Deceleration-dependent shortening of the QT interval: a new electrocardiographic phenomenon?

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