Assessment of the relationship between non-dipping phenomenon and heart rate turbulence

BACKGROUND: The aim of this cross-sectional study was to evaluate cardiac autonomic function by heart rate turbulence (HRT) indices in normotensive and hypertensive individuals with either non-dipper or dipper type circadian rhythm of blood pressure (BP). METHODS: A total of 122 patients were allocated into four groups: normotensive/dipper, n = 33; normotensive/non-dipper, n = 31; hypertensive/dipper, n = 29; and hypertensive/non-dipper, n = 29. HRT indices (turbulence slope [TS] and turbulence onset [TO]) were calculated from 24-h ambulatory electrocardiographic recordings. RESULTS: TS values were higher (TS = 10.0 ± 3.4 vs 8.0 ± 1.5, p = 0.004) and TO values were lower (TO = -2.9 [-3.6, -2.2] vs -2.0 [-2.3, -1.9], p = 0.037) in the dipper subgroup of normotensive cases than in the non-dipper subgroup of normotensive cases. Similarly, TS values were higher (TS = 8.4 ± 3.5 vs 6.2 ± 2.9, p = 0.012) and TO values were lower (TO = -2.1 [-3.4, -2.0] vs -1.6 [-1.9, -0.2], p = 0.003) in the dipper subgroup of hypertensive cases than in the non-dipper subgroup of hypertensive cases. Spearman's correlation analyses revealed a high positive correlation between percentage of dipping and TS (r = 0.600, p = 0.001) and a higher negative correlation between percentage of dipping and TO (r = -0.653, p = 0.001). CONCLUSIONS: Blunting of the nocturnal fall in BP is associated with impaired HRT indices in both normotensive and hypertensive groups.