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Ventricular repolarization is prolonged in nondipper hypertensive patients: role of left ventricular hypertrophy and
Claudio Passino1, Armando Magagna, Fabrizio Conforti
1Institute of Clinical Physiology, National Research Council, Pisa, Italy. passino@ifc.cnr.it
Insights
Hypertensive patients who do not experience a nighttime blood pressure drop (nondippers) have a prolonged QTc interval, linked to increased left ventricular mass and reduced parasympathetic activity.
Area of Science:
- Cardiology
- Hypertension Research
- Autonomic Function Studies
Background:
- Circadian variations in blood pressure are crucial in hypertension.
- Left ventricular hypertrophy (LVH) and autonomic dysfunction are common in hypertensive patients.
- The QTc interval reflects ventricular repolarization and is a marker for arrhythmia risk.
Purpose of the Study:
- To investigate how circadian blood pressure patterns, left ventricular hypertrophy, and autonomic function influence QTc interval duration in untreated hypertensive individuals.
- To compare these factors between hypertensive patients with and without a nocturnal blood pressure fall (nondippers vs. dippers) and normotensive controls.
Main Methods:
- Simultaneous 24-hour ambulatory blood pressure and ECG monitoring were performed on hypertensive patients.
- Patients were categorized into dippers and nondippers based on nocturnal blood pressure fall.
- QTc intervals were automatically calculated, spectral analysis of RR intervals was conducted, and left ventricular mass index (LVMI) was determined via echocardiography.
Main Results:
- Nondippers exhibited significantly longer QTc intervals compared to dippers and normotensive subjects, especially during nighttime.
- Nondippers showed higher LVMI and reduced parasympathetic activity compared to dippers.
- LVMI positively correlated with QTc interval, while parasympathetic activity negatively correlated with QTc interval.
Conclusions:
- Nondippers demonstrate prolonged ventricular repolarization over a 24-hour period.
- The combination of left ventricular hypertrophy and reduced vagal tone in nondippers may prolong the QTc interval.
- This prolonged QTc interval in nondippers could increase the risk of ventricular arrhythmias.
Objective:
The aim of this study was to investigate the influence of circadian behavior of blood pressure, left ventricular hypertrophy, and autonomic function on QTc interval duration in untreated hypertensive patients.
Design:
Hypertensive patients underwent simultaneous blood pressure and ECG 24-h ambulatory monitoring. Patients were classified into two groups on the basis of a lack of nocturnal fall in blood pressure, as dippers and nondippers. A group of normotensive healthy subjects was studied as controls.
Methods:
QT and QTc intervals were automatically computed and spectral analysis was applied to RR interval time series from the same electrocardiogram (ECG) recordings. Left ventricular mass index (LVMI) was computed by echocardiogram.
Results:
No difference among the three groups was found concerning mean values and circadian pattern of heart rate; by contrast, QTc was significantly longer in nondippers compared to dippers or to normotensive subjects, particularly at night-time, whereas all groups exhibited similar circadian variations in heart rate. Compared to dippers, nondippers showed significantly higher LVMI, which positively correlated with QTc, and parasympathetic withdrawal, which negatively correlated with QTc.
Conclusions:
Nondippers show a prolonged ventricular repolarization throughout the 24-h period, absent either in dippers or normotensives. The association of left ventricular hypertrophy and vagal deactivation may lead to prolongation of QTc, potentially facilitating ventricular arrhythmias in nondipper hypertensive patients.