A single-lead handheld electrocardiogram (ECG) device was found to achieve reproducible measurements of QTc intervals, through the capture of multiple vectors — not a single lead, according to an article published in the Journal of the American College of Cardiology: Clinical Electrophysiology.

The coronavirus disease 2019 (COVID-19) is a global pandemic that is wreaking havoc on human health, leading to increased interest in using off-label medications, including drugs which have been shown to prolong the QT interval (eg, hydroxychloroquine and azithromycin). In this study, researchers investigated the handheld ECG device and standard 12-lead ECG QT intervals in patients being evaluated for an inherited arrhythmia syndrome.

A total of 22 individuals (median age, 38 years; 32% women) were enrolled in this prospective study. Participants were evaluated with 12-lead ECG, and underwent cardiac imaging, and treadmill and genetic (if applicable) testing. Subsequently, patients recorded sequential single-lead ECGs in the lead I, lead II, and precordial lead positions using a handheld ECG device. The precordial lead ECG was recorded on the upper precordium. The longest QT interval measured across all leads in the 12-lead ECG was used.


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QTc intervals were found to be measured reproducibly using a single-lead handheld device. However, their measurement required capture of multiple vectors with the handheld device. The median QRS duration was 92 ms (interquartile range [IQR], 89-103), and the median QTc interval measured with the 12-lead ECG was 400 ms (IQR, 385-414). The median QTc interval measured by the handheld device in leads I, II, and in the precordial lead were 360 ms (IQR, 344-376), 366 ms (IQR, 354-386), and 354 ms (IQR, 340- 392), respectively. The QTc intervals were comparable when measured using the 12-lead ECG vs the handheld device across multiple positions (401 vs 404 ms, respectively; P =.259). However, QTc measured using the 12-lead ECG was consistently longer than the QTc interval measured in any single lead position alone. Lastly, the longest QTc intervals recorded using the 12-lead ECG were often in the precordial leads.

Limitations of the study include the small sample size, and a possible under-reporting of the QTc interval resulting from measurements in a single lead.

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“It is appealing to use the handheld ECG device as a QT screening tool in patients with COVID-19,” noted the study authors. “In the context of off-label medications that prolong the QT interval, handheld devices should be used in multiple lead positions to determine baseline QTc intervals. The practical application of these results is to perform a 12-lead ECG, multi-lead handheld ECG, or single-lead handheld ECG in at least three lead positions.”

Reference

Cheung CC, Davies B, Gibbs K, Laksman ZW, Krahn AD. Multi-lead QT screening is necessary for QT measurement: Implications for management of patients in the COVID-19 era (published online April 7, 2020).  J Am Coll Cardiol EP. doi:10.1016/j.jacep.2020.04.001