Mitral regurgitation and lone atrial fibrillation

BAKERSFIELD, CALIFORNIA. Mitral regurgitation (MR) is defined as an abnormal reversal of blood flow from the left ventricle to the left atrium. The most common causes of MR are mitral valve prolapse (MVP), rheumatic heart disease, and ischemic heart disease. A group of researchers from Bakersfield Heart Hospital now report that MR is significantly more prevalent in patients with lone atrial fibrillation (LAF) than in patients without this condition.

Their study involved 57 patients with LAF who underwent transesophageal echocardiography (TEE) prior to cardioversion and 100 patients without LAF who underwent TEE for various other reasons. All of the study participants had structurally normal mitral valves. LAF was defined as AF without concomitant heart disease, hypertension or diabetes, and age less than 60 years.

The researchers found that LAF patients were far more likely to exhibit moderate MR than were controls (66% vs 6%). Mild MR was found in 18% of LAF patients vs 31% in controls, and absence of MR was noted in 16% of LAF patients vs 63% of controls. Left ventricular ejection fraction and left atrial diameter did not differ between the two groups, but the diameter of the mitral annulus was significantly greater in the LAF group.

The researchers conclude that moderate MR may be a risk factor for the development of LAF primarily by causing mechanical stretch of the left atrium or conversely, that LAF may predispose to the development of MR over time. They also suggest the possibility that the observed MR may be a transient phenomenon that resolves once normal sinus rhythm is restored.
Sharma, S, et al. Clinically unrecognized mitral regurgitation is prevalent in lone atrial fibrillation. World Journal of Cardiology, Vol. 4, May 26, 2012, pp. 183-87

Editorís comment: The finding that mitral regurgitation and lone atrial fibrillation are somehow connected is most interesting. It is not clear from the study which is cause and which is effect, although the authors clearly lean toward the hypothesis that moderate MR is the forerunner for LAF. Another possibility obviously has to be that MR and LAF have the same origin. If this is indeed the case, then magnesium deficiency is likely to be the common factor since both LAF and mitral valve prolapse have been found to be associated with magnesium deficiency[1,2].
[1] Khan, AM, et al. Low serum magnesium and the development of atrial fibrillation in the community. Circulation, Vol. 127, January 1, 2013, pp. 33-38
Reference 1
[2] Bobkowski, W, et al. The importance of magnesium status in the pathophysiology of mitral valve prolapse. Magnesium Research, Vol. 18, No. 1, March 2005, pp. 35-52
Reference 2