Comparison of QT interval duration and dispersion in elderly population versus healthy young subjects

Association between C-reactive protein, corrected QT interval and presence of QT prolongation in hypertensive patients

C-reactive protein (CRP) and corrected QT (QTc) interval are predictors of cardiovascular disease. Whether CRP is associated with QTc interval and QT prolongation is unknown in hypertensive patients. We recruited hypertensive patients from a cardiovascular clinic in a tertiary medical center in Taiwan. All received standard 12-lead electrocardiogram examination. QT prolongation was defined as QTc interval ≥ 440 ms in men or ≥ 450 ms in women. High-sensitive CRP kits were used for the measurement of the CRP levels. A total of 466 consecutive patients were finally enrolled. Mean age was 60.6 ± 12.0 years. CRP level was correlated with QTc interval (p < 0.001) and presence of QT prolongation (p = 0.014). Multivariate regression analysis showed that CRP level (p = 0.001), age (p = 0.004), sex (p < 0.001), height (p = 0.001), low-density lipoprotein (p = 0.041), and QRS interval (p < 0.001) were associated with QTc interval. Furthermore, CRP level [odds ratio (OR) = 1.203, 95% confidence interval (CI) = 1.027-1.410, p = 0.022], age (OR = 1.040, 95% CI = 1.010-1.071, p = 0.009), waist (OR = 1.033, 95% CI = 1.000-1.066, p = 0.047), triglyceride (OR = 0.993, 95% CI = 0.987-0.999, p = 0.021) and QRS interval (OR = 1.046, 95% CI = 1.028-1.065, p < 0.001) independently predicted the presence of QT prolongation. Because CRP is an independent predictor of QTc interval and presence of QT prolongation, it could be considered in the risk assessment for hypertensive patients.

Aging modulates dispersion of ventricular repolarization in the very old of the geriatric population

Aging plays an essential role in cardiac pathophysiology. Knowledge on the ventricular repolarization in very old individuals is limited. An increase of QT dispersion is associated with higher cardiovascular mortality. The purpose of this study is to investigate whether aging changes the QT dispersion in the very old. Heart rate, P wave duration, PR interval, QRS axis, QRS duration, QT interval, and QTc interval were measured from 12-lead resting ECG. QT dispersion (46 ± 21, 47 ± 17, 69 ± 31 ms, p < 0.005) was significantly increased in the age group ≧85 years (n = 29, 89 ± 4 years) than in the age group 75-84 years (n = 33, 79 ± 3 years) and the age group 65-74 years (n = 32, 68 ± 3 years). Aging modulates dispersion of ventricular repolarization, which may contribute to the cardiac mortality in the very old Asian population.

Diurnal variation and dispersion in QT interval in cirrhosis: relation to haemodynamic changes

BACKGROUND/AIMS

A long QT(C) interval has been described in a substantial fraction of patients with cirrhosis, but information on QT variation and dispersion is sparse. The aim was to determine QT variation with time and QT dispersion (QT(disp)).

METHODS

The study population comprised 23 patients with cirrhosis, undergoing a haemodynamic investigation. 24-h 12 lead Holter monitoring provided information on QT and heart rate variability.

RESULTS

Mean QT(C) was above upper normal limit (440 ms(1/2)) in eleven patients (47%) and significantly higher than in controls (441 vs 400 ms(1/2), p<0.01). The minimum value of QT(C) (but not the maximum value) showed a significant diurnal variation both in cirrhosis and controls. QT(disp) in cirrhosis and controls was similar (33 vs 36 ms, ns), but related to indicators of liver dysfunction, central circulation time, and arterial blood pressure (r=0.44-0.58, p=0.03-0.001). No diurnal variation of QT(disp) was found in cirrhosis. Heart rate variability was reduced with a significant relation to central hypovolaemia (r=0.55, p=0.01).

CONCLUSIONS

Twenty-four hours QT(C) is prolonged in a substantial fraction of patients with cirrhosis, but with normal diurnal variation. The combination of long QT(C) and normal QT(disp) suggests delayed myocyte repolarisation on the cellular level, rather than temporal and spatial heterogeneity in the myocardial wall.