Biomedical Engineering Application Brief

Cardiology

The Solution

Dr. Evans's team uses the graphic display data processing software DADiSP, by DSP Development Corporation, to meet their data processing needs. Dr. Evans states, "The use of DADiSP has dramatically decreased the time spent extracting and analyzing data, markedly increasing research output. Since more research means more patients helped, DADiSP is a vital part of Dr. Evans's team.

Multiple Channels

To record the signal from an arrhythmia patient's heart, Dr. Evans inserts a small catheter with a wire tip into the heart, an operation so exacting that it has to be done under x-ray guidance. The signal from the beating heart is recorded by an EP Lab System, a cardiac mapping system manufactured by Bard. This device digitizes and displays in real time 20 channels of data from the waveforms being picked up inside the heart, stores them to optical disk, and sends them to a chart recorder which records them on paper. Only three or four of the 20 recorded channels are necessary, so these are put into a single binary file by an application supplied by Bard for this purpose and read directly into DADiSP.

Neural Network Preprocessing

DADiSP is used to extract and analyze relevant information from the cardiac signal. Since there are several types of arrhythmia, the analysis must yield the basic shape of a patient's heartbeat waveform for submission to the neural network, where its precise type is determined.

Heartbeat Peak Analysis

To begin the analysis, DADiSP pulls apart the binary file into separate channels, then gets the peaks of each individual heartbeat using a peak detection algorithm. Each peak is used as a guide for a first-approximation extraction of the significant part of the waveform surrounding it. The first derivative of the extracted data is taken, which permits a more accurate extraction of the original signal. The amplitude of the waveform has to be normalized, a process easily accomplished with DADiSP, so that amplitude differences will not interfere with the neural network's assessment of the overall shape. After this and several other steps, the waveform is concatenated with the rest of the extracted data to create the final data series. A long segment of cardiac electrical activity is now ready for submission to the neural network for evaluation of the type of arrhythmia present.

DADiSP - Simple, Powerful and Flexible

Dr. Evans says, "DADiSP is simplicity in itself to use." He appreciates the power and flexibility of DADiSP's many commands and simple command structure, and says he likes the fact that a change in one command or input parameter can enable DADiSP to accommodate a wide range of input data. He also appreciates how helpful the support staff at DSP have been in helping him set up and maintain his system.