Use of nitroglycerin in the active phase of tilt testing: is there a difference in elderly patients?

The importance of tilt testing has been demonstrated in the evaluation of patients with syncope of unknown cause, and it is the gold standard technique for the diagnosis of neurocardiogenic syncope, particularly with the use of pharmacological provocative agents to improve diagnostic accuracy. Stimulation with sublingual nitroglycerin is generally well tolerated and increases test sensitivity, shortening the test duration; this also allows the test to be applied in elderly patients.

To evaluate, in a population referred for syncope of unknown etiology, the value of tilt testing with sublingual nitroglycerin and to compare the responses obtained in elderly and younger patients.

We studied 158 patients who underwent tilt testing using nitroglycerin as a provocative agent. We compared patients aged <65 years (Group A, n=74) and > or =65 years (Group B, n=84). Tilt testing was performed according to the Italian protocol, with continuous monitoring of the electrocardiogram and blood pressure (Task Force Monitor, CNSystems). Only patients who were asymptomatic in the passive phase of the test were included. The test was considered positive for neurocardiogenic response when symptoms were reproduced with bradycardia and/or hypotension; the responses were classified as cardioinhibitory, vasodepressor or mixed. A gradual and parallel decrease in blood pressure after nitroglycerin administration, followed by syncope, was considered an exaggerated response to nitrates.

There were no differences in gender distribution between groups. Tilt testing was positive in 57% of group A and 51% of group B patients (p=NS), with an exaggerated response to nitrates in 11% and 16% respectively (p=NS). With regard to neurocardiogenic responses, vasodepression was more frequent in group B (53% vs. 24%; p=0.001), while a mixed response tended to be more frequent in group A (59% vs. 40%; p=0.07), with no significant difference in cardioinhibitory responses (17% in group A vs. 7% in group B; p=NS).

In a population with syncope of unknown origin, tilt testing potentiated with nitroglycerin: a) makes a significant contribution to clarifying diagnosis and is of equal value in both elderly and younger patients; and b) is associated with a higher incidence of neurocardiogenic vasodepressor response in the elderly, although with a similar rate of exaggerated responses to nitrates.