A Stress Test.... Free Associations

I was just starting to breathe a little heavier.  The nurse running the test has been talking to me - continuously for the last nine minutes.  She was bright, pleasant, a great conversationalist but more to the point - everything she said seemed highly relevant. From time to time she would ask how I was doing, check my blood pressure and tell me what my heart rate was.  Some time at about the 9 minute mark she said that I might need to break into a jog for the next level.  It was a 16% grade at 4.1 mph.  The treadmill tilted up and it was a smooth transition.  I was still walking at a fast pace.  "Your heart rate is 160 are you OK?"  I was feeling very good.  Still talking in full sentences and not feeling stressed at all.  My left knee was sore and I said: "My knee is sore and I don't want to break into a jog.  I will complete this stage and call it a day."

I did have room at the end and am fairly confident I could have knocked off the next stage.  I have done it many times in the past starting with a test at about ago 42.  There were a number of considerations holding me back.  The knee.  It was nothing big.  When you exercise a lot as an adult - episodic knee pain is all part of it.  Secondly, a history of paroxysmal atrial fibrillation.  I probably got it in the first place from running heart rates too high for my age.  I did not want to flip into another episode of atrial fibrillation.  Third, the target rate.  Before starting, the supervising nurse told me that the target heart rate for a guy my age was 140 bpm and I was over that with no signs of ischemia or more importantly a widening QRS interval (I take flecainide).  Fourth, I was just happy to be there.  Even though I have had 5 exercise stress tests over the last 25 years, the last one was at the Mayo Clinic about 10 years ago.  These things are a lot less certain with age. As I was on the treadmill, I kept thinking of a review I read in the Medical Clinics of North America many years ago: "40% of 85 year olds have significant coronary artery disease".  Of course those are the 85 year olds who survived to that age.

I had other associations while I was walking and talking. I take a cardiac history on every person I talk with. Some are more detailed than others. I know a number of ways that stress tests can be failed. I know from talking with people what happens when your ECG suddenly shows signs of ischemia. Generally the next step is a Cardiologist spraying nitro into your mouth.  I also know that passing a stress test is a generally a good sign, but it is not a guarantee. Nothing in medicine is.  Too many people have told me about cardiac problems in the absence of a positive stress test, including an infarction in the absence of any occlusions.  Irrespective of the result, I would maintain humility and strive even more to avoid the trans fats that are quantitatively too low to make it on the food label.  And of course all of that bakery with thick frosting - the first display you encounter in any supermarket.           

I had the exercise stress test two weeks ago.  Four days earlier I was doing my usual dictation of an assessment in my office and as I stretched back - I experienced an intense sharp burning pain going down the left side of my sternum.  It lasted about 5- 10 seconds.  I have been having this pains for at least a year all over the chest, left shoulder and back.  At one point they were clearly musculoskeletal in origin and I could replicate them by certain movements or flexing certain muscles.  But then the discriminatory ability was gone.  All of the tricks I learned in medical school and residency about the  difference between musculoskeletal pain and true cardiac pain or angina did not apply.  One of the things they never teach you is that when you get old - all of the routine pains that you live with every day meld into vague pains all over your torso.  Was that chest pain or did it originate in my back, neck or shoulder?  Arthritic pain or pain from trying to do too many pull ups last night?  At some point I just decided to go in to see my internist to see if we could figure it out.

My internist has known me for 30 years.  Any chest pain in the early part of that period was immediately dismissed as musculoskeletal pain.  He knew I was a compulsive exercise fanatic and between the ages of 30 and 55 probably cycled 200 miles per week or the equivalent. In the winter, I would speedskate as much as possible.  My goal was to end the season by doing as many laps as possible in an hour on the John Rose Oval - one of the few refrigerated speedskating outdoor tracks in North America.  Doing that kind of exercise gets the heart rate up to very high levels.  During interval training up to 190+ beats per minute.  Whenever the subject came up during those years my internist would say: "You do a stress test every time you exercise".

That all changed at age 55.  I was out doing a warm up on the speed skating track.  I looked down at my heart rate monitor and it read 170 bpm.  One lap later it was chirping loudly and now it read 240 bpm.  I felt my carotid pulse and it was the irregularly irregular rhythm of atrial fibrillation.  That led to 2 hospital admissions, 2 cardioversions, 2 consultations with a sports cardiologist at the Mayo Clinic and 2 exercise stress tests on a bicycle at Mayo.  I ended up on flecainide  with the advice to consider an ablation procedure at some point in the future as long as the flecainide continued to work and "if the technology improves".  That is a direct quote from one of my electrophysiologists.

During the bicycle stress tests, I ran my heart rate up to 170 bpm and could have gone higher, but was concerned about triggering another episode of atrial fibrillation that would no longer respond to flecainide.  On echocardiography, I have features that are seen in some series of cyclists who do high levels of dynamic exercise - primarily an large left atrium and a slightly enlarged aortic root.  During dynamic exercise, there is a steady increase in blood pressure despite the fact that stroke volume peaks at about 120 bpm and main contributor after that point is heart rate and sympathetic nervous system output.  My adaptation was to try to keep my heart rate at 140 bpm or lower when exercising and lately 130 bpm.  It is good to know I can go higher even for brief periods of time.

So the coronary arteries may be OK, but that leaves paroxysmal afib and the enlarged aortic root/aorta.  We have only recently discovered the role of the layered extracellular matrix in aortic anatomy. Like most of these structures disruption of those layers can result in permanent weakness.  It is also known that high levels of dynamic exercise results in aortic enlargement.  I have not seen any outcome studies of those individuals - but it would be useful to find an expert. 

My next step is to see a Sports Cardiologist about the afib and aorta.  I anticipate that he or she will wonder about why there is an old man in the examination room trying to get as much performance as possible out of an aging cardiovascular system.  If that question comes up, the response is simple:

"I don't want to die on the side of the road from a blown aorta because I tried to race a 40 year old up a hill.  I need your most conservative estimate on how I can prevent that."

And so it goes......


George Dawson, MD, DFAPA


Supplemental:

Previous exercise stress test done on a bike at the Mayo Clinic in 2012 showed a similar result (possibly low BP and heart rate this time but I find that it is easy to over rev on a bike as opposed to a treadmill).