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Atrial Fibrillation - 12/11/2012

posted Dec 11, 2012, 7:32 AM by Rohit Das   [ updated Feb 13, 2013, 11:36 AM by Purnema Madahar ]

Today at intern report, we spoke about an interesting case of acute cerebellar infarction in the context of newly diagnosed atrial fibrillation (AF). This brings a number of issues to light. As I’m sure you all know, the main issue with atrial fibrillation is its associated embolic risk, and rhythm versus rate control. The AFFIRM trial in 2002 showed that rate control was as good as rhythm control, if not better, for several important clinical outcomes. Furthermore, several risk stratification schemes were developed for AF, the most notable and validated of which is the CHADS2 scoring system. I wanted to talk about a few things today, so here goes:

·         What was the AFFIRM Trial and its outcomes? What additional data is there to guide rate control-oriented management? What are the limitations of the AFFIRM trial in today’s world?

·         How exactly does the CHADS2 score correlate to stroke risk, and why is warfarin recommended over aspirin at certain CHADS2 scores? What’s the CHA2DS2-VASc Score and how does it change who we consider for anticoagulation?

·         I feel cardioversion is a bit of a grey area…what are the indications? Who does well with cardioversion, and who doesn’t?

What was the AFFIRM Trial and its outcomes? What additional data is there to guide rate control-oriented management? What are the limitations of the AFFIRM trial in today’s world?

·         So…the AFFIRM trial was published in 2002 in the NEJM (attached), and randomized 4000+, 65 year old or older patients to rate control with warfarin, or rhythm control (mainly with amiodarone and/or sotalol) with warfarin utilized at the discretion of the investigator. That is, if patients were maintained at sinus rhythm, they could be withdrawn from warfarin during the study.

·         The goal heart rate was <80bpm at rest and <110bpm exercising in the rate control arm, and at five years, 80% of patients were adequately controlled. In the rhythm arm, 63% maintained sinus rhythm at 5 years.

·         With a mean follow-up of 3.5 years, there was a trend towards a decreased mortality in the rate control arm, and in certain subgroups (heart failure and >65 years old) a significant mortality reduction was found. Otherwise, there was no difference in several other cardiovascular outcomes, evaluated via a secondary composite outcome.

·         A controversial topic has always been to what degree rate control should be achieved. The RACE II trial (attached), published a couple of years ago, sought to answer that question by randomizing patients to a “lenient” goal (<110bpm resting heart beat) versus “strict” control, as defined by the AFFIRM trial. In a composite primary outcome, there was no significant difference between the two groups. Based on that study, for minimally symptomatic AF patients, it’s reasonable to be more lenient…

·         The main gripes with the AFFIRM trial was that it didn’t address atrial fibrillation in a younger population, a group which may benefit from more aggressive rhythm control therapies. Additionally, the trend towards increased mortality in the rhythm control was attributed to drug-related adverse effects, and not cardiovascular causes; new antiarryhthmics with better safety profiles, e.g. dofetilide, may lead to better outcomes with rhythm control. In support of this, follow up studies of the AFFIRM trial also showed that maintenance of sinus rhythm was associated with a lower mortality (HR of 0.53). Finally, catheter ablation for rhythm management, something we see a lot of here, has an as of yet undefined impact…

How exactly does the CHADS2 score correlate to stroke risk, and why is warfarin recommended over aspirin at certain CHADS2 scores? What’s the CHA2DS2-VASc Score and how does it change who we consider for anticoagulation?

·         Annual stroke risk is dependent on one’s clinical risk factors, ranging from 2 % to 18% with a CHADS2 of 1-6, respectively. Aspirin basically reduces annual stroke by 1-2%, which I think gives a good understating as to why warfarin (which reduces relative risk by about two-thirds) is recommended once the score reaches 2. “Net clinical benefit” (i.e., combining the benefit of preventing ischemic events and the risk of major bleeding) studies have also been done with warfarin, and long story short, NCB became significant at a CHADS2 of 2, which correlates to 1 prevented event for every 100 patient-years.

·         Starting in 2010, studies began to try to “refine” the CHADS2 score, mainly because of the large variability within the “low-risk” category. As the ESC guidelines review, studied showed that at a score of 0, the annual event rate ranges from 0.84% to 3.2%. Authors ultimately defined the CHA2DS2-VASc score which adds a point for female gender, age 65-74 (age >75 is 2 points), and vascular disease (total potential score of 9). As per the guidelines:

o   at a score CHA2DS2-VASc  ≥2, oral anticoagulation recommended (IA)

o   at a score CHA2DS2-VASc of 1, oral anticoagulation should be considered, and weighed against bleeding risk (IIA)

o at a score CHA2DS2-VASc  of 1 dictated by only female gender, NO antithrombotic therapy should be considered (IIB)

o   at 0…you’re good to go.

I feel cardioversion is a bit of a grey area…what are the indications? Who does well with cardioversion, and who doesn’t?

·         Some quick words on cardioversion…the main indications are – unstable hemodynamics, first symptomatic episode and patients with persistent AF who are limited symptomatically. In general, DC cardioversion is preferred and more efficacious than pharmacologic methods.

·         People who generally don’t do well with cardioversion are those with AF for more than year, the elderly (>80 years In studies), big left atriums, LV dysfunction, and those whose AF has recurred despite pharmacologic antiarrhythmic therapy. Taken all together…the people who do best with cardioversion are younger patients with minimal structural heart disease…overall probably a minority of our AF patients…

There’s plenty more to know about AF, so definitely take a look at the ESC guidelines which provide a nice overview. The AFFIRM and RACE II trials are also attached. Have a good one…

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