Ability of new heart rate monitors to measure normal and abnormal heart rate

The extended use of heart rate monitors to non sportive people, and older ones increases the risk to be facing heart rate troubles. Questions exist upon the ability of this devices to detect such abnormalities. The purpose of the investigation was to evaluate the accuracy of two third generation heart rate monitors, Accurex Plus and Vantage NV and to compared these data with those of an older one, PE 4000. Then we investigate responses of this monitors to abnormal heart rate.

The three heart rate monitors were tested in the laboratory, wired in parallel to an ECG simulator under two modes: a normal heart rate program (7 stable heart rate stages with two marked transitions) and an automatic arrhythmia one.

1st program: Values generated by the ECG simulator were compared to the values produced by the three devices. Particular attention was paid to the transition phases (heart rate drop and heart rate fall). Results of heart rate monitors accuracy were expressed at the exact value (devices value=simulator value) and at approximated value of +/-3 beats x min(-1) (devices value=simulator value +/-3 beats x min(-1)); 2nd program: Abnormal rhythms were analysed using an ambulatory ECG recorder (Synésis) as control data, and compared to the data from the three devices.

Correlation between simulator generated true values and HRMs read values were calculated.

In the 1st normal heart rate program, with an accuracy of exact value, Accurex Plus and Vantage NV, were more accurate than the PE 4000 (94% and 89% of values respectively versus 33% for the PE4000). At +/-3 beats x min(-1), the three devices gave good results: over 98% of total values. In transition phases: the three devices showed a smoothing effect, which was stronger in decelerating heart rate than in accelerating heart rate. In the 2nd program: isolated heart rhythm troubles (missing beat, pause <4 sec, supra-ventricular ectopic activity, and ventricular ectopic activity) were either not detected or were rejected. Signal changes such as changes in QRS (ventricular bigeminy) may cause detection losses, and so modify calculated heart rate. The HR signal rising/dropping slopes caused by sudden heart rhythm disorders, were notably attenuated, with a consequent loss of HR accuracy.

In laboratory stable heart rate conditions, third generation HRMs are more accurate than earlier ones. Heart rate monitors are less accurate in transient phases and have not been improved in that domain. The three HRMs ignore isolated heart rate troubles. As expected, the usefulness of HRMs in detecting HR disorders is limited. Nevertheless, these devices have some value with serious troubles, like pause, bradycardia or tachycardia, lasting longer than 4 sec, and especially if they coincide with functional symptoms. The use of such even more accurate devices may consequently be recommended to healthy public for which they were built.