ABSTRACT
BACKGROUND: A prolonged QT interval can lead to malignant ventricular arrhythmias and sudden cardiac death, and has frequently been found in end-stage liver disease (ESLD). However, myocardial repolarization lability has not yet been fully investigated. We evaluated the QT variability index (QTVI), a marker of temporal inhomogeneity in ventricular repolarization and an abnormality associated with re-entrant malignant ventricular arrhythmias. We determined whether QTVI is affected by the head-up tilt test in ESLD. METHODS: We assessed 36 ESLD patients and 12 control subjects without overt heart disease before and after the 70-degree head-up tilt test. The electrocardiography signal (lead II) was recorded on a computer with an analog-to-digital converter. The RR interval (RRI) and QT interval were measured after recording 5 min of the digitized electrocardiography. Then, the QT intervals were corrected with Bazett's formula (QTc). QTVI was calculated through the following formula: QTVI = log10 [(QTv/QTm2)/(RRIv/RRIm2)], QTv/RRIv: variance of QTI/RRI, QTm/RRIm: mean of QT interval/RRI. RESULTS: Cirrhotic patients exhibited an elevated QTVI. In particular, Child class C patients had a significantly increased QTVI compared to Child class A patients and the control subjects in the supine position. However, the head-up tilt test did not cause a significant difference in QTVI in relation to the severity of ESLD. CONCLUSIONS: Myocardial repolarization lability was significantly altered in end-stage liver disease. Our data suggest that the severity of ESLD is associated with the degree of the alteration in the QT variability index.
Subject(s)
Child , Humans , Arrhythmias, Cardiac , Death, Sudden, Cardiac , Electrocardiography , Heart Diseases , Liver Diseases , Liver , Supine PositionABSTRACT
El propósito fue investigar si la naturaleza de la respuesta compensatoria de la masa ventricular izquierda (MVI) es un factor determinante del grado de labilidad temporal de la repolarización miocárdica. Se evaluaron 263 pacientes hipertensos y 52 sujetos controles normotensos mediante ecocardiografía y electrocardiografía de alta resolución. Se definió MVI inapropiada como un índice de compensación de la MVI (ICMVI) > 128%. El grado de labilidad temporal de la repolarización miocárdica se evaluó a través del índice de variabilidad del intervalo OT (IVQT) determinado en forma automatizada. Pacientes hipertensos con MVI inapropiada presentaron valores significativamente más altos del IVQT (-0,92 ± 0,25) en comparación con sujetos normotensos (-1,53 ± 0,21) y pacientes hipertensos con MVI apropiada (-1,24 2410,18) (P<0,001). El ICMVI se correlacionó en forma dirtecta con el IVQT (r=0,49, P<0,001). en el análisis multivariante de regresión lineal, el nivel de MVI inapropiada. medido a través del ICMVI, se comportó como un predictor independiente del grado de labilidad temporal de la repolarización miocárdica (ß=0,007; P<0,001). Los resultados de este estudio indican que, en pacientes con HTA-E, la presencia de MVI inapropiadamente alta para el estímulo hemodinámico del ventrículo izquierdo se relaciona con aumento de la variabilidad temporal del intervalo QT.
The goal of this study was to investigate whether the compensatory nature of left ventricular mass (LVM) is a determinant factor of the temporal lability of the myocardial repolarization. Two hundred and sixty three hypertensive patients and 52 normotensive control subjects were studied by Doppler echocardiography and high resolution electrocardiography. A compensatory index of LVM (CILVM) > 128% defined inapropiate LVM. The degree of myocardial repolarization lability was evaluated by the QT interval variability index (QTVI). Hypertensive patients with inapropiate LVM had QTVI values significantly higher (-0,92 ± 0,25) than those with appropriate MVI (-1.24 ± 0.18) and normotensive control subjects (-1.53 ± 0.21) (P<0.001). The CILVM was positively correlated with QTVI (r=0.49; P<0.001). A stepwise multivariate linear regtession analysis showed that the level of inappropriate LVM was an independent predictor of QTVI (ß=0.007; P<0.001). Our result indicate that inappropriately high LVM for hemodynamic stimuli are associated with increased QT temporal variability.
Subject(s)
Humans , Male , Female , Ventricular Dysfunction, Left/diagnosis , Blood Pressure/physiology , Myocardial Reperfusion/methodsABSTRACT
PURPOSE: The object of this study is to determine whether QT interval variability in patients with postoperative tetralogy of Fallot increases. METHODS: We enrolled 41 patients who had total correction of tetralogy of Fallot, and 31 healthy controls. They were 6-12 years old. Patients were divided into 2 groups : arrhythmia-positive patients(n=10) who had ventricular premature contractions more than 30/hour or who had couplets, and arrhythmia-negative patients(n=31). We selected the 10-minute arrhythmia-free portion of 24-hour ambulatory ECG recorded during sleep(1-3AM). We selected the 2nd beat of recordings for a template, then found the QT interval for each beat. The method was that T-wave shape best matches template T-wave under the time-stretch model. The mean heart rate and variance and mean QT interval and variance were computed and then a QT variability index(QTVI)-which represents the log ratio between QT interval variability and heart rate variability-was derived. RESULTS: Postoperative tetralogy of Fallot patients with/without ventricular arrhythmia showed significantly increased QTVI compared with the control(-0.481+/-0.310/-0.661+/-0.376 vs -1.200+/-0.380, P<0.0001). There was a trend that QTVI in patients with ventricular arrhythmia increased more than in patients without ventricular arrhythmia, but there were no statistical significances. CONCLUSION: QT interval variability increased in repaired tetralogy of Fallot patients with/without ventricular arrhythmia compared with the control. And this finding indicates that inhomogeneity of temporal ventricular repolarization exists in repaired tetralogy of Fallot patients.