Key result
Abrupt heart rate acceleration shortens the time constant for QT change by ~54% versus slowing.
Why the study?
The rate of change of the QT interval following an abrupt increase or decrease in heart rate was not well characterized.
Population
Healthy, anesthetized, thoracotomized dogs with junctional rhythm induced by sinoatrial node destruction
Comparison
Sudden change in heart rate via atrial pacing from 800 to 600 ms or 600 to 800 ms cycle duration
Design
Experimental study measuring QT intervals after induced heart rate changes
Authors
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QT adaptation faster with rate acceleration in canines; leaves open beat-count dependence for human repolarization dynamics.
Absolute Event Rate: 1.7% vs 3.7%
p-value: p=< 0.01
In a canine model, the adaptation of the QT interval to sudden changes in heart rate depends on the number of heart beats rather than absolute time.
OGUCHI et al. (1994) studied Healthy dogs. Abrupt acceleration in heart rate vs. Abrupt slowing in heart rate (800-millisecond cycle duration) was evaluated on Time constant for change in QT interval duration vs duration after sudden change in heart rate (seconds) (p=< 0.01). Abrupt acceleration of heart rate resulted in a significantly shorter time constant for QT interval change (1.7 seconds) compared to slowing of heart rate (3.7 seconds, P < 0.01).
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