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August 21, 2010AJP Heart and Circulatory PhysiologyOpen Access

Increased expression of β-MHC in hypothyroid rats reduced left ventricular torsion and fiber strain, and delayed the development of peak torsion and strain during systole compared to euthyroid rats.

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Population

Hypothyroid rats and euthyroid rats

Comparison

Hypothyroidism and dobutamine infusion vs Euthyroid rats

Design

Preclinical

Key result

Increased expression of β-MHC in hypothyroid rats reduced left ventricular torsion and fiber strain, and delayed the development of peak torsion and strain during systole compared to euthyroid rats.

Authors

YCYong ChenASAleefia SomjiXYXin Yu

Discussion

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Overview

Should not alter hypothyroidism management; hypothesis-generating for β-MHC effects on human LV mechanics.

Key Points

  • The aim is to investigate how altered myosin heavy chain isoform expression impacts left ventricular torsion and strains in hypothyroid rats.
  • Used MRI to assess in vivo mechanical performance.
  • Compared contractile properties in hypothyroid rats expressing slow β-MHC and euthyroid rats with fast α-MHC.
  • Measured unloaded shortening velocity and force development rate constants in isolated ventricular myocardium.
  • Hypothyroid rats exhibited decreased LV torsion and fiber strain, with slower peak development in systole.
  • V(o) and k(tr) were significantly slower in hypothyroid rats compared to euthyroid rats.
  • Dobutamine infusion in hypothyroid hearts resulted in smaller increases in torsion and strained patterns.

Structured PICO

P
Population
Hypothyroid rats (expressing only the slow β-MHC isoform) and euthyroid rats (predominantly expressing the fast α-MHC isoform)
I
Intervention
Hypothyroidism (altered MHC isoform expression to β-MHC) and dobutamine infusion
C
Comparator
Euthyroid rats
O
Outcome
In vivo left ventricular torsion, fiber strain, unloaded shortening velocity (Vo), and apparent rate constants of force development (ktr)surrogate

Increased expression of β-MHC in hypothyroid rats alters the pattern and decreases the magnitude of LV rotation, contributing to reduced mechanical performance during systole.

Cite This Study

Chen et al. (2010) studied Hypothyroidism. Hypothyroidism (increased β-MHC expression) vs. Euthyroid state (predominant α-MHC expression) was evaluated on In vivo left ventricular torsion, principal strains, unloaded shortening velocity (V(o)), and apparent rate constants of force development (k(tr)). Increased expression of β-MHC in hypothyroid rats reduced left ventricular torsion and fiber strain, and delayed the development of peak torsion and strain during systole compared to euthyroid rats.

synapsesocial.com/papers/6a0c05a43b45b6e80888522ahttps://doi.org/10.1152/ajpheart.00406.2010
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Also Consider

Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context:

  1. 1Role of myosin heavy chain composition in kinetics of force development and relaxation in rat myocardium1998 · 114 citations
  2. 2Role of myosin heavy chain composition in the stretch activation response of rat myocardium2006 · 62 citations
  3. 3Maximum speed of shortening and ATPase activity in atrial and ventricular myocardia of hyperthyroid rats1995 · 39 citations
  4. 4Role of microtubules versus myosin heavy chain isoforms in contractile dysfunction of hypertrophied murine cardiocytes2003 · 25 citations
  5. 5Influence of the thyroid state on left ventricular tension-velocity relations in the intact, sedated dog1969 · 115 citations