Significance of dobutamine-induced changes in QT dispersion early after acute myocardial infarction

QT dispersion is determined by the relative extent of normal, hibernating, and scarred myocardium in patients with chronic ischemic cardiomyopathy. A dobutamine stress echocardiography study before and after surgical revascularization

INTRODUCTION

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.

METHODS

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).

RESULTS

QTd was significantly lower in the minor compared with the major scar group at baseline and follow-up (mean [SD], 61 [22] vs 98 [33] milliseconds, P = .008, and 45 [18] vs 68 [21] 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).

CONCLUSIONS

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.

Predictors of rapid QRS widening in patients with coronary artery disease and left ventricular dysfunction

To assess the predictors of rapid QRS widening in patients with chronic ischemic left ventricular dysfunction, 82 patients who underwent > or =2 electrocardiograms and exercise Doppler echocardiography were studied. In a multivariate analysis, left ventricular end-diastolic volume, a large increase in mitral regurgitant volume during exercise, and diabetes emerged as independent predictors of QRS widening.

QTc dispersion as a prognostic factor in intracerebral hemorrhage

QTc dispersion in the electrocardiogram (ECG) is a new important prognostic factor for many diseases, but its role in intracerebral hemorrhage (ICH) is not clear. This study was performed to investigate the prognostic significance of QTc dispersion in the acute ICH patients. We studied the differences of QTc dispersion from the initial ECG in the ED between the survival to discharge and nonsurvival patients retrospectively. We found that the patients had lesser chance to survival to discharge if they had increased QTc dispersion, longer maximal QTc interval, lower Glasgow Coma Scale (GCS), and brainstem involvement in the univariate analyses. The QTc dispersion and GCS were the statistically significant independent predictors in the multiple logistic analyses. Increased QTc dispersion in the initial ED electrocardiograph is an important prognostic factor for ICH patients. More attention to the disposition and intensive care should be given for these patients.

QT dispersion and myocardial viability in patients after acute myocardial infarction

BACKGROUND

In recent years QT dispersion (QTd) in post-infarct patients was estimated in many studies, but still little is known about its association with the presence of dysfunctional but viable myocardium.

AIM

We investigated the relation between dispersion of QT interval and myocardial viability in patients after acute myocardial infarction (AMI).

MATERIAL AND METHODS

In 52 patients (mean age 67.2+/-11.7) treated thrombolytically because of AMI 12-lead ECG and low dose-high dose dobutamine echocardiography was performed on 14th day after treatment. QTd and regional myocardial contractility were estimated three times: at baseline, low dose dobutamine (LDD) (10-15 microg/kg per min) and high dose dobutamine (HDD) infusion (up to 40 microg/kg per min).

RESULTS

Patients with viable myocardium had lower baseline QTd than patients with only necrosis in infarct zone. Significant increase in QTd was shown during LDD and HDD both in patients with and without myocardial viability. During infusion of HDD QTd was significantly higher in patients with myocardial ischemia. The greatest percentage increase of QTd at HDD was shown in patients with biphasic response to dobutamine infusion i.e. with myocardial viability evidenced at LDD and myocardial ischemia at HDD.

CONCLUSION

Patients with preserved myocardial viability had lower QTd values compared to those with similar left ventricular dysfunction but caused only by post-infarction necrosis. Ischemia evoked on 14th day after AMI was accompanied by greater increase in QTd in patients with myocardial viability in infarct region than in patients without. It may be one of the reasons of greater risk of serious ventricular arrhythmias in such patients during myocardial ischemia.