Pseudo preexcitation syndrome.

During the course of investigation for palpitations, a 62-year-old man underwent exercise testing using a MARQUETTE CASE 12 computerized exercise testing system. By stage III of the modified Bruce protocol, the computer-generated electrocardiogram appeared to show the development of exercise-induced preexcitation. Closer examination of the raw unfiltered data showed this to be a computer-generated artifact rather than true preexcitation. This artifact arose due to inherent limitations common to all computerized exercise testing systems and emphasizes the need to always review raw data, even when a seemingly clear-cut abnormality is present on a computer-averaged electrocardiogram.