Diagnostic implications of modified treadmill and head-up tilt tests in exercise-related syncope: comparative studies...

The precise pathophysiological basis of exercise-related vasodepressor syncope is not well understood.

The diagnostic values of head-up tilt and modified treadmill tests with abrupt termination were tested in patients with exercise-related syncope and compared with those of patients with situational or vasovagal syncope.

Diagnostic accuracies of head-up tilt and modified treadmill exercise tests were examined in 44 patients with unexplained syncope (26 men, 18 women, aged 46 19 years) and in 20 control subjects. Results for 18 patients with syncope during exercise (short-distance dash [n=7], jogging [n=3], going up stairs [n=6], swimming [n=1] or cycling [n=1]), defined as exercise-related syncope, were compared with those for 26 patients with exercise-unrelated syncope (including situational [n=7] and vasovagal [n=14] syncope).

No differences were found between the clinical backgrounds of subjects with and those without exercise-related syncope. Head-up tilt testing had good diagnostic sensitivities, specificities and accuracies in both exercise-related and exercise-unrelated groups (84% versus 77%, 84% versus 85%, 84% versus 80%, respectively). The corresponding values of modified treadmill tests in the two groups were 78% versus 19% (P<0.05), 95% versus 95% and 86% versus 52% (P<0.05), respectively. The results of exercise tests were of limited diagnostic value for exercise-unrelated syncope. Beta-blockade had good short term efficacy in subjects with exercise-related syncope (nine of 15, 60%) as well as in subjects with exercise-unrelated syncope (seven of 10, 70%).

Modified treadmill exercise testing is thought to be useful for diagnosing exercise-related syncope.