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Figure 5 Anatomical M-Mode Through the LV Cavity

Axial movement of contrast bubbles is shown in relation to the mitral valve (MV) and the aortic valve (AV) during sinus rhythm (A, B) and during epicardial pacing (C, D). Blue arrows indicate the time of MV closure (A, C) and AV opening (B, D). Yellow arrows indicate the time of isovolumic flow redirection. The delay in flow redirection (C, D) accompanies a delay in MV closure and AV opening after pacing of the left ventricle (LV) from the LV base. Dashed white lines indicate the onset of the QRS complex on surface electrocardiography. HR = heart rate.