Age and QT variability index during free breathing, controlled breathing and tilt in patients with chronic heart failure and healthy control subjects.
The QT variability index (QTVI) indicates temporal dispersion in myocardial repolarization, and a high QTVI is associated with a propensity for sudden death from malignant ventricular arrhythmias in subjects at high risk. In this study, the authors assessed the effects of free breathing, controlled breathing, and sympathetic stress (tilt) on the QTVI in patients with chronic heart failure (CHF) and healthy control subjects. The authors also examined the influence of age on the same variables. To obtain normative data, they calculated 95% confidence intervals for healthy subjects grouped according to age. Under all experimental conditions, the QTVI was larger in the CHF group overall and in the age subsets than in controls. In patients and controls, the QTVI increased significantly during tilt, although no differences were found between the QTVI measured during free and controlled breathing. In healthy controls, the following variables correlated significantly with the QTVI: age and baseline heart rate (P < 0.001). In patients with CHF, aging had no influence on the QTVI.


CONCLUSIONS
Age, sympathetic stress, and CHF all tend to increase the QTVI and could potentially induce sudden death. Further studies should assess the usefulness of the QTVI as a marker predicting sudden cardiac death under the various conditions of risk.
Piccirillo
Gianfranco
G
Dipartimento di Scienze dell'Invecchiamento, Policlinico Umberto I, Universitá La Sapienza, Rome, Italy. gianfranco.piccirillo@uniroma1.it
Magnanti
Marzia
M
Matera
Sabrina
S
Di Carlo
Silvia
S
De Laurentis
Tiziana
T
Torrini
Alessia
A
Marchitto
Nicola
N
Ricci
Renato
R
Magrí
Damiano
D
D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D016022:Case-Control Studies; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012119:Respiration; D018667:Tilt-Table Test