Markers of increased risk in primary mitral regurgitation.

Myxomatous degaeneration is the most common etiology of primary mitral regurgitation (MR) in the developed world (1). Severe MR can impose significant hemodynamic stress on the left ventricle (LV). However, LV can remain in a compensated asymptomatic stage for long time with preserved ejection fraction (EF). After long period of time, EF drops and overt heart failure ensues (2). Mitral surgery is the cornerstone in management of severe MR to halt this process. Nonetheless, LV sustains subclinical structural and microscopic damage early before traditional indications for MV surgery is met (3). Current class I indications for MV surgery are development of symptoms or abnormal ejection fraction (4), and both of these conditions are associated with non-optimal postoperative outcomes. There is a growing concern that EF does not reflect true LV systolic function and it merely reflects ventricular ejection which is a fraction derived from end diastolic volume (EDV) (5). In conditions with supra-physiological EDV and reduced afterload such as severe MR, EF is doomed to be normal even in suboptimal LV performance. LV global longitudinal strain (LV-GLS), which measures myocardial systolic deformation, has been proposed to be more reflective of true LV systolic function (6). As a result to the aforementioned factors, timing of surgery in asymptomatic severe MR patients with preserved EF remains a challenging and a controversial decision (7). With the new advances in cardiac surgery and improvements in perioperative care, postoperative mortality in patients undergoing MV surgery in the last few years is less than 0.1%, with hospital stay as short as 5 days and more than 97% success rate in achieving trivial MR with MV repair (8), which argues for earlier intervention in patients with severe MR before it is too late.