Identifying the optimal time for mitral valve surgery in the setting of severe mitral regurgitation (MR) remains an ongoing challenge due to continually improving surgical options and outcomes. Hence, the threshold for surgical intervention has been reduced in successive iterations of the valve disease guidelines of the American and European cardiology communities.1 ,2 Nevertheless, timing of surgical intervention in primary MR remains arbitrary, as patients can remain apparently asymptomatic for prolonged periods and are understandably reluctant to undergo a potentially hazardous procedure without objective evidence of definitive benefit. This is compounded by the diverse variation in outcomes of morbidity, mortality, size of incision and likelihood of repair at different centres. Hence, in the asymptomatic patient, objective evidence of impaired exercise capacity or other pathophysiological surrogates may be valuable in optimising the timing of surgery. Exercise stress echocardiography (ESE) has been widely used for this purpose to assess symptoms and exercise capacity, determine MR severity with exercise, examine LV contractile reserve and establish peak exercise pulmonary pressure.3 These variables have been used to predict the need for surgical intervention based upon the likelihood of adverse outcomes.

Pulmonary hypertension (PHT) is seen in a minority of patients with severe primary MR at rest. It is usually associated with more severe MR and with higher surgical morbidity, although it typically improves and may even normalise after successful mitral valve surgery. The mechanism of PHT relates to high left atrial (LA) pressure from the regurgitant mitral jet, though individual factors related to the pulmonary vasculature may also be important.4 The significance of exercise PHT in primary MR is somewhat more controversial. Prior to the 2014 revision of the American College of Cardiology/American Heart Association guidelines in valve …