11, 13 Other authors, however, have reported inadequate sympathovagal balance in response to orthostatism with a decrease in LF/HF in patients with positive HUT. Most authors agree that HUT induces a decrease in high frequency (HF) power, calculated in absolute (ms 2) and/or normalised units (nu), variable changes of the low frequency (LF) component and an increase in the LF/HF ratio both in patients with VVS and controls. Previous studies have shown contradictory HRV results during HUT in patients with VVS and healthy controls. 9, 10 Thus, HRV analysis is a powerful, non-invasive tool to explore dynamic interactions between physiological, mental, emotional and behavioural processes, whose interplay can also be pivotal in the genesis of syncopal attacks and has been used to evaluate autonomic adaptation/reaction induced by HUT. Through the analysis of the heart rate variability (HRV), a physiological phenomenon resultant from the dynamic modulation of HR by the interaction of the sympathetic and parasympathetic nervous systems activity, it is possible to study the dynamics of event-induced changes of cardiac autonomic modulation. 5, 7, 8 Moreover, in a very recent study carried out in patients with likely VVS, HUT with nitroglycerine had a low-diagnostic value in predicting long-term outcomes, suggesting that HUT is of limited value in the management of patients with suspected neurally mediated syncope. 2–4 The Italian protocol has the highest sensitivity, 5, 6 but has at times been criticised for lower specificity due to the administration of nitroglycerine. 1ĭifferent protocols have been established over the years, with different strengths and weaknesses.

Head-up tilt testing (HUT) has a central part in the diagnosis of vasovagal syncope (VVS).

Heart rate analysis software