New Onset Atrial Fibrillation
What can be done for stroke prevention in new onset atrial fibrillation? What is the necessary duration of atrial fibrillation that will mandate anticoagulation? Should anticoagulation be started at one-hour of new onset atrial fibrillation or one-day of new onset atrial fibrillation? The answer is unknown. This uncertainty in diagnosing burden of disease leads to uncertainty in prescribing appropriate stroke prophylaxis regimens.
Warfarin and Newer Anticoagulants
As mentioned earlier, warfarin has been used for TAVR patients in the setting of atrial fibrillation. However, this comes with multiple issues. The first is a high risk of bleeding complications,21 both major and minor. In addition, there are issues of compliance. Some studies have shown that only a third of all patients are eligible for warfarin, are taking warfarin in the community non-trial setting.22 Finally, the amount of time that patients taking warfarin in clinical trials with therapeutic international normalised ratio (INR) has been less than ideal, up to 38.7 % of the time. In a real-life study, patients had non-therapeutic INR up to 50 % of the time.23,24
New anticoagulants, such as dabigatran, rivaroxaban and apixaban, provide great promise for stroke prophylaxis in patients with atrial fibrillation. These medications operate through mechanisms other than vitamin K antagonism, including oral direct thrombin inhibitor (dabigatran) and oral direct factor Xa inhibitor (rivaroxaban and apixaban). While the new medications were likely to decrease haemorrhagic stroke in published studies, they all are associated with an increase in major bleeding. In addition, they all have discontinuation rates of more than 20 % in a heavily controlled clinical trial setting.25– 27 Causes for discontinuation include interactions with drugs, interactions with diet, polypharmacy, side effects, cost, nuisance bleeding or need for an invasive procedure. There has been no data looking at newer anticoagulants for chronic atrial fibrillation in patients after TAVR; however, the increased risk of bleeding and high non-compliance rate would be issues also applicable to this population.
Left Atrial Appendage Closure
There have been multiple studies showing the benefit of LAA closure. The Watchman™ device (Boston Scientific, Natick MA, US) has significant positive data. Early issues of safety and treatment failures were addressed with continued access registry, late versus early analysis with Watchman Left Atrial Appendage System for Embolic Protection in Patients With AF (PROTECT-AF), and the second randomised controlled Randomized Trial of LAA Closure vs Warfarin for Stroke/ Thromboembolic Prevention in Patients with Non-valvular Atrial Fibrillation (PREVAIL) trial, which all showed increasing rates of implant success with decreasing rates of vascular complications and pericardial effusions needing intervention.28 In addition, the four-year analysis of the PROTECT-AF trial showed that LAA closure was superior to warfarin, specifically in the area of all-cause mortality.29 Finally, LAA occlusion was found to be effective in patients with contraindication to warfarin,30 tolerant of small peri-device leaks,31 cost- effective32 and correlated with an improvement in quality of life.33 The Amplatzer™ Cardiac Plug (ACP) system (St. Jude Medical, St. Paul, Minnesota, US) also has significant long-term safety and efficacy data.34–37
However, all of these patients enrolled in these trials had ‘non-valvular atrial fibrillation’. This definition is often, unfortunately, unclear. What exactly is valvular atrial fibrillation?
According to the European Society of Cardiology (ESC) 2012 Valvular Heart Disease Guidelines, “It is conventional to divide AF into cases which are described as ‘valvular’ or ‘non-valvular’. No satisfactory or uniform definition of these terms exists. In this guideline, the term valvular AF is used to imply that AF is related to rheumatic valvular disease (pre-dominantly mitral stenosis) or prosthetic heart valves”.