QT dispersion and hypertensive heart disease in the elderly

Aim To determine the predictors and risk of increased QT dispersion in the elderly hypertensive patients. Methods A 12-lead electrocardiogram (ECG), M-mode echocardiography and ambu latory blood pressure as well as Holter monitoring were performed for 67 pa tients over 60 years of age with essential hypertension (I and II degrees W HO). The presence of ischaemic changes on ECG was evaluated based on the Mi nnesota Code. QT intervals were corrected with Bazett's formulae and QT dis persion was determined as the difference between maximal and minimal QTc in tervals. Interventricular septal thickness (IVSTd), left ventricular intern al diameter (LVDd) and posterior wall thickness (PWTd) were measured and le ft ventricular mass index (LVMI) was calculated. Subjects were divided acco rding to the median of QTc dispersion (0.10 s). The differences between gro ups were assessed using chi-squared and Students's t-test. Results Subjects with increased QTc dispersion did not differ from those wi th low QTc dispersion when age, gender and body mass index were analysed. S imilarly, the average systolic blood pressure, diastolic blood pressure and blood pressure variability were comparable in both groups. The mean QTc in terval was similar in both groups. In patients with increased QT dispersion , left ventricular hypertrophy (LVH) and ischaemic changes on ECG were more frequently recognized (respectively 41.2 versus 18.2%, P < 0.001; 47.1 ver sus 21.2%, P < 0.05). Moreover. these subjects presented a significantly gr eater number of premature ventricular beats (317.1 +/- 665.6 versus 64.88 /- 188.6, P < 0.05) and higher classes of Lown's arrhrythmia scale (classes III-IV, 23.35% versus 9.1%). LVMI was insignificantly higher in the group with greater QTc dispersion (165.82 +/- 54.5 versus 145.07 +/- 36.47 g/m(2) ). Other echocardiographic indices of LVH were similar in both groups. On t he other hand, the analysis of regression indicated positive correlation be tween the dispersion of QTc interval and thickness of left ventricle walls (for IVSd - r = 0.37; for PWd - r = 0.31), relative wall thickness (r = 0.2 8) and LVMI (r = 0.28). Conclusions QTc dispersion is increased in the elderly hypertensive individ uals, with the presence of LVH and myocardial ischaemia on ECG. These patie nts are more likely to demonstrate severe ventricular dysrhythmias. J Hyper tens 2000, 18:461-464 (C) Lippincott Williams & Wilkins.