Equivalence of analog and digital high-frequency electrocardiogram: validating Sydäntek for ischemia detection.

High-frequency electrocardiography (HF-ECG) enhances ischemia detection by capturing microvolt-level changes in the QRS complex; however, clinical adoption requires validating digital systems against Analog standards. We recorded HF-ECG signals simultaneously from 12 healthy subjects (84 beats total) using a five-stage Analog reference (100-500 Hz band-pass, gold connectors) and Sydäntek's 10× capacitive sensors; both outputs were digitized using a Texas Instruments ADS1298. Signals underwent 10× amplification with a low-noise op-amp, the Analog output was scaled to match, and data were processed in PulseTek™ and stored in PulseVault™. Root mean square (RMS), Amplitude, Kurtosis, and Frequency content were compared using Bland-Altman analysis (Analog as the reference); values reported reflect pre-amplified measurements in microvolts (µV). Mean differences between the Analog setup and Sydäntek fell within the 95% limits of agreement (LOA): RMS, 6.39 µV (- 49.74 to 62.52 µV); amplitude, 1.82 µV (- 57.09 to 60.73 µV); kurtosis, 1.93 (- 5.13 to 1.54); and frequency, 2.1 Hz (- 5.8 to 6.2 Hz), all within a 5% clinical tolerance when scaled 10× (~ 10-20 mV). Sydäntek matched analog fidelity, with frequency peaks near ~ 150 Hz, indicating digital HF-ECG performance equivalent to that of the Analog system on key metrics. Its wearable design and cloud integration provide a portable, reliable alternative for ischemia detection with broader clinical applicability.