Hypercholesterolemia and myocardial function evaluated via tissue doppler imaging

Abstract

Objective: To establish a link between hypercholesterolemia and myocardial dysfunction.

Background: Heart failure is a complex disease involving changes in systolic and diastolic function. Newer echocardiographic imaging modalities may be able to detect discreet changes in myocardial function associated with hypercholesterolemia. Therefore we sought to establish a link between hypercholesterolemia and myocardial dysfunction with tissue Doppler imaging (TDI).

Methods: Twenty-seven rabbits were studied: 7 were fed normal chow (group 1) and 20 a high cholesterol diet (10 with ezetimibe, 1 mg/kg/day; group 2 and 10 without, group 3). Echocardiographic images were obtained under general anesthesia. Serum cholesterol levels were obtained at baseline, 3 and 6 months and myocardial cholesterol levels measured following euthanasia.

Results: Doppler measurements, including E/A, E'/A' and S' were significantly lower in group 3 compared to both groups 1 and 2 but no significant differences were noted in chamber sizes or ejection fraction among the groups. Average serum cholesterol was higher in group 3 compared to groups 1 and 2 respectively (495 +/- 305 mg/dl vs. 114 +/- 95 mg/dl and 87 +/- 37 mg/dl; p < 0.01). Myocardial cholesterol content was also higher in group 3 compared to group 2 (0.10 +/- 0.04 vs. 0.06 mg/dl +/- 0.02; p = 0.05). There was significant correlation between S', E'/A', E/E' and serum cholesterol (r2 = 0.17 p = 0.04, r2 = 0.37 p = 0.001 and r2 = 0.24 p = 0.01).

Conclusion: Cholesterol load in the serum and myocardium was significantly associated with decreased systolic and diastolic function by TDI. Moreover, lipid lowering was protective.

Figure 1

Tissue Doppler images from the septal wall of the ventricle. Tissue Doppler images (bottom) obtained from the Septal wall (top) in two different rabbits on hypercholesterolemic diet with (right) and without ezetimibe (left). E' = peak early diastolic velocity, A' = peak atrial velocity, S' = peak systolic velocity.

Figure 2

Tissue Doppler image from the lateral wall of the ventricle. Tissue Doppler image (bottom) obtained from the lateral wall of the ventricle (top) in a control rabbit. E' = peak early diastolic velocity, A' = peak atrial velocity, S' = peak systolic velocity.

Figure 3

Myocardial Function by Subgroups. E'/A' (septal wall), E'/A' lat (lateral wall) and S' measurements in hypercholesterolemic rabbits with and without ezetimibe and control rabbits. *p < 0.05 for group without ezetimibe vs. with ezetimibe and control.