13 Jun Atrial fibrillation for exercise professionals part 1
Atrial fibrillation: summary of what is AF, the main therapeutic approaches including medications and ablation therapies, and what to do as an exercise professional
Hi, I’m Steve Selig, the founder of fit.test. Some of my subscribers have asked me to put the main issues concerning atrial fibrillation (AF) into a summary presentation about AF for exercise professionals. Here it is!
What is atrial fibrillation?
Let’s look at the normal heart first. In the normal heart, the sinoatrial node (SAN) or sinus node is the main pacemaker tissue located in the upper right atrium that drives both the rate and the rhythm of the heart. The normal electrical wave goes down the atria and enters the bottom pumping chambers (ventricles) via the other main pacemaker tissues, the atrioventricular node (AVN).
Functionally, the contraction of the upper chambers (atria) is responsible for about 20% of the filling of the lower chambers (ventricles). In AF, this pumping action of the atria is missing due to the atria fibrillating, but this does not endanger life because the ventricles still have more than adequate blood supply to produce sufficient cardiac output to sustain life not only at rest, but also exercise up to reasonable intensities. On ECG for normal sinus rhythm, we see the atrial contractions as small P waves, followed by large spiked QRS waves (ventricular contractions), followed by broader T waves (ventricular relaxation). In sinus rhythm, we see a rhythm for both atria and ventricles, with a rate of about 60 to 70 bpm at rest.
In AF, the atria become electrically chaotic with small disconnected wavelets of excitation occurring all over the atria; AF essentially blocks out normal sinus node activity and so the arrhythmia dominates. In AF, the ventricles are not in fibrillation. Instead, the ventricles are activated at random times via the AVN. The ventricles still pump blood efficiently (hence the rhythm is not life threatening), but the ventricles are activated at random intervals and so a ventricular arrhythmia is a feature of AF. On ECG in AF, we see no P waves but instead a “fibrillatory” baseline throughout each cardiac cycle, interspersed by random times by normal looking QRS and T waves.
What are the clinical and lifestyle (especially exercise) problems with atrial fibrillation? How are these managed?
- The atria are fibrillating instead of pumping and so , shimmering like a jellyfish. This lack of proper movement can cause a blood clot to form in the atria (left and/or right) as early as 48-72 hours after the onset of AF. So the first message is that if you as an exercise professional see a new client with this arrhythmia when it is not on the referral and is unexpected, then you need to assume that this is a new finding and the client is not being protected against intra-atrial thrombus. This means you need to refer the client to a medical practitioner urgently (this day…not this week). If the heart rate is very high too, then ring 000 or get the client to ED department of a hospital quickly. An intra-atrial thrombus is unlikely to cause sudden death, but there is a real risk of a stroke or some other thromboembolic emergency. Undiagnosed and untreated AF is one of the most common causes of stroke in Australia. Do not muck around with new (i.e. undiagnosed and untreated) AF! Patients with permanent AF should be prescribed an anti-thrombogenic medication (e.g. oral anti-coagulant such as rivaroxaban = Xarelto, or other anti-coagulant). The primary care medical practitioner will decide if and when such a medication needs to be prescribed.
- The 2nd problem is that heart rate can be too fast and potentially unsafe. There are many medications that can control for fast heart rates, including beta blockers and digoxin.
- The 3rd challenge is to try to restore sinus rhythm.
- Potassium channel blockers (e.g. amiodarone and sotalol) may be used to try to restore sinus rhythm.
- Elective cardioversion can be tried to restore sinus rhythm, as is ablation of the pulmonary veins where they insert into the let atrium, thereby isolating the arrhythmia into these regions and enabling the sinus node to recapture the rhythm of the heart (sinus rhythm).
- For some clients, pulmonary vein isolation (ablation) is not likely to be successful and instead they may offered a different form of ablation therapy (AVN ablation). Ventricular rhythm is restored and maintained in these clients by the implantation of a permanent pacemaker (PPM) before AVN ablation, but the atria remain in fibrillation. This does not really matter, except that that they need to be taking an anti-coagulant. If you take a radial pulse in these individuals, the pulse feels normal and these clients are essentially in normal heart rhythm (except for the atrial arrhythmia). Look at my other posts for AF for more information on this treatment pathway.
Exercise and atrial fibrillation
The exercise professional must be aware of AF if it is present. Sometimes, this means identifying a new problem if it is not on a referral and/or unknown to the client. I have written above why this is so important. You must be vigilant and take action in this situation.
For permanent AF (i.e. diagnosed and treated / managed), the exercise professional needs to work within the parameters of the medical interventions / treatments. This might mean making allowances for beta blockers (much lower heart rates but still out of rhythm) or dealing with the parameters of a permanent pacemaker (PPM) and/or automated implantable cardioverter defibrillator (AICD).
I hope you got something useful out of this topic. If you want to contact me as always, email@example.com. Bye for now. Have a great day.