Return of sinus rhythm after 6 years of atrial fibrillation with severe left atrial dilatation: A rare event in an 86-year-old woman

Chronic atrial fibrillation rarely evolves towards a return to normal sinus rhythm, although the phenomenon may be observed very occasionally, This is illustrated in the present case of a patient suffering from mitral valve regurgitation with severe dilatation of the left atrium who, after 6 years of atrial fibrillation, returned to stable sinus rhythm. No clinical improvement was observed following normalization of the electrocardiogram. This late return to sinus rhythm was accompanied by mechanical dissociation of the atria - the right contracting while the left remained inert We also suggest, on the basis of short, low amplitude P-waves, that because there was electrical dissociation of the atria, left atrial depolarization did not occur, The fibrous transformation of the left atrium together with loss of the parenchyma account for the absence of contraction and depolarization, and the disappearance of atrial fibrillation.