Electrocardiology Adv. Cardiol., vol. 16, pp. 98-101 (Karger, Basel 1976)
Data-Reduced Surface Potential Map Display Methods 1,2 E. J. FISCHMANN, G. H. WEISS, S. WEINSTEIN, P. P. MEHROTRA and M. L. McNEEL Howard University, Washington, D. c.; John Hopkins University, Baltimore, Md., and National Institutes of Health, Bethesda, Md.
1 Abstract of paper presented at the First International Congress on Electrocardiology (15th Symposium on Vectorcardiography), Wiesbaden 1974. 2 Supported by grant RRO-QS016 from the National Institutes of Health and grant N6R 09-011-055 from the National Aeronautics and Space Administration.
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Conventional electrocardiography and vectorcardiography show significant limitations in terms of false positive and false negative diagnoses. Some of the most widely used Q wave criteria in myocardial infarction for instance show 25-50% false positives in anatomically controlled studies. Total surface potential maps have yielded valuable information about cardiac excitation. It seems that, when available for wider use, they will also offer practical diagnostic advantages over the conventional ECG. We attempted a stepwise reduction of QRS maps to a point where increased diagnostic efficiency and a view of excitation are both preserved, while using a clinically feasible system of smaller electrode numbers and a relatively familiar, easily obtained display. The multiple surface potential measurements needed for this experiment were obtained from patients directly, or from the taped and digitized data in the University of Alabama Data Bank [1]. The reduction was a combined stepwise man-machine operation. Data processing and plotting was by machine. Whether a new reduced display still had meaning in terms of cardiac excitation had to be a man-made decision between stages.
FISCHMANN
99
et al.
Three-Belt, 54-Electrode Display of Raw Potential Data A schematic representation of a three-dimensional Q RS surface potential map shows that in essence the map consists of parallel electrode belts starting in the right axilla at V6R and returning over VI, V4, V6 and the back to V6R. The map is a set of potential against chest surface distance plots along the belts. Inspection suggests that after erasing 4 of the 7 belts of a map, the remaining 3 belts still retain an approximate image of the total map. We also have the advantage of a saving in electrodes, and of three familiar scalar curves for quantitation and display. Further experience indicated that using only the 1st and 3rd belt did not reduce diagnostic efficiency in MI. This left us with a system of 36 electrodes. Figure 1 shows the normal three belts, recorded at 8-msec intervals. The two verticals indicate VI and V6 positions. The back of the patient, --!_-++-+-4
4 t.IS
72 MS
6
------_/ .-- -- -',I
- -...--'00' MS
/::::-Jj '-~
/ - 8
4
4
96~
6
8
Fig. 1. Potential versus chest circumference curves of a normal subject recorded at 8-msec intervals during QRS, resulting in 12 instantaneous time frames. The numerals 4, 6 and 8 indicate the positions of the top, middle and lower belts, respectively. Each belt commences in the right midaxilla on the reader's left, and returns to right midaxilla on the reader's right. The two verticals indicate the VI and V6 positions. For interpretation of the curves see text.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 12:39:33 PM
4~4
FISCHMANN
100
beyond V6, is foreshortened in relation to the front. The main events of excitation can be followed. The initial frames show the anterior septal and right ventricular bulge with posterior negativity. Later frames show the gradual leftward drift of the bulge due to LV dominance, with terminal posterobasal dominance. Detail such as the Taccardi saddle and terminal crista-pulmonary conus activation is also indicated. Three abnormalities, all in the 24-, 32- and 40-msec frames, are encountered in MI. First, in the top belt the normal negativity on the back is replaced by positivity. The top belt, therefore, shows abnormal circumferential positivity. Second, in the bottom belt the normal anterior positivity is replaced by extensive anterior negativities. Third, the top or low belt curves show gross abnormal splintering. Energy Normalized Display of 24-,32- and 40-msec Frames
This display was obtained by polynomial interpolation and by scaling the area under each curve to unity. This reduces to a pure pattern representation, while quantitative voltage information is discarded. The reduction does not impair MI-normal discrimination. The display was introduced to test in MI some signal classification methods used in communications engineering. It is useful also for detecting pattern trends in related groups, and to scan for areas of normal-abnormal differences. Binary Display of 24-, 32- and 40-msec Frames
Further data compression is achieved by discarding shape as well as instantaneous voltage measurement and regress to a 'binary' plus-minus definition of 36 electrodes. The binary representation is the least costly and diagnostically most effective of the display still allowing a direct appreciation of how surface potentials are distributed. They also serve as a means of finding high-information areas and thus serve as a bridge to the most effective 7-electrode MI diagnostic method. Surface Map Representation by Seven Electrodes
Using binary plots MI patients could be separated into six abnormal groups. One such group for instance is identifiable as abnormal by the simultaneous positivity of electrodes V6R and V8R on belt I at 40 msec (fig. 2). All subjects showing this criterion had known MI and total circumferential positivity of the top belt at either 24, 32 or 40 msec. The V6R-V8R abnormality criterion was not found in normal subjects. There were six such 1-, 2- or 3-electrode abnormality criteria, each indicating either abnormal
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 12:39:33 PM
I
et at.
Data-Reduced Surface Potential Map Display Methods
101
Belt 1, 24 msec, V2 and V6 negative normal controls 001 003 006 007 009 010 012 015 020 023 024 042 046 062
11 11 11 11 11 11 11 11 11 11 11 11 11 11
+------++++++++---+++++++++++-----1 ++++++++++-----+++ -+++++++------1---++++1++++++-----++++++-+---+-----+++++++++++++---++ ------1--++1------+++++++-+-1+----------++++++++1+---+++++-------1---+++++++++++------++++++++++---------+++++++++-----V V 2 6
MI cases 067 110 124 127 177 182 289 298 449 470 473 615 617 622
11 11 11 11 11 11 11 11
11 11 11 11 11 11
------------------ '" ------------------ '" ------------1----- *
-----------------1 +1++--------11++++ +-------------+--+ -+-------+----+--------------++++-----------+--+---+ ----------------+---------+----------------------1-+-----------++++++
'"
* * * *
'"
* *
'"
*
------------------ '" V 2
V 6
Fig. 2. Comparing the binary display of surface potentials in normals and in MI. This display method considers only positivity or negativity of the voltage on each electrode. Simultaneous positivity of V6R and V8R on the top belt was found in the 19 MI cases shown; it was not seen in any of a normal series, of whom the 19 normals are a sample. Six such 2- or 3-electrode sets, made up of a total of seven electrodes gave over 90% sensitivity and specificity in MI diagnosis. 1 = missing electrode.
superior positivity or anterior negativity. A total of seven electrodes was required to define the six criteria. Used together they yielded sensitivity and specificity in excess of 90%. Since some of the six criteria had 0 or 1% false positives, over half of patients can be recognized at an unusually low false alarm risk.
References HOLT, J. H. jr.: BARNARD, A. C. L., and KRAMER, J.O. jr.: Quantitative electrocardiography using a mUltiple dipole method. Adv. Cardiol., vol. 16, pp. 117-120 (Karger, Basel 1976).
EUGENE J. FISCHMANN, MD, Department of Medicine, Freedmen's Hospital, 6th and Bryant Street NW, Washington, DC 20001 (USA)
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 12:39:33 PM
H.
Data-Reduced Surface Potential Map Display Methods 1,2 E. J. FISCHMANN, G. H. WEISS, S. WEINSTEIN, P. P. MEHROTRA and M. L. McNEEL Howard University, Washington, D. c.; John Hopkins University, Baltimore, Md., and National Institutes of Health, Bethesda, Md.
1 Abstract of paper presented at the First International Congress on Electrocardiology (15th Symposium on Vectorcardiography), Wiesbaden 1974. 2 Supported by grant RRO-QS016 from the National Institutes of Health and grant N6R 09-011-055 from the National Aeronautics and Space Administration.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 12:39:33 PM
Conventional electrocardiography and vectorcardiography show significant limitations in terms of false positive and false negative diagnoses. Some of the most widely used Q wave criteria in myocardial infarction for instance show 25-50% false positives in anatomically controlled studies. Total surface potential maps have yielded valuable information about cardiac excitation. It seems that, when available for wider use, they will also offer practical diagnostic advantages over the conventional ECG. We attempted a stepwise reduction of QRS maps to a point where increased diagnostic efficiency and a view of excitation are both preserved, while using a clinically feasible system of smaller electrode numbers and a relatively familiar, easily obtained display. The multiple surface potential measurements needed for this experiment were obtained from patients directly, or from the taped and digitized data in the University of Alabama Data Bank [1]. The reduction was a combined stepwise man-machine operation. Data processing and plotting was by machine. Whether a new reduced display still had meaning in terms of cardiac excitation had to be a man-made decision between stages.
FISCHMANN
99
et al.
Three-Belt, 54-Electrode Display of Raw Potential Data A schematic representation of a three-dimensional Q RS surface potential map shows that in essence the map consists of parallel electrode belts starting in the right axilla at V6R and returning over VI, V4, V6 and the back to V6R. The map is a set of potential against chest surface distance plots along the belts. Inspection suggests that after erasing 4 of the 7 belts of a map, the remaining 3 belts still retain an approximate image of the total map. We also have the advantage of a saving in electrodes, and of three familiar scalar curves for quantitation and display. Further experience indicated that using only the 1st and 3rd belt did not reduce diagnostic efficiency in MI. This left us with a system of 36 electrodes. Figure 1 shows the normal three belts, recorded at 8-msec intervals. The two verticals indicate VI and V6 positions. The back of the patient, --!_-++-+-4
4 t.IS
72 MS
6
------_/ .-- -- -',I
- -...--'00' MS
/::::-Jj '-~
/ - 8
4
4
96~
6
8
Fig. 1. Potential versus chest circumference curves of a normal subject recorded at 8-msec intervals during QRS, resulting in 12 instantaneous time frames. The numerals 4, 6 and 8 indicate the positions of the top, middle and lower belts, respectively. Each belt commences in the right midaxilla on the reader's left, and returns to right midaxilla on the reader's right. The two verticals indicate the VI and V6 positions. For interpretation of the curves see text.
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 12:39:33 PM
4~4
FISCHMANN
100
beyond V6, is foreshortened in relation to the front. The main events of excitation can be followed. The initial frames show the anterior septal and right ventricular bulge with posterior negativity. Later frames show the gradual leftward drift of the bulge due to LV dominance, with terminal posterobasal dominance. Detail such as the Taccardi saddle and terminal crista-pulmonary conus activation is also indicated. Three abnormalities, all in the 24-, 32- and 40-msec frames, are encountered in MI. First, in the top belt the normal negativity on the back is replaced by positivity. The top belt, therefore, shows abnormal circumferential positivity. Second, in the bottom belt the normal anterior positivity is replaced by extensive anterior negativities. Third, the top or low belt curves show gross abnormal splintering. Energy Normalized Display of 24-,32- and 40-msec Frames
This display was obtained by polynomial interpolation and by scaling the area under each curve to unity. This reduces to a pure pattern representation, while quantitative voltage information is discarded. The reduction does not impair MI-normal discrimination. The display was introduced to test in MI some signal classification methods used in communications engineering. It is useful also for detecting pattern trends in related groups, and to scan for areas of normal-abnormal differences. Binary Display of 24-, 32- and 40-msec Frames
Further data compression is achieved by discarding shape as well as instantaneous voltage measurement and regress to a 'binary' plus-minus definition of 36 electrodes. The binary representation is the least costly and diagnostically most effective of the display still allowing a direct appreciation of how surface potentials are distributed. They also serve as a means of finding high-information areas and thus serve as a bridge to the most effective 7-electrode MI diagnostic method. Surface Map Representation by Seven Electrodes
Using binary plots MI patients could be separated into six abnormal groups. One such group for instance is identifiable as abnormal by the simultaneous positivity of electrodes V6R and V8R on belt I at 40 msec (fig. 2). All subjects showing this criterion had known MI and total circumferential positivity of the top belt at either 24, 32 or 40 msec. The V6R-V8R abnormality criterion was not found in normal subjects. There were six such 1-, 2- or 3-electrode abnormality criteria, each indicating either abnormal
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 12:39:33 PM
I
et at.
Data-Reduced Surface Potential Map Display Methods
101
Belt 1, 24 msec, V2 and V6 negative normal controls 001 003 006 007 009 010 012 015 020 023 024 042 046 062
11 11 11 11 11 11 11 11 11 11 11 11 11 11
+------++++++++---+++++++++++-----1 ++++++++++-----+++ -+++++++------1---++++1++++++-----++++++-+---+-----+++++++++++++---++ ------1--++1------+++++++-+-1+----------++++++++1+---+++++-------1---+++++++++++------++++++++++---------+++++++++-----V V 2 6
MI cases 067 110 124 127 177 182 289 298 449 470 473 615 617 622
11 11 11 11 11 11 11 11
11 11 11 11 11 11
------------------ '" ------------------ '" ------------1----- *
-----------------1 +1++--------11++++ +-------------+--+ -+-------+----+--------------++++-----------+--+---+ ----------------+---------+----------------------1-+-----------++++++
'"
* * * *
'"
* *
'"
*
------------------ '" V 2
V 6
Fig. 2. Comparing the binary display of surface potentials in normals and in MI. This display method considers only positivity or negativity of the voltage on each electrode. Simultaneous positivity of V6R and V8R on the top belt was found in the 19 MI cases shown; it was not seen in any of a normal series, of whom the 19 normals are a sample. Six such 2- or 3-electrode sets, made up of a total of seven electrodes gave over 90% sensitivity and specificity in MI diagnosis. 1 = missing electrode.
superior positivity or anterior negativity. A total of seven electrodes was required to define the six criteria. Used together they yielded sensitivity and specificity in excess of 90%. Since some of the six criteria had 0 or 1% false positives, over half of patients can be recognized at an unusually low false alarm risk.
References HOLT, J. H. jr.: BARNARD, A. C. L., and KRAMER, J.O. jr.: Quantitative electrocardiography using a mUltiple dipole method. Adv. Cardiol., vol. 16, pp. 117-120 (Karger, Basel 1976).
EUGENE J. FISCHMANN, MD, Department of Medicine, Freedmen's Hospital, 6th and Bryant Street NW, Washington, DC 20001 (USA)
Downloaded by: University of Cambridge 131.111.164.128 - 3/20/2019 12:39:33 PM
H.
