The ratio of the T wave peak-to-end interval to the QT interval is prolonged in a number of conditions associated with fatal ventricular arrhythmias. The ratio is a simple and noninvasive means to identify a patient who may be at risk for certain ventricular arrhythmias.
The ratio is an index of ventricular repolarizaton. Prolongation of the ratio indicates that functional re-entry contributes to the genesis of the arrhythmia.
Parameters:
(1) time interval from peak of the T wave to its end in milliseconds (ms)
(2) duration of the QT interval in milliseconds
ratio of T wave peak-to-end interval to QT interval =
= (interval for the T wave peak-to-end) / (interval QT)
Interpretation:
• The normal ratio is relatively constant over the interval of 0.15 to 0.25 with a mean 0.21 (page 571).
• The ratio is stable for heart rates from 60 to100 beats per minute.
Conditions associated with an increased ratio (>= 0.26):
