What Does the Future Hold for Atrial Fibrillation? There's an app for that – and more, as the paradigm shifts
ACCEL | Do you have atrial fibrillation (AF)? There's an app for that – which uses an iPhone to produce an electrocardiogram (ECG). Given the increasing incidence of AF, community screening programs might be helpful in detecting undiagnosed AF, but such widespread screening with ECGs has not been considered cost effective for AF detection – until now. An iPhone application records a high-quality, single-lead ECG, perhaps making mass ECG screening feasible.
Investigators assessed the accuracy of the iPhone ECG as a diagnostic screening tool by comparing it with a contemporaneous 12-lead ECG interpreted by a cardiologist.1 An ECG was easily recorded in patients in only 1 minute. Recording began with finger placement of right and left hands on two electrodes at the back of the iPhone case.
There were 109 patients in the original learning set and 204 patients in a subsequent validation set. Compared to standard ECG assessment, the high sensitivity, specificity, and accuracy of the algorithm and widespread distribution of smartphones, might make this approach ideal for community screening. The investigators are currently using this device, with only manual reading by a cardiologist, in an ongoing study in community pharmacies with pharmacists trained in the use of the iPhone ECG.
NEW DRUGS, NEW USES
The app approach to detecting AF is one of what Irina Savelieva, MD, describes as a number of fascinating advances that are now or soon may be improving the management of atrial fibrillation. For example, she said new anticoagulants are like buses in London: you wait and you wait and you wait – and then they all arrive at once and you're not sure which one to take.
At this point, she said, rather than concentrating on which of the oral anticoagulants is better, the goal should be to move away from using warfarin and instead utilize these newer agents in appropriate patients, "because, as a class, these drugs out-performed warfarin in terms of their efficacy" and safety.
In just one example, Gregory Y. H. Lip, MD, and colleagues have reported that in the setting of everyday clinical practice, there were similar stroke/systemic embolism and major bleeding rates with dabigatran compared to warfarin, but mortality, intracranial bleed, pulmonary embolism, and myocardial infarction were lower with dabigatran.2
Many physicians have begun switching to the novel, non-vitamin K oral anticoagulants (NOACs), like rivaroxaban, in AF patients undergoing cardioversion. Good news: that was not a bad idea.
X-Vert (which may be going for a record in trial titles: eXplore the efficacy and safety of once-daily oral riVaroxaban for the prevention of caRdiovascular events in patients with non-valvular aTrial fibrillation scheduled for cardioversion) is the first prospective, randomized trial to examine the safety and efficacy of rivaroxaban compared to vitamin A antagonist (VKA) therapy in patients undergoing elective cardioversion for the treatment of AF.3 The pharmacological characteristics of rivaroxaban might be particularly useful in this setting because it has a rapid onset of action – within 2 to 4 hours – that could expedite cardioversion.
The study included 1,504 patients scheduled for either electrical (almost 98%) or pharmacological cardioversion. Using established guidelines, patients were assigned to either early or delayed cardioversion. Compared to treatment with a VKA, rivaroxaban was associated with an overall 50% reduction in the risk of cardiovascular events and a 24% lower risk of major bleeding, the primary safety outcome. (While not powered for statistical significance, it was thought this large of a trial still would give clinically meaningful information.)
According to first author Riccardo Cappato, MD, University of Milan, Italy, "You should be aware that many physicians are already switching to novel oral anticoagulants despite the absence of any information about their use. So we thought that bringing this methodologically sound information would provide more consistent evidence for those who are doing this anyway and a little bit more evidence for those who may be reluctant to use the novel oral agents."
Dr. Savelieva notes other studies are underway evaluating edoxaban and epixaban in this same setting with results likely in 2015 or 2016. However, like the US, Europe too is already using these anticoagulants for cardioversion, with one survey of 45 centers showing that VKA is still preferred for elective cardioversion in nearly half of the centers (46.9%), while one of the newer anticoagulants is preferred in 21.9%, and 32.3% had no preference.4
(Editor's note: Along with John Camm, MD, Dr. Savelieva recently published a review examining practical considerations related to the use of NOACS in patients with atrial fibrillation.5)
Recently, Dr. Savelieva published a review of pharmacological cardioversion of atrial fibrillation with vernakalant.6 Despite a rough regulatory road in the US, the drug has been approved in Europe and is included in the guidelines there. Vernakalant's advantage is a rapid effect, with the median time to conversion ranging between 8 and 14 minutes, and with the majority of patients (75% to 82%) converting after the first dose.
Vernakalant retains its efficacy in subgroups of patients with associated cardiovascular disease such as hypertension and ischemic heart disease, but Dr. Savelieva's review noted that its benefit may be lower and risk of adverse effects higher in patients with heart failure. In the post-market reports, cardioversion rates with vernakalant are 65-70%.
For patients undergoing AF ablation, a recent meta-analysis suggested that dabigatran has similar efficacy and safety compared with warfarin when used for periprocedural anticoagulation during AF ablation.7
One final example: recently, investigators assessed the prognostic value of N-terminal pro-B-type natriuretic peptide (NT-proBNP) in patients with AF enrolled in the ARISTOTLE trial (18,201 patients randomized to apixaban or warfarin).8 The authors found that levels of NT-proBNP are often elevated in AF and are independently associated with an increased risk for stroke and mortality. During 1.8 years of follow-up, the annual rates of stroke or systemic embolism ranged from 0.74% in the bottom NT-proBNP quartile to 2.2% in the top quartile (adjusted hazard ratio [HR]: 2.33; p<0.0001). Adding NT-proBNP levels to CHA2DS2-VASC score improved the c-statistics from 0.62 to 0.65 (p=0.0009) for stroke or systemic embolism and from 0.59 to 0.69 for cardiac death (p<0.0001).
Said Dr. Savelieva, "We are facing many changes in our practices in how we manage the AF patient." She sees a paradigm shift with the NOACs eventually replacing VKA in the majority of AF patients. She said refining risk stratification may lead to better patient-tailored therapy and lower rates of complications, whereas active screening will identify more patients who can benefit from early treatment.
- Atrial fibrillation is an old problem with some new solutions, such as an app that gives iPhones the ability to produce a single-lead ECG.
- There is a paradigm shift with the invention of oral anticoagulants that are being used more broadly and evaluated in settings such as cardioversion and AF ablation.
- Refining risk stratification may lead to better patient-tailored AF therapy and lower rates of complications.
- Lau JK, Lowres N, Neubeck L, et al. Int J Cardiol. 2013;165:193-4.
- Larsen T, Rasmussen L, Skjøth F, et al. J Am Coll Cardiol. 2013;61:2264-73.
- Cappato R, Ezekowitz MD, Klein AL, et al. Eur Heart J. 2014;35:3346-55.
- Lip GY, Bongiorni MG, Dobreanu D, et al. Europace. 2013;15:1526-32.
- Savelieva I, Camm AJ. Clin Cardiol. 2014;37:32-47.
- Savelieva I, Graydon R, Camm AJ. Europace. 2014;16:162-73.
- Hohnloser SH, Camm AJ. Europace. 2013;15:1407-11.
- Hijazi Z, Wallentin L, Siegbahn A, et al. J Am Coll Cardiol. 2013;61:2274-84.
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