Comparing manual versus automatic measurements of the QT-interval and QTc

Every beat of the heart activates and resets to be ready for its next activation. This process of activation-reset-activation is an electrical process that can be recorded on an electrocardiogram (ECG). The time the heart needs for the separate processes is determined by time intervals. The activation time of the hart is reflected on the ECG as the QRS-duration and the reset time is reflected as the QT-interval. The QT-interval depends on the heart rate (number of heart beats per minute), and is therefore corrected for the heart rate (QTc, the ‘c’ stands for corrected). Monitoring the QTc is essential because abnormalities in the duration can indicate an increased risk for malign arrhythmias with can be life-threatening.

             Despite the importance of the QT-interval and QTc, no commonly accepted standard exists for their assessment. QT-interval experts advocate manual measurements, however for convenience, many healthcare professionals routinely use QT-interval and QTc values that are automatically provided by ECG recorders. The agreement between manual and automatic measurements of the QT-interval and QTc is not sufficiently clear.

In this study, we sought to investigate if there is a difference in manual and automatic QT-interval and QTc assessments. QT-interval and QTc assessments are particularly challenging in case of complex T-wave morphologies as often present in patients with long QT syndrome. To evaluate a cohort enriched for aberrant QT-intervals, QTc values and T-wave morphologies, we analysed the ECGs of 720 patients with long QT syndrome and 543 controls for a discrepancy between manual and automatic QT-interval and QTc findings. We found that the pairwise agreement between manual and vendor-provided automatic assessments of QT-interval and QTc was highly discrepant, which was not the case for other intervals on the ECG. This indicates that the QT-interval and QTc are more vulnerable to mis-assessment which may lead to incorrect and possibly consequential conclusions, whenever the length of QT-interval and QTc is of importance.

We encourage manual review of automatic QT-interval and QTc assessments. However, the advantages of confidently using automatic assessments in clinical routine are evident. We have therefore tested a recently developed, novel ECG analysis algorithm. Applying this algorithm to our cohort, the discrepancy between automatic and manual QT-interval and QTc assessments was markedly smaller, narrowing the range recommended for manual review 1.57-fold compared with vendor-provided automatic measurements. Pending independent validation, we envision future improvements in automatic QT-interval measurements including the application of artificial intelligence will further narrow and eventually close the range for manual QTc reassessment.

Link to full article

Neumann B, Vink AS, Hermans BJM, Lieve KVV, Cömert D, Beckmann BM, Clur SB, Blom NA, Delhaas T, Wilde AAM, Kääb S, Postema PG, Sinner MF. Manual versus Automatic Assessment of the QT-Interval and QTc. Europace 25, 1-12, 2023. PMID: 37470430.