Effects of afterload on regional left ventricular torsion

Guy A. MacGowan, Daniel Burkhoff, Walter J. Rogers, Douglas Salvador, Haim Azhari, Paul S. Hees, Jay L. Zweier, Henry R. Halperin, Cynthia O. Siu, Joao A.C. Lima, James L. Weiss, Edward P. Shapiro

Research output: Contribution to journalArticlepeer-review

Abstract

Objective: To determine if left ventricular torsion, as measured by magnetic resonance tissue tagging, is afterload dependent in a canine isolated heart model in which neurohumoral responses are absent, and preload is constant. Methods: In ten isolated, blood perfused, ejecting, canine hearts, three afterloads were studied, while keeping preload constant: low afterload, high afterload (stroke volume reduced by approx. 50% of low afterload), and isovolumic loading (infinite afterload). Results: There were significant effects of afterload on both torsion (P < 0.05) and circumferential shortening (P < 0.0005). Between low and high afterloads, at the anterior region of the endocardium only, where torsion was maximal, there was a significant reduction in torsion (15.1 ± 2.2° to 7.8 ± 1.8°, P < 0.05). Between high afterload and isovolumic loading there was no significant change in torsion (7.8 ± 1.80 to 6.2 ± 1.5°, P = NS). Circumferential shortening at the anterior endocardium was significantly reduced both between low and high afterload (-0.19±0.02 to -0.11 ± 0.02, P < 0.0005), and also between high afterload and isovolumic loading (-0.11 ± 0.02 to 0.00 ± 0.02, P < 0.05). Plots of strains with respect to end-systolic volume demonstrated a reduction in both torsion and shortening with afterload-induced increases in end-systolic volume. Torsion, but not circumferential shortening, persisted at isovolumic loading. Conclusions: Maximal regional torsion of the left ventricle is afterload dependent. The afterload response of torsion appears related to the effects of afterload on end-systolic volume.

Original languageEnglish (US)
Pages (from-to)917-925
Number of pages9
JournalCardiovascular research
Volume31
Issue number6
DOIs
StatePublished - Jun 1996

Keywords

  • Afterload
  • Dog, anesthetized
  • Magnetic resonance tagging
  • Torsion

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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