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Reduction in postsystolic wall thickening during late preconditioning
Xavier Monnet1, Laurence Lucats, Patrice Colin
1Laboratoire de Pharmacologie, INSERM U660, Faculté de Médecine de Créteil, 8, rue Général Sarrail, 94010 CRETEIL Cedex, France.
American Journal of Physiology. Heart and Circulatory Physiology
|August 22, 2006
Summary
Late preconditioning significantly reduces postsystolic wall thickening (PSWT) and enhances systolic wall thickening (SWT) after brief coronary artery occlusion (CAO). This contractile adaptation improves myocardial function during stunning, offering insights into repetitive ischemia effects.
Area of Science:
- Cardiovascular Physiology
- Myocardial Ischemia Research
- Cardiac Electrophysiology
Background:
- Brief coronary artery occlusion (CAO) and reperfusion cause myocardial stunning and late preconditioning.
- Postsystolic wall thickening (PSWT) is a known consequence of CAO, but its temporal dynamics during stunning and its modulation by preconditioning are not well understood.
Purpose of the Study:
- To investigate the evolution of PSWT during myocardial stunning.
- To determine how late preconditioning modifies PSWT and regional myocardial function.
Main Methods:
- Dogs underwent chronic instrumentation for sonomicrometric measurement of systolic wall thickening (SWT), PSWT, total wall thickening (TWT), and maximal rate of thickening (dWT/dt(max)).
- Two 10-minute CAO of the circumflex artery were performed 24 hours apart.
- A non-ischemic preconditioning stimulus (rapid ventricular pacing) was also tested.
Main Results:
- CAO on day 0 decreased SWT and increased PSWT; PSWT evolution mirrored SWT during early stunning.
- On day 1, baseline SWT was unchanged, but PSWT was reduced by 66%, while dWT/dt(max) and the SWT/TWT ratio increased by 48% and 14%, respectively, indicating reduced stunning.
- Late preconditioning significantly reduced PSWT and enhanced dWT/dt(max) and SWT/TWT ratio, suggesting improved ejection efficiency.
Conclusions:
- Late preconditioning induces significant contractile adaptations, including enhanced wall thickening rate and near abolition of PSWT.
- These observed phenotype adaptations offer potential markers for characterizing myocardial stunning and late preconditioning in response to repetitive ischemia in humans.
