Severe mitral regurgitation due to atrial tachyarrhythmia: Cure by DC cardioversion

Abstract

A 62-year-old man admitted with palpitations had a 12-lead ECG that revealed atrial flutter with 2:1 AV block (rate 150 bpm). Transthoracic echocardiography (TTE) revealed normal left ventricular size with impaired systolic function and severe MR (Fig. 1, panels A, B and Videos 1, 2). No MV prolapse was seen. The admitting doctor informed the patient that mitral valve surgery was the likely outcome. However, after senior review, the patient was commenced on rate-control, diuretic and anticoagulant medications. He was discharged and returned 6 weeks later for direct current cardioversion, which successfully restored sinus rhythm. TTE 2 months later showed normal LV function and trivial MR (Fig. 1, panel C and Video 3). This case highlights the importance of understanding the mechanism underlying MV dysfunction. The mitral annulus is a thin fibrofatty ring that geometrically resembles a parabola; its sphincteric contraction reduces MV annular area by ~25% during the cardiac cycle, facilitating normal leaflet coaptation (1). Consequently, the onset of atrial flutter – and loss of annular contraction – resulted in MR, and this was exacerbated by the rapid heart rate, which reduces the normal ventricular closing forces on the valve leading to incomplete mitral leaflet coaptation. Clinicians are reminded that atrial arrhythmias with high heart rates can disrupt normal MV function, producing MR which can be resolved by treating the underlying abnormality (i.e. atrial arrhythmia) (2, 3) and thus avoiding unnecessary cardiac surgery.