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The "QT" interval is found on an electrocardiogram (ECG).
The QT represents the electrical activity of the heart. The start of the
QT interval is demonstrated in the figure below. It is measured
from the initiation of the QRS complex to the end of the T-wave.
The duration of the QT-interval in normal
people at a heart rate of 60 beats per minute is about four-tenths of a
second (350 and 440
milliseconds). In patients with SQTS it is usually shorter than
three-tenths of a second (less than 300 milliseconds).
Another finding in
patients with SQTS is the QT interval changes very little as the heart rate
changes. Normal individuals QT interval lengths when the heart
rate is slow, and shortens during fast heart rates. Patients with SQTS have a
near constant QT interval with slow heart rates and fast heart
rates.
Although these difference seem minor, they
are not found in the normal population, and have proven to be predispose
those with SQTS to arrhythmias.
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