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 (TPRR; P<0.001), low-frequency power (LFRR; P<0.05), high-frequency power (HFRR; P<0.001) and HF expressed in normalized units (HFnuRR; P<0.001) were all higher, and LF expressed in normalized units (LFnuRR) 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, HFnuRR and LFnuRR, 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 (LFSBP) and LFnuRR than controls, and higher TPRR, HFRR, HFnuRR and α 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.
Heart rate and blood pressure variability in subjects with vasovagal syncope
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Gianfranco PICCIRILLO, Camilla NASO, Antonio MOISÈ, Marco LIONETTI, Marialuce NOCCO, Silvia DI CARLO, Tiziana DE LAURENTIS, Damiano MAGRÌ, Mauro CACCIAFESTA, Vincenzo MARIGLIANO; Heart rate and blood pressure variability in subjects with vasovagal syncope. Clin Sci (Lond) 1 July 2004; 107 (1): 55–61. doi: https://doi.org/10.1042/CS20030327
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