801-2 The Electrocardiographic Ventricular Repolarization During Stress from Awakening on Alarm Call

Abstract

Ambulatory electrocardiograms of 30 physicians were recorded during alarm calls at night while on dutyin hospital. Men/women were 21/9, mean age was 37 ± 7 years, all were healthy. At the arousal from sleep, T-wave inversion (TWI) in lateral chest lead, ST-segment depression (STD) ≥ 0.1 mV. heart rate (HR) and QT interval (QT) were determined before and 5, 10, and 30 sec after signs of reaction in electrocardiogram, and at peak HR coinciding at 17 see on average. For comparison, QT was also measured outside the arousal episodes at corresponding HR levels but while the rate had remained stable (QTs) for at least 1 min. Number of subjects (N) or mean ± SD values were: Before 5 sec 10 sec 17 sec 30 sec TWI (N) 0 0 10 12 4 STD (N) 0 0 5 7 1 HR (/min) 55 ± 7 92 ± 12 100 ± 15 112 ± 18 97 ± 24 QT (msec) 428 ± 28 397 ± 23 390 ± 40 362 ± 41 352 ± 40 QTs (msec) 410 ± 18 334 ± 16 323 ± 15 303 ± 15 327 ± 14 QT – QTs (msec) +18 +63 +67 +59 +25 Overall, short-lasting episodes of TWI occurred in 18 (60%) and STD in 8 (27%) subjects, signifying sudden sympathetic overactivity. During the early part of the arousal, till the time of peak HR, QT markedly exceeded QTs, but at 30 sec the difference had almost disappeared. In conclusion, commonly encountered events like a wake-up call can evoke changes in ventricular repolarization, associated with a delay in its adaptation to heart rate. Same phenomena in electrically unstable hearts may mediate stress-provoked arrhythmias.