When do we remain with the devil we know (the vitamin K antagonists) … in atrial fibrillation? The case of “valvular atrial fibrillation”
De Caterina pointed out that the term valvular AF has been poorly defined, although this is used as a criterion not to prescribe NOACs. Together with John Camm, he has proposed a more restrictive term, namely mechanical and rheumatic mitral valvular AF (MARM-AF) as an accurate description of conditions in which NOACs should not be used.11
In a large study evaluating edoxaban vs. warfarin in patients with and without valvular heart disease, no evidence was found that valvular disease affects efficacy of this NOAC, nor was there evidence of a differential safety (Renda et al., presented at ACC 2016). Pooling the four large NOAC trials also suggests that efficacy with respect to prevention of stroke/systemic embolism is similar for patients with and without mitral disease, and the signal for safety was also about the same. One situation exists in which NOACs should never be used, namely in the presence of mechanical heart valves, as more bleeding and more stroke has been seen in these patients when treated with dabigatran.
Patients with aortic stenosis, aortic insufficiency and mitral insufficiency can safely receive a NOAC. Unexplored areas include valve repair and bioprostheses. Mitral stenosis might be an interesting area for future research. There are reasons why mitral stenosis, associated with up to three times the risk of stroke as compared to other types of AF, may be different. For instance, because of the absence of foreign surfaces or metal, thus preservation of the valvular
endothelium and fibrotic tissue. Blood rheology changes and left atrial stasis, but this is common to other types of ‘non-valvular’ AF. And, contrary to most mechanical valves, vitamin K antagonist standards recommend a similar INR intensity as in other forms of non-valvular AF.
Mitral stenosis, as a rheumatic heart valve disease, is most prevalent in Africa, especially sub-Saharan Africa, and in the Maori people in Australia, followed by India, Pakistan, Bangladesh and parts of China. In these countries, the need to prevent stroke in patients with rheumatic heart disease is generally not adequately addressed, because warfarin is not given, and/or because INRs are poorly controlled.
Raffaele De Caterina, MD Professor of Cardiology, G. d’Annunzio University in Chieti, Italy