Curso temporal das alterações na variabilidade da frequência cardíaca e da pressão arterial após infarto do miocárdio em ratos

• Autor(a) principal: Aires, Rafaela
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/8013
• topic: Myocardial infarction; Heart rate variability; Blood pressure variability; Autonomic nervous system; Power spectral analysis; Infarto do miocárdio; Variabilidade da frequência cardíaca; Variabilidade da pressão arterial; Sistema nervoso autônomo; Análise espectral da potência; Fisiologia; 612

Introduction: Myocardial infarction (MI) acutely impairs the cardiac pump and reduces the cardiac output (CO). Blood pressure (BP) control depends on continuous adjustments of the autonomic balance directed to the heart and blood vessels. Such adjustments change after MI and may vary over time Objective: To determine the time course of the autonomic balance adjustments in the acute (1-3 days), sub-acute (7 days) and chronic (21 days) phases of MI in rats. Methods: The autonomic balance was assessed by temporal and spectral analysis of the blood pressure (BPV) and heart rate (HRV) variability. Pulsatile BP recordings (30 min) were obtained in the awake and unrestrained animals with MI or sham operated (SO). Data are means ± SE. Results: Heart rate remained unchanged in the SO group over time and it was higher (P<0.01) in MI rats at 1 and 3 days after MI (SO-1= 356±9.7 vs MI-1= 438±13 bpm; SO3= 346±17; MI-3= 411±8.4 bpm) with tendency to recover normal values thereafteer (SO-7= 345±4.2 vs MI-7= 382±14 bpm; SO-21= 339±10 vs MI-21= 375±17 bpm) (P<0.001 for the interaction F-test, two-way ANOVA). MI was followed by an overall reduction of HRV in both HF and LF bands of the spectral analysis. The power of HF (n.u.) was significantly lower in MI-1 (P <0.01) and MI-3 days rats (P <0.05) compared with their time-control groups (SO-1= 68±4 vs MI-1= 35.3±4.3; SO-3= 71±5.8 vs MI-3= 45.2±3.8) without difference thereafter (SO-7= 69.2±4.8 vs MI-7= 56±5.8; SO-21= 73±4 vs MI-21= 66±6.6), (P=0.001 for the interaction F-test, two-way ANOVA). Along the observation period, MI rats also showed reduced BPV, mostly dependent on significant reduction of the LF band in absolute and normalized units (SO-1= 39.3±7 vs MI1= 13±3.5; SO-3= 55±4.5 vs MI-3= 35±4.7; SO-7= 46.8±4.5 vs MI-7= 25±2.8; SO-21= 45.7±5 vs MI-21= 21.4±2.8; P=0.001 for the interaction F-test; two-way ANOVA). The HF component of BPV was unaffected after MI Conclusion: Our data suggest that the initial tachycardia in the acute phase MI seems to be mainly due to removal of the parasympathetic modulation on heart beats. Recovery of basal heart rate values is timely associated to the recovery of the HF component of HRV