The skeptical cardiologist is asked this question or variations of it (such as what caused me to go out of rhythm?) on a daily basis.
Most patients would like to have a reason for why their atria suddenly decided to fibrillate. It’s understandable. If they could identify the reason perhaps they could stop it from happening again.
There are two variations on this question:
For the patient who has just been diagnosed with afib the question is really “what is the underlying reason for me developing this condition?”
For the patient who has had afib for a while and it comes and goes seemingly randomly the question is “what caused the afib at this time? i.e. what triggers my episodes?”
For most patients, there is no straighforward and simple answer to either one of these questions
The Underlying Cause of Atrial Fibrillation
My stock response to this first question goes like this:
“Atrial fibrillation is associated with getting older and having high blood pressure. 10 % of individual >/= 80 years have atrial fibrillation. 90% of patients with afib have hypertension.
Aging and hypertension may increase scarring or damage in the left atrium or pulmonary veins that drain into the left atrium setting up abnormal electrical signals.
There are some specific things that cause afib and we will be doing a complete history and physical and some testing to check for the most common. We’ll check you for thyroid or electrolyte abnormalities and we will do an echocardiogram to look for any structural problems with your heart.
If we do find a treatable cause such as hyperthyroidism or a cardiac valve problem we will fix that and the afib may go away, however chances are we won’t find a specific reason why you developed atrial fibrillation.
Finally, and possibly most importantly, let’s take a close look at your lifestyle. Are you overweight? If so, losing 10% of your body weight will substantially lower your risk of recurrent atrial fibrillation. Let’s get you exercising regularly and eating a healthy diet, Make sure your sleep is optimized and your stress minimized.”
If you’d like a more sophisticated look into what causes afib take a look at this graphic from a recent paper.
Current theory has it that factors that we know are associated with atrial fibrillation including obesity, hypertension and sleep apnea cause atrial structural abnormalities or remodeling which then create various atrial electrical abnormalities.
Exhaustive List of Causes
If you’d like an exhaustive list of factors associated with atrial fibrillation, you can memorize the acronym P.I.R.A.T.E.S. which is sometimes used by medical students to remember the causes of atrial fibrillation which include:
- Pulmonary disease (COPD, PE)/Phaeochromocytoma
- Ischemia (ACS)
- Rheumatic heart disease (mitral stenosis)
- Anemia (high output failure/tachycardia)/Atrial myxoma/Acid-base disturbance
- Thyrotoxicosis (tachycardia)
- Ethanol/Endocarditis/Electrolyte disturbance (hypokalaemia, hypomagnesaemia)/Elevated BP
- Sepsis/Sick Sinus Syndrome/Sympathomimetics (Drugs)
And here’s a cute mnemonic from the Family Practice Notebook using ATRIAL FIB itself (although you have to use the ph of pheochromocytoma to make the f of fib)
- Alcohol Abuse
- Thyroid Disease
- Rheumatic Heart Disease
- Ischemic Heart Disease
- Atrial Myxoma
- Lung (Pulmonary Embolism, Emphysema)
- Blood Pressure (Hypertension)
Both of these mnemonics are a little outdated. For example, rheumatic mitral stenosis is quite rare as a cause of afib in the US but degenerative and functional mitral regurgitation is a common cause.
Ischemic heart disease (aka coronary heart disease) isn’t felt to cause atrial fibrillation unless it results in a myocardial infarction and subsequent heart failure. Way too many cardiac catheterizations are performed on patients who present with atrial fibrillation by doctors who don’t know this.
Congenital heart defects (not mentioned in either mnemonic) especially atrial septal defects often are associated with afib
There may be case reports of pheochromocytoma (a catecholamine-secreting neuroendocrine tumor) causing afib but they are few and far between.
Finally, genetics clearly play a role in the younger patient with afib without any known risk factors. One of my patients and his twin brother both developed symptomatic afib in their 40s.
In The Chronic Afibber What Triggers An Episode?
Alas, for most afibbers we won’t identify specific reasons why you go in and out of afib although there are some triggers you should definitely avoid such as excessive alcohol.
Some of the “causes” listed in the mnemonic are acute triggers of afib episodes.
For example low potassium or magnesium (typically induced by diuretics, diarrhea or vomiting) can bring on episodes .(See my discussion on potassium and PVCS here-much of it is relevant to afib.)
And I have definitely seen patients go into atrial fibrillation who have acute pulmonary problems such as pneumonia, pulmonary embolism or exacerbation of COPD. In these cases, it is felt that the lung process raises pressure in the pulmonary arteries thereby putting strain on the right heart leading to higher right atrial pressures.
Sleep apnea is associated with afib and I have had a few cases where after identifying that a patient’s afib always began during sleep we were able to substantially lower episodes by treatment of sleep apnea.
Pericarditis with inflammation adjacent to the left atrium not uncommonly causes afib. This is the likely mechanism for the afib that occurs frequently after cardiac surgery. Since pericarditis may never recur (especially in the cardiac surgery patient) we think the risk of afib recurring is low in these patients.
Anything that raises stress and stimulates the sympathomimetic nervous system can be a trigger. For example, a young and otherwise healthy patient of mine went into afib after encountering a car in flames along the side of the road. We found that beta-blockers (which block the sympathetic nervous system) helped prevent her episodes.
Some patients have odd but reproducible triggers. One of my patients routinely went into afib when he ate ice cream. I had a simple , very effective treatment plan for him.
Caffeine and Chocolate
Many afibbers have been told to avoid caffeine but a recent study of 34,000 women found that there was no increased risk of afib with increasing caffeine content and no sign that any of the individual contributors to caffeine in the diet (coffee, tea, cola, and chocolate) were more likely to cause afib.
Higher chocolate consumption, in fact, has recently been linked to a lower rate of afib. An observational study of 55 thousand Danish men and women found that those who consumed 2 to 6 servings per week of 1 oz (30 grams) of chocolate had a 20% lower rate of clinically apparent afib.
Alcohol and Atrial Fibrillation
Binge drinking has long been known to cause acute atrial fibrillation.
However, it appears that even light to moderate chronic alcohol consumption increases the risk of going into atrial fibrillation.
This graphic from an excellent recent review of the topic gives the potential mechanisms:
The review concludes that although light to moderate alcohol consumption lowers your risk of dying, any alcohol consumption increases your risk of afib.
This graph shows the relationship between dying from heart disease (red line) and risk of going into afib (blue line) and amount of alcohol consumed.
Looking at the 15 drinks per week point on the x-axis (about 2 drinks per day) we see that your CV mortality is reduced by 20% whereas your risk of afib has increased by 20%.
A better point on the x-axis is 7 (1 drink per day) which has a 25% lower CV mortality but only a 10% higher risk of afib.
Whatever caused you to go into afib the good news is that with lifestyle changes and the care of a good cardiologist chances are excellent that you can live a normal, happy, healthy , long and active life.