Cardiovascular dynamics in blood phobia: Evidence for a key role of sympathetic activity in vulnerability to syncope

Abstract

This study was aimed at clarifying the mechanism predisposing people with blood phobia to syncope by investigating the complete hemodynamic response pattern and the underlying autonomic control. Blood phobics and controls were shown 3 film-clips: phobia-related, phobia-unrelated, and neutral. Hemodynamic responses were recorded using impedance cardiography and Finapres. Preejection period and respiratory sinus arrhythmia were employed as indices of cardiac sympathetic and parasympathetic activity. Self-ratings of emotion were also collected. Blood phobics displayed global heart rate and cardiac output increases to the phobic film, mediated by augmented cardiac sympathetic activity. Systolic blood pressure and total peripheral resistance markedly declined, with no evidence of diphasic reaction or parasympathetic activation. An impaired vasomotor response under sympathetic control might be the key mechanism underlying the phobic dysfunctional response.

Preattentive processing of feared stimuli in blood–injection–injury fearful subjects

“…It has been proposed that the absence of a defence response in BII phobics exposed to their fear stimuli may be explained by a dysregulation of the sympathetic activity, especially in the cardiovascular system (e.g., Sarlo et al, 2008) as well as in other response systems, like skin conductance (e.g., Hamm et al, 1997). Our data are compatible with this hypothesis, since the unconscious perception of the feared pictures did not result in an increase of their sympathetically mediated SCRs.…”

“…For example, while some researchers have found HR deceleration when BII phobics are exposed to blood-related stimuli, like pictures (e.g., Hamm et al, 1997), other authors, using longer exposures, like surgery film-clips, have found an initial HR acceleration (during the first 66 seconds of exposure) followed by a diminution of the HR, that falls under baseline (i.e., deceleration) at the end of the exposure, (e.g., Sarlo et al, 2002). Other studies have only found HR acceleration when BII subjects are exposed to blood-related film-clips, but accompanied by a marked fall in systolic blood pressure (Sarlo et al, 2008). As proposed by these authors, the dysfunctional cardiovascular reaction observed in BII phobics would depend more on the involvement of the sympathetic system, rather than the parasympathetic system.…”

“…Several explanations have been proposed for these atypical responses observed in BII phobics when they are exposed to bloodrelated stimuli: a) a conflicting activation of both branches of the autonomic nervous system (Graham et al, 1961) or, at least, a dysregulation of the sympathetic reactivity (Sarlo et al, 2008); b) the prevalence of an emotional response of disgust over fear, which would exert conflicting influences on autonomic reactivity (Page, 1994); c) a disturbance in the cognitive regulation of emotion, as shown by diminished activity in the medial prefrontal cortex when exposed to blood-related pictures (Hermann et al, 2007), a region critically related to the cognitive regulation of emotion (Ochsner and Gross, 2005); and d) a lack of attentional bias, i.e., BII phobics do not assign more attentional resources to blood-related stimuli than non-phobic controls (Sarlo et al, 2010(Sarlo et al, , 2011.…”

Physiological Correlates of Applied Tension May Contribute to Reduced Fainting During Medical Procedures

“…Despite the implication of a predominant role of parasympathetic activity in the traditional term, vasovagal response, the importance of sympathetic withdrawal has been acknowledged for many years and is related to common use of the alternative term, vasodepressor response [40][41][42][43]. In a recent laboratory study of blood phobics' responses to a film depicting surgery, Sarlo et al [44] observed a pattern of results somewhat similar to those of the present study. That is, the phobics had an increase in CO during the surgery film but a decrease in TPR, which may be a primary reason for their susceptibility to fainting in such circumstances.…”

How carryover has an effect on recovery measures related to the area under the curve: theoretical and experimental investigations using cardiovascular parameters

“…In this case, a certain degree of BP elevation corresponding to the strength of mental stress has to be almost always sought by the central nervous system. The only exception to this, to the present authors' knowledge, is the observation of marked decline in systolic BP that occurred in blood phobics during viewings of phobia-related films [25].…”