Evaluation of heart rate changes: electrocardiographic versus photoplethys-mographic methods

Abstract

The heart rate (HR) variation to forced deep breathing (HR_DB) and to the Valsalva maneuver (Valsalva ratio; VR) are the two most widely used tests of cardiovagal function in human subjects. The HR is derived from a continuously running electrocardiographic (ECG) recoding. Recently, HR derived from the arterial waveform became available on the Finapres device (Finap_HR), but its ability to detect rapid changes in HR remains uncertain. We therefore evaluated HR_DB and VR derived from Finap_HR using ECG-derived HR (ECG_HR) recordings as the standard. We also compared the averaged HR on Finapres (Finap_av) with beat-to-beat Finapres (Finap_BB) values. Studies were undertaken in 12 subjects with large HR variations: age, 34.5±9.3 (SD) years; six males and six females. Finap_BB values were superimposable upon ECG_HR for both HR_DB and VR. In contrast, Finap_av failed to follow ECG_HR for HR_DB and followed HR_ECG with a lag for the VR. To evaluate statistically how closely Finap_HR approximated ECG_HR, we undertook regression analysis, using mean values for each subject. To compare the two methods, we evaluated the signifiance of the difference between test and standard values. For HR_DB, Finap_BB reproducibly recorded HR (R²=0.998), and was significantly (p=0.001) better than Finap_av (R²=0.616;p<0.001). For VR, HR_BB generated a VR that was not significantly different from the correct values, while HR_av generated a value that was slightly but consistently lower than the correct values (p<0.001). We conclude that Finap_HR reliably records HR variations in the beat-to-beat mode for cardiovascular HR tests.