course, I wouldn't be wearing out my legs every day carrying a forty-pound backpack, sleeping on the hard ground, and eating freeze-dried food like David; nor would I be completing my 2,200 miles in 19 days of hard racing like Lance. Still, I would be logging the same number of miles, and the habit of writing down my miles on the calendar after each ride gradually turned into obsessive number-crunching.

By the end of that summer I was starting to record times and average speeds for my standard ride--at least when they were fast enough to be worth writing down. I bought my first serious road bike, an entry-level Giant OCR3, in September of 2002--and dutifully weighed it on my bathroom scale (24 pounds). To me, it was an amazingly beautiful and light bike, with its gleaming yellow paint job like the yellow jersey in the TDF. I still enjoy riding that bike and have now modified it into a touring/cyclocross rig.

I kept logging my miles and best time trials. In the spring of 2004 I retired from teaching, creating the opportunity for improved physical conditioning and more-obsessive number-crunching. In the fall of that year, as a retirement present, I bought myself the lightest production bike I could find--a Motobecane Le Champion SL, weighing a feathery 16.5 pounds! I was in number-crunching heaven and started to hammer out some very fast time trials. My calendars for those years are stored away at the moment, but I think it was in 2005 that I pegged my "personal record" at 18.2 MPH for the TT. That record stood until June 26, 2008, when I recorded a (for me) astonishing time of 1:41:46 -- or just over 18.5 MPH. Note that by this time I was recording my times to the nearest second!

Although 2009 was a very good year for me, the fastest rides I could manage came in at 1:43:14 and 1:43:46--about a minute and a half off the record--and they flattened me! I could hardly move when I got off my bike after those time trials. In 2010 I trained more diligently than ever. I had now moved on to recording my speed whenever I happened to average more than 16 MPH (a "good ride"); and whenever I averaged more than 17 MPH, I rewarded myself with a two-beer lunch. During 2010 I smashed my past achievements by recording fifty-seven "good rides" and enjoying eighteen two-beer lunches. Yet, in not one of these rides did I crack the daunting 18 MPH barrier! Well, at 62 what can one expect? One can't be a young man forever.

So the first time I strapped on my Garmin 305, I felt confident that I would collect a lot of interesting data--GPS mapping, average speed, max speed, elevation, percent grade, feet climbed and descended, heart rate, maximum heart rate, and average heart rate. All were of mild interest to me as a way of feeding my addiction to numbers, but my performance in January and February was pretty pathetic. I did manage a few 16 MPH rides, but that seemed to be pushing the limit of what I could do. I returned from them exhausted and without much hope of cracking 17 MPH -- let alone the impenetrable barrier of 18 MPH.

Still, by studying all the data recorded on my yearly calendars, I began to form a plan. I noticed that my fastest time trials came at the end of extended periods of diligent training, followed by one or two days of rest. For example, I biked every day from June 15th through June 24th of 2008, took one day off, and then ripped my TT at an average speed of 18.5. A couple of other hypotheses also emerged from the data. First, I did my best in spring and fall. Winter never allows the religious daily riding necessary to train for a TT; in contrast, summer temperatures inhibit performance because of the strength-sapping build-up of body heat. Second, I knew that my best performances came on calm days; the benefit of a tail-wind never quite equals the harm of a head-wind. And in the final stage of obsessive behavior, I became superstitious. A cup of coffee to jump-start my heart, a handful of mixed nuts for preride fuel, and a couple of fig newtons for a mid-ride sugar-rush became almost ritualistic requirements in a TT.

Then there was the Garmin factor. Most of what the device can do is put numbers to things I already knew. I knew my TT course was hilly; the Garmin measured half-a-mile of climbing. I knew that my legs started to burn and my lungs to burst if I pushed too hard at the very top of Woods Point Hill and Cemetery Hill. The Garmin told me that my heart-rate was hitting 155-160 beats per minute in those sections. (Maximum heart rate is age-related and can be measured by field tests or calculated by several formulas, the simplest of which is "220 minus your age". So in my case max heart rate should be about 158.) I knew that on a fast time-trial I felt drained at the end and on a recovery ride I felt re-energized. The Garmin told me that my average heart rate was over 140 (i.e., 90% of Max HR) in a fast TT and about 125 in a recovery ride (<80% of Max HR).

I had hoped that the Garmin might give me percent gradient for the hills, but GPS coordinates don't do a good job measuring vertical elevation. In total capitulation to number-crunching I drove over to Cemetery Hill and measured the grade using a long, straight board, a level, a tape measure, and a calculator. It turns out that nastiest, steepest part--right at the top of a long slog upward--hits 16%.

Perhaps more usefully, the Garmin can put numbers to some of the signs of improved conditioning that one feels "in the legs." For example, on January 27th I ground out a hard TT at 16.1 MPH with an AveHR of 140 BPM. Last week I took a "recovery ride" with an AveHR of 130 BPM and had an average speed of 16.5 MPH.

As a training tool, however, there was always just one reason why I bought the Garmin 305: inside that somewhat boxy wristwatch, the geniuses at Garmin have imprisoned a "virtual training partner," a tiny demon, a hyper-competitive cyclist who matches you peddle-stroke for peddle stroke--pacing you up the hills--indeed almost always beating you up those damnable hills--and swooping down the descents just in the lead. On a good day he is almost in reach. Sometimes he hangs out 500 feet ahead of you, sometimes only 18 feet ahead, and sometimes--on the rare, glorious day when you are really on form--the little devil falls steadily behind. (The photo used here shows a runner, but for cycling it shows a little man on a bike.)That little demon is what helped me set my new personal record on April 12, 2011. In the middle of March I had put in a number of consecutive training days. In late March and early April I was coming into form with a series of good time trials: 3/28 a 16.7 MPH ride, then two rest days, 3/31 a 17.8 MPH ride followed by training rides on the next two days, then two rest days, 4/5 an 18.3 MPH ride (less than a minute away from the record!), 4/7 a 17.6 MPH ride, 4/9 a short training ride, and finally two rest days on 4/10-11. So on the morning of April 12th I thought that conditions could be ripe for a record. I set up the Garmin so that I was racing against my performance of April 5th and peddled hard out of the starting gate.

From past experience I knew that I can usually tell after the first four miles if I have a chance at a good TT, but by racing against myself on the Garmin I was getting continuous feedback. Unfortunately, the news was not comforting. I was losing; the little demon from the past was beating me again. But I wasn't losing by much and I was confronting a bit of a head-wind that would become a tail-wind at the Highway 412 turnabout. When I got to 412 for the first time, I was about 500 feet behind. What's that? Fifteen seconds at most. I knew the trick would be to go so fast on the downhill section to Woods Point that my tail-wind would become a virtual head-wind. I had actually pulled ahead of the demon before getting to the store and clobbered the little devil in the final miles to the landing. Sweet! I was winning. But then I turned into the head-wind again and started to climb out of the valley and my lead kept on dwindling. By the time I returned to 412 for the final turn, I was again behind, and my hopes of victory were fading. Once again, though, the turn gave me the tail-wind and the tail-wind eventually gave me the lead. So now the question was whether I could have enough of a lead by the top of Cemetery Hill that I would gain the minute I needed to set an all-time record. Of course, I did it--but the point is, I couldn't tell I would do it until the very end. My margin of victory amounted to two minutes and forty-seven seconds; so for about the last mile I knew that I "had it in the bag," but until then even the victory itself was in doubt.

I salute you, little demon. You were a valiant opponent and gracious in defeat.

On April 30th I put the Garmin to good use again, logging the route and elevation of the Tour de Hills--more popularly and appropriately known as "The Jasper Disaster" because of its punishing hills. (I also like the logo on the free tee-shirts--"Gravity Always Wins.") This year the ride was especially challenging because at the top of the first long climb we found ourselves riding into a cold, steady drizzle. (We were actually in the clouds.) The drizzle stayed with us until the final descent to Harrison. Here is the profile for that ride: