How the model works
Pulse amplification, transit delay and damping are display measurements, not new diseases.
The peripheral arterial line is derived from central aortic pressure with representative transit and pulse amplification. Central and peripheral systolic/pulse pressures can differ while their mean pressures remain close in the model.
Overdamping and underdamping are applied to the recording, separately from the patient’s circulation. Selecting a transducer artifact does not change true forward output, ventricular loading or a valve lesion.
The peripheral model modifies pulsatile content and timing, with disease/support-specific limits. Low-output and continuous-flow traces are not normalized to a healthy pulse height. Central pressure remains the reference for LV–aortic gradients.
Amplification is a representative transfer relationship, not an arterial tree with measured age, stiffness, catheter site or wave-reflection distances. Femoral pressure in the Carabello study serves a separate comparison.
A unity-DC-gain second-order filter illustrates catheter/transducer response. Overdamped settings use a 3 Hz natural frequency and damping ratio 1.6; underdamped settings use 6 Hz and 0.14. Filtering runs at 500 Hz in deterministic two-second chunks with a four-second warm-up. These settings are teaching choices, not clinical device calibration.
Overdamping rounds the upstroke, reduces peaks and raises troughs. Underdamping rings and exaggerates extrema. A constant pressure remains constant; the filter’s purpose is to preserve the mean/DC component while changing dynamic detail.
Clinical Controls → Display & ECG → Catheter Artifacts applies None, Catheter Whip, Overdamped or Underdamped to RA, RV, PA, PAWP and LV recordings, including the overlay and LV/LVOT pullback segments. It is separate from Arterial Line Response. The same selection and clock are shared with students. Canonical teaching-case recordings remain fixed; this selector is available in the sandbox.
Classic RV/PA catheter whip is an early-systolic spike from catheter motion/contact. The synthetic pulse is centered at cardiac phase 0.225, with a width capped at 12 ms. Its positive and negative portions nearly cancel over a complete beat. Illustrative peak scales are RA 4, RV 18, PA 16, PAWP 5 and LV 24 mmHg, multiplied by the recorded native pulse range relative to 6, 25, 15, 8 and 100 mmHg respectively, capped at 1.4. These are teaching coefficients, not measured device behavior. Smaller RA/PAWP motion and LV catheter motion are illustrative extensions of the RV/PA example.
The artifact follows the deterministic ventricular beat schedule, including irregular beats. It is absent during modeled missing beats, zero rate, VF and a truly constant-pressure signal. Its values are repeatable when paused or scrubbed. Recorded trace numbers and overlay gaps include distortion; the hemodynamic table, Wiggers and PV loops keep the underlying physiology. Pause and inspect the trace for an artifact explanation. None or Reset restores the clean recording.
Compare an artifact with a correctly damped reference before interpreting peaks or apparent gradients. Whip amplitude and timing are schematic; the model does not reproduce a specific catheter, contact location, tubing length, air bubble, flush, leveling/zeroing error or frequency-response test.
