Technique for maximizing the frequency response of the signal averaged Frank vectorcardiogram

This system for signal averaging of the Frank vectorcardiogram incorporates several important features: 1, simultaneous analogue to digital conversion of three orthogonal leads; 2, interactive editing of the data; 3, optimization of the fiducial timing point using a template derived from the calculated QRS vector magnitude; and 4, simultaneous display of both the averaged recording and the noise level at high amplification, which facilitates the assessment of low amplitude signals in the ST segment. The effective frequency response of the system approached theoretical expectation and background noise was low. The effect of exclusion versus inclusion of the fiducial timing point optimizing routine in the signal averaging program was examined in 21 patients. Exclusion of the optimizing routine effectively reduced the high frequency response of the system at the -3dB point from 350 Hz to about 60 Hz. The QRS complex was prolonged, and attenuation and spreading of signals in the ST segment occurred so that some delayed potentials merged with background noise and were no longer visible. We conclude that the system has several theoretical and practical advantages when compared with other techniques. A major benefit is the inclusion of a routine to optimize the QRS fiducial timing point. This minimizes distortion and attenuation of signals in the ST segment, thereby enhancing the probability of detecting the signals.