Fig. 2.

Strain echocardiography graphs in a representative Callospermophilus lateralis during active and hibernating/early arousal states. The lower left-hand corner of each panel depicts the left ventricular chamber with eight points tagged to the circumferential endocardial region. Movement of each of these regions is displayed as a colored line in the graphs to the right (endocardial circumferential strain and strain rate). Higher values of systolic strain (St_s) were found in the hibernation–early arousal period; diastolic strain (St_d) was not significantly different. Strain rates were lower during early arousal, particularly the rate of systolic strain (SR_s), which was a fraction of the active SR_s, in comparison with the rate of diastolic strain (SR_d), which tended to be closer to active SR_d. Note the overall undulation of the SR values. This finding was common in early arousal and suggests heterogeneity in the rates of myocardial deformation across regions and throughout progression of the cardiac cycle. The upper left-hand corner of each panel depicts radial displacement of endocardial wall motion. Increasing intensities of blue color indicate increasing distances of myocardial movement as systole progresses. Note the greater gradation of movement and the undulating pattern of the early arousal period that correlates to the heterogeneity of the strain rate curve. In this individual, systolic contraction was 155 ms in the active period and 1090 ms during early arousal.