Issue 31 Spring 2012 - Bases

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Exercise and atrial fibrillation Dr Gary Brickley provides an overview of this condition, its impact of exercise tolerance, and considerations for exercise. What is atrial fibrillation? Atrial fibrillation (AF) is a common but largely under-recognised cardiac arrhythmia, which is demonstrated in Figure 1 as an increase in the number of P waves relative to the number of QRS complexes. In many cases this can mean that the atria are contracting over 150 times per minute whilst the ventricles contract around 60 times per minute. Figure 1. A trial fibrillation as demonstrated from an ECG Approximately 100,000 people in the UK have AF. It is often associated with a poor lifestyle, alcoholism, a poor diet and obesity. In some cases individuals have no symptoms (Lone AF), but many experience shortness of breath, poor exercise tolerance, dizzy spells and palpitations. When presented with these symptoms an ECG may determine the presence of AF. A follow up echocardiogram is normally carried out. AF may then be treated initially with medication such as amiodarone, beta blockers and ACE inhibitors. Later this may involve surgery including AF ablation. Aside from being common in the elderly population, AF is also common in highly-trained endurance athletes (Mont, Elosua & Brugada, 2009; Turagam, Velagapundi & Kocheril, 2012); however, the mechanisms behind this are poorly understood. Nevertheless, as for the differences in left ventricular hypertrophy in the diseased and athletic heart, the causes of AF are probably different in athletes compared to typical older adults. Causes in athletes might include increased vagal tone, inflammation and fluid shifts, whereas in the elderly it is usually due to hypertension, “We as practitioners working with patients and athletes need to be confident in detecting AF, as well as ensuring referral to the appropriate cardiology team. ” valvular disease or previous myocardial infarction. The prognosis is also worse for non-athletes; these have a relatively high risk of stroke and heart failure. Exercise tolerance in people with AF We recently presented a paper at the Australian Conference of Sports Science and Medicine in Perth Australia (Brickley et al., 2012) where we were interested in the differences in cardiorespiratory fitness in AF patients versus healthy controls. We exercised both groups to volitional exhaustion on a cycle ergometer and measured expired air. We also assessed quality of life using the SF-36 questionnaire (Ware et al., 1993). Markers of aerobic fitness were generally lower in the AF group (see Table 1), as were the physical functioning domains of quality of life. The ability to exercise at high intensity is often related to deterioration in aerobic fitness. The associated symptoms of shortness of breath during exercise, dizziness on exertion and poor heart rate regulation certainly lead to a reduction in aerobic fitness in AF patients. Treatment with medication and surgery may alleviate some of these symptoms and allow for an improvement in exercise tolerance and quality of life. Exercise considerations in people with AF Is it dangerous to exercise with AF? Although the risk of a cardiac event is greater in those with heart disease and irregular rhythms, the risk for exercising with AF is poorly understood. Typically this patient may be given a cocktail of medication to slow their heart rate down and manage their rhythm. Once exercise is added to this cocktail it is important to monitor not only the symptoms during exercise but other parameters such as blood pressure and the incidence of ectopic beats. Exercise stress testing using ECGs is initially recommended to those who have been diagnosed. However, the European Society of Cardiology guidelines for exercise suggest that heart rate should be controlled between 90-115 bpm during moderate exercise (Camm et al., 2010). There is evidence to suggest that limiting physical activity can reduce the number of incidents of AF in those with recent diagnosis. However, as Mont, Elosua and Brugada (2009) point out, it is often hard for those who regularly exercise to follow this advice. She knows about making an impact Make one too To find out about attention-grabbing advertising opportunities in The Sport and Exercise Scientist visit www.bases.org.uk/SES-Advertisers 10 The Sport and Exercise Scientist n Issue 31 n Spring 2012 n www.bases.org.uk
Table 1. Cardiorespiratory fitness data for AF patients and healthy controls. Values are mean ± SD AF Control (n = 10) (n = 9) Ventilatory Threshold VO 2 (L·min -1 ) 0.80 ±0.32 0.91 ± 0.30 VO 2 (mL ·kg -1·min-1 ) 10.44 ± 3.63 13.43 ± 2.96 % of VO 2peak 63.6 ± 12.7 65.5 ± 11.8 Power output (W) 50 ± 24 60 ± 20 St Mary’s University College Twickenham London School of Sport, Health & Applied Science Maximal exercise VO 2 (mL ·kg -1·min-1 ) 14.63 ± 6.39 21.04 ± 6.05* V E (L·min -1 ) 35.45 ±14.48 42.4 ± 18.78 Exercise time (min) 7.47 ± 2.00 8.54 ± 1.86 Power output (W) 84 ± 42 107 ± 39 6-min walk distance (m) 424 ± 65 577 ± 38** *P
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