Age-dependent depression of cardiac function in CBK, but not littermate control, mice. Left ventricular wall thickness during diastole (A), end diastolic diameter (B), left ventricular volume during diastole (C), stroke volume (D), left ventricular fractional shortening (E), and left ventricular ejection fraction (F). Mice were housed in a 12-hr light:12-hr dark cycle (lights on at ZT0). Serial echocardiography was performed at 4 week intervals, always at ZT6. Values are expressed as mean ± SEM (n=5–7). *, p<0.05 for CBK versus littermate control at a distinct age (post-hoc pair-wise comparison).