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

Sarlo et al. (2002; 2008) measured T-wave amplitude or pre-ejection period during film presentation and observed initial decreases followed by subsequent increases in these indices, suggesting elevated and reduced sympathetic activity, respectively.

“Sarlo et al. (2002; 2008) measured T-wave amplitude or pre-ejection period, respectively, during film presentation and observed initial decreases followed by subsequent increases in these indices, suggesting elevated and reduced sympathetic activity, respectively.”

The literature on BII phobia has typically drawn heavily on regulatory events observed in response to orthostatic tests.

“The literature on BII phobia has typically drawn heavily on regulatory events observed in response to such tests (Sarlo et al., 2008).”

Sarlo et al. (2008), who compared a surgery film with a landscape film and cockroach invasion or spider films, were also not able to demonstrate a biphasic pattern in HR and BP on average, when taking into account the levels reached during these neutral and negative comparison films.

“Sarlo et al. (2008), who compared a surgery film with a landscape film and cockroach invasion or spider films, were also not able to demonstrate a biphasic pattern in HR and BP on average, when taking into account the levels reached during these neutral and negative comparison films.”

In the same two studies, analysis of RSA remained uninformative, but no control for influences of respiration rate and volume had been attempted.

“In the same two studies, analysis of RSA remained uninformative, but no control for influences of respiration rate and volume had been attempted.”

In both studies, only the initial increase in sympathetic activity, not the subsequent decrease, exceeded the levels reached during neutral and negative comparison films.

“In both studies, only the initial increase in sympathetic activity, not the subsequent decrease, exceeded the levels reached during neutral and negative comparison films.”

BII patients in Sarlo et al. showed continuous falls in systolic blood pressure starting from the outset of a surgery film lasting slightly longer than 5 min; none were reported to have fainted.

“On the other hand, BII patients in Sarlo et al. (2008) showed continuous falls in SBP, which started from the outset of their surgery film presentation lasting slightly longer than 5 min. None of the patients in these studies were reported to have fainted.”

Other hemodynamic indices such as cardiac output, total peripheral resistance, or myocardial contractility have rarely been explored in BII phobia-related fainting.

“However, other hemodynamic indices such as cardiac output, total peripheral resistance, or myocardial contractility, which could improve the understanding of cardiovascular dynamics, have rarely been explored in BII phobia-related fainting (Sarlo et al., 2008).”

During tilt-table testing-induced vasovagal syncope, muscle sympathetic nerve activity is reduced in late phases.

“Indeed, during tilt-table testing-induced vasovagal syncope, muscle sympathetic nerve activity is reduced in late phases (Jardine et al., 2002; see also Sarlo et al., 2008).”