In clinical cardiology, deceleration-dependent QT interval shortening is co
nsidered to be an extraordinary electrocardiographic phenomenon. We present
an early premature born 4-year-old African-American girl with complication
s related to her premature birth, developmental delay, and several episodes
of cardiac arrest. An episode of severe transient bradyarrhythmia was docu
mented on Holter monitoring. The unique feature of the rhythm strips was pa
radoxical gradual shortening of the QT interval to 216 ms with accompanying
transient T-waves abnormalities. The activation of the Ik,ACh due to an un
usually high vagal discharge to the heart is proposed as a possible mechani
sm responsible for both slowing of the heart rate and shortening of the QT
interval.