Limited Impact of β-Adrenergic Receptor Activation on Left Ventricular Diastolic Function in Rat Models of Hypertensive Heart Disease.

BACKGROUND

Hypertension is a major cause of left ventricular (LV) diastolic dysfunction. Although β-adrenergic receptor (β-AR) blockers are often used to manage hypertension, the impact of β-AR activation on LV lusitropic effects and hence filling pressures in the hypertensive heart with LV diastolic dysfunction is uncertain.

METHODS

Using tissue Doppler imaging and Speckle tracking software, we assessed LV function in isoflurane anesthetised spontaneously hypertensive (SHR) and Dahl salt-sensitive (DSS) rats before and after β-AR activation [isoproterenol (ISO) administration].

RESULTS

As compared to normotensive Wistar Kyoto control rats, or DSS rats not receiving NaCl in the drinking water, SHR and DSS rats receiving NaCl in the drinking water had a reduced myocardial relaxation as indexed by lateral wall e' (early diastolic tissue velocity at the level of the mitral annulus) and an increased LV filling pressure as indexed by E/e'. However, LV ejection fraction and deformation and motion were preserved in both SHR and DSS rats. The administration of ISO resulted in a marked increase in ejection fraction and decrease in LV filling volumes in all groups, and an increase in e' in SHR, but not DSS rats. However, after ISO administration, although E/e' decreased in DSS rats in association with a reduced filling volume, E/e' in SHR remained unchanged and SHR retained greater values than Wistar Kyoto control.

CONCLUSIONS

The hypertensive heart is characterized by reductions in myocardial relaxation and increases in filling pressures, but β-AR activation may fail to improve myocardial relaxation and when this occurs, it does not reduce LV filling pressures.