Detect QRS Complexes in an ECG Signal (Pan-Tompkins Algorithm)

Detects R-peaks in a raw ECG signal using the Pan-Tompkins algorithm. Implements bandpass filtering, derivative, squaring, moving-average integration, and adaptive dual-threshold peak detection with T-wave rejection and search-back for missed beats.

Usage

detect_qrs(ecg, fs)

Arguments

ecg

Numeric vector. Raw ECG signal.

fs

Numeric. Sampling frequency in Hz. If ecg comes from read_philips_physlog(), use rec$HDR$sfreq.

Value

A list of class mrpheus_qrs with components:

qrs_i

Integer vector of R-peak sample indices (1-based), referenced to the bandpass-filtered signal.

qrs_amp

Numeric vector of R-wave amplitudes at each detected peak (normalised bandpass signal units).

delay

Numeric. Sample delay introduced by the moving-average stage (half the 150 ms window length).

fs

Numeric. Sampling frequency passed to the function.

Details

Processing pipeline (Pan & Tompkins, 1985):

1. Bandpass filter 5–15 Hz (Butterworth N=3). At fs = 200 Hz, implemented as separate 12 Hz low-pass then 5 Hz high-pass stages.

2. Derivative filter — 5-point kernel interpolated to match fs.

3. Squaring — non-linear emphasis of dominant peaks.

4. 150 ms moving-average integration.

5. Adaptive thresholding — dual-threshold scheme with T-wave rejection and search-back for missed beats (initialised on 2-second training window).

R-peak indices are returned relative to the bandpass-filtered signal. Account for delay if you need indices aligned to the raw ECG.

References

Pan J, Tompkins WJ. A real-time QRS detection algorithm. IEEE Trans Biomed Eng. 1985;32(3):230–236. doi:10.1109/TBME.1985.325532

See also

read_philips_physlog(), compute_hr_signal(), compute_hrv_sleep()

Examples

if (FALSE) { # \dontrun{
rec  <- read_philips_physlog("sub-01_physlog.log")
qrs  <- detect_qrs(rec$C[, "v1raw"], fs = rec$HDR$sfreq)
qrs

# Downstream HR signal
hr <- compute_hr_signal(qrs)
} # }