Obesity: A growing problem that increases risk of atrial fibrillation

A 67-year-old lawyer comes for review. He has a two-year history of intermittent fast palpitations, which occur every few months. These episodes last two to five minutes, but no electrocardiogram record has ever been obtained during their occurrence. They can come on at any time and make him short of breath and a little “light-headed” until they resolve.

You had previously encouraged him to come forward for an ECG to try to catch these episodes, but he has not been able to attend in time before the “usual” normal rhythm returns. You had also suggested an AliveCor KardiaMobile device or a smart watch, which could capture these events without the need to attend the clinic. However, on this occasion, the palpitation is still present after 45 minutes.

He has a history of being overweight – something which doesn’t unduly trouble him. Your patient is always remarkably cheerful, but he is certainly not fit and does not exercise. He has been generally well, although he has a history of hypertension, now being treated with candesartan 16mg each morning.

He is married without children; he had married late to his secretary of the time – a mature woman who also enjoys the social aspects of his position. His parents died in their 80s from cancer. He is an only child. Naturally, he enjoys good food and wine, and also a good Scotch whisky!

On examination, he is overweight, with a height of 172cm, a weight of 130kg and a BMI of 44kg/m². His blood pressure is 145/90mmHg, and his pulse is irregular and fast at approximately 100 beats per minute. Otherwise, he has a normal general examination. A resting ECG is taken by your nurse.

1. What does the ECG show?
2. What tests might you arrange that day?
3. What is his current risk of a thromboembolic event?
4. What are the objectives of management?
5. How would you initially manage him?
6. What additional tests are important?
7. How does obesity affect the risk for developing atrial fibrillation?
8. How could you significantly help his prognosis long term?

1. The ECG shows atrial fibrillation, with a ventricular rate of 94 beats per minute, a normal axis and a complete right bundle branch block pattern.

2. You arrange a chest x-ray and blood tests: creatinine and electrolytes, liver and thyroid function tests, serum glucose and HbA1c levels, lipids, C-reactive protein, ferritin level, creatine kinase and urate levels, and a full blood count. These routine tests help to exclude many significant problems and allow a baseline for your treatment.

3. Thromboembolic risk is assessed by the CHA₂DS₂-VASc score. He has a score of 2 (hypertension = 1; age 65–74 years = 1), corresponding to an annual stroke risk of approximately 2 per cent. An oral anticoagulant drug reduces this risk by two-thirds (67 per cent).

4. For patients with atrial fibrillation, there are three principal management concerns:

• Prevention of a thromboembolism, particularly to avoid a large stroke.
• Good rate control of a fast ventricular rate, to avoid a rate-related cardiomyopathy.
• Optimal management of any additional heart disease, especially coronary or heart valve disease, which is easily missed as a contributor to atrial fibrillation.

5. You manage the fast heart rate with a prescription for oral bisoprolol 5mg each morning. Bisoprolol is usually well tolerated and is easily up titrated to a higher dose, if needed for rate control.

You plan to manage him with the maintenance of sinus rhythm as his best option. You assume he will soon self-revert, which he does in three hours’ time.

You discuss the risk of thromboembolism and start him on dabigatran 150mg twice daily. You prefer to start patients with dabigatran – the direct thrombin inhibitor – as you feel the availability of the reversal agent in the hospital system is an important safety factor.

However, you recognise that dabigatran is less well tolerated than the once-daily factor Xa inhibitor rivaroxaban. If needed, you are also happy to change from dabigatran to rivaroxaban in the future.

You realise that the probable cause of his atrial fibrillation is his obesity, hypertension and age.

6. You would like to exclude significant coronary and valve disease as a contributor to the onset of atrial fibrillation. You refer him for an echocardiogram and an exercise ECG test. The echocardiogram shows signs of mild hypertensive heart disease, and the exercise ECG test is negative.

The cardiologist also arranges a CT calcium score test to personalise his cardiovascular risk, and he is found to be in the 50–75th percentile. Hence, you then start 20mg of atorvastatin to reduce his cardiovascular risk.

7. Obesity is a significant and growing problem for our community. From the cardiac perspective, it increases the risk of vascular events, including heart attacks, strokes, peripheral vascular disease and death. It often leads to type 2 diabetes, additional hypertension and a worsening of lipid profiles. In addition, it is a major contributor to the epidemic of atrial fibrillation affecting New Zealand and the world.

A recent review of a previously well, middle-aged cohort of 18,493 people, followed to beyond the age of 65, concluded that being overweight in middle age increases the risk of atrial fibrillation by an extra 5 per cent for each unit of increase in BMI (eg, a BMI of 26kg/m² compared with 25kg/m²). This was independent of cardiovascular fitness or standard risk factors recorded in the patients’ middle age.¹

Several studies have demonstrated an increased likelihood of maintaining sinus rhythm if patients with atrial fibrillation lose weight.

8. You ask to review your patient with his wife. You discuss these issues and explain that he is at a “watershed” for his health. You urge him to lose a considerable amount of weight, and, with humour, you encourage 1kg of weight loss per month for the next three years. Both he and, in particular, his attentive wife are motivated to start a weight-loss programme immediately.

You maintain the “medical pressure” with a diarised follow-up with them both every six months, which becomes both useful and fun for all three of you!

A little to your surprise, he has no further bouts of atrial fibrillation over the next three years, and he reduces his weight to 90kg in that time.

He sends you a bottle of his best whisky at Christmas. You comment to your own wife that medicine is really enjoyable when it goes well!

Details have been changed to protect patient confidentiality

Chris Ellis is a consultant cardiologist at The Heart Group and Mercy Hospital, Auckland