Cor Vasa 2002, 43(10):401-407

The relationship between QRS amplitude and left ventricular mass in the initial period of left ventricular hypertrophy in spontaneously hypertensive rats

Ján Klimas^1,*, Ljuba Bachárová², Ján Kyselovi¹

¹ Farmaceutická fakulta, Univerzita Komenského

² Medzinárodné laserové centrum, Bratislava, Slovenská republika

Aim:
In this study, we tested the hypothesis of the relative voltage deficit in an experimental model of spontaneously hypertensive rats (SHR) in the initial period of an increase in blood pressure.

Material and methods:
Frank orthogonal electrocardiograms of male SHR aged 12 and 20 weeks were recorded. During this period, systolic blood pressure (sBP) increased from 165 ± 3 mm Hg to 195 ± 1 mm Hg (p < 0.001). Age- and sex-matched WKY rats were used as control groups. The sBP values in WKY normotensive control groups were not changed (122 ± 8 mm Hg and 130 ± 4 mm Hg, respectively). The maximum QRS spatial vector magnitude (QRS_max.) was calculated from the X, Y, Z amplitudes of the orthogonal electrocardiograms. The animals were sacrificed and the left ventricular mass (LVM) was determined. The "specific potential of the myocardium" (SP), quantifying the relative voltage deficit, was calculated as a ratio of QRS_max. to LVM.

Results:
The LVM in SHR (0.86 ± 0.05 g and 1.05 ± 0.07 g, respectively) was significantly higher as compared to WKY (0.65 ± 0.07 g and 0.70 ± 0.02 g), and the increase in LVM correlated closely with the sBP increase. The QRS_max. in SHR did not follow the increase in LVM. The QRSmax. values in SHR did not differ from those of WKY at the age of 12 weeks (SHR 12: 0.46 ± 0.05 mV, WKY 12: 0.59 ± 0.14 mV), and were even lower in SHR at the age of 20 weeks (WKY 20: 0.44 ± 0.05 mV compared to SHR 20: 0.74 ± 0.08 mV, p < 0.001). The values of SP were significantly lower in SHR as compared to WKY controls. The values decreased significantly in SHR with increasing age, sBP and LVM, i. e., with progression of hypertrophic left ventricular remodeling.

Conclusions:
The results of this study support the hypothesis of a relative voltage deficit in left ventricular hypertrophy (LVH). These results are consistent with the finding of a high number of false negative EKG results in clinical EKG diagnosis of LVH, and could contribute to an understanding of the diagnostic importance of the false negative EKG results, their re-evaluation and utilization for clinical diagnosis. They could be potentially informative in the evaluation of effects of antihypertensive drugs on LVH.

Keywords: Left ventricular hypertrophy; Spontaneously hypertensive rats; Electrocardiography; Relative voltage deficit; Specific potential of the myocardium

Published: October 1, 2002  Show citation