Author's Reply.

To the Editor,

We would like to thank the authors of the letter for their interest about our article in press entitled “Apical transverse motion is associated with speckle-tracking radial dyssynchrony in patients with nonischemic dilated cardiomyopathy,” published in this issue of The Anatolian Journal of Cardiology (1). Apical transverse motion (ATM), to quantify apical rocking, has recently been proposed by Voigt et al. (2) as a new parameter for assessing left ventricular (LV) dyssynchrony. They demonstrated that ATM contained information on both regional and temporal function inhomogeneities of the LV and that it has a potential role in the clinical context.

In our study, we investigated the relation of the ATM with LV radial dyssynchrony assessed by speckle-tracking echocardiography, which is a reliable indicator of regional myocardial contraction (3, 4), in patients with non-ischemic dilated cardiomyopathy. Speckle-tracking analysis, myocardial rotation, twist, torsion, and ATM analysis were performed as previously described (2, 3, 5). After the analysis, ATM (ATM loop, ATM4CV, and ATM3CV) was found to be significantly correlated to the speckle-tracking derived radial dyssynchrony, and a 2.5 mm cut-off value for ATM loop could distinguish between patients with and without radial dyssynchrony, with high sensitivity and specificity. Patients with radial dyssynchrony also showed disturbed rotational dynamics and significantly decreased LV twist and torsion.

Despite a large number of publications in this field, we currently cannot advise one ideal parameter for the success of cardiac resyn-chronization therapy (CRT). Multiple interrelated mechanisms, including myocardial viability within the paced area, underlying myocardial conditions such as fibrosis and hypertrophy, and location of the pacing lead, may affect the response to CRT. However, echocardiography has an attractive role in guiding us for understanding how CRT actually works and how to select candidates for this specific therapy. Because up to 30% of patients undergoing CRT do not respond favourably with the currently accepted criteria for the patient selection (QRS duration, NYHA class, and ejection fraction), several echocardiographic methods have been identified so far to quantify LV dyssynchrony. We believe that the evaluation of ATM together with other echocardiographic methods may be practical and useful for the selection of CRT candidates.