IngentaConnect Dynamic Changes in the QT-R-R Relationship during Head-Up Tilt Te...

Authors: Koichi Mizumaki¹; Akira Fujiki¹; Masao Sakabe¹; Kunihiro Nishida¹; Masataka Sugao¹; Takayuki Tsuneda¹; Hidehiko Nagasawa¹; Hiroshi Inoue¹

Source: Annals of Noninvasive Electrocardiology, Volume 10, Number 1, January 2005 , pp. 16-24(9)

Publisher: Blackwell Publishing

Abstract:

Background: QT interval is influenced by preceding R-R intervals and autonomic nervous tone. Changes in QT intervals during vasovagal reflex might reflect autonomic modulation of ventricular repolarization; however, this issue has not been fully elucidated. This study aimed to evaluate dynamic response of QT interval to transient changes in R-R interval during vasovagal syncope (VVS) induced by head-up tilt test.

Methods: Eighteen patients with VVS and 18 age-and sex-matched controls were studied. All patients with VVS had a positive mixed-type response to head-up tilt and all controls had a negative response. CM5-lead digital electrocardiogram (ECG) was recorded and QT intervals were analyzed using Holter ECG analyzer. Using scatter plots of consecutive QT and the preceding R-R intervals, QT–R-R relations during tilt-up and tilt-back or during vasovagal reflex were independently fitted to an exponential curve: QT (second) = A + B × exp[k × R-R (second)].

Results: During the tilt-up, A, B, and k did not differ between patients with VVS and controls. During the tilt back, k showed equivalent positive value compared to the tilt-up (4.1 ± 1.3 vs -4.6 ± 0.9) in controls. However, k remained negative (-1.3 ± 1.5) during vasovagal reflex in patients with VVS. In six patients, in whom metoprolol was effective in eliminating VVS, QT–R-R relationship during the tilt-back became similar to that in controls.

Conclusions: In patients with VVS, hysteresis of the QT–R-R relation is similarly shown during tilt-up as in controls, whereas this hysteresis is no longer evident and failure of QT prolongation is observed during VVS.

A.N.E. 2005;10(1):16–24

Keywords: syncope; QT interval; head-up tilt; autonomic nervous system

Document Type: Research article

DOI: 10.1111/j.1542-474X.2005.00587.x

Affiliations: 1: Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Toyama, Japan

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Dynamic Changes in the QT–R-R Relationship during Head-Up Tilt Test in Patients with Vasovagal Syncope