Open AccessDynamic Changes in the QT–R‐R Relationship during Head‐Up Tilt Test in Patients with Vasovagal Syncope
Author(s) -
Mizumaki Koichi,
Fujiki Akira,
Sakabe Masao,
Nishida Kunihiro,
Sugao Masataka,
Tsuneda Takayuki,
Nagasawa Hidehiko,
Inoue Hiroshi
Publication year - 2005
Publication title -
annals of noninvasive electrocardiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.494
H-Index - 48
eISSN - 1542-474X
pISSN - 1082-720X
DOI - 10.1111/j.1542-474x.2005.00587.x
Subject(s) - vasovagal syncope , medicine , tilt (camera) , qt interval , cardiology , reflex , electrocardiography , anesthesia , tilt table test , heart rate , blood pressure , mathematics , geometry
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.