Three-dimensional echocardiography for optimization of cardiac resynchronization therapy

We read with great interest the nice review by Stanton et al.1 concerning techniques for optimization of cardiac resynchronization therapy (CRT). In addition to the methods discussed by the authors, a promising technique in this context is represented by three-dimensional echocardiography (3D-echo). Although there are still no definite data regarding the effective clinical value of 3D-echo for optimization of CRT, several potential applications have emerged in the last years. Three-dimensional echocardiography followed by semi-automated left ventricular (LV) contour tracing analysis has been shown to be a feasible technique to identify the most delayed contracting segment and to select the optimal pacing site during CRT.2 For optimization of interventricular and atrioventricular delays aimed at maximizing cardiac output, 3D-echo can provide accurate estimates of LV stroke volume that are more reliable than those obtained by standard Doppler or two-dimensional imaging.3,4 For optimization of delays aimed at minimizing dyssynchrony, 3D-echo can be used to assess the dispersion of the time taken to reach the minimum systolic volume across multiple LV segments in the same cardiac cycle,5 a feature that may reflect the effective loss in stroke volume due to asynchronous contraction better than myocardial velocity-based indices,6 and that is a powerful predictor of acute response to CRT.7 Furthermore, recent evidences on the usefulness of 3D-echo in the assessment of LV diastolic flow dynamics suggest an intriguing potential application even for optimization algorithms aimed at maximizing LV diastolic filling.8 Lastly, 3D-echo assessment of acute changes in LV systolic function and dyssynchrony before and after resynchronization can be used as a validation tool for other CRT optimization techniques.9 Based on these considerations, a progressive expansion of the applications of 3D-echo for guiding and optimizing CRT could be expected to occur in the next future.