To use smartphone applications (apps) to measure heart rates during supraventricular tachycardia (SVT) in pediatric patients and compare them with heart rates measured by standard electrocardiogram (ECG).

Patients <18 years of age (n = 26) undergoing an electrophysiology study were enrolled. During the study, heart rates were measured at baseline and during SVT by the use of 2 smartphone apps. The obtained heart rates were compared with a simultaneous standard ECG. Pearson correlation coefficient (r) was used to compare the accuracy of the apps with ECG.

At baseline, 33 heart rates were obtained with apps and all were within ±4 beats per minute (bpm) of the ECG heart rate. During SVT, 38 heart rate measurements were attempted during 21 SVT events in 18 patients. App 1 failed to provide a measured heart rate in 11 of 21 attempts. The 10 heart rates obtained had an r of 0.56. When tachycardia rates were <210 bpm, accuracy increased (r = 0.86) and when tachycardia rates were <200 bpm, the accuracy increased further (r = 0.99). App 2 failed to provide a measured heart rate in 12 of 17 attempts. The 5 heart rates obtained had an r of −0.43.

During tachycardia, neither of the 2 apps consistently determined an accurate heart rate at rates >200 bpm. The apps tested should not be considered an accurate tool for assessment of heart rates during SVT in pediatric patients. Select apps may have utility detecting slower SVT or confirming normal heart rates with further validation.