Cardiac hypertrophy in spontaneously hypertensive rats: Vectorcardiographic investigation of myocardial depolarization (QRS-loop)

The aim of our work was vectorcardiographic study of myocardial depolarisat ion in genetically predisposed to spontaneous hypertension rats. Spontaneou sly hypertensive rats (SHR), normotensive animals (WKY)and F1 and F2 hybrid s of SHRxWKY intercross were used. Arterial blood pressure (BP), cardiac el ectrical activity (evaluated by vectorcardiography) and heart morphometry w ere studied in 144 animals. SHR, WKY and F1 and F2 hybrid male animals demo nstrated following levels of systolic BP: 193+/-5, 139+/-3, 163+/-2, 164+/- 2 mm Hg, respectively. Heart and left ventricular weights in F1 and F2 male rats were significantly different from those in SHR and WKY males. In all groups females compared with males of the same group had similar values of BP, but decreased values of body and heart weights. Vectorcardiography anal ysis demonstrated differences in direction of maximal QRS vector, terminal part of maximal QRS and the loop's width between SHR and WKY rats. Moreover , same differences were found between either of these groups and F1 and F2 animals. In F2 hybrids, values of BP were not in correlation with morpholog ical data of the hearts. On the contrary, a close correlation between chara cteristics of QRS vector and heart or left ventricular weight was demonstra ted for both sexes. These data indicate that: 1) according to vectorcardiog raphy, ventricular depolarisation in F1 and F2 hybrids are similar to that in WKY rats despite cardiac hypertrophy in hybrid groups; 2) in F2 hybrids, vectorcardiographic parameters significantly correlate with myocardial wei ght, but not with BP.