Abnormal ventricular repolarization in hypertensive patients: role of sympatho-vagal imbalance and left ventricular hypertrophy.
BACKGROUND
An increased risk for life-threatening arrhythmias and sudden death has been observed in hypertensive patients, associated with either left ventricular hypertrophy (LVH) or prolonged QT interval. To investigate the influence of autonomic imbalance and LVH on QT interval in hypertensive patients, we compared two different models of LVH: hypertension and endurance physical training.


METHODS
Forty-seven untreated subjects affected by essential hypertension and 35 endurance runners, with a similar degree of LVH, were enrolled into the study. All subjects underwent 24-h ambulatory ECG recording and morning blood sampling for catecholamines. Heart rate variability was evaluated by spectral analysis and a computerized algorithm was used to measure the QT interval; QTc was then computed by the Bazett's formula. Left ventricular mass index (LVMI) was assessed by echocardiogram.


RESULTS
No difference in LVMI was found between hypertensive patients and athletes. Athletes showed lower heart rate (64 +/- 1 vs. 75 +/- 1 bpm, p<0.001, mean +/- S.E.M.) and shorter QTc (401 +/- 3 vs. 434 +/- 4 ms, p<0.001) than hypertensive patients throughout the 24-h period. Athletes showed a higher vagal drive compared to hypertensive patients as suggested by bradycardia and higher values of vagal indices, which negatively correlated with QTc. Plasma norepinephrine was significantly lower in athletes than in hypertensive patients (p<0.05) and positively correlated with QTc.


CONCLUSIONS
Despite similar degrees of LVH, hypertensive patients show QTc lengthening, as compared to athletes. Heart rate variability and plasma norepinephrine levels suggest sympathetic predominance in hypertensive patients, which could contribute to abnormal ventricular repolarization, thus identifying patients with an increased arrhythmic risk.
Passino
Claudio
C
Institute of Clinical Physiology, National Research Council, Via Moruzzi 1, 56124 Pisa, Italy. passino@ifc.cnr.it
Franzoni
Ferdinando
F
Gabutti
Alessandra
A
Poletti
Roberta
R
Galetta
Fabio
F
Emdin
Michele
M
D001341:Autonomic Nervous System / Q000503:physiopathology; D002940:Circadian Rhythm; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000503:physiopathology*; D017379:Hypertrophy, Left Ventricular / Q000150:complications / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged