Estudo da modulaÃÃo autonÃmica em funÃÃo da variabilidade da freqÃÃncia cardÃaca em hipertensos com e sem hipertrofia ventricular esquerda concÃntrica

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

This is a study of autonomic modulation as a function of heart rate variability through the time and frequency domains using 24h-Holter signals in hypertensives with and without concentric left ventricular hypertrophy (LVH), correlating the latter with cardiac arrhythmias. The data from a sample of 108 mild, moderate or severe hypertensives were analysed. The mean age of the sample was 55.2 years (range: 23-77 years), all patients being on anti-hypertensive medication, except for betablockers and calcium channel blockers of the diltiazem and verapamil groups. Two thirds were suffering from some degree of concentric LVH. This was an observational study. The results of the 24h-Holter examination were used as the gold standard for typifying and measuring cardiac arrhythmias. Five types of arrhythmias were considered: isolated or runs of supraventricular premature contractions; supraventricular tachycardia; isolated or bigeminism of ventricular premature contractions; runs of ventricular premature contractions and non-sustained ventricular tachycardia. In addition to the classification and measurement of the arrhythmias by the 24h-Holter method, the statistical values of the time domain were recorded. These values were calculated taking into account all recorded values of the RR intervals during the 24-hour period. Four segments out of 128 24h-Holter measurements (two segments during the awake and two segments during the sleep periods) free of any arrhythmic events were chosen for both methodologies employed (Spectral Analysis and Poincarà Map). The diagnosis of LVH by the echocardiogram was the gold standard adopted in this study. The presence of LVH increases the likelihood of the individual having arrhythmias of the isolated or runs of supraventricular premature contractions or that of isolated or coupled ventricular premature contractions kinds. It also increases the likelihood the correlations between the various types of arrhythmias and between the values of such correlations. This finding is corroborated by the existence of significant correlations between the left ventricular mass index (LVMI) and arrhythmias of the isolated or runs supraventricular premature contractions, supraventricular tachycardia and isolated or bigeminism ventricular premature contraction types. The indicators of the spectral analysis and Poincarà map during the awake period point more specifically to atrial arrhythmias and those of the sleep period to ventricular arrhythmias. In this study, the classical 24h-SDNN indicator of variability of the RR segment over the 24 hours was not shown to be associated with any event of interest. Furthermore, this indicator identified neither LVH nor arrhythmias. It did, however, present a low negative, albeit significant correlation (p=0.0490) with arrhythmia of the isolated or bigeminism ventricular premature contraction

ASSUNTO(S)

modulaÃÃo autonÃmica do sistema nervoso left ventricular hypertrophy systemic arterial hypertension autonomic modulation of the nervous system variability of heart rate medicina cardiac arrhythmias hipertensÃo arterial sistÃmica variabilidade da freqÃÃncia cardÃaca hipertrofia ventricular esquerda arritmias cardÃacas

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