Atrial fibrillation: the effects of obesity and exercise

 In Cardiology

Many people are troubled by a irregular heart beat called atrial fibrillation. As the population ages so the likelihood of developing the abnormal heart rhythm to the extent that 10% of people over the age of 80 years are in this heart rhythm.

It is not benign with some people developing clots in the heart whilst others simply don’t feel well when their hearts are in this rhythm. Whilst medication helps there are also complex and lengthy operations that can prevent the atrial fibrillation developing. These are becoming more successful and as a result more commonplace.

Evidence is now coming to light that it is possible for the patient to help themselves and hopefully avoid the need for operations and possibly medication.

Previously we had understood the relationship between alcohol and atrial fibrillation; I vividly remember a consultant asking me to feel his pulse after he had been drinking heavily. The pulse was very irregular. He asked “what do you think, John” I replied “it feels like atrial fibrillation” “Aye it was a fantastic Burns night last night- the whisky was excellent” Alcohol is directly toxic to the heart and heavy alcoholic binges trigger atrial fibrillation. Drinking sensibly will reduce the chance of developing atrial fibrillation. Controlling other risk factors for heart disease such as blood pressure has also been shown to be helpful.

Over the last 6 months we have obtained evidence that increasing your fitness level and reducing your weight if obese both can significantly reduce the chances of developing atrial fibrillation.

The LEGACY trial 1 has recently presented the data for 355 patients with atrial fibrillation who had a body mass index ≥27 kg/m2 (a marker for being overweight) and were offered weight management. They were followed for 5 years. Weight loss was categorized into 3 groups; group 1 (≥10%), group 2 (3% to 9%), and group 3 (<3%). The amount of time and symptom severity decreased more in group 1 compared with groups 2 and 3. Arrhythmia-free survival was greatest in group 1 compared with groups 2 and 3. Weight loss ≥10% resulted in a 6-fold greater probability of being arrhythmia-free compared with the other 2 groups. The message seems clear – don’t be overweight.

Another group have looked at this from a different perspective 2.They overfed a group of sheep over a 36 week period so that they were double their normal size (110kg compared to 60kg). They then studied them for a further 36 weeks. They showed not only fat being deposited in the left atrium but showed the left atrium became bigger and had electrical changes which would make atrial fibrillation more likely. As a result when the heart was stimulated to go into atrial fibrillation it did so much more readily in the obese sheep and also stayed in atrial fibrillation for longer. This study shows how the obesity can actually be detrimental to the heart.

More research suggests beneficial effects from lifestyle changes 3. This time, cardiorespiratory fitness (CRF) was shown to help not only with relieving symptoms of atrial fibrillation (AF), but it also predicted recurrence in patients who were obese 3.

The Cardiorespiratory Fitness on Arrhythmia Recurrence in Obese Individuals with Atrial Fibrillation (CARDIO-FIT) observational study of 308 patients showed that those who had high cardiorespiratory fitness (CRF) at baseline were significantly more likely to have arrhythmia-free survival at follow-up more than 4 years later than the participants who had low or even adequate cardiofitness.

After patients enrolled in a tailored exercise program, both CRF fitness gain and weight loss were associated with significantly improved outcomes. In addition, the patients who gained at least two peak metabolic equivalents (METs) had a greater decrease in AF burden and symptom severity and more incidence of arrhythmia-free survival with those with fewer METs gained—and a twofold greater probability of arrhythmia-free survival.

The overall message is loud and clear. Exercise and maintaining your ideal weight is good for you especially if you have atrial fibrillation. Patients troubled by atrial fibrillation have the power to help themselves!

1. Pathak R K. et al J Am Coll Cardiol. 2015;65(20):2159-2169. Long-term Effect of Goal-directed Weight Management in an Atrial Fibrillation Cohort . A Long-term Follow-up Study (LEGACY)

2. Mahajan R et al., J Am Coll Cardiol 2015 Jul 7; 66:1 Obese sheep are more susceptible to atrial fibrillation.

3. Pathak RK et al J Am Coll Cardiol. 2015 Jun 20.
Impact of CARDIOrespiratory FITness on Arrhythmia Recurrence in Obese Individuals with Atrial Fibrillation: The CARDIO-FIT Study.

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