Authors' Reply

Abstract

Ring et al. 1 It is a very well-documented report assessing the need for earlier surgical intervention in patients with mitral valve prolapse and moderate to severe mitral regurgitation, using novel echocardiographic indices such as left atrial (LA) wall strain derived from speckle-tracking imaging. The authors stated that contractile and reservoir strain of the left atrium displays subtle early alterations that precede the development of clinical or classical echocardiographic features regarding LA function. It is well established that a dilated left atrium has impaired compliance and contractility, 2 leading to tissue remodeling, which changes the stress/strain distribution because of altered pressure/flow and stress realationship. 3 In their Table 1, as LA functional indices, the authors used both volumetric (total LA emptying fraction) and myocardial (reservoir and contractile strain) indices. 1 We suggest that the impaired myocardial indices are due to the change of geometry of the left atrium (dilated left atrium, impaired total LA emptying fraction), not vice versa. The authors did not clearly state in their statistical analysis regarding the multivariate Cox proportional-hazard models that the possible confounding versus effect modification or interaction was examined, 4 because the LA volume variable may act as an effect modifier and a confounder at the same time.We would like to thank the authors for their intriguing work and to emphasize that myocardial-derived speckle-tracking imaging indices of the left atrium may reflect the degree of tissue remodeling that occurs in the stretched LA wall. Figure 1 Sequential Cox proportional-hazard models demonstrating the incremental discriminatory value of differing echocardiographic markers in the identification of patients with MR who are at risk for surgical intervention: (A) including maximal LA volume and (B) including minimal LA volume. EROA, Effective regurgitant orifice area; LVIDd, LV internal diameter in diastole; PA, pulmonary artery.

The assessment of mitral valve disease: a guideline from the British Society of Echocardiography

“…As such, in moderate and severe MR there are only minor reductions in reservoir and contractile strain, but in patients with a guideline indication for MV surgery, LA function is markedly reduced, almost certainly as a consequence of interstitial fibrosis developing within the LA myocardium 44,46,47 . In prospective studies, reductions in reservoir strain are associated with poor cardiovascular survival, increased likelihood of AF during follow-up, or the development of a guideline indication for cardiac surgery 46,[48][49][50] .…”

“…In asymptomatic patients with moderate to severe MR and no guideline indication for mitral valve surgery, a TLAEF <51%, or reservoir strain <29% may be useful in identifying those patients in whom early surgical intervention may be indicated, or at least identifying those patients who may benefit from increased frequency of follow-up 49 .…”