Electromechanical imaging is a novel technique for the noninvasive mapping of electrical conduction waves in the left ventricle through the combination of ECG gating, high frame rate and RF-based displacement estimation techniques. In this paper, we identify and separate the electromechanical waves from the hemodynamically induced waves and determine the dependence of the wave direction and velocity at different pacing scenarios. In vivo imaging (30 MHz) was performed on anesthetized wildtype mice (n=12) at high frame rates (Vevo 770, Visualsonics, Inc.) in order to better explore the electromechanical coupling within the heart muscle. The acquisition was triggered on the mouse electrocardiogram (ECG) and yielded a high frame rate of 8000 fps. RF frames from long-axis views were digitized at 160 MHz. Axial, frame-to-frame displacements were estimated using ID cross-correlation (window size of 240 microns, overlapping at 90%).Three pacing protocols were applied in each mouse: 1) sinus rhythm (SR) (natural pacing), 2) right-atrial (RA) pacing and 3) right-ventricular (RV) pacing. Pacing was achieved using a nine-electrode catheter and catheterization through the right side of the heart, with each separately activated for varying the pacing location. Throughout the entire cardiac cycle, several waves were shown on the electromechanical images that propagated transmurally and/or from base to apex (septum) or apex to base (posterior wall). Through comparison of the ciné-loop images obtained at different pacing protocols, we were able to identify and separate the electrically induced, or contraction, wave from the hemodynamic (or, blood-wall coupling) waves. The contraction wave was best observed along the posterior wall starting at the S-wave of the ECG, which occurs after Purkinje and during myocardial activation. Only the contraction wave changed direction when the pacing origin changed, i.e., it propagated from apex to base at SR and RA pacing and from base to apex at RV pacing. This reversal in the wave propagation direction was found to be consistent in all mice scanned and the wave velocities were found to be within the reported conduction wave range with statistically significant differences between SR/RA pacing (0.8496 +/- 0.2214 m/s and 0.8379 +/- 0.1967 m/s), respectively and RV pacing (0.5213 +/- 0.3125 m/s). This pacing study demonstrates that electromechanical imaging may constitute the sole noninvasive method for conduction mapping of the entire left ventricle and thus diagnosis and treatment of dyssynchrony, arrhythmia or other conduction abnormalities.