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PubMedDate not supplied

[The variability of the QRS loop in the orthogonal lead system of frank and schmitt (SVEC III) (author's transl)].

A method has been previously described, to test the accuracy of lead fields. This method is used here to compare in 7 persons the relative validity of the two orthogonal lead systems of Frank and Schmitt (SVECC III). The variables the variation of which characterizes the validity of the systems, are the spatial position (represented by the spatial angles of the normal of the broadside view) and the variations in shape of the vector loops. The latter are measured by a comparison of the length of vectors in a distance of 5 degrees, starting with the maximal vector and proceeding from here to both sides. The vectors of loops in two different heart positions are compared by means of their correlation coefficients, and one of the loops is rotated in space as long as this correlation coefficient reaches a maximum. The data are handled by a computer. The optimal correlation coefficients, the regression coefficients and the differences in the spatial angles of the planes, in which the loops show their broadside view, are compared. The Frank system has a significantly lower variability of these values, by extreme dislocations of the heart, either by respiratory or by positional dislocations.

Adult↗
PubMedDate not supplied

[New functions and variables to characterize and compare vectorcardiograms (author's transl)].

1. The variability of electrographic data used up to now is too large to discriminate easily between normal and abnormal. 2. This variability is partly caused by errors in the measuring process and its consequences. A sepcial difficulty is found in determining the beginning and the end of QRS, so that instantaneous vector magnitudes related to the starting or ending moment of QRS will have a high variance and therefore a low comparability. Displacements of the heart will play an important role as a source of errors. 3. It therefore seems to be more appropriate to describe structure and changes in time of the vector loop. To this end 3 new functions v, w and u are described, all three invariant towards positional changes of the heart in space. The term v means a time-dependent function describing the first derivative of the length of the instantaneous resulting vector of all electrical sources. The term w indicates the projection of the first derivative of the instantaneous vector into a plane orthogonal to the resulting vector. Therefore, v is dependent on the change of all resulting electrical forces, whereas w is the velocity of the peak of the resulting vector on its way along the vector loop. The interpretation of u is complicated; u is a measure of how much the vector leaves a plane, in which it normally more or less remains; u is therefore a measure for the edgeside view of the vector loop. 4 These data are combined with the well-known vectorial data to form a system of vectorial description. 5 The interpretability of these data in physiological terms is exemplified. The description presented here allows to go back to cardiac processes in the proper sense and to largely elimenate external influences like those of the thoracic shape on the ecg and vcg. 6. This way of describing an ecg is specially adapted to the discrimination of normal and abnormal in preventive tests.

Adult↗
PubMedDate not supplied

Investigation of Frank's vectorcardiographic lead system on homogeneous rabbit torso model.

The applicability of Frank's lead system in experiments on rabbits is studied by using a homogeneous rabbit torso model. The influence of dipole localization on the modules of the lead vectors at the level of 4th, 5th and 6th intercostal spaces is studied. The lead vector modules along the axes X, Y and Z for the level of the dipole are calculated to be equal to 1:0.99:0.92. The maximum angular errors in the planes XY, XZ and YZ are calculated, being for the same level theta yz = -6 degrees 50', theta xy = theta xz = 0 degrees 00'. The authors have reached the conclusion that Frank's system produces good levelling of the lead vector modules and has satisfactory orthogonality on rabbit torso model.

Animals↗
PubMed2003

Detection of body position changes using the surface electrocardiogram.

A method for detecting body position changes that uses the surface vectorcardiogram (VCG) is presented. Such changes are often manifested as sudden shifts in the electrical axis of the heart and can erroneously be interpreted as acute ischaemic events. Axis shifts were detected by analysing the rotation angles obtained from the alignment of successive VCG loops to a reference loop. Following the rejection of angles originating from noise events, the detection of body position changes was performed on the angle series using a Bayesian approach. On a database of ECG recordings from normal subjects performing a predefined sequence of body position changes, a detection rate of 92% and a false alarm rate of 7% was achieved.

Adult↗
PubMed1989

Dipole moment of in vivo and isolated perfused rabbit hearts.

We have measured magnitude and location of heart dipole moment during QRS in 46 New Zealand white rabbits. The spatial magnitude curve had one to three peaks. Mean values were M1 = 80 +/- 10 microA-cm (N = 5) pointing to right anterior and caudal, M2 = 260 +/- 15 microA-cm (N = 42) directed slightly to left of due anterior and caudal, and M3 = 236 +/- 9 microA-cm (N = 43) pointing towards left posterior and cephalad. The mean thorax resistivity was 250 ohm-cm. For 23 rabbits, M2/M3 greater than 1 and for 16 rabbits, M2/M3 less than 1. Mean times of occurrence of the three peaks were 5.8, 11.2, and 19.6 ms, respectively. Spatial magnitude curves for hearts perfused at the center of a sphere showed usually one major peak at about 19 ms. Locuscardiograms of in vivo hearts were also measured. By comparing M values for in vivo and isolated hearts, we found that M1 values agreed closely but mean M2 measured from the hearts in vivo was 2.5 times that for the isolated hearts, and M3 for in vivo hearts was about two-thirds that for isolated hearts. We relate these differences to the effects of intracardiac blood and lungs on the measured dipole moment.

Animals↗
PubMed1986

Frank vectorcardiograms during the first year of life: a longitudinal study of 62 healthy children.

A longitudinal vectorcardiographic study of 62 healthy children was carried out at the ages of one and six days and 1, 2, 4, 6, 9, and 12 months. Recordings were made using the Frank x, y, and z leads and the equipment developed by Arvedson [2]. In each age group 25 spatial vectors were examined. Planar projections of 13 timed QRS vectors were presented as mean QRS loops in the main planes. The results were in agreement with earlier studies but gave a more accurate representation of cardiac activation. The maximal spatial vectors to the right and to the left, the 0.035 and 0.04, the mean QRS and the partial mean 2/3 QRS vectors clearly reflected a decrease in right ventricular dominance during the first two months and an increase in left ventricular dominance during the first year. Vectorcardiographic development in each child, from the newborn pattern onward, occurred individually. None of the 12 vectors examined on 22 children from whom there were recordings in each age group from one day to nine months by the Spearman rank correlation test revealed any significant correlation.

Child Development↗