RT-138
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QT interval dynamicity in patients with previous myocardial infarction and impaired vs preserved left ventricular function
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Nicolo Franchetti Pardo, Alessandro Mezzani, Gabriele Iraghi, Umberto Parravicini, Marco Zanetta.
Divisione di Cardiologia, Ospedale S.S. Trinita, Borgomanero, Italy
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Abstract
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An increased QT interval dynamicity (i.e. QT interval/heart rate
relationship) has been indicated as a marker of arrhythmogenicity in patients with previous myocardial infarction
and normal left ventricular function, but no data are available as to patients with dysfunctioning left ventricle. QT
interval dynamicity was thus compared between a group of 13 post-myocardial infarction patients with reduced
left ventricular function and a group of 25 patients with previous myocardial infarction and preserved left
ventricular contractility. Intervals from Q wave to the peak (Qta) and to the end (Qte) of the T wave and both
Qte and Qta/heart rate regression slopes were calculated in each patient over a 24-hour period using a
dedicated Holter algorithm (ELA Medical). One diurnal (D; 6.00 am to 10.00 pm) and one nocturnal (N; 11.00
pm to 6.00 am) interval were considered. A trend toward an increased QT interval rate-dependence, expressed
as a higher QT interval/heart rate regression slope, was observed in patients with left ventricular dysfunction.
Moreover, two-way ANOVA showed significant and opposite effects of left ventricular dysfunction and
beta-blockade on QteD. In conclusion, patients with previous myocardial infarction and impaired left ventricular
function show an increased diurnal Qte interval rate-dependence, which seems to be corrected by beta-blockers
administration. These data set the stage for further studies evaluating the relationship linking ventricular
repolarization to heart rate and autonomic tone in post-myocardial infarction patients with reduced left
ventricular function.
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Key Words
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