The other week one of our Crickles members recorded something odd. He was cycling on Zwift (Zwift Fondo Wk1 Wo2), and is a keen cyclist, typically putting in 3-4 sessions per week. It’s ideal for the time-crunched, particularly over winter.
He had been noticing something odd for a while, but he and his doctor had dismissed the symptoms. He would notice that his heart had gone “mad” and that he had to slow down or sometime stop. The symptoms would last for 10 minutes at most. He could then carry on.
In recent months he has been wearing a heart rate chest strap more regularly, but still sporadically, and then this happened:
There was a sudden jump in his heart rate. Most importantly he felt odd with it too. It came at the end of the ride. The heart rate was out of kilter with his power output. It wasn’t “geometric” – that is there was variability in the heart rate. It fell slightly as his power output fell. Naturally he finished the ride.
For all of these reasons, it looked like a genuine heart rhythm problem. So, he got an AliveCor. This is a small device which pairs with a smartphone or tablet and can record a single lead electrocardiogram. You can buy them from the manufacturer, or Amazon.
A few days later, whilst running, his heart rate jumped again, and this time he caught it on the AliveCor:
This shows a supraventricular tachycardia, with a heart rate of 220bpm or so. It’s just gone back to normal at the end of the trace. Although you can’t quite see a “QRS” complex (a sign that the bottom part of the heart, the ventricle, has activated), you can see a pause and a “p wave” (a sign that the top part of the heart, the atrium, has activated).
This is a common, not life-threatening, rhythm problem. Most people have a single connection between the atria (at the top) and the ventricles (at the bottom, the pumping chambers of the heart). Some people have two (or more), and then, under certain circumstances, the electrical signals can pass down one of the connections and back up the other, looping round in a small circuit and stimulating the heart to go quickly. This is technically known as an atrio-ventricular (nodal – if the pathways are in a structure called the atrio-ventricular node) re-entrant tachycardia. In this case, it’s most likely that both connections in the node.
The definitive treatment is an electrophysiology study and ablation. This maps out the pathways and burns or freezes one of them. It has a good success rate, and is usually curative (about 90-95%), and a low (but not zero) complication rate.
He is on the list for this procedure (thanks Graham!), and in the meantime is on a drug called flecainide, as he will have to wait a little while. The drug is working. But drugs aren’t ideal when there is a procedure that can cure the situation.
The irony is that it’s my son. I never thought that when we started this project, the work would help me directly.
Good luck to those running the marathon today. I’m out for a ride. With my son. It will be his longest to date at 100K. I’ll be honest to say I am a little nervous.