We test the accuracy of two third generation heart rate monitors (HRM), Accurex Plus and Vantage NV and compare these data with those of an older monitor, PE 4000. Then we investigate responses of the HRM's to abnormal heart rhythms (HR). Accurex Plus and Vantage NV, and PE 4000 were tested in the laboratory under both stable and transient conditions. The Phantom 320 HR simulator gave 7 stable heart rates, each lasting 3 min. The responses of the HRM's to abnormal heart rhythms were tested with an automatic arrhythmia program lasting 17 min. The new HRM's, Accurex Plus and Vantage NV, were more accurate (89 to 94% and over 98% at +/-3 beats per min) in the stable state than the PE 4000. They all showed a smoothing effect in transient measurements, which was stronger in decelerating HR (1(st) case) than in accelerating HR (2(nd) case). - 1(st) case: Accurex Plus Vantage NV PE 4000 - 2(nd) case: PE 4000 Accurex Vantage. Most isolated heart rhythm disorders (missing beat, pause 4 s, SVEA, and SVT) were either not detected or rejected. Signal changes such as changes in QRS (ventricular bigeminy) may cause detection losses, and so modify calculated heart rate. HR signal rising/dropping slopes caused by sudden heart rhythm disorders, was notably attenuated, with a consequent loss of HR accuracy. Although the usefulness of HRM's in detecting HR disorders is limited, they have some value with serious disorders, like pause 4 s, important bradycardia or tachycardia.
