Figure 8.

Mechanical response to electrical activation during pacing. The pacing fully captures both electrical and mechanical activation of the heart up to a frequency of about f_p <8Hz. In particular, for pacing frequencies below f_p <8Hz the mechanical contraction and motion of the heart is enslaved to the electrical pacing. Each electrical pacing stimulus leads to a contraction and equally a mechanical forth and back motion. (A) At pacing frequencies below f_p = 3Hz (here CL = 350ms or f_p = 2.86Hz) the electrical activation leads to moderately strong motion. (B) The motion amplitude becomes maximal for pacing frequencies ranging in between 3 − 4Hz (see also Figure 5B). At pacing frequencies above f_p = 4Hz (here CL = 240ms or f_p = 4.17Hz) the rapid periodic electrical activation leads to a highly correlated back and forth motion of the heart. A similar behavior can be observed until f_p <8Hz. The powerspectrum is mono-modal. (D) At a pacing frequency of f_p = 6.25Hz both powerspectra are mono-modal and exhibit a single dominant frequency. (E) With pacing frequencies >8Hz, the pacing still fully captures electrically, but the mechanical powerspectrum is no longer mono-modal.