Fig. 1

Panel a 1a Twelve-lead electrocardiograms of a patient with heart failure pre-cardiac resynchronization therapy demonstrates a QRS duration of 125 ms. 2a Real-time three-dimensional transthoracic echocardiography full volume mode, one beat: very heterogeneous (orange regional pattern) dynamic map of the time minimum volume that looks at a 10 % of heart cycle time window when it moves through the heart cycle, with individual segments reaching end-systole at different times, and relative high Systolic Dyssynchrony Index of 9.6 %. 3a The polar histogram shows the orientation and relative magnitude of blood-induced intraventricular forces which are not properly aligned along the left ventricle axis. 4a Relative magnitude of blood-induced hemodynamic forces which are not properly aligned along the left ventricle axis. Panel b Changes in electrical activation settings modify the orientation, φ, of intraventricular forces during acute study. The setting (A1-can in the top right, arrow) corresponding to the most aligned intraventricular forces is selected. Panel c 1c At follow-up, 12-lead electrocardiograms post-cardiac resynchronization therapy demonstrate a QRS duration of 126 ms. 2c Real-time three-dimensional transthoracic echocardiography full volume mode, one beat: low heterogeneous (orange regional pattern) dynamic map of the time minimum volume that looks at a 10 % of heart cycle time window when it moves through the heart cycle, with individual segments reaching end-systole at similar times, with low Systolic Dyssynchrony Index of 2.3 %. 3c These settings provided a positive response to therapy, which was associated with improved alignment of intraventricular forces. 4c Left ventricle flow was more regular and the associated hemodynamic forces followed the base–apex orientation. CRT cardiac resynchronization therapy, echo-PIV echo-particle imaging velocimetry, EF ejection fraction, EKG electrocardiogram, ESV end-systolic volume, NYHA New York Heart Association, RT3D-TTE real-time three-dimensional transthoracic echocardiography, SDI Systolic Dyssynchrony Index