Paroxysmal Atrioventricular Block Induced During Head‐Up Tilt Testing in an Apparently Healthy Man

Paroxysmal AV Block During HUT Testing. Introduction : Prolonged asystole during head‐up tilt testing has been reported, but the occurrence of paroxysmal AV block appears to he rare. Methods and Results : A 25‐year‐old man with no history of syncope underwent head‐up tilt testing. After 11 minutes of 80° tilting, he developed syncope with paroxysmal AV block and asystole lasting 10.5 seconds. However, this response was not reproduced during a subsequent tilt test 4 weeks later. Treadmill exercise testing and Holter monitoring showed no abnormalities. Power spectral analysis of heart rate variability revealed a marked increase in sympathetic activity several minutes before the induction of paroxysmal AV block. Conclusion : We report a case of paroxysmal AV block that occurred during head‐up tilt testing but did not recur on a subsequent test in an apparently healthy young man.