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International Journal of Bioelectromagnetism Vol. 4, No. 2, pp. 139-140, 2002. |
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inverse Relationship between QRS amplitude and left ventricular mass IN rats exposed to physical training L. Bacharova1, J. Klimas2,
K. Michalak2, J. Kyselovic2 Abstract: Changes of QRS amplitude and their relationship to left ventricular mass (LVM) in the early stage of experimental left ventricular hypertrophy of different etiology were studied in rats. Four groups of experimental animals were studied: a) control WKY rats, b) spontaneously hypertensive rats, c) WKY rats exposed to training by intermittent swimming, d) WKY rats exposed to training by intermittent swimming with s.c application of nandrolon decanoate 15 mg/kg per week. Orthogonal electrocardiograms were recorded in all groups at the age of 12 and 20 weeks, and the maximum spatial QRS vector (QRSmax) was calculated. Then the animals were sacrificed and LVM was measured. The specific potential of myocardium (SP) was calculated as a ratio of QRSmax to LVM. At the end of the follow-up period the values of LVM increased in all groups compared to control animals, with the maximum increase in SHR. The QRSmax values did not follow the changes in LVM. Compared to control animals, the lowest values were observed in the SHR group, but the QRSmax values were lower in both groups of rats exposed to intermitent swimming. Analogical changes were observed in the SP values. In all models of experimental LVH in rats we observed a decrease in QRSmax and of the relative voltage deficit quantified as SP, what is probably associated with the electrophysiological remodeling of myocardium in LVH. INTRODUCTIONIn our previous work [1] we reported discrepancies in changes of QRS amplitude and LVM in the early stage of left ventricular hypertrophy (LVH) in spontaneously hypertensive rats (SHR). We observed a relative voltage deficit, e.g. a decreased QRS amplitude and decreased QRS voltage/LVM ratio, what contrasted with the increased left ventricular mass. Similar results, the decreased QRS amplitude was found in the first stage of experimental LVH due to volume overload in rabbit [2]. The aim of this study was to investigate the changes of QRS amplitude and their relation to LVM in rats exposed to regular training by intermittent swimming, and the effect of anabolic steroids on these changes, compared to healthy rats as well as to spontaneously hypertensive rats. METHODSFour groups of age matched male experimental animals were investigated: a) control normotensive WKY rats, b) spontaneously hypertensive rats, c) normotensive WKY rats exposed to training by intermittent swimming, d) normotensive WKY rats exposed to training by intermittent swimming with s.c application of nandrolon decanoate (Decadurabolin, Organon) 15 mg/kg per week. The arterial systolic blood pressure (sBP) and orthogonal electrocardiograms were recorded at the age of 12 and 20 weeks. sBP was measured by the tail-cuff method. Frank orthogonal electrocardiograms were recorded in thiopental anesthesia (Thiopental, VUAB, Czech Republic, 45 mg/kg, i. p.) using the electrocardiograph 3NEK-1, GDR. The maximum deflections of QRS complex were taken as X, Y, Z components of the maximum spatial QRS vector magnitude (QRSmax). At the age of 20 weeks, after ECG recording the animals were sacrificed and the left ventricular mass was weighted. The left ventricular mass (LVM) and the left ventricular mass to body weight ratio (LVM/BW) were used as measures of anatomical left ventricular hypertrophy. RESULTSThe results are presented in Table 1. At the end of the follow-up period, the values of LVM/BW were significantly increased in SHR group and in WKY rats exposed to training by intermittent swimming with s.c application of nandrolon decanoate as compared to control animals. The maximum increase of 51.6% was observed in the group of SHR, in the group of swimming WKY the LVM/BW increased of 6.3%, which was not significant, and in the group of swimming WKY combined with the application of nandrolon of 14.6%. The QRSmax values did not follow the differences in LVM/BW between groups. The highest values of QRSmax were observed in the control normotensive WKY rats. QRSmax values were significantly lower in all groups with experimental LVH as compared to control animals. The maximum difference of 45% was found in the group of SHR. In the group of swimming WKY the QRSmax were lower of 33.7% and in the group of swimming WKY combined with the application of nandrolon of 11.2%. Similarly, the SP values were significantly lower in all groups with experimental LVH as compared to control animals, while the highest values of SP were observed in the control normotensive WKY rats. The maximum difference of 63.2% was found in the group of SHR. In the group of swimming WKY the SP were lower of 51.8% and in the group of swimming WKY combined with the application of nandrolon of 40.4%. The relationships between the LVM/BW and QRSmax values are presented in Figure 1. TABLE 1 The basic statistics of blood pressure, left ventricular mass to body weight ratio (LVM/BW), maximum spatial vector magnitude (QRSmax) and the specific potential (SP). WKY: control normotensive WKY rats, SHR: spontaneously hypertensive rats, SW normotensive WKY rats exposed to training by intermittent swimming, SW+A: normotensive WKY rats exposed to training by intermittent swimming with s.c application of nandrolon decanoate. Average values ± S.D. are presented. * : p < 0.05, **: p < 0.01, ***: p < 0.001
It can be seen that the highest LVM/BW values in SHR are associated with the lowest QRSmax values as opposite to the lowest LVM/BW values in control normotensive WKY which are associated with the highest QRSmax values. In the two groups of WKY rats exposed to intermittent swimming and those with the s.c. application of nandrolon, respectively, the increase of LVM/BW was associated with the increase of QRSmax. However, the QRSmax values in both groups were significantly lower as compared to control WKY rats. Figure 1: The relationship between the average values of left ventricular mass to body weight ratio (LVM/BW) and the maximum QRS spatial vector magnitude (QRSmax) in the groups under the study. WKY: control normotensive WKY rats, SHR: spontaneously hypertensive rats, SW normotensive WKY rats exposed to training by intermittent swimming, SW+A: normotensive WKY rats exposed to training by intermittent swimming with s.c application of nandrolon decanoate. DISCUSSION The main finding of this study was the finding of decreased values of QRSmax in WKY rats exposed to intermittent swimming for 8 weeks, in both groups with or without the application of nandrolon. This decrease contrasted with the higher QRSmax values in control WKY rats on one hand, and on the other hand it was not as pronounced as it was observed in the SHR group. In our previous work [1] we presented a finding of the incongruent relationship between the increase of LVM and the decrease of QRSmax in spontaneously hypertensive rats at the age of 12 and 20 weeks. We attributed this finding to the changes in electrogenetic properties of myocardium at the early stage of developing hypertension and left ventricular hypertrophy, in other words to the changes of the non-spatial determinants influencing the resultant QRS voltage in terms of the solid angle theory. In this study we used the rats exposed to intermittent swimming as an experimental model of the “physiological” hypertrophy. And it was shown that also in this type of LVH a relative voltage deficit was observed. Moreover, it was also shown, that there was a difference between the two groups of swimming rats. The values of QRSmax, as well as of the relative voltage – the specific potential of myocardium – were higher in swimming rats with the application of nandrolon. We assume that this difference reflects the modification of electrogenetic properties due to the effect of anabolics on the developing LVH. Acknowledgments: This study was supported, in part, by the grant 1/7189/20 from The Science Grant Agency (VEGA), Slovak Republic and the grant 875/2000 from the Pharmaceutical Faculty Comenius University, Bratislava, Slovak Republic. REFERENCES[1] L. Bacharova, J. Kyselovic, J. Klimas, A. Radman: “The decrease of specific potential of myocardium in early stage of experimental hypertension”, in: M.P. Roshchevsky, editor. Electrocardiology ’99. Syktyvkar; Institute of Physiology of the Komi Science Centre: 2000. p. 30 – 37. [2] M. Bernadič, A. Fízeľ, A. Fízeľová, M. Bakošová, E. Sapáková: Orthogonal electrocardiogram in rabbits during the long-term volume overload. (Ortogonálny elektrokardiogram u králikov počas dlhodobej adaptácie srdca na objemové preťaženie). Bratisl lek Listy 84, 1985, s. 683-xxx. (In Slovak, summary in English). [3]L. Bacharova, J. Kyselovic: “Electrocardiographic diagnosis of left ventricular hypertrophy: is the method obsolete or should the hypothesis be reconsidered?,” Medical Hypotheses, vol. 57, pp.487-490, 2001.
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