How Many Heart Beats Do You Want?
So there I was, at the end of April 2015, off all my prescription meds. (I still took a baby aspirin and a multivitamin, don’t ask me why.) I was feeling great and knew I needed to exercise, but knowing and doing are two very different things.
Before my heart attack I had a very simple exercise routine. Every morning I worked out with free weights, did my crunches, then headed out for my aerobic exercise. I walked briskly half a mile to the foot of one of Pittsburgh’s steepest hills—Negley Avenue running south from Fifth Avenue to Dunmoyle Place. I would power up the hill, walk back down it and so on to home.
But in the spring of 2015 I could barely walk to the corner of my street and back. It took almost six months of Herculean effort just to get to the bottom of Negley Hill, at which point the idea of actually trudging up that hill was comical. When I finally started up the hill, several months later, I got exactly 17 paces and then had to sit down and rest before heading back home.
But a few weeks later I made it to 18 steps, then 19, and so on until only 18 months later I’d made it all the way to the top. It was now the spring of 2017 and I hadn’t stood at the top of that hill since the summer of 2014.
People who have had heart attacks tend to baby their hearts afterward. They are always saying something like, “I’ve got a bad ticker.” In fact, people who think they have heart disease almost always actually have coronary artery disease. Their arteries became occluded and eventually blocked blood flow to the heart and that caused a heart attack.
During a heart attack, some heart muscle dies due to a lack of oxygen—the worse the attack, the more heart muscle that dies. But the heart muscle that survives is as healthy as it ever was. It can be exercised and strengthened just like any other muscle in the human body.
Fitness experts tell us that, for exercise to be effective at improving our heart and lung capacity (not just maintaining it), we need to exercise at an aerobic level. While different experts follow different protocols, the Mayo Clinic definitions of exercise intensity are typical:
First, calculate your maximum heart rate by subtracting your age from 220 (152 for me in 2015).
Next, find your resting heart rate (78 for me in 2015).
Subtracting the first from the second gives you your heart’s “reserve” (74 for me in 2015).
Moderate exercise requires that you multiply your reserve by 50% to 70%, then add that number to your resting heart rate. I.e., for me, that would have been between 115 beats per minute and 130 bpm.
Vigorous exercise is between 70% and 85% of your reserve plus your resting heart rate, or, for me, between 130 bpm and 151 bpm.
The first time I made it to the top of Negley Hill my heart rate was 162 bpm, perilously above my maximum heart rate. But soon it started going down, and before long I had to recalculate all the aerobic exercise numbers because, as my damaged heart got stronger and stronger, my resting heart rate went down. It’s now 61 bpm, barely above where it was pre-heart attack.
So today the exercise numbers for me are: moderate exercise heart rates are between 107 and 125 bpm, vigorous exercise heart rates are between 125 and 138 bpm.
Pre-heart attack, my heart rate would be 59 bpm when I left home, and by the time I reached the foot of Negley Hill (the route is one-half mile, gently up-hill) my heart rate would be in the mid-seventies. Today it’s 61 when I leave home but at the foot of the hill it’s in the mid-nineties.
Well, of course it is. What’s left of my heart muscle has to do the same work that the much larger heart muscle used to do, so it has to work harder. But so what? The whole point of the exercise (!) is to strengthen the smaller heart until it is so strong it can do roughly the work the larger heart had to do.
Instead of the 162 bpm my heart used to produce at the top of the hill, today I rarely exceed 130. And if I take my time I can get to the top with a heart rate of 124 bpm—not even quite into the vigorous exercise range.
But here’s a puzzler for you. I leave home with a heart rate of 61, but reach the bottom of the hill at, say, 92. That’s 31 bpm faster. By the time I’m halfway up the hill, my heart rate is at about 120 bpm, or 28 bpm higher than it was at the bottom. But, as I just pointed out, I rarely exceed 130 bpm at the top, and sometimes come in around 125 bpm—only 10 to 15 bpm faster than at mid-hill.
What gives? How can my heart accelerate so rapidly between home and the bottom of the hill, then continue to accelerate rapidly ‘til the mid-point of the hill, then accelerate much more slowly, even though I’m at the edge of exhaustion and at the steepest part of the hill? It doesn’t seem to make physiological sense.
The answer, as we’ll see next week, is PVCs.
Next up: Why We Don’t Take Our Meds (Again), Part V