The body surface isopotential mapping of the QRS wave in myocardial infarction. A comparative study of the scintigram with thallium-201

J. ELECTROCARDIOLOGY 15 (3), 1982, 241-248

The Body Surface Isopotential Mapping of the QRS Wave in Myocardial Infarction. A Comparative Study of the Scintigram with Thallium-201 BY SEIICHI

TOYAMA,M.D., KEIKO SUZUKI,M.D., MASAO KOYAMA,M.D., KoJI YOStIINO, M.D., AND K I Y O S t I I F U J I M O T O , M.D.

SUMMARY When body surface isopotential mapping (MAP) is used in clinical cases of myocardial infarction, it is necessary to determine the location of the infarcted area. The present authors presumed that the positive area of M A P in normal subjects, which was altered to a negative area of MAP in myocardial infarction, was the infarcted area. In order to confirm the presumed location of the infarcted area, the location of the infarcted area on M A P and the location of infarction presumed by the scintigram with thallium-201 ISCG) were compared. MAP was divi:ded into ten regions and a comparison between the presence or absence of an infarcted area in each segment on the M A P and of abnormal findings in each segment of the SCG was made. Consequently, the highest percentage of agreement in eachregion of the segment in SCG was picked up, and each region on MAP which corresponded to the segment in SCG was determined. Thereafter, each segment of MAP was matched with a wall of the ventricle: region 1 - - the septum; region 2 - - the apex; region 3 - - the anterior wall; region 4 -- the posterior portion of the apex; the upper portion of region 5 - - the lateral wall; region 6, 8 and 10 -- the inferior wall; and region 7 - - the posterior wall. In this way, the classification of myocardial infarction was carried out in 51 cases.

msec. from the beginning of the QRS wave were compared and the positive area before infarction, which was altered to a negative area after the infarction, was picked up. This area was located in the left precordial region, which corresponded to the location of the anterior infarction in that case (Fig. 1). Accordingly, in the present study, it was determined that the abnormal depolarization area (the infarcted area} was a positive area in normal subjects which was altered to a negative area in cases with myocardial infarction. It was necessary, however, to confirm which wall of the ventricle corresponded to the location of the abnormal depolarization area on the mapping. Consequently, the location of the abnormal depolarization area was compared to the location of the abnormal findings of a scintigram with thallium-201, and each region of the mapping was matched to a wall in the ventricle.

There are many studies on body surface isopotential mapping of the QRS wave in myocardial infarction 19" ,8 in which the characteristic findings of mapping in myocardial infarction are described. However, it is also important to determine the infarcted area in the study of mapping. In acute myocardial infarction, ST mapping has been used to presume the location of the infarcted area. In old myocardial infarction, only Yamada et al. have reported a substruction method using the difference of the amplitude of the QRS wave in normal subjects and cases with myocardial infarction. Recently, the present authors were able to study mappings taken before and after an attack of myocardial infarction in one case of myocardial infarction. Both mappings of the QRS wave at 20 From the Department of Cardiology and Cardiovascular Hemodynarrdcs, Center for Adult Diseases, Osaka. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. w 1734 solely to indicate this fact. Reprint requests to: Seiichi Toyama, M.D., Department of Cardiology, Center for Adult Diseases, Osaka, Nakamichi 1-Chome, Higashinariku, Osaka, Japan.

MATERIALS AND METHODS Fifty one cases of myocardial infarction were selected from among patients being treated at the Center for Adult Diseases, Osaka. In each of these cases, the onset of myocardial infarction

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h a d o c c u r r e d a t least one m o n t h before a n d each was e x a m i n e d w i t h t h e V C G u s i n g t h e F r a n k s y s t e m , the s e i n t i g r a m w i t h thaUium-201 (SCG), a n d i s o p o t e n t i a l m a p p i n g u s i n g t h e Y a m a d a lead s y s t e m (MAP). 1~ I n the mapping, t h e r i g h t a n d left edges (A) were e q u i v a l e n t to the r i g h t mid-axillar line a n d t h e lines B, E, H, I a n d J c o r r e s p o n d e d to the r i g h t a n t e r i o r axillar line, t h e mid-sternal line, the

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b) The mapping at 20 msec. in the case with anterolateral infarction. (0.5 and --0.5 = isopotential lines of 0.5 mV and --0.5 mV). c) The mapping b was superimposed on the mapping a. The negative area on the mapping b which overlapped the positive area on the mapping a was judged to be the abnormal depolarization area (the area of the oblique line). In tMs case, the abnormal depolarization area was positive at region 3 and region 5 and the abnormal finding of the scintigram was observed at the anterior and lateral segments. J. ELECTROCARDIOLOGY 1 5 (3), 1 9 8 2

M A P P I N G O F THE ORS WAVE IN MI

infarction which overlapped" with the positive area on the normal mapping was judged to be the abnormal depolarization area (the area of the oblique line) as in another report 15 by the present authors (Fig. 2). The normal mappings at each 10 msec. were made by using the mean value of the amplitude in ten normal subjects. The mapping was divided into regions 1 to 10 as shown in Fig. 2. When the abnormal depolarization area occupied more than a half area of a region, or t h a t a t region 7 was located over the line at region 5, the area at t h a t region was counted as a positive (+) on the mapping (MAP+).

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Scintigraphy was performed after intravenous injection of 3 mCi thallium-201 and was obtained with a Toshiba 200 scintillation camera using a low-energy collimator. Scintiscans were obtained from three different views {anterior, 45 ~ left anterior oblique, 90 ~ left lateral} and were read by two observers. The scintiscans were graded as "defective", "decreased a c t i v i t y " (low uptake} and "normal". The defective and low uptake were picked up as abnormal findings and these locations were divided into the septal, anterior, apical, lateral, inferior and posterior segments following Wackers' criteria. The findings of the mapping, VCG and scintigram were judged by two or three doctors independently. The presence or absence of the a b n o r m a l depolarization area on M A P and the abnormal finding in SCG was compared at each region and at each segment. Cases which agreed (MAP-t-, S C G + and MAP--, S C G - ) were counted. Sensitivity was also calculated.

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Fig. 3. The abnormal depolarization areas (the areas of the oblique line) of the mappings at 20, 30, 40, 50 and 60 msec. in the case with anterior infarction. This area at 20 msec. was located at the precordlal region (the region 1, 2, 3 and 4). J. ELECTROCARDIOLOGY 1 5 (3), 1 9 8 2

I. The movement of the abnormal depolarization area at each 10 msec. 1. In the case with anterior infarction diagnosed by VCG (Fig. 3), the abnormal depolarization area at 20 msec. was widespread at the precordial region (the region 1, 2, 3 and 4). Those areas at 30 msec., 40 msec. and 50 msec. were located at the precordial region but these were narrower than those found at 20 msec. The area at 60 msec. was limited to the edge of the right side of the mapping. 2. In the case with inferior infarction {Fig. 4), the abnormal depolarization area at 20 msec. was located mainly at the lower and middle regions on the mapping (the region 1, 2, 4, 6, 8 and 10). Those areas at 30 msec., 40 msec. and 50 msec. were located at the lower region away from the center area on the mapping. The area at 60 msec. was similar to t h a t at 60 msec. in the case of anterior infarction and was limited to the edges of the mapping. 3. In the case with high posterior and inferior infarction {Fig. 5), the abnormal depolarization areas at 20 msec. and 30 msec. were located mainly a t the posterolateral region (the region 5, 6, 7 and 8) and had a triangular shape. T h a t area at 50 msec. was wider than a t 20 msec. in this case. Cases with wider area t h a n t h a t at 20 msec. were 11 cases at 30 msec., two at 40 msec. and one at 50 msec. B u t in those cases, the area at 20 msec.

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was obviously observed at the posterolateral region. There were 13 cases with the widest area a t 20 msec. Accordingly, the abnormal depolarization area was widest at 20 msec. except in some cases with t h a t area at the posterior region (the region 7 and 9) -- high posterior infarction and even in such exceptional cases, the abnormal depolarization area was observed a t the posterolateral region on the mapping at 20 msec. Therefore, in the following, the abnormal depolarization area at 20 msec. was used to compare the abnormal finding of the scintigram with thallium-201.

II. The relation b e t w e e n the abnormal depolarization area at each region on the mapping

Fig. 5. The abnormal depolarization areas of the mappings at 2(i, 30, 40, 50 and 60 msec. in the case with high posterior and inferior infarction. That area at 20 msec. was located at the posterolateral region (the region 5, 6, and 7).

(MAP) and the abnormal finding at each segment in the scintigram using thallium-201 (SCG) (Table 1). The coincidence of the abnormal depolarization area at each region on M A P and the abnormal finding at each segment in SCG was examined and the percentage of agreement ( M A P + , S C G + and M A P - , S C G - ) and disagreement ( M A P + , S C G - and M A P - - , SCG+) was calculated between each region and each segment. The highest percentage of agreement at region 1 was 68.6% to the septal segment. The percentage of agreement at region 2 was 49.0%, 68.6% or 62.7% with the septal segment, apical segment or inferior segment respectively. J. ELECTROCARDIOLOGY 1 5 ~3), 1982

MAPPING OF THE ORS WAVE IN MI

245

T A B L E I.

T A B L E II.

The percentage of a g r e e m e n t and sensitivity b e t w e n the abnormal depolarization area at 2 0 msec. of M A P and the abnormal finding in S C G .

The percentages of a g r e e m e n t at 2 0 , 3 0 , 4 0 , 5 0 and 6 0 msec.

MAP Region on M A P

Segment in SCG

Region 1 Region 2

Septal segment Septal segment Apical segment Inferior segment Anterior segment Apical segment Post. apical segment Inferior segment Lateral segment

68.6% 49.0% 64.7% 62.7% 92.2% 54.9%

47.6% 32.3% 80.6% 58.1% 95.5% 76.9%

64.7% 64.7 % 68.6%

65.4% 61.5 % 41.7%

Lateral segment Inferior segment Posterior segment Inferior segment inferior segment

78.4% 76.5% 78.4% 90.2% 92.2%

52.4% 73.1% 63.2% 82.8% 85.7%

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Concerning region 3, the percentage of agreement in the anterior segment in SCG was 92.2% and it could be said that the abnormality of region 3 corresponded to the abnormality of the anterior segment in SCG. The percentage of agreement between region 4 and the apical segment was only 54.9%. However, when the apical segment in SCG was divided into the anterior apical segment and the posterior apical segment, the percentage of agreement to the posterior apical segment was 64.7%. The percentage of agreement between region 5 and the lateral segment was 68.6%. But if the abnormal depolarization area at the upper portion of region 5 and the abnormal finding at the lateral segment were compared, that percentage in ~ creased to 78.4%. Therefore, the abnormal depolarization area at the upper portion of region 5 correlated closely to the abnormal finding at the lateral segment in SCG. The highest percentage of agreement at region 6, 8 or 10 on MAP was 76.5%, 90.2% or 92.2% to the inferior segment in SCG respectively, and the percentage of agreement between region 7 and the posterior segment was 78.4%. At region 9, there was no case with the abnormal depolarization area on the mapping at 20 J. ELECTROCARDIOLOGY 1 5 (3), 1982

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92.2% 68.6% 52.9% 52.9% 52.9% 78.4% 74.5% 78.4% 76.5% 78.4% 90.2% 76.5% 68.0% 58.8% 54.9% 78.4% 78.4% 68.6% 68.6% 70.6%

msec., even though region 9 was occupied by abnormal depolarization on the mapping at 30 msec., 40 msec. or 50 msec. in cases with high posterior infarction. In addition to the above mentioned results, when the area of abnormal depolarization was at region 1 and the absence of the right anterior location in the initial QRS vector in VCG was compared, the percentage of agreement was 78.4% and that was higher than that between region 1 and septal segment in SCG. III. The comparison of the percentage of agreement and sensitivity at 20 msee., 30 msec., 40 msec., 50 msec and 60 msec. The percentages of agreement at 20, 30, 40, 50 and 60 msec. were compared at region 3 to the anterior segment, the upper portion of region 5 to the lateral segment, region 8 to the inferior segment and region 7 to the posterior segment. As

T A B L E III. Sensitivity at 2 0 , 3 0 , 4 0 , 5 0 and 6 0 msec.

MAP

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Anterior segment Upper portion Lateral of Region 5 segment Region 8 Inferior segment Region 7 Posterior segment

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82.8% 87.5% 90.0% 83.3%

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246

TOYAMA ET AL

shown in Table 2, the percentages of agreement at 20 msec. were higher than those at 30, 40, 50 and 60 msec. Sensitivity at 20, 30, 40, 50 and 60 msec. is shown in Table 3. A t region 3 to the anterior segment and the upper portion of region 5 to the lateral segment, sensitivity at 20 msec. was highest, b u t at region 8 to the inferior segment and at region 7 to the posterior segment, sensitivity at 20 msec. more than 80%, or second highest. Moreover, the number of cases with M A P ( + ) , SCG (+) at 20 msec. was more than at 30, 40, 50 and 60 msec. Consequently, it was confirmed that mapping at 20 msec. was better to use in the present s t u d y than mapping at other msec.

DISCUSSION In! order to use M A P clinically in cases of myocardial infarction, it is necessary to first determine the area of myocardial infarction. In M A P studies of myocardial infarction, the characteristic findings of M A P have been repoi:ted b y a number of authors, b u t the infarcted area was determined mainly b y means of ST mapping in acute myocardial infarction. In old myocardial infarction, Yamada et al. only described the method of the substruction MAP. In the present study, we determined that the positive area in normal subjects, which was later altered to a negative area in infarction, was the infarcted area. However, it is important to confirm that the location of the infarcted area corresponds to the true location of the infarction. Simultaneously, it is necessary to determine which M A P region is equivalent to which wall of the ventricle. For purposes of this study, it was necessary to compare the infarcted area indicated b y M A P and the location of infarction as shown b y other methods: autopsy findings, scintigram with thallium-201 or other isotopes, vectorcardiographic findings, the abnormal movement of the left ventriculogram and the location of stenosis in coronary arteriogram. Only a few of the 51 cases were autopsied. On the other hand, recently, the scintigram with thallium-201 was used to presume the location of the infarcted area. Of course, SCG was not a perfect standard, because abnormal findings in the lateral and posterior walls were observed less than in anterior and inferior walls, and false p o s i t i v e findings in t h e apical s e g m e n t were sometimes found. B u t it was believed that

when abnormal findings (defect or low uptake of thallium-201) were observed with SCG, infarction m a y be presumed. The present authors have already reported the diagnostic criteria for myocardial infarction in the VCG, and have shown that the location of infarction presumed b y the VCG is related to the location of the abnormal movement in the left ventriculogram and the abnormal findings of SCG with thallium-201. The percentage of agreem e n t (82.9%) in VCG and SCG was higher than that in VCG and LVG (73.1%). Consequently, in the present study, a comparison between M A P and SCG was initially adopted. However, the abnormal findings of SCG were not an absolute standard, so agreement and disagreement in M A P and SCG were calculated rather than sensitivity and specificity. The percentages of agreement of region 3 to the anterior segment and regions 8 and 10 to the inferior segment were more than 90%. B u t the percentages of agreement of the upper portion of region 5 to the lateral segment and region 7 to the posterior segment were lower. This might be a result of the same diagnostic weakness in SCG. After comparing them, the following relations between M A P regions and SCG segments. were presumed: region 1 -- the septal segment (the septum); region 2 -- the apical segment (the apex); region 3 -- the anterior segment (the anterior wall); region 4 -- the posterior apical segment (the posterior portion of the apex); the upper portion of region 5 -- the lateral segment (the lateral wall); region 6, region 8 and region 10 -the inferior segment (the inferior wall); and region 7 - the posterior segment (the posterior wall). When the above result was used, the classification of myocardial infarction in 51 cases was: seven cases of anterior infarction, 11 cases of anterolateral infarctionT, seven cases of inferior infarction, 13 cases of inferior and high posterior infarction, four cases of anterior and inferior infarction, one case of anterolateral and inferior infarction, one case of lateral and high posterior infarction, four cases of anterolateral, inferiorinferior and high posterior infarction, two cases of lateral, inferior and high posterior infarction and one case of lateral infarction. I t is necessary, however, to confirm the location of each M A P region compared to other methods. The present authors are investigating the relation of the location of the infarcted area between M A P and the VCG or the left ventriculogram. J. ELECTROCARDIOLOGY 15 {3), 1982

MAPPING OF THE ORS WAVE IN MI

Acknowledgment: We express our thanks to Miss Ryeko Kurata for her technical assistance. 1.

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A series of judgements, revised without ceasing, goes to make up the incontestable progress of science. --Duclaux