Detecting a sound heartbeat.At roughly one beat per second, the rhythm of the human heart can serve as a reasonably steady timekeeper. Subtle variations in that rhythm, however, may signal whether or not a heart is healthy. Reporting in the Sept. 26 Nature, Plamen C. Ivanov of Boston University Boston University, at Boston, Mass.; coeducational; founded 1839, chartered 1869, first baccalaureate granted 1871. It is composed of 16 schools and colleges. and his coworkers have developed a mathematical technique for finding patterns in a sequence of beat-to-beat intervals. These patterns enable the researchers to distinguish between healthy people and those suffering from certain heart irregularities. Ivanov and his colleagues start by measuring for each person the time intervals between successive beats on an electrocardiogram electrocardiogram /elec·tro·car·dio·gram/ (-kahr´de-o-gram?) a graphic tracing of the variations in electrical potential caused by the excitation of the heart muscle and detected at the body surface. (EKG EKG: see electrocardiography. ). These values, derived from 6 hours of heartbeat data, are then plotted against time (top). The researchers use a technique, based on mathematical forms called wavelets See wavelet compression. Wavelets The elementary building blocks in a mathematical tool for analyzing functions. The functions can be very diverse; examples are solutions of a differential equation, and one- and two-dimensional signals. , that enables them to identify large-scale patterns even when the signals change as a result of background influences. For a healthy heart, these correlations appear as arches in plots displaying the wavelet (mathematics) wavelet - A waveform that is bounded in both frequency and duration. Wavelet tranforms provide an alternative to more traditional Fourier transforms used for analysing waveforms, e.g. sound. analysis (bottom). Data from sick hearts lack these arches. - I. Peterson |
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