QT Interval: How to Measure It and What Is "Normal"

Ilan Goldenberg, M.D.; Arthur J. Moss, M.D.; Wojciech Zareba, M.D., Ph.D.


J Cardiovasc Electrophysiol. 2006;17(3):333-336. 

In This Article

Repolarization Morphology

Recent advances have been made in quantitating repolarization using such measurements as the symmetry of the T wave, T-wave area, or the interval between the end of the S wave and the maximum amplitude of the T wave. However, quantitative analysis of the T-wave shape and pattern requires computer software and electronically stored ECG data.

The morphology or configuration of repolarization can be described from visual inspection of the T wave and placed into prespecified categories. In our assessment of ventricular repolarization, we incorporate this information into the data obtained from QT-interval duration measurement. Distinctive T-wave patterns have been observed in patients with each of the three major LQTS genotypes (Fig. 3).[3] In LQT1 a single, smooth, broad-based T wave is common, as well as a late-onset normal-appearing T wave; in LQT2, bifid T waves are a hallmark ECG feature; in LQT3, the T waves are typically late-onset, prominent, and usually peaked.

Figure 3.

Specific LQTS T-wave patterns: broad-based T-wave pattern in LQT1, bifid T waves in LQT2, and late-onset peaked/biphasic T waves in LQT3.