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Beat‐to‐Beat Assessment of QT/RR Interval Ratio in Severe Heart Failure and Overt Myocardial Ischemia:
Author(s) -
FABER THOMAS S.,
GROM ANDREAS,
SCHÖPFLIN MARKUS,
BRUNNER MICHAEL,
BODE CHRISTOPH,
ZEHENDER MANFRED
Publication year - 2003
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1046/j.1460-9592.2003.t01-1-00147.x
Subject(s) - medicine , cardiology , qt interval , ejection fraction , repolarization , electrocardiography , heart failure , heart rate , rr interval , heart rate variability , blood pressure , electrophysiology
FABER, T.S., et al. : Beat‐to‐Beat Assessment of QT/RR Interval Ratio in Severe Heart Failure and Overt Myocardial Ischemia: A Measure of Electrical Integrity in Diseased Hearts.The study was designed to assess the beat‐to‐beat variation of ventricular repolarization in patients with myocardial ischemia, heart failure, and in normal subjects. Autonomic tone may alter the dynamic QT/RR interval relation and thus may be involved in ventricular arrhythmia development, especially in the diseased heart. The study included 145 patients (age 16–86 years) with CHF (LVEF ≤ 0.30) or unstable angina pectoris(LVEF > 0.60). The control group consisted of healthy volunteers giving physiological baseline measures for the evaluated parameters: cycle length, QT interval, and QT/RR interval ratio during three time periods. In patients with myocardial ischemia(LVEF > 0.60)and healthy subjects the QT/RR interval ratio did not reveal significant differences between both groups (QT/RR CAD = 0.36 ± 0.77 vs QT/RR controls = 0.28 ± 0.83; NS). In sharp contrast, in patients with severe heart failure, RR dependent instantaneous variation of the QT interval was almost missing and regression line analysis disclosed a QT/RR interval slope substantially enhanced by 196% (compared to normal subjects) and 131% (compared to CAD patients; P < 0.05) with a complete loss of circadian modulation (QT/RR CHF = 0.83 ± 0.71 vs QT/RR CAD = 0.36 ± 0.77 vs QT/RR controls = 0.28 ± 0.83; P < 0.05). Beat‐to‐beat QT interval assessment provides a dynamic parameter of physiological and altered repolarization in defined study groups. Compared to other groups (preserved LVEF), patients with left ventricular impairment exhibited a significantly increased sensitivity of repolarization to cycle length (enhanced QT/RR interval ratio) and a blunted circadian modulation of the QT interval. This is consistent with concept that increased repolarization disparity may be deleterious being a potential pathophysiological basis for enhanced arrhythmic risk. (PACE 2003; 26[Pt. I]:836–842)