Heart rate and blood pressure variability in subjects with vasovagal syncope.
Autonomic nervous system control in subjects with vasovagal syncope is controversial. In the present study, we used short-term spectral analysis to evaluate autonomic control in subjects with recurrent vasovagal syncope. We assessed the ability of spectral indices of HR (heart rate) variability to predict tilt-test responses. A series of 47 outpatients with recurrent vasovagal syncope and with positive responses to head-up tilt testing underwent a further study of RR variability during controlled breathing at rest and during tilt testing. During controlled breathing, RR interval variability of total power (TP(RR); P<0.001), low-frequency power (LF(RR); P<0.05), high-frequency power (HF(RR); P<0.001) and HF expressed in normalized units (HFnu(RR); P<0.001) were all higher, and LF expressed in normalized units (LFnu(RR)) and LF/HF ratio were lower in subjects with vasovagal syncope than in controls (P<0.001). To assess the ability of spectral components of RR variability to predict tilt-test responses, we prospectively studied 109 subjects with recurrent vasovagal syncope. The two normalized measures, HFnu(RR) and LFnu(RR), determined during controlled breathing alone predicted a positive tilt-test response (sensitivity, 76%; specificity, 99%; positive predictive value, 96%; and negative predictive value, 90%). During tilting, subjects with vasovagal syncope had lower SBP (systolic blood pressure; P<0.05), LF component of peak SBP variability (LF(SBP)) and LFnu(RR) than controls, and higher TP(RR), HF(RR), HFnu(RR) and alpha HF (P<0.001). These spectral data indicate that vagal sinus modulation is increased at rest in subjects with vasovagal syncope. Spectral analysis of RR variability during controlled breathing, a procedure that predicts tilt-test responses, could be a useful guide in choosing the method of tilt testing.
Dipartimento di Scienze dell'Invecchiamento, Policlinico Umberto I, Università La Sapienza, 00161 Rome, Italy. gianfranco.piccirillo@uniroma1.it
Gianfranco
G
Piccirillo
Camilla
C
Naso
Antonio
A
Moisè
Marco
M
Lionetti
Marialuce
M
Nocco
Silvia
S
Di Carlo
Tiziana
T
De Laurentis
Damiano
D
Magrì
Mauro
M
Cacciafesta
Vincenzo
V
Marigliano
D000328:Adult; D000886:Anthropometry; D001794:Blood Pressure; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012008:Recurrence; D015656:Respiratory Mechanics; D012815:Signal Processing, Computer-Assisted; D019462:Syncope, Vasovagal / Q000503:physiopathology*; D018667:Tilt-Table Test / Q000379:methods