Markers of electrical instability in hypertensive patients with and without ventricular arrhythmias. Are they useful in identifying patients with different risk profiles?

Background Markers of electrical instability of the ventricular myocardium, namely abnormal repolarization and late potentials, are frequently observe d in patients with hypertension when both ventricular arrhythmias and left ventricular hypertrophy are present. This information cannot be extrapolate d to the population of hypertensive patients with ventricular arrhythmias b ut without left ventricular hypertrophy. Objective To evaluate QT duration, QT dispersion and the incidence of ventr icular late potentials in patients with essential hypertension, already on anti-hypertensive therapy, both with and without non-sustained ventricular arrhythmia. Design The study population consisted of 49 patients with essential hyperte nsion who were compared to 89 control normotensive subjects both with and w ithout frequent ( > 30 per h) ventricular ectopic beats (VPBs), Patients we re divided into four groups: (1) hypertensive patients without VPBs (H, n = 19), (2) hypertensive patients with VPBs (HA, n = 30), (3) normotensive su bjects without VPBs (C, n = 28), and (4) normotensive subjects with VPBs (C A, n = 61). Methods Echocardiographic parameters, QT interval, QT dispersio n and signal-averaged ECG were evaluated without withdrawing anti-hypertens ive drugs. Results In no case was left ventricular hypertrophy documented. The number of VPBs during 24 h Holter recording (median 11 343 versus 7617) and the in cidence of repetitive VPBs (37 versus 46% of patients) were similar in the two groups of patients (HA versus CA). Signal-averaged ECG parameters were normal and not different between the four groups. QT interval was longer in hypertensive patients compared to controls irrespective of the presence of VPBs. QT dispersion was slightly greater in subjects with VPBs, both hyper tensive and normotensive, compared to subjects without arrhythmias. Conclusions In patients with hypertension well-controlled by drug therapy a nd without left ventricular hypertrophy, frequent VPBs are not associated w ith markers indicating an electrophysiological substrate for re-entrant arr hythmias. However, QT prolongation suggests the persistence of a higher ris k of cardiovascular. mortality that is independent of the presence of VPBs. J Hypertens 2000, 18:763-768 (C) Lippincott Williams & Wilkins.