Mapping of regional myocardial strain and work during ventricular pacing: experimental study using magnetic resonance imaging tagging

Abstract

Ventricular pacing causes a threefold difference in myofiber work within the LV wall. This difference appears large enough to regard local myocardial function as an important determinant for abnormalities in perfusion, metabolism, structure and pump function during asynchronous electrical activation. Pacing at sites that cause more synchronous activation may limit the occurrence of such derangements.

Mechanoelectric Feedback as a Trigger Mechanism for Cardiac Electrical Remodeling: A Model Study

“…Compared with the normal values (RA pacing), strain and external work during LV pacing were approximately zero in regions near the pacing site, and gradually increased to more than twice the normal value in remote regions. 51 These results are similar to our results for Fiber B without remodeling. With remodeling, we found a more homogeneous distribution of shortening and external work for Fibers A and B.…”

“…In Fiber A, external work was almost homogeneous with remodeling (Fig. 6), which is in agreement with the measurements during RA pacing (normal stimulation) of Prinzen et al 51 Ashikaga et al 4 investigated transmural dispersion of mechanics in vivo. They found that the onset of myofiber shortening was earliest in the endocardial layers, while the onset of myofiber relaxation was latest in the endocardial layers.…”

“…Prinzen et al 51 measured systolic fiber strain and external work at different locations in the left ventricle during right atrial pacing (RA pacing) and during left ventricular pacing (LV pacing). Compared with the normal values (RA pacing), strain and external work during LV pacing were approximately zero in regions near the pacing site, and gradually increased to more than twice the normal value in remote regions.…”

“…These mechanisms include immediate influence on the action potential through stretch-activated channels (SACs), 16,22,31 force-feedback on the intracellular Ca 2+ concentration ([Ca 2+ ] i ), 38 and long-term effects involving cell signaling pathways. 58 Prinzen et al 50,51 and Delhaas et al 13 observed homogeneous strain and mechanical work when the heart was paced from the right atrium (normal stimulation). However, during ventricular pacing, systolic fiber strain and mechanical work were approximately zero near the stimulation site, and gradually increased to more than twice the normal value in remote regions.…”

“…However, during ventricular pacing, systolic fiber strain and mechanical work were approximately zero near the stimulation site, and gradually increased to more than twice the normal value in remote regions. 51 We hypothesize that the deviation from normal mechanical work observed after ventricular pacing functions as a trigger for electrical remodeling.…”