Recurrence Plots and Cross Recurrence Plots

FASEB Journal, 23, LB89p. (2009) DOI:10.1096/fasebj.23.1_supplement.LB89

Recurrence quantification analysis (RQA) used for detection of ST segment deviation

The current clinical gold standard for the detection of acute myocardial ischemia is ST segment deviation from baseline. Unfortunately, ST segment deviation as a marker for ischemia has well documented limitations. Recent studies have used RQA to quantitatively analyze changes in heart rate variability. The purpose of this study is to use nonlinear dynamical approaches, RQA, to test the hypothesis that R-R beat patterns are different in ischemia compared to control states. RR intervals were analyzed from 24hr ECG recordings of transient myocardial ischemia patients from PhysioNet's Long-term ST database. The CRP Toolbox was used for RQA computation. RQA parameters included: embedding dimension=4, time delay=4, window size=500, and radius .8. All RQA statistics for ischemic patients were compared to healthy controls, supine and tilt. Results show that %recurrence (2±1 vs. 15±5, mean±SD), %determinism (0.5±0.28 vs. 0.95±0.04), and entropy (1.04±0.69 vs. 2.61±0.55, mean±SD) are significantly elevated in ischemia patients during ST deviation compared to healthy controls. Furthermore, these same RQA statistics reveal significant differences between ischemia with ST segment elevation and ∼1.5hrs pre-ischemia. This study suggests that RQA can be used to detect ischemia without the use of the current clinical gold standard ST deviation.