Predictive value of very low frequency at spectral analysis among patients with unexplained syncope assessed by head-up tilt testing

BACKGROUND

The role of heart rate variability (HRV) in the prediction of vasovagal syncope during head-up tilt testing (HUTt) is unclear.

AIM

To evaluate the ability of the spectral components of HRV at rest to predict vasovagal syncope among patients with unexplained syncope referred for HUTt.

METHODS

Twenty-six consecutive patients with unexplained syncope were enrolled in the study. All patients underwent HRV evaluation at rest (very low frequency [VLF], low frequency [LF], high frequency [HF] and LF/HF ratio) and during HUTt. HUTt was performed using the Westminster protocol. Continuous electrocardiogram and blood pressure monitoring were performed throughout the test.

RESULTS

Eight (31%) patients developed syncope during HUTt. There were no baseline differences in terms of clinical features and HRV variables among patients who developed syncope and those who did not, except for VLF (2421 vs 896ms²; P<0.001). In the multivariable logistic regression analysis, including age and sex, VLF was the only independent variable associated with syncope during HUTt (odds ratio 1.002, 95% confidence interval 1.0003-1.0032; P=0.02). The area under the curve at rest was 0.889 for VLF, 0.674 for HF and 0.611 for LF. A value of VLF>2048ms² was the optimal cut-off to predict syncope during HUTt (sensitivity 87.5%, specificity 72.2%).

CONCLUSIONS

VLF at rest predicted the incidence of syncope during HUTt. Further studies are warranted to confirm these preliminary data.

[Blood-injection-injury phobia: Physochophysiological and therapeutical specificities]

INTRODUCTION

Seventy-five percent of patients with blood-injection-injury phobia (BII-phobia) report a history of fainting in response to phobic stimuli. This specificity may lead to medical conditions remaining undiagnosed and untreated, incurring considerable cost for the individual and society. The psychophysiology of BII-phobia remains poorly understood and the literature on effective treatments has been fairly sparse. Aims of the systematic review: to synthesize the psychophysiology of BII-phobia and to propose a systematic review of the literature on effectiveness of different treatments evaluated in this indication.

RESULTS

Firstly, the most distinct feature of the psychophysiology of BII-phobia is its culmination in a vasovagal syncope, which has been described as biphasic. The initial phase involves a sympathetic activation as is typically expected from fear responses of the fight-flight type. The second phase is characterized by a parasympathetic activation leading to fainting, which is associated with disgust. Subjects with syncope related to BII-phobia have an underlying autonomic dysregulation predisposing them to neurally mediated syncope, even in the absence of any blood or injury stimulus. Many studies report that BII-phobic individuals have a higher level of disgust sensitivity than individuals without any phobia. Secondly, behavioral psychotherapy techniques such as exposure only, applied relaxation, applied tension, and tension only, have demonstrated efficacy with no significant difference between all these techniques. The disgust induction has not improved effectiveness of exposure.

CONCLUSION

We have explained the psychophysiology of BII-phobia, the understanding of which is required to study and validate specific techniques, in order to improve the prognosis of this disorder, which is a public health issue.