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An Open-Source Standard T-Wave Alternans Detector for Benchmarking

An Open-Source Standard T-Wave Alternans Detector for Benchmarking. S.Nemati Massachusetts Institute of Technology (MIT). G.D.Clifford M IT, Harvard-MIT Division of Health Sciences and Technology (HST). A.Khaustov St.-Petersburg Institute of Cardiological Technics (Incart). Open Source.

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An Open-Source Standard T-Wave Alternans Detector for Benchmarking

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  1. An Open-Source Standard T-WaveAlternans Detector for Benchmarking S.Nemati Massachusetts Institute of Technology (MIT) G.D.Clifford MIT, Harvard-MIT Division of Health Sciences and Technology (HST) A.Khaustov St.-Petersburg Institute of Cardiological Technics (Incart)

  2. Open Source ? = Solution - an open source algorithm • detailed • repeatable The software is at www.physionet.org/challenge/2008/ ?

  3. Preprocessing • Baseline wander filtration • QRS and T detection • Independent QRS and T alignment • Abnormal, noisy beat rejection via cross-correlation on QS and ST-T segments QT variation necessitates alignment on ST-T segment (sample from a real record) Aligned T waves A – even B – odd

  4. Spectral method (SM) Successive beats Alternans series Averaged periodogram Periodogram for a point on ST-T

  5. Modified Moving Average (MMA) • ‘Continuous’ estimate (vs 128 beat segment in SM) • Maximum difference on ST-T (vs averaging in SM) Even vs odd average Alternans trend

  6. Tests on synthetic data TWA amplitudes were 2, 4, 6, 8, 10, 16, 22, 28, 34, 40, 60 mV Maximum error after scaling: • Clean records – all methods better than 2 mV • White noise with standard deviation of 5, 10, 20, 30, 40 mV • SM ‘standard’ better than 6 mV, SM ‘differences’ better than 5 mV where successful (TWA greater than 0.35*noise level) • MMA better than 5 mV where SM is successful; fails to reject low TWA/noise ratio • All methods improve as noise decreases and TWA increases • Baseline wander (NST DB) added – all methods better than 7 mV Tests on CinC challenge data • Possible global bias in challenge results Challenge score and maximum error on synthetic records after scaling: • SM ‘differences’ – 0.881 (third in challenge) and 8 mV • SM ‘standard’ – 0.880and 10 mV • MMA – 0.400 and 12 mV (0.834 with SM as noise detector!)

  7. To Do • Noise vs TWA estimation for MMA • Determining noise floor • HR interval selection • Periodogram normalization (TWA in mV) • TWA interpretation: positive, negative, indeterminate • Lead-specific requirements • TWA: from separate leads to ‘space’?

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