QT dispersion correlates to myocardial viability assessed by dobutamine stress echocardiography in patients with severely depressed left ventricular function due to coronary artery disease.
ABSTRACT QT dispersion is prolonged in numerous cardiac diseases, representing a general repolarization abnormality.
To evaluate the influence of viable myocardium on QT dispersion in patients with severely depressed left ventricular (LV) function due to coronary artery disease.
103 patients with ischemic cardiomyopathy (LV ejection fraction [EF]: 25+/-6%) were studied. Patients underwent 12-lead electrocardiography to assess QT dispersion, and two-dimensional echocardiography to identify segmental dysfunction. Dobutamine stress echocardiography (DSE) was then performed to detect residual viability. Resting echo demonstrated 1260 dysfunctional segments; of these, 476 (38%) were viable. Substantial viability (> or =4 viable segments on DSE) was found in 62 (60%) patients. QT dispersion was lower in these patients, than in patients without viability (55+/-17 ms vs. 65+/-22 ms, P=0.012). Viable segments negatively correlated to QT dispersion (r=-0.333, P=0.001). In contrast, there was no correlation between LVEF and QT dispersion (r=-0.001, P=NS).
There is a negative correlation between QT dispersion and the number of viable segments assessed by DSE. Patients with severely depressed LV function and a low QT dispersion probably have a substantial amount of viable tissue. Conversely, when QT dispersion is high, the likelihood of substantial viability is reduced.
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ABSTRACT: It is well established that cardiac resynchronisation therapy (CRT) using biventricular pacing prolongs survival by its effects on pump failure. The rate of sudden cardiac death in patients undergoing CRT, however, remains high. Animal and human studies have shown that reversal of normal sequence of myocardial activation during epicardial pacing, as applied during CRT, increases the transmural dispersion of repolarisation (TDR), a substrate for ventricular arrhythmias. Cohort studies in humans suggest that CRT has a differential effect on the arrhythmogenic substrate, antiarrhythmic in some and proarrhythmic in others. This review the focuses on the possibility that CRT may, under certain circumstances, promote arrhythmogenesis.Indian pacing and electrophysiology journal 02/2008; 8(4):268-80.
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ABSTRACT: The aim of the article is to review the literature data about the significance and problems of the QT dispersion and heart rate variability in sudden death risk stratification in patients with coronary heart disease. QT dispersion is defined as the difference between the longest and the shortest QT intervals as measured in the 12-lead electrocardiogram. A direct relationship between the prolongation of QT dispersion and myocardial ischemia has been reported by several authors. Our previous study showed that QT dispersion assessed immediately after bicycle exercise test was significantly higher in patients with coronary stenoses of > 50% as compared to the patients without coronary artery disease. Despite some controversial data, several studies showed that QT dispersion is a significant predictor of cardiovascular mortality. Heart rate variability representing a relationship between the autonomic nervous system and cardiovascular mortality, including sudden cardiac death, is one of the most promising markers. The predictive value of heart rate variability is independent of other factors established for postinfarction risk stratification, such as depressed left ventricular ejection fraction, increased ventricular ectopic activity, and presence of late potentials. For prediction of all-cause mortality, the value of heart rate variability is similar to that of left ventricular ejection fraction, but heart rate variability is superior to left ventricular ejection fraction in predicting arrhythmic events (sudden cardiac death and ventricular tachycardia).Medicina (Kaunas, Lithuania) 02/2006; 42(6):450-4. · 0.55 Impact Factor
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ABSTRACT: The aim of the present study was to evaluate a possible association between QT dispersion (QTd) and the amount of viable and scarred myocardial tissue after revascularization in patients with coronary artery disease and impaired left ventricular (LV) function. Twenty-two patients with ischemic LV dysfunction underwent dobutamine stress echocardiography (DSE) before and 6 months after surgical revascularization. Mean corrected QT-interval value and QTd were calculated at baseline and follow-up. Segments consisting of transmural scar were determined as the segments that remained akinetic in all stages of DSE despite reperfusion. Patients were divided into 2 groups according to the number of definitive segments consisting of transmural scar (minor scar group, < or =2 scarred segments; major scar group, >2 scarred segments). QTd was significantly lower in the minor compared with the major scar group at baseline and follow-up (mean [SD], 61  vs 98  milliseconds, P = .008, and 45  vs 68  milliseconds, P = .01, respectively). Segments consisting of transmural scar positively correlated to QTd at baseline (r = 0.53, P = .01) and follow-up (r = 0.62, P = .002). QTd is positively correlated with the extent of scarred myocardial tissue assessed by DSE. Surgical revascularization results in reduction of QTd in all patients with hibernating myocardium and LV dysfunction.Journal of Electrocardiology 01/2006; 39(1):103-9. · 1.09 Impact Factor