Effect of lead exclusion for the manual measurement of QT dispersion

Area of Science:

• Cardiology
• Electrocardiography
• Cardiac Electrophysiology

Background:

• QT dispersion (QTd) is a measure of repolarization variability on an electrocardiogram (ECG).
• Accurate QTd measurement is crucial for assessing cardiac risk.
• Standardized lead exclusion criteria for manual QTd calculation are not well-established.

Purpose of the Study:

• To evaluate the impact of various lead exclusion criteria on manual QTd measurements.
• To determine the optimal lead exclusion strategy for differentiating healthy subjects from those with cardiac pathology.

Main Methods:

• Simultaneous 12-lead ECGs were recorded from 75 subjects (25 healthy, 25 myocardial infarction, 25 arrhythmias).
• Leads were excluded based on T wave amplitude (absolute and relative) and QT interval (smallest/largest).
• QTd was calculated as the QT range, and its ability to discriminate between groups was assessed.

Main Results:

• Excluding no leads or leads with low T wave amplitude showed limited differentiation between normal and pathological groups.
• Excluding the lead with the smallest T wave amplitude or shortest QT interval significantly improved differentiation (P < 0.05).
• Excluding the two leads with the smallest T wave amplitudes or shortest QT intervals yielded the greatest differences between normal and pathological groups (P < 0.005).

Conclusions:

• Lead exclusion criteria significantly influence QTd measurements and diagnostic capability.
• Excluding leads with minimal T wave amplitude or shortest QT intervals enhances QTd's ability to identify cardiac abnormalities.
• The proposed exclusion method, particularly removing the two leads with the smallest T wave amplitudes or shortest QT intervals, offers a more robust approach for QTd assessment.