Quantitative analysis of T wave abnormalities and their prognostic implications in the idiopathic long QT syndrome.

OBJECTIVES

We evaluated the diagnostic and prognostic value of morphologic abnormalities of the T wave (mainly notched or biphasic T waves) in patients affected by the idiopathic long QT syndrome.

BACKGROUND

In the long QT syndrome, these abnormalities in T wave morphology are often observed and are of uncertain significance.

METHODS

The T wave abnormalities in the electrocardiogram (ECG) of 53 patients with the long QT syndrome and 53 control subjects of similar age and gender were analyzed, and their association with major cardiac events was defined.

RESULTS

Notched or biphasic T waves were defined according to morphologic criteria. They were present in 33 (62%) of 53 patients with the long QT syndrome and in 8 (15%) of 53 control subjects (p < 0.001). Moreover, among patients with the long QT syndrome they were much more frequent in symptomatic (history of syncope or cardiac arrest) than in asymptomatic subjects (30 [81%] of 37 vs. 3 [19%] of 16, p < 0.001). The same distribution was observed within families with the long QT syndrome, in which symptomatic members had more pronounced T wave abnormalities than did their asymptomatic siblings or parents. In symptomatic patients, the occurrence of T wave abnormalities was independent of the length of repolarization (corrected QT). These T wave abnormalities were associated with the presence of a specific pattern of abnormal left ventricular wall motion.

CONCLUSIONS

This study has quantified an ECG pattern typical of the long QT syndrome and provides the first evidence that morphologic analysis of T wave abnormalities may contribute to the diagnosis of the long QT syndrome and the identification of patients at higher risk for syncope or cardiac arrest.