Global T-wave inversion: limited QT dispersion despite QTc prolongation--a correlate of benignity in patients with strikingly abnormal electrocardiograms.

BACKGROUND: The global T-inversion (GTI) electrocardiogram (ECG) is strikingly abnormal with major QTc prolongation, but with a surprisingly good prognosis by Kaplan-Meier curve. This contrasts with most significant QTc prolongations. HYPOTHESIS: This study was undertaken to ascertain QT interval dispersion (QTd) in global T wave inversion, a clinically benign long QTc ECG. METHODS: Longest and shortest QT intervals in all 12 leads in 35 consecutive patients with GTI were determined by two mutually blinded observers. QTd was determined by subtraction (maximum-minimum) and QTc was calculated using the Bazett formula. RESULTS: There was a 2:1 female preponderance QTc was prolonged and equal for men (0.471) and women (0.469). Observer variability of under 2% permitted averaging of QT measurements. Composite mean QTd was 55 ms. The literature revealed a range of QTd in normal subjects of 39 to 59 ms (mostly 49 to 59 ms). Patient series with abnormal QTd were well above this level. CONCLUSION: Despite a strikingly abnormal ECG with marked QTc prolongation, QT dispersion was limited in global T inversion, consistent with its previously demonstrated benignity.