Atrial fibrillation (AF) and its related disorder, atrial flutter (AFlut), are common abnormal heartbeats. Because they are similar and AFlut is rare compared to AF, they are usually treated similarly and discussed as one disorder. AF is an extremely common arrhythmia affecting more that 5% of the population over 65 years of age. It is an independent risk factor for death. AF is considered a progressive disease increasing in prevalence with age and converting from paroxysmal to permanent within a single individual. The projected lifetime risk of AF is 1 in 4 for men. AF occurs when there is an electrical short circuit in the top parts of the heart (atria). This causes the atria to beat at \>300 times per min in an irregular and ineffective manor. This has two consequences. The blood tends to pool in the atria allowing for clotting. Second, the bottom parts of the heart (ventricles) beat too rapidly in response to impulses arising in the atria. The rapid ventricular contraction without adequate filling time results in a reduced ejection of blood. This can cause heart failure symptoms such as shortness of breath and reduced blood flow to organs resulting in lightheadedness or collapse.
One logical therapy to correct the defects arising from AF is return the abnormal heartbeats back to the normal rhythm. This can be done with electrical shock therapy (cardioversion) or by drugs called antiarrhythmic agents. Often, they are used together. While its stands to reason that using these techniques to restore rhythm to normal would be beneficial, clinical trials show that leaving patients in AF and thinning the blood to prevent blood clots is equally efficacious to trying to restore normal beating (sinus rhythm). The common explanations for this are that AF returns rapidly despite antiarrhythmic drugs and that antiarrhythmic drugs can make worse abnormal heart beats, a phenomenon known as proarrhythmia.
Based on the lack of efficacy of current therapies and similarities between risk factors for atherosclerosis (hardening of the arteries) and AF, we began to investigate whether oxidative stress, a mechanism similar to inflammation thought to be responsible for atherosclerosis, might be playing a role in causing AF. We studied this in pigs first and found that when we put pigs into AF, they had a large increase in oxidative stress markers. Then, we made a mouse that had too much oxidative stress in the heart, and this mouse developed AF. Based on this and other data in humans, we hypothesized that oxidative stress can cause AF.
Atorvastatin is a cholesterol lowering medication that works by blocking production of cholesterol at an early stage. This has the effect of preventing the synthesis of molecules required to assemble the most common enzymatic source of oxidative stress, the NADPH oxidase. Therefore, atorvastatin decreases oxidative stress in addition to reducing cholesterol, and if our hypothesis is correct, atorvastatin should reduce the incidence of AF.
In this study we chose to look at patients undergoing cardioversion. This is because this group has a high likelihood of recurrence of AF and would benefit most by an effective drug. Once the decision is made to have the patient undergo cardioversion, we will approach the patient about enrolling in this trial. The only change in their medical therapy will be the addition of the study drug. The study requires no other alterations to the standard of care. If patients agree to participate, then they will be started on the study drug and followed for recurrence of AF by a variety of surface electrocardiogram techniques. All of which are noninvasive. To insure the medicine is not causing side effects, examinations and blood tests will be done, and to study whether the drug actually affects oxidative stress, blood will be analyzed. The subjects participation ends when AF recurs or after 1 year. This will be a double blind, placebo controlled trial and will be analyzed on an intention to treat basis.
The risks of this study to the patient are likely to be small compared to the potential benefit of reduced AF burden. Based on a previous trial using the same dose of study medication, the risks of all study drug related adverse events is likely to be \<3%. All of these are expected to be reversible with discontinuation of the drug.
The significance of this research is that currently treatments to address AF are less than optimal. Antiarrhythmic drugs are variably effective and are associated with potentially lethal proarrhythmic side effects. The common treatment to prevent strokes in subjects with AF is chronic warfarin administration, but warfarin therapy requires frequent monitoring and adjustment of dose and is associated with bleeding complications. This research may provide the first new therapeutic strategy in many years for AF and the most serious consequence of AF, stroke.
