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.



(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)



• 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):

(1) long QT syndrome

(2) Brugada syndrome

(3) short QT syndrome

(4) acute ST-segment elevation myocardial infarction


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