Manual QT interval measurement with a smartphone-operated single-lead ECG versus 12-lead ECG: a within-patient diagnostic validation study in primary care

Abstract

ObjectiveTo determine the accuracy of QT measurement in a smartphone-operated, single-lead ECG (1L-ECG) device (AliveCor KardiaMobile 1L).DesignCross-sectional, within-patient diagnostic validation study.Setting/participantsPatients underwent a 12-lead ECG (12L-ECG) for any non-acute indication in primary care, April 2017–July 2018.InterventionSimultaneous recording of 1L-ECGs and 12L-ECGs with blinded manual QT assessment.Outcomes of interest(1) Difference in QT interval in milliseconds (ms) between the devices; (2) measurement agreement between the devices (excellent agreement <20 ms and clinically acceptable agreement <40 ms absolute difference); (3) sensitivity and specificity for detection of extreme QTc (short (≤340 ms) or long (≥480 ms)), on 1L-ECGs versus 12L-ECGs as reference standard. In case of significant discrepancy between lead I/II of 12L-ECGs and 1L-ECGs, we developed a correction tool by adding the difference between QT measurements of 12L-ECG and 1L-ECGs.Results250 ECGs of 125 patients were included. The mean QTc interval, using Bazett’s formula (QTcB), was 393±25 ms (mean±SD) in 1L-ECGs and 392±27 ms in lead I of 12L-ECGs, a mean difference of 1±21 ms, which was not statistically different (paired t-test (p=0.51) and Bland Altman method (p=0.23)). In terms of agreement between 1L-ECGs and lead I, QTcB had excellent agreement in 66.9% and clinically acceptable agreement in 93.4% of observations. The sensitivity and specificity of detecting extreme QTc were 0% and 99.2%, respectively. The comparison of 1L-ECG QTcB with lead II of 12L-ECGs showed a significant difference (p=<0.01), but when using a correction factor (+9 ms) this difference was cancelled (paired t-test (p=0.43) or Bland Altman test (p=0.57)). Moreover, it led to improved rates of excellent (71.3%) and clinically acceptable (94.3%) agreement.ConclusionSmartphone-operated 1L-ECGs can be used to accurately measure the QTc interval compared with simultaneously obtained 12L-ECGs in a primary care population. This may provide an opportunity for monitoring the effects of potential QTc-prolonging medications.

Comparison of AliveCor KardiaMobile Six-Lead ECG with Standard ECG in Pediatric Patients

“…The QRS results were slightly better than in our study, with a mean difference of -3 ms and a standard deviation of 7 ms (margin of error 14 ms) [12]. Our study's agreement rate of ACKM QTc measurements with 20 ms of the standard ECG was only slightly lower (64%) than those reported by Garabelli et al and Beers et al (72% each) [9,13].…”

Should all electrocardiography be ambulatory?

“…The QT interval was 396 ± 30 and 395 ± 30 ms in lead I of the mECG and 12-lead ECG, respectively. The mean absolute QT interval difference using lead I was 14 ± 13 ms, and 44% of the patients showed a < 10 ms difference in this lead, whereas the mean absolute difference in lead II was 12 ± 9 ms (< 10 ms difference in 55% of subjects), which was similar to a previous QT interval comparison between a single-lead mECG and conventional ECG [ 8 ]. In patients with QT prolongation > 480 ms, the sensitivity and specificity for QT prolongation were 80% and 99%, respectively.…”

Smart devices to measure and monitor QT intervals

“…QT intervals were significantly ( p < 0.001) shorter in the KardiaMobile 6-lead ECG than in the 12-lead ECG. Beers et al ( 31 ) determined the accuracy of QT measured by KM-1l in 125 patients. These patients had a non-acute indication for a 12-lead ECG.…”