This paper presents a non-invasive virtual medical instrument for the clinical assessment of cardiovascular and autonomic function. The virtual instrument was developed with the aim of analysing and understanding the physiological changes that occurs in the heart and circulation during vasovagal blackout attacks. The automated virtual instrument allows impedance cardiography analysis, time and frequency heart rate and blood pressure variability analysis, invasive and non-invasive baroreflex sensitivity assessment and forearm blood flow measurements. Using this virtual instrument five control subjects (3 male, mean age 30.6 ± 5.4) and five vasovagal syncope suffers (2 male, mean age 38.6 ± 6.3) were used in a study to try to identify the differences between the two groups to tilt induced syncope. The results obtained suggest that there are fundamental differences in the physiological responses to orthostatic stress between vasovagal patients and controls, which are evident before the onset of major haemodynamic changes.