1:1 AV Conduction

One of my heart rate peaks, as measured by the
Holter Monitor.

Late today, I had my Cardiologist appointment to discuss my recent Echocardiogram and Holter Monitor results.  He was a fit-looking guy in his fifties and was sympathetic to my plight and my desire to resume running.

It seems that my efforts to give them something to look at while I was wearing the Holter Monitor a week ago were more successful, and risky, than I thought.  The two episodes I had of palpitating heart and lightheadedness while walking up a steep hill, matched recorded instances of my heart rate reaching around 230 beats per minute.

Diagram of the heart showing the path of the macro-reentry
circuit (wavy red line).

Normally, the upper (Atrium) and lower (Ventricle) chambers of the heart beat at the same rate.  However, with Atrial Flutter (AFl), the Atrium beats significantly faster than usual because of a sort of electrical short-circuit (macro-reentry circuit) and a proportion of these faster beats stimulate beats in the Ventricle.  The rate of conduction is determined by a physiological barrier between the chambers and is usually 2:1 for people with AFl (and sometimes 3:1 or 4:1).  When I walk too hard, or run, my ratio appears to change to 1:1 where every superfast beat in the Atrium stimulates a corresponding beat in the Ventricle.

One medical website I found says "Atrial flutter with 1:1 conduction is associated with severe haemodynamic instability and progression to ventricular fibrillation", so I need to keep my heart rate lower until I get treatment.  This diagnosis was a little more worrisome than I had anticipated.

The cardiologist is scheduling me for an Electrocardioversion within the next week aimed at resetting my heart's electrical system (in layman's terms) using externally-delivered electrical stimulus (the paddles, or similar).  The cardiologist warned that this procedure may not yield a long-lasting solution, so I shouldn't get my hopes up.  I will be able to resume my running, but the AFl could return, and I will have to stop again.

If that happens, then when I'm no longer considered at risk of further Deep Vein Thrombosis or Pulmonary Embolism, they will try a Cardiac Ablation using a catheter inserted into the heart through the femoral vein to cauterise the tissue where electrical short-circuit is occurring in the Atrium.  This procedure has a high success rate and provides a longer-lasting solution, but I know everybody is different and I'm not counting my chickens yet.

I walked about 5km today, with no significant hills, and felt fine.

[Disclaimer:  I have no medical qualifications at all and there may be significant errors in this blog post.]