In recent years Smartphone apps that allow you to self-assess and monitor heart rate and rhythm have multiplied. A quick search in the Apple or Google app stores easily returns dozens of solutions that can be installed on any smartphone. Although these applications can be useful, you should understand how they work and how reliable they are. This text refers only to smartphone applications that do not require peripherals. Read about the so-called wearables, such as the Apple Watch, Fitbit, among others, which have other functionalities . How do apps that measure heart rate work? Applications that assess heart rate and rhythm and that can be installed on any smartphone, work with photoplethysmography . This technology identifies changes in light absorption by the tissues, which allows to measure, indirectly, variations in the blood volume of the arteries and capillaries. The cardiac activity evaluated by the apps using photoplethysmography, is measured indirectly through the pulse of our arteries and capillaries and not through the cardiac electrical activity, like is done, for example, on an electrocardiogram. Depending on the app used, heart rate and rhythm measurement can be done by: Capillary analysis by contact, that is, placing a finger on the smartphone camera; Facial recognition, pointing the camera at the face. Apps that work by contact, have shown to be more reliable in measuring heart rate. Are these applications reliable? These apps are very reliable at measuring heart rate (number of heartbeats per minute). When compared to a conventional electrocardiogram, the variations are 2 to 8 beats per minute. However, there are multiple artifacts that can interfere with the measurement , such as: Pressure applied to the finger contact; Light intensity in the place; Movement; Skin tone. So, when in doubt, it may be necessary to validate the results found with other types of equipment, or even with manual palpation of the wrist. Another limitation is the use of these applications during exercise , in which the measurement of heart rate can be unreliable. For this reason, they should not be used to monitor the pulse during physical training. In addition to heart rate measurement, some apps also detect changes in heart rhythm ( arrhythmias ). However, in most cases, it is not possible to identify the type of arrhythmia in question. To do this, other tests are necessary, like an electrocardiogram or a 24-hour Holter. Choose an app to measure heart rate and rhythm If you want to try, Cardiio or Fibricheck are examples of applications that have been tested and validated to measure heart rate and detect arrhythmias. Also remember: Any abnormal results that an application identifies should be discussed with your doctor and it may be necessary to perform some additional diagnostic tests for a clinical suspicion. In addition to measuring heart rate and detecting arrhythmias, smartphone apps should not be used for measuring blood pressure or diagnosing heart disease . In these cases, depending on the objective, complementing the application with properly certified and validated peripherals - wearables - may be an option. References Chan PH, Wong CK, Poh YC, Pun L, Leung WW, Wong YF, et al. Diagnostic performance of a smartphone-based photoplethysmographic application for atrial fibrillation screening in a primary care setting . J Am Heart Assoc 2016;5:e003428. Li KHC, White FA, Tipoe T, Liu T, Wong MCS, Jesuthasan A, et al. T he current state of mobile phone apps for monitoring heart rate, heart rate variability, and atrial fibrillation: Narrative review . JMRI 2019;7:e11606. Proesmans T, Mortelmans C, Van Haelst R, Verbrugge F, Vandervoort P, Vaes B. Mobile phone-based use of the photoplethysmography technique to detect atrial fibrillation in primary care: Diagnostic accuracy study of the FibriCheck App . JMRI 2019;7:e12284 Sana F, Isselbacher EM, Singh JP, Heist EK, Pathik B, Armoundas AA. Wearable devices for ambulatory cardiac monitoring: JACC state-of-the-art review . J Am Coll Cardiol 2020;75:1582-92. Author : José Ferreira Santos November 2020 Meet the cardiology team from Hospital da Luz network. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
