Key result
A nondipping blood pressure pattern in healthy subjects was associated with an increased QT variability index (-1.28 vs -1.52; P<0.05) and decreased baroreflex effectiveness index.
Why the study?
Is a nondipping blood pressure pattern associated with altered myocardial repolarization lability and arterial baroreflex function in healthy individuals?
Cross-Sectional (n=95)
Is a nondipping blood pressure pattern associated with altered myocardial repolarization lability and arterial baroreflex function in healthy individuals?
Absolute Event Rate: -1.28% vs -1.52%
p-value: p=<0.05
A nondipping blood pressure pattern in healthy individuals is associated with increased myocardial repolarization lability and impaired baroreflex function, suggesting underlying autonomic nervous system dysfunction.
Nondipping pattern linked to repolarization lability in healthy adults; leaves open prognostic value for arrhythmia risk and need for prospective studies.
BACKGROUND: The "nondipping" pattern (NDP) of blood pressure, characterized by the absence of the reduction in blood pressure (BP) that typically takes place during the night time, has been associated with elevated cardiovascular morbidity, including stroke, myocardial infarction, and sudden cardiac-related death. In various cardiovascular diseases, reduced vagal control of cardiac function and elevated lability of cardiac repolarization have been associated with increased risk for ventricular arrhythmia and sudden death. The aim of this study was to assess temporal QT variability, arterial baroreflex sensitivity (BRS), and baroreflex effectiveness index (BEI) in two groups of otherwise healthy subjects, one group consisting of those with a normal BP pattern and the other with a nondipping BP pattern. METHODS: Ninety-five healthy subjects underwent 24-h ambulatory BP (AMBP) monitoring. A minimum of 10% reduction in BP during the night relative to daytime levels is considered normal (as found in "dippers"). These individuals were classified as "dippers" (n = 59) and individuals without 10% reduction in BP during night were classified as "nondippers" (n = 36). Electrocardiogram (ECG) readings and beat-to-beat BP were recorded at 1,000 Hz with the subjects at rest in the supine posture for 20 min. BRS, BEI, and QT variability index (QTVI) were calculated. RESULTS: There were no differences between the study groups with respect to age, gender, and average BP. Nondippers showed an increase in QTVI (-1.28 +/- 0.48 in nondippers vs. -1.52 +/- 0.29 in dippers, P < 0.05) and a decrease in BEI (0.34 +/- 0.17 in nondippers vs. 0.43 +/- 0.17 in dippers, P < 0.05), whereas BRS did not differ between the groups. CONCLUSION: A nondipping BP pattern in healthy subjects is associated with elevated myocardial repolarization lability and impaired baroreflex function, suggesting dysfunction of the autonomic nervous system.
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Myredal et al. (2010) conducted a cross-sectional in Healthy subjects (n=95). Nondipping blood pressure pattern vs. Dipping blood pressure pattern was evaluated on QT variability index (QTVI) (p=<0.05). A nondipping blood pressure pattern in healthy subjects was associated with an increased QT variability index (-1.28 vs -1.52; P<0.05) and decreased baroreflex effectiveness index.
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