Kardia Mobile 6-Lead Applicability for Hydroxychloroquine Baseline ECG Testing and Monitoring in Systemic Lupus Erythematosus

Objectives Hydroxychloroquine is the first line treatment for systemic lupus erythematosus and is used to treat several other autoimmune conditions. One potential side effect is the prolongation of the QT interval, which can be monitored with a 12-lead ECG.[1] However, there are several barriers to obtaining ECGs and most patients do not receive one, despite the recognized risk.[2] An emerging solution is the use of mobile devices. The objective of this study is to evaluate and compare the accuracy and clinical utility of the 6-Lead KardiaMobile ECG device to the standard 12-lead ECG for monitoring QT interval in patients on hydroxychloroquine.

Methods 6-L KardiaMobile ECG readings were obtained from patients on hydroxychloroquine at the Ottawa Hospital Rheumatology Clinic, which involves a 30 second reading, holding the device with 2 thumbs on the left leg. 12-lead ECGs were recorded within a year of the KardiaMobile reading. A chart review was conducted for patients, and we extracted data related to age, sex, indication, dose and duration of use, concomitant QT-prolonging drug use, smoking, and QT interval length. Bland-Altman, paired t-tests, and Pearson correlation were performed using R.

Results KardiaMobile readings were obtained from 34 patients, of which 13 patients had corresponding ECGs. Mean QTcF measured using the KardiaMobile device was 12.2 ± 16.4 ms lower than the 12-Lead ECG. Bland-Altman analysis showed 95% limits of agreement from −44.3 ms to +19.8 ms, with no evidence of proportional bias across the QTcF range. QTcF values from both methods were moderately correlated (r = 0.69, p = 0.009). 69% of patients were taking at least 1 other QT-prolonging medication. The most common classes were proton pump inhibitors (34%) and antidepressants (26%). Variances between groups were analyzed, including dose, number of QT-prolonging medications, and time on hydroxychloroquine; no trends were identified. QTcF was moderately correlated with age (r = 0.50, p = 0.007).

Conclusion The KardiaMobile device shows mild underestimation of the QTcF interval in real world practice, however this discrepancy is small and unlikely to affect clinical decision-making. The difference was within the expected range of inter-method variability reported in previous validation studies. Additionally, the device was easy and feasible for patients to use. These findings suggest that mobile ECGs may provide a clinically acceptable alternative for QTcF monitoring in patients on HCQ, particularly in resource-limited settings, while considering its limitations in high-risk patients. However, more data are needed and patient recruitment is ongoing.

References [1.] Siegel C. JAMA 2024;331:1480-91. [2.] Choi M. Rheumatol Int 2022;42:1767-74.