Abstract:

To evaluate the quantitative acoustic densitometry (AD) technique in myocardial fibrosis diagnosis and to explore the effects of benazepril and valsartan on myocardial fibrosis. MethodsSixty tenweekold male spontaneously hypertensive rats (SHRs) were randomly assigned to the control group(SHRc group), the benazepril group(SHRb group), the valsartan group(SHRv group) and the combination group(SHRb+v group), which were subjected to an intragastric administration for ten weeks. Fifteen male agematched WistarKyoto (WKY) rats served as the control group. The integrated backscatter (IBS) and cyclic variation of the integrated backscatter (CVIB) were assessed with the AD technique. The cardiac collagen fraction(CVF) and perivascular circumferential area(PVCA) were determined by Masson staining. Myocardial hyproconcentration(HC) were measured by a spectrophotometric method. Also, systolic blood pressure(SBP), left ventricular mass (LVM) and left ventricular mass index(LVMI) were observed. Correlation analysis among the above indexes was analyzed. ResultsCompared with the WKY group, levels of SBP, LVM, LVMI, HC, CVF, PVCA and IBS were all significantly increased in the SHRc group(P<0.01), while CVIB was significantly decreased(P<0.01), and the indexes were substantially ameliorated in the three treated SHR groups(P<0.05, P<0.01). Except for SBP, the combination group showed a more pronounced amelioration than the other two monotherapy groups (P<0.05, P<0.01). An intimately positive correlation was found between HC and CVF(r=0.921, P<0.01)　or PVCA　(r=0.885, P<0.01). Normalized values of integrated backscatter at the interventricular septum and left ventricular posterior wall were positively related to CVF　(r=0.731, 0.756，P<0.01)　and PVCA　(r=0.776, 0.788，P<0.01), while both CVIBs were inversely related to CVF（r=-0.642,-0.716，P<0.01）and PVCA　（r=-0.720, -0.755, P<0.01）. ConclusionMyocardial ultrasonic backscatter parameters are closely correlated with the alteration of myocardial collagen contents. Quantitative myocardial acoustic densitometry is a reliable technique for detecting myocardial fibrosis and evaluating its severity. Benazepril and valsartan decrease the blood pressure and can reverse an early myocardial fibrosis in SHRs. Benazepril in combination with valsartan is more effective in ameliorating myocardial fibrosis than either one alone.

Key words: Hypertension, Spontaneously hypertensive rat, Acoustic densitometry, Myocardial fibrosis