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Myofiber prestretch magnitude determines regional systolic function during ectopic activation in the tachycardia-induced failing canine heart. | LitMetric

AI Article Synopsis

  • Electrical dyssynchrony in heart failure contributes to prestretch in regions activated late, disrupting the normal contraction sequence and affecting heart mechanics.
  • A study on failing dog hearts identified that prestretch magnitude increases with early-activated tissue, resulting in higher end-systolic strains, particularly at the heart's outer and inner layers.
  • The findings suggest that local activation times influence fiber strains during heart contraction, but the connections between electrical activation and mechanical properties are complex and not fully explained by muscle length and velocity changes.

Article Abstract

Electrical dyssynchrony leads to prestretch in late-activated regions and alters the sequence of mechanical contraction, although prestretch and its mechanisms are not well defined in the failing heart. We hypothesized that in heart failure, fiber prestretch magnitude increases with the amount of early-activated tissue and results in increased end-systolic strains, possibly due to length-dependent muscle properties. In five failing dog hearts with scars, three-dimensional strains were measured at the anterolateral left ventricle (LV). Prestretch magnitude was varied via ventricular pacing at increasing distances from the measurement site and was found to increase with activation time at various wall depths. At the subepicardium, prestretch magnitude positively correlated with the amount of early-activated tissue. At the subendocardium, local end-systolic strains (fiber shortening, radial wall thickening) increased proportionally to prestretch magnitude, resulting in greater mean strain values in late-activated compared with early-activated tissue. Increased fiber strains at end systole were accompanied by increases in preejection fiber strain, shortening duration, and the onset of fiber relengthening, which were all positively correlated with local activation time. In a dog-specific computational failing heart model, removal of length and velocity dependence on active fiber stress generation, both separately and together, alter the correlations between local electrical activation time and timing of fiber strains but do not primarily account for these relationships.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3726954PMC
http://dx.doi.org/10.1152/ajpheart.00186.2012DOI Listing

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