Heart disease 101: AF and Coronary Artery Disease — related, incidental or both?

There were many good questions raised on my last post. Thanks. One particularly relevant theme concerned the relationship of atrial fibrillation (AF) and coronary artery disease (CAD). There’s a great deal of misunderstanding out there on how these two common disease relate to each other. I thought a few paragraphs might be useful.

On the matter of ‘arrhythmia’ and coronary artery disease:

I stated in the George Bush piece that a good reason to open a partially occluded artery with a stent was to treat an arrhythmia. I should have said ventricular arrhythmia or ventricular tachycardia (VT). I told you a partially blocked artery might cause an imbalance of nutrient flow to an area of downstream heart muscle–so-called ischemia. It is well-known that ischemia (low blood flow) can cause electrical irritability in the ventricle. The treatment of an arrhythmia in the presence of ischemia is often directed at improving blood flow. The president might have had ventricular tachycardia on the stress test. If this were the ‘abnormality,’ then stenting a blockage would have been excellent therapy. Ischemia-related ventricular tachycardia is common.

The relationship between atrial fibrillation and coronary artery disease is more complex. It’s an important topic because much of the excess fear that comes with AF stems from misunderstanding the relationship between electrical and structural heart disease. And you know what happens when fear and confusion get plugged into the equation of medical decision-making in the US. The default is to monitor, and test, and treat, and reinforce illness. Such excitement is rarely good therapy for atrial fibrillation. In treating patients with AF, it’s good to give peace a chance. Please put that IV away.

AF and coronary artery disease are very different diseases.

Although technically both are considered heart disease, having AF does not mean there will be coronary disease. And vice versa, having CAD does not mean one will also have AF. Atrial fibrillation is an electrical disease of the atria and coronary disease is a structural disease of blood vessels.

Here is where medicine (and writing about medicine) gets complicated.

AF and CAD are often independent of each other:

Both diseases share associated factors–hypertension, diabetes, sleep apnea, obesity, and chronic stress, for example. Inflammation plays a causative role in both diseases. In my writings here, this is why I emphasize lowering of inflammation; doing so prevents and treats both diseases. It’s also important to recognize that both diseases can exist together, but not because of the diseases themselves but rather because of the shared risk factors. Let me clarify with two examples:

When a 32 year-old stressed out engineer (without CAD risk factors like hypertension, diabetes, smoking, family history) develops AF while training for an Ironman, I don’t suspect coronary disease. He rarely has CAD. It’s a different story when the 72 year-old overweight, diabetic, hypertensive smoker presents with AF. The latter patient could easily have CAD and warrants a different outlook. In other words, it’s not the AF that suggests CAD; it’s the patient’s risk factors. (Though it’s not always that clear.)

Another thing that confuses doctors is that AF can cause symptoms similar to those of coronary disease. AF can present as chest pain, shortness of breath, arm or jaw pain and near passing out. So can coronary artery disease. The patient with AF can look like they are having a heart attack even though their arteries may be smooth and clear. Confusing, yes, but the take home message is that the presence of AF does not indicate CAD. It’s also true that CAD is not likely the direct reason for AF. CAD is often an incidental finding in patients with AF.

Coronary artery disease affects AF treatment:

The reason why this sort of nuance is important is that treating AF often requires the use of anticoagulant drugs. An AF patient with a stent faces the problem of having to take two or three drugs that block normal clotting–one (or two) for the stent and one for the AF. That’s a lot of bleeding risk. If the blockage is causing problems, yes, by all means stent it, but AF alone should not be the reason to place a stent.

The relationship between AF and CAD also comes up when we consider treating AF with rhythm control drugs. The Class IC anti-arrhythmic drugs Flecainide and Propafenone can be useful AF suppressing agents. (I took Flecainide myself.) IC drugs work pretty well for the treatment of patients with symptomatic paroxysmal AF. They are less effective for persistent AF.

But there is a huge safety caveat: Studies done in the 1980s and 1990s showed that patients with CAD or congestive heart failure who took this class of medicine (Class IA and C) had less arrhythmia but a higher risk of death. I know that sounds crazy but it is true. In the absence of significant blockages or ischemia the risk of IC drugs are low. Really low. But if there is CAD, the drugs increase the risk of death. We call the paradox in which rhythm drugs can both suppress and promote arrhythmia–pro-arrhythmia. All AF drugs are burdened by the risk of pro-arrhythmia–not just the ICs.

When a patient has both symptomatic AF and structural heart disease or CAD, we often have to choose Class III drugs–sotalol, dofetilide, dronedarone, or amiodarone. Although this class of drugs are mortality neutral, they too can cause pro-arrhythmia. I won’t go further here; you would need medical school for that. Suffice it to say that the presence of CAD deeply affects the choice of AF drugs.

You can see why AF ablation (or not getting AF in the first place) is so attractive.

Hope this helps.

JMM

P.S. > A reminder and request: I would kindly ask that commenters refrain from leaving personal medical details or requests for specific medical advice here. I blocked a comment today for that very reason. There are very useful patient forums for that sort of discussion. Thanks.

Comments

  1. Jeff says

    Dr John,
    In the Flutter article you characterized those IC’s as “favoring” atrial flutter circuits, making it worse. Here you equate pro-arrhythmia with death – in the context of CAD. That sounds like ventricular arrhythmia. Quite a set of disadvantages to these drugs.
    Do you have a view on the anti-arrhythmia usefulness and pro-arrhythmia safety of ranolazine?

  2. Bruce Gilman says

    Could you comment on living with permanent Afib? Many of us have that and are trying to find ways to live with it and worry about the long term effects.

  3. Jackie Gulbe says

    Hi John – My boyfriend was diagnosed with AF while in the air force in his late 20′s, he just turned 50. The diagnoses ended his career as a pilot. He hasn’t been to a doctor for any follow up in 30 years. I think he’s crazy – your thoughts??

  4. Lynn says

    As a family practice NP, we were taught in school that “arrhythmia” meant NO rhythm as in not beating. “Dysrrhythmia” meant a dysfunction of the rhythm.

    When I see you use both words, I chuckle. Any comment? Was my instructor just a ‘word’ guy? ha

  5. Pete says

    Dr. John: I took the liberty of doing a little edit below. I didn’t change any of your words, I just compressed them. It clearly explains what I have been trying to understand since I was diagnosed with afib 2 1/2 years ago.

    “Although technically both are considered heart disease, having AF does not mean there will be coronary disease. And vice versa, having CAD does not mean one will also have AF. Atrial fibrillation is an electrical disease of the atria and coronary disease is a structural disease of blood vessels. AF and CAD are often independent of each other. Both diseases share associated factors–hypertension, diabetes, sleep apnea, obesity, and chronic stress, for example. Inflammation plays a causative role in both diseases. In my writings here, this is why I emphasize lowering of inflammation; doing so prevents and treats both diseases. It’s also important to recognize that both diseases can exist together, but not because of the diseases themselves but rather because of the shared risk factors.

    The take home message is that the presence of AF does not indicate CAD. It’s also true that CAD is not likely the direct reason for AF. CAD is often an incidental finding in patients with AF.”

    Thanks for your explanation. For me, “clarity” is as important as “no inflammation”.

  6. jane says

    I’m surprised to hear you say that some of the rhythm control drugs usually thought to be most toxic don’t have an effect on death rates. There’s been a meta-analysis somewhere that estimates a doubled death rate with amiodarone – which can certainly kill people, not only with lung injury – and a tripled death rate with sotalol.