Optimization of heartbeat detection based on clustering and multimethod approach

In this paper, an approach for optimizing heartbeat locations as detected in time by multimethod approach is proposed. The approach builds a two-dimensional representation of heartbeat locations obtained by several independent detection methods. The representation depends on heartbeat time instants and beat-to-beat intervals. It is first transformed into a smoothed two-dimensional histogram of points indicating individual heartbeat detections. Heartbeat time instants are determined as local maxima in the histogram. We tested our approach on signals acquired by optical interferometer. Seven subjects participated in the experiment, beginning by an ergometer exercise until they reached submaximal heart rate. A resting period followed, during which optical interferometric signal was taken unobtrusively in parallel with referential ECG. The proposed detection procedure was capable of tracking the changing heart rhythm by analyzing optical interferometric signals and comparing the results to the referential ECG recordings. Sensitivity 97.13±2.00% and precision 97.82±2.09% were obtained. Mean absolute error between detected beat-to-beat and referential RR intervals yielded 20.05±8.38 ms and corresponding mean relative error 7.47±3.19%.