Sequential radial and circumferential strain and oxidative stress assessment in dogs with tachycardia-induced cardiac dysfunction.

Abstract

UNLABELLED: Quantitative analysis of left ventricular (LV) deformation based on two-dimensional speckle tracking echocardiography (2D STE) has increasingly been used to assess segmental and global function because conventional echocardiography is influenced by tethering effects of adjacent myocardium and cardiac translational motion. HYPOTHESIS: (1) 2D STE can be useful to detect subtle regional changes in the LV contractility during development of tachycardia-induced cardiomyopathy (TIC) to heart failure in awake dog; (2) oxidized glutathione (GSSG) and reduced glutathione (GSH) levels are associated with the development of its respective segmental wall motion abnormalities (WMA). 6 healthy canine female Beagles were examined using 2D STE myocardial strain analysis before and for 8 weeks on week basis of rapid ventricular pacing (RVP) and at the end of study each myocardial segment were evaluated for oxidative status (GSH:GSSG ratio). 2D STE showed an initial peak of reduced global radial strain at 2 weeks of RVP in all three cardiac levels analyzed in which the affected segments showed a decreased transmural fiber shortening from anteroseptal to inferior segments distributed in helical pattern suggesting impaired contractility from part of left band to apical loop of spiral muscle band while global circumferential strain showed to be reduced since the fifth week of RVP particularly in the base and midventricular levels of ascending segment in clockwise direction from lateral to inferior segments. The most affected segments are localized in the lateral to posterior wall, however, segmental oxidative stress analysis did not show correlation with WMA detected by strain. 2D STE strain demonstrated to be a reliable tool for evaluation of LV myocardial deformation in TIC canine model showing an earlier significant WMA using radial strain and later using circumferential strain which may be of importance for improvement of diagnosis and therapy in naturally occurring canine cardiomyopathy and for earlier detection of WMA after suboptimal pacemaker lead placement.