Influence of age, the autonomic nervous system and anxiety on QT-interval variability.
As QT variability increases and heart rate variability diminishes, the QT variability index (QTVI) - a non-invasive measure of beat-to-beat fluctuations in QT interval on a single ECG lead - shows a trend towards positive values. Increased QT variability is a risk factor for sudden death. Aging lengthens the QT interval and reduces RR-interval variability. In the present study we investigated the influence of aging and the autonomic nervous system on QT-interval variability in healthy subjects. We studied 143 healthy subjects, and divided them into two age ranges (younger and older than 65 years). For each subject we measured two QTVIs: from the q wave to the end of the T wave (QTeVI) and to the apex of the T wave (QTaVI). Both indexes were calculated at baseline and after sympathetic stress. In 10 non-elderly subjects, both QTVIs were determined after beta-adrenoreceptor blockade induced by intravenous infusion of propranolol or sotalol. The QTVI was higher in elderly than in younger subjects (P<0.001). QTVIs obtained during sympathetic stress remained unchanged in the elderly, but became more negative in the younger group (P<0.05). QTeVI and QTaVI at baseline were correlated positively with age (P<0.01) and anxiety scores (P<0.05), but inversely with the low-frequency spectral power of RR-interval variability (P<0.001). QTVIs were higher in subjects with higher anxiety scores. In younger subjects, sotalol infusion increased both QTVIs significantly, whereas propranolol infusion did not. In conclusion, aging increases QT-interval variability. Whether this change is associated with an increased risk of sudden death remains unclear. The association of abnormal QT-interval variability with anxiety and with reduced low-frequency spectral power of heart rate variability merits specific investigation. In healthy non-elderly subjects, acute sympathetic stress (tilt) decreases the QTVI. beta-Adrenoreceptor blockade inhibits this negative trend, thus showing its sympathetic origin. Because a negative trend in QTVI induced by sympathetic stress increases only in younger subjects, it could represent a protective mechanism that is lost with aging.
Piccirillo
G
G
Dipartimento di Scienze dell'Invecchiamento, I Clinica Medica, Policlinico Umberto I, 00161 Rome, Italy. piccirillog@uniroma1.it
Cacciafesta
M
M
Lionetti
M
M
Nocco
M
M
Di Giuseppe
V
V
Moisè
A
A
Naso
C
C
Marigliano
V
V
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D001007:Anxiety / Q000503:physiopathology*; D001341:Autonomic Nervous System / Q000503:physiopathology*; D004562:Electrocardiography / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011433:Propranolol / Q000494:pharmacology; D012815:Signal Processing, Computer-Assisted; D013015:Sotalol / Q000494:pharmacology
D000319:Adrenergic beta-Antagonists; D000889:Anti-Arrhythmia Agents; D011433:Propranolol; D013015:Sotalol