RESUMEN
BACKGROUND: The aim of this study was to investigate the effects of chronic treatment with carvedilol in blood pressure (BPV) and heart rate (HRV) variability of rats with myocardial infarction (MI). METHODS: MI was produced in male rats by ligature of anterior interventricular branch of left coronary artery. Control rats were submitted to a sham surgery (SO). MI and SO rats were randomized to receive for 30 days placebo (Plac 0.5% metilcelulose) or carvedilol (Carv, 2mg/Kg body weight/day, drinking water): SO-Plac (N = 10), SO-Carv (N = 10), MI-Plac (N = 12), MI-Carv (N = 13). Blood pressure (BP) was directly recorded in the awake animals and BPV was determined, in time (variance, mmhg(2)) and frequency domains by the autoregressive method. Statistical significance was set in P<0.05. Data are median and interquartile range. RESULTS: No significant changes in HRV was observed in MI rats, while BPV showed significant decreasing of blood pressure variance (SO-Plac = 42.08 (39.21) mmHg(2) vs. MI-Plac = 21.67 (12.58) mmHg(2), P<0.05), reversed by the Carv treatment (MI-Plac = 21.67 (12.58) vs. MI-Carv = 38.64 (29.25), P<0.05). In the frequency domain analyses, MI reduced absolute and normalized LF component (LF (mmHg(2)): SO-Plac = 8.98 (14.84) vs. MI-Plac = 2.08 (4.84), P<0.05; LF(nu): SO-Plac = 79.48 (45.03) nu vs. MI-Plac = 24.25 (40.67) nu, P<0.05) and increased the normalized HF component of the BPV (SO-Plac = 20.51 (39.18) vs. MI-Plac = 60.51 (39.73). Carv treatment significantly attenuated the LF component fall. CONCLUSION: Chronic treatment with carvedilol restored the variance of BPV altered by the MI.