This study assesses the vasovagal collapse pattern changes, i.e, heart rate (HR) and arterial blood pressure (BP) with a 2-stage tilt-test protocol using glyceryl trinitrate (GTN) provocation. With use of the 45-minute 60 degrees head-up Westminster protocol, 102 consecutive patients were studied. Sublingual GTN 300 microg was given to those with a negative passive tilt. Heart rate and BP patterns were classified according to the Vasovagal International Study classification (VASIS) and then compared between those with a positive passive tilt and those with a positive tilt after having been given GTN. Twelve patients did not tolerate tilt testing, and 16 had a negative response despite taking GTN. Thirty-five patients (20 women and 15 men, mean age 45 +/- 21 years [mean +/- SD]) did not take GTN and 38 (26 women and 12 men, mean age 53 +/- 22 years) had positive passive test results. When comparing the VASIS classification between the 2 groups, results showed: type 1, mixed BP and HR decreased without severe bradycardia (31% [passive] vs 54% [with GTN], p = NS); type 2A, BP decreased before HR decreased (20% vs 22%, p = NS); type 2B, HR decreased before or coincident with BP (34% vs 8%, p = 0.003); type 3, BP decreased without HR decrease (9% vs 0%, p = NS); exception 1, chronotropic incompetence (0% vs 13%, p = 0.026); and exception 2, excessive HR increase (6% vs 3%, p = NS). Thus, GTN use increases frequency of positive results from 34% to 73%. Older people with chronotropic incompetence, who may benefit from pacing, were identified. In younger people there was an increase in those with cardioinhibition.