Age-related hemodynamic changes during vasovagal syncope

The aim of our study was to identify specific age-related hemodynamic changes during upright tilt test in patients with vasovagal syncope.

We studied 115 subjects who were referred to us for unexplained syncope during 65 degrees tilt with pharmacological challenge (s.l. nitrate) by noninvasive monitoring of blood pressure (Finometer). Two derived variables were also considered: total peripheral resistance and stroke volume. The patients were divided into 3 groups by age: Group 1, 10-30 yrs; Group 2, 31-50 yrs; and Group 3, >51 yrs.

The test was positive in 65 patients (57%). During the first 20 min of the test, older patients experienced lower increases in heart rate (p<0.00001) and premature reduction of total peripheral resistance (p<0.005) and systolic blood pressure (p<0.005). Group 1 showed more pronounced decreases in stroke volume (p<0.01). No differences emerged between negative and positive patients. In the 5 min that preceded syncope, younger subjects experienced a distinct, transient increase in heart rate immediately before symptom onset (p<0.005). Blood pressure was prematurely and progressively decreased in Group 3, whereas it decreased only in the 90 s prior to syncope in Groups 1 and 2 (p<0.01).

Our results suggest that blunted sympathetic activation occurs during passive orthostatism in older patients. On the other hand, hemodynamic changes before symptom onset seem to indicate as in younger subjects syncope results from an excessive sympathovagal reaction, whereas in older subjects it is related to an overwhelming, progressive central vagal activity that is associated with a defective peripheral sympathetic activation.