BACKGROUND: The QT interval shortens in response to sympathetic stimulation and its response to epinephrine infusion (in healthy individuals and patients with long QT syndrome) has been thoroughly studied. Head-up tilt-table (HUT) testing is an easy way to achieve brisk sympathetic stimulation. Yet, little is known about the response of the QT interval to HUT. METHODS: We reviewed the electrocardiograms of HUT tests performed at our institution and compare the heart rate, QT, and QTc obtained immediately after HUT with the rest values. RESULTS: The study group consisted of 41 patients (27 females and 14 males) aged 23.9 +/- 8.4 years. Head-up tilting led to a significant shortening of the RR interval (from 825 +/- 128 msec at rest phase to 712 +/- 130 msec in the upward tilt phase, P < 0.001) but only to a moderate shortening of the QT interval (from 363.7 +/- 27.9 msec during rest to 355 +/- 30.3 msec during upward tilt, P = 0.001). Since the RR interval shortened more than the QT interval, the QTc actually increased (from 403 +/- 21.5 msec during rest phase to 423.2 +/- 27.4 msec during upward tilt, P < 0.001). The QTc value measured for the upward tilt position was longer than the resting QTc value in 33 of 41 patients. Of those, 4 male patients and 2 female patients developed upward-tilt QTc values above what would be considered abnormal at rest. CONCLUSIONS: During HUT the QT shortens less than the RR interval. Consequently, the QTc increases during head-up tilt.
BACKGROUND: The QT interval shortens in response to sympathetic stimulation and its response to epinephrine infusion (in healthy individuals and patients with long QT syndrome) has been thoroughly studied. Head-up tilt-table (HUT) testing is an easy way to achieve brisk sympathetic stimulation. Yet, little is known about the response of the QT interval to HUT. METHODS: We reviewed the electrocardiograms of HUT tests performed at our institution and compare the heart rate, QT, and QTc obtained immediately after HUT with the rest values. RESULTS: The study group consisted of 41 patients (27 females and 14 males) aged 23.9 +/- 8.4 years. Head-up tilting led to a significant shortening of the RR interval (from 825 +/- 128 msec at rest phase to 712 +/- 130 msec in the upward tilt phase, P < 0.001) but only to a moderate shortening of the QT interval (from 363.7 +/- 27.9 msec during rest to 355 +/- 30.3 msec during upward tilt, P = 0.001). Since the RR interval shortened more than the QT interval, the QTc actually increased (from 403 +/- 21.5 msec during rest phase to 423.2 +/- 27.4 msec during upward tilt, P < 0.001). The QTc value measured for the upward tilt position was longer than the resting QTc value in 33 of 41 patients. Of those, 4 male patients and 2 female patients developed upward-tilt QTc values above what would be considered abnormal at rest. CONCLUSIONS: During HUT the QT shortens less than the RR interval. Consequently, the QTc increases during head-up tilt.
Authors: Sami Viskin; Pieter G Postema; Zahurul A Bhuiyan; Raphael Rosso; Jonathan M Kalman; Jitendra K Vohra; Milton E Guevara-Valdivia; Manlio F Marquez; Evgeni Kogan; Bernard Belhassen; Michael Glikson; Boris Strasberg; Charles Antzelevitch; Arthur A M Wilde Journal: J Am Coll Cardiol Date: 2010-01-29 Impact factor: 24.094
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