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PRIORITY PRESS - Canadian Cardiovascular Congress (CCC)

Montréal, Quebec / October 23-27, 2010

Delegates are getting a second chance to hear the almost finalized guidelines on the treatment and investigation of atrial fibrillation (AF) during a case-based workshop on the management of AF Tuesday morning.

Dr. Brent Mitchell, Professor of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, Edmonton, will present highlights from the freshly minted 2010 CCS guidelines that will be published in the Canadian Journal of Cardiology early next year. The guidelines were initially discussed on Monday, October 25, during a special AF guideline workshop. Since the last CCS guidelines on AF were published, focus on several aspects of AF investigation and management has shifted and the new guidelines will likely incorporate new data and drugs now approved for the treatment of AF.

“I think the ‘new’ news in AF is that we understand more that AF is an expression of underlying cardiovascular disease (CVD) rather than ‘just an arrhythmia,’” remarked 2004 AF guidelines panel member Dr. Paul Dorian, Professor of Medicine, University of Toronto, in an interview. In fact, probably 80% of patients with AF have one or more co-existing CVD conditions—hypertension, obesity, diabetes, coronary artery disease (CAD), peripheral arterial disease (PAD), valvular disease and sleep apnea key among them. Knowing this, physicians have a golden opportunity to thoroughly investigate patients who present with AF; if they do identify an underlying disorder, they need to treat it independently of the AF, he added.

Since the last guidelines were published in 2005, specialists have started to place less emphasis on rate vs. rhythm control. “We used to be very focused on slowing the heart rate to 80 bpm at rest,” Dr. Dorian related. New data, however, suggest that physicians do not have to be as concerned about getting the heart rate down to 80 bpm as they once were, as prognosis for patients whose heart rate at rest remains at, for example, 95 bpm, can be as good as a patient’s whose heart rate is strictly controlled.

Physicians are also recognizing that there are many patients with AF whose ECG may be abnormal but the patient feels fine. In such a patient, the goal may still be to reduce the number of symptomatic episodes of AF and slow the heart rate somewhat; again, though, “the focus here is not on looking at the ECG, it’s on looking at how the patient feels or whether they are in the hospital because of AF,” he stressed.

Dr. Dorian continued, “On top of that,” there is a new antiarrhythmic called dronedarone which has been approved since the last guidelines and which has to be incorporated into the new guidelines as well.” As the only new antiarrhythmic to have been approved since the last guidelines, a discussion of the new agent’s risks and benefits and its use relative to the older antiarrhythmics will likely be included.

Stroke Prevention and Risk Management

At the same time, the 2010 guidelines may place a renewed emphasis on stroke prevention. It was understood in the past that stroke was a major problem in AF; even so, “it’s probably even worse than we thought,” Dr. Dorian noted, “and we as a medical community have not done as good a job as we could in stroke prevention.” Part of this may be the result of the shortcomings of warfarin, the only currently available systemic anticoagulant which has been approved for stroke prevention. More than ever, physicians are now “very invested” in calculating the estimated risk of stroke in an individual patient, Dr. Dorian explained. “Once we estimate the risk of stroke, we use that risk estimate to help guide our decisions about anticoagulation therapy in the same way we use the estimated risk of myocardial infarction to help guide our treatment for cholesterol-lowering.”

On the horizon is dabigatran, a direct thrombin inhibitor (DTI). Unlike warfarin, which inhibits 4 different clotting factors, dabigatran only inhibits factor IIa and it has the potential to cause fewer drug-drug interactions than warfarin. Most importantly, it does not require regular INR monitoring. Other emerging strategies include the factor Xa inhibitors, for example, that are being tested in large phase III trials. The final dataset for the ROCKET study on the novel agent rivaroxaban will be presented at the American Heart Association meeting in November, and results from several other large anticoagulant trials are expected next year.

Dr. Dorian predicted, “These new drugs will probably change the landscape of stroke prevention and the guidelines will have to take this into account.” Of course, anticoagulants are not the only agents used for stroke prevention and the guidelines will discuss other strategies, including good blood pressure control and the use of ASA for stroke prevention.

Emphasis on Outcomes in AF Management

The emphasis on outcomes in the management of AF has also shifted over the past 5 years. “In no particular order,” Dr. Dorian indicated, “the important outcomes in AF in my view are patient well-being; freedom from serious morbidity which includes stroke, hospitalization, heart failure and myocardial ischemia; and freedom from serious adverse events from any drugs that we use.”

In the previous guidelines, it was implicit that the eradication of AF was a desirable outcome. Now, as Dr. Dorian explained, physicians are again recognizing that this approach has limitations, in that many patients may appear as if they are not experiencing AF but in fact are simply just asymptomatic. “In 2005, we may have said, that is not a good outcome,” Dr. Dorian noted. Today, that same outcome might be considered desirable provided that patients are not experiencing side effects and they do not feel unwell, even if they are having AF. (This scenario can be reversed: patients may no longer have AF but if they are experiencing many side effects and their quality of life is poor; this could still be considered a bad outcome.)

If physicians decide to use an antiarrhythmic for rhythm control, treatment choice should remain patient-focused. “We are not only looking at the ECG to see if the drug is working,” he stressed, “we are also looking at the patient and asking: Is this drug likely to keep patients out of the hospital or to keep them alive?” Dr. Dorian also noted that physicians should ask themselves a number of questions prior to initiation of treatment, including the purpose of using a particular antiarrhythmic drug in a particular patient, i.e. should one eliminate all episodes of AF or reduce or eliminate symptoms? And what is the expected effect that the drug will have on morbidity, adverse effects and mortality risk?

Dr. Dorian stated, “Before we use any antiarrhythmic drug, we have to understand what our expectations are from an antiarrhythmic, as well as from the particular one we are going to use. We now have a new one that is added to the mix, so we always have to weigh the whole range of risks and benefits as with any drug.”