To the Editor:
We congratulate Drs Ayala and Greentree for their experience and we totally agree that in order to obtain optimal ventricular systolic resynchronization the areas to be stimulated should be those with electromechanical delay in the left ventricle. In our work1 the posterolateral region was chosen based on the echocardiographic study and the pre-intervention left catheterization. With tissue Doppler echocardiography it is possible to identify with high accuracy the segments with greater electromechanical activation delay. Regarding catheterization, we carried out temporal endocardial pacing in different segments of the left ventricle in order to determine which anatomical site provides the best improvement in dP/dt.