It is well recognised that patients with mitral stenosis (MS) and atrial fibrillation (AF) face a substantial risk of systemic thromboembolism. Anticoagulation with vitamin K antagonists partially offsets this risk.¹ However, because of our preoccupation with non-valvular AF, the haemodynamic consequences of AF in patients with MS² have received little attention in recent times. The article by Hu and colleagues,³ in this issue of Heart, presents an opportunity to review the value of sinus rhythm (SR) in the haemodynamics of MS.

Clinical deterioration with the onset of AF occurs because of the loss of atrial contraction and increase in heart rate, resulting in reduced cardiac output and functional capacity.² Symptom status, exercise capacity and quality of life all improve with conversion to SR.^2,4 While the detrimental effects of the reduction in diastolic filling time with increase in heart rate are well understood, the role of the loss of atrial systole is not as clear.

ATRIAL CONTRIBUTION TO VENTRICULAR FILLING IN MITRAL STENOSIS

Normally, most of the ventricular filling occurs during early diastole, independent of atrial contraction. Atrial contraction contributes to no more than a quarter of the ventricular inflow during SR in normal, young individuals. This proportion rises to about 40% with increasing age and impairment of ventricular relaxation.⁵ Ventricular filling differs in three important ways in the presence of MS (figs 1 and 2). Firstly, early peak mitral flow is reduced despite increases in left atrial (LA) pressure and flow velocities. Secondly, the rate of deceleration of transmitral flow is reduced, concomitantly reducing the rate of fall of the atrioventricular pressure gradient. As a result, in contrast to …