Echocardiographic study of left ventricular geometry in spontaneously hypertensive rats

PINILLA OA; CARRANZA VB; ESCUDERO EM

Buenos Aires Argentina

Congreso; World Congress of Cardiology; 2008

 Introduction: the purpose of this study is to analyze by echocardiogram LV geometry in spontaneously hypertensive rats (SHR) and its relationship with LV. Material and Methods M-mode echocardiographic was performed under two-dimensional control in 114 male 4-month old rats 73 SHR and 41 Wistar (W); systolic blood pressure (SBP) was determined by the tail-cuff method and heart rate (HR) was obtained in each rat. LV mass (LVM) , LVM index (LVMI) as LVM / body weight and relative wall thickness (RWT) as  2 x LV posterior wall thickness / diastolic diameter was calculated with echocardiographic parameters. Normal limits of LVMI and RWT were defined considering the mean plus 2 standard deviation of W determinations. Patterns of abnormal LV geometry were: LV concentric remodeling, LVMI < 2.06 mg/g - RWT > 0.71; eccentric LVH, LVMI > 2.06 mg/g - RWT < 0.71; and concentric LVH, LVMI > 2.06 mg/g - RWT > 0.71. Cardiac output (CO) was calculated with LV stroke volume (LVDD3 – LVSD3) and HR. SBP and CO was used to obtain total peripheral resistance (TPR). Observed / predicted, midwall fractional shortening (MFS) and myocardial performance index (MPI) were used to evaluate LV systolic function and global LV function Results: four different groups were identified in 73 SHR: 9 (12%) had LVMI and RWT within normal limits; in 13 (18%), LVMI was normal but RWT was increased; 24 (33%) showed concentric LVH and 27(37%) had eccentric LVH. LV concentric remodeling had the smallest CO (34.7± 3.5 cm3. min-1 p <0.05) )with similar HR and SBP compared to the other groups and the highest TPR (6.09 ± 0.59a.u-p< 0.05) of any group. Rats with eccentric LVH showed similar SBP and HR as the other SHR groups and high CO (86.1 ± 3.6 cm3. min-1 p < 0.05) with lower TPR (2.23 ± 0.09 au p < 0.05). MFS was higher than concentric LV remodeling (118.3± 1.2 % vs 106.34 ± 3.3%-p < 0.05); MPI was similar to any SHR group. Concentric LVH had similar CO than normal LV geometry (61.6 ± 3.1 cm3. min-1 vs 60.2 ± 4.9 cm3. min-1 -ns) lesser than eccentric LVH and higher than concentric remodeling. MFS and MPI were similar than any group. Conclusions: Our findings in a large series of SHR exhibit different patterns of LV geometry like in humans, suggesting that factors able to influence ventricular chamber size or stroke volume could be involved in this modulation. The results of the present study strengthen the similarities between SHR and human essential hypertension, reinforcing its use as suitable model to study hypertension development