[Measurement dispersion of the QT interval and its significance in different diseases].
QT dispersion reflects in homogenecity of ventricular repolarization. It is calculated using 12-leads standard synchronized ECG or 24-hours Holter monitoring. The most common used indicators are: QT dispersion (QTd), based on Bazett's formula corrected for heart rate QT dispersion (QTcd) and QT dispersion ratio (QTdR). QT apex and QTd corrected for total number of leads ECG in which QT interval was counted are rare used. Increased QT dispersion is observed among others: following myocardial infarction (MI), coronary heart disease (CAD), hypertension, chronic heart failure (CHF), long QT syndrome, as well as diabetes. Following mentioned diseases increased QT dispersion has prognostic value for sustained ventricular tachycardia. Dispersion of repolarization > or = 80 ms after MI is a risk factor for sudden cardiac death. Following acute MI decrease of QT dispersion after successful thrombolytic therapy is observed and its value > or = 100 ms is regarded as a marker of reperfusion insufficiency. QT dispersion in patients with CAD correlates with extent of ischemia and decreases after coronary angioplasty (PTCA). In recent years beneficial effect of angiotensin-converting enzyme inhibitors and beta-adrenolytic therapy on QT dispersion was described. Actually the improvement of computerised methods in assessment of QT dispersion is observed, but it require further investigations.
Sredniawa
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I Katedra i Oddział Kliniczny Kardiologii Sl. AM, Slaskie Centrum Chorób Serca w Zabrzu.
Musialik-Łydka
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A
Pasyk
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D004562:Electrocardiography; D015716:Electrocardiography, Ambulatory; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis*