- Kenny Lin, MD
For many years, the standard thinking regarding treatment of patients with atrial fibrillation was that drug therapy to restore sinus rhythm (rhythm control) was superior to drug therapy to slow the ventricular response rate (rate control). That all changed in 2002, when a clinical trial found no difference in survival between patients randomized to rhythm or rate control, and a higher incidence of adverse effects in the rhythm control group.
This trial and other evidence led the American Academy of Family Physicians to issue a guideline that recommended rate control with chronic anticoagulation as the preferred strategy for most patients with atrial fibrillation. A recent AFP review article echoed this guidance, assigning an "A" strength of evidence rating to the following statement: "Rate control is the recommended treatment strategy in most patients with atrial fibrillation. Rhythm control is an option for patients in whom rate control is not achievable or who remain symptomatic despite rate control."
On occasion, however, evidence-based interventions achieve different results in primary care than in clinical trials. A study published earlier this month in the Archives of Internal Medicine used administrative databases in Quebec, Canada to compare mortality between older patients with atrial fibrillation who were initially prescribed rhythm or rate control therapy after their diagnoses. After experiencing similar mortality through 4 years of follow-up, patients in the rhythm control group had a significantly lower risk of death, with 23% lower relative mortality than patients in the rate control group at 8 years. These surprising results beg the question: was this new study somehow flawed? If not, as the subtitle of an accompanying editorial asked, can observational data trump randomized trial results?
Although it is unlikely that treatment guidelines will change any time soon, this study should remind clinicians that management of patients with newly diagnosed atrial fibrillation should be individualized, and the risks and benefits of different strategies discussed in detail before making treatment decisions.
Thursday, June 28, 2012
Subscribe to:
Post Comments (Atom)
The question "Rate Control vs Rhythm Control" for treatment of Atrial Fibrillation (AFib) is an ongoing and evolving one - as alluded to in the above summary by Kenny Lin. No one strategy fits all - and I think the "Bottom Line" by Kenny - "that management of newly diagnosed AFib should be individualized" - is the KEY. That said - there ARE a number of important points that should be made.
ReplyDeletei) There probably will never be a universal "answer". Reasons for that are multiple - including difficulty of carrying out a true randomized, prospective clinical trial on all potential subsets of patients with adequate follow-up to judge whether one strategy is truly "better" than another. It is very difficult to "grade" impact from adverse nonfatal medication side effects - and virtually impossible to assess true onset of AFib when much persistent AFib is initially intermittent, and ~ 90% of intermittent (= paroxysmal = PAF) AFib is asymptomatic (We primarily see AFib patients who come to us because they have symptoms ... ).
ii) Some AFib patients definitely do better with rhythm control. Such patients tend to be intensely symptomatic from their AFib (palpitations, exercise intolerance) - and function as well as feel much better if maintained in sinus rhythm.
iii) If adequately anticoagulated - AFib is for the most part a non-life-threatening disease (ie, a "nuisance arrhythmia"). As such - "Treatment should not be worse than the disease". However, one may NOT know IF treatment is (or will become) "worse" than the disease unless one embarks upon an initial trial of treatment. At first - antiarrhythmic drug therapy may maintain sinus rhythm and be tolerable. It may in some cases only be after "time" that the treatment becomes worse than the disease - in which case, STOP TREATMENT. The need to treat (or not treat) AFib is not always static - and weighing pros and cons of one or the other strategy may change with time.
iv) Attaining and maintaining sinus rhythm is NOT indication to stop anticoagulation. The AFFIRM Trail taught us that substantial risk of stroke persists in patients with prior AFib even after restoration of sinus rhythm. Whether this is due to persistence of intermittment AFib that is silent ... (with risk of stroke perhaps increased in this group who silently go in-and-out of AFib) - or whether it is due to some underlying structural abnormalities that preidispose to stroke is uncertain. Bottom Line - Taking antiarrhythmics to maintain sinus rhythm is not an excuse to stop anticoagulation ...
v) Approximately 50% of all cases of new-onset AFib will be in sinus rhythm within the next 24 hours - even if NO treatment is undertaken .... Much more than this will spontaneously convert IF you identify and treat an underlying precipitating cause (such as heart failure or hypoxemia). Therefore - there is RARELY a need for immediate cardioversion with new AFib in patients who are hemodynamically stable (as well over 95% of new AFib patients are). - CONT (PART II- IN A MOMENT)
THIS IS PART II of MY COMMENT:
ReplyDeletevi) The best chance to initially convert a patient with new-onset AFib (and the best chance of maintaining sinus rhythm) is with the VERY 1st EPISODE of AFib. Atrial remodeling (structurally and electrically) begins very soon after onset of AFib - this being the reason why it is so hard to convert and maintain to sinus rhythm in patients with longstanding AFib. It is for this reason - that the management approach to the 1st EPISODE of AFib should be looked at differently - with if anything, greater tendency to consider medical or electrical cardioversion. Some such patients (esp. if there was a specific potentially reversible cause of their AFib) may never have another AFib episode. Most will - but the amount of time until that 2nd recurrence may be substantial.
vii) Number vi) does NOT mean that in 2012 all patients with a 1st episode of AFib should undergo attempted cardioversion (by either meds or electricity). For example - the older patient who may have been silently in-and-out of AFib for years wil often not be a candidate for cardioversion at any time. Similarly, the patient with severe LV dysfunction and left atrial dilatation may be one to forego even a single attempt at cardioversion - since it is highly unlikely that you'll be able to maintain sinus rhythm for any appreciable period of time.
viii) The "world of AFib" has changed dramatically in just the past few years. EP (electrophysiologist) cardiologists reign supreme in this area, where a significant percentage of patients with new AFib (perhaps the majority with new PAF) can be "cured" by ablative therapy. Longterm anticoagulation may still be needed - but the issue in 2012 is no longer about antiarrhythmic drug maintenance vs rate control - but now with added consideration as to which AFib patients are likely to be good candidates for EP referral and ablative therapy.
ix) Ultimately - the decision of what to do should be made in conjunction with patient preference whenever this is possible - to the extent that the patient is able to appreciate to pros and cons and timing of the various strategies (this being an IMPORTANT role for the family physician to assist with).
x) Management of AFib will continue to evolve.