A study on the evaluation of instantaneous heart rate estimation accuracy

研究成果の概要 (和文) : 心拍数は自律神経により制御され変化している。心拍数の考え方を精密化し各時刻における心拍数を定義し瞬時心拍数と呼ぶ。瞬時心拍数の周波数分布を調べることにより交感神経と副交感神経の働きの程度とバランスを知ることができる。様々瞬時周波数の推定方法が提案されているが推定精度の評価法が確立しておらず、どの方法が最適であるか定説に至っていない。本研究では新たな評価指標を導入し瞬時心拍数推定手法の比較を行った　研究成果の概要 (英文) : Heart rate is fluctuating due to the autonomic nervous activity. Spectral analysis of the heart rate variability has been known to be effective for noninvasive evaluation of the autonomic nervous activity. There are several methods to reconstruct the instantaneous heart rate signals from RR intervals, but researchers are selecting the method heuristically. This research intend to introduce indices to evaluate the accuracy of instantaneous heart rate reconstruction method. A new index named effective bandwidth has been shown to be effective for the evaluation. DCSI has been identified as the best heart rate reconstruction method but accompany the estimation bias at the high frequency region. The research found a blending method of DCSI and SIHR yielded a better estimation accuracy without any bias in estimated spectral pattern. The proposed method will be useful not only to evaluate the accuracy of the heart rate reconstruction accuracy but also useful to create new algorith

長時間心電図に基づく心臓突然死リスク評価：複数指標の併用による分類精度の向上

This study proposes a method of cardiac risk assessment based on the long term Holter ECG recordings. The risk assessment is important to prevent the sudden cardiac death incidents which are one of the major cause ofdeath worldwide, e.g. 70,000 in Japan and 400,000 in the U.S. annually. Conventional risk assessment indices are obtained by short term ECG record recorded at the clinical laboratory in the hospital. Such practice tend to miss important symptoms because of the short observation period. For that reason, characterization of the long term ECG record draw a considerable attention. This research adopted several such indices based on the long termECG record for the cardiac risk assessment. Namely, Indices based on QT and RR intervals, such as cRRI-QT, RRI-Amplitude, QT-Amplitude, QTc-Amplitude, SDNN and those based on T wave morphology as AR or ARPare introduced and examined. Logistic regression analysis is applied to those indices obtained from 11 cardiac high risk (SCD-H), 14 low-risk (SCD-L) patients and 25 control subjects (Control). It has been shown that the combination of RRI-amplitude, ARP and cRRI-QT yielded the best classification accuracy. Sensitivity andspecificity were larger than 0.8 except for SCD-L sensitivity being 0.7. The number of cases should be increased to validate the result.Key Words : SCD risk assessment, Holter ECG, T-wave alternans, Heart rate variability, QT-RR intervalco-variability, Logistic regression analysis

RR-QT Interval Trend Covariability for Sudden Cardiac Death Risk Stratification

This paper examines the feasibility of the trend covariability between QT and RR Intervals (QTIs and RRIs) be a novel mean of the sudden cardiac death (SCD) risk stratification. Twenty four hour beat to beat QTIs and RRIs are measured from Holter ECG recordings of 25 normal control subjects (SCD-C),14 low SCD risk patients (SCD-L) with high blood pressure or light cardiac arrhythmia and 11 SCD high risk patients (SCD-H) with heart attack history. The Kalman filtering technique has been applied to decompose 24 hour short term mean QTIs and RRIs sequences into trend components and additive random variations. The correlation coefficients (TC-QT/RR) and cross entropies (TE-QT/RR) between the QT and RR trend signals are estimated. Cross entropy TE-QT/RR achieved the best stratification of subject groups. TE-QT/RR distribution for SCD-C, -L –H subject groups were 1.697±0.058, 1.160±0.099, 0.920±0.067. The differences in entropy values are statistically significant for all classespairs (SCD–H and –C (p<0.00001); -L and –C (p<0.001); -H and –L (p<0.05) The result indicates that the TE-QT/RR could be a novel index for the SCD risk stratification