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Differentiation between right and circumflex coronary artery disease on thallium myocardial perfusion scanning
DifferentiationBetween Right and Circumflex Coronary Artery Disease on Thallium Myocardial PerfusionScanning HENRY N. NEWMAN, MB, BS, FRACP, RICHARD F. DUNN, MB, BS, FRACP, PHILLIP J. HARRIS, MB, BS, DPhil, FRACP, GEORGE J. BAUTOVICH, MB, BS, PhD, FRACP, ANDREW F. MCLAUGHLIN, MB, BS, FRACP, and DAVID T. KELLY, MB, ChB, FRACP
Thallium defects in the inferior and lateral walls of the heart were correlated with right and circumflex coronary artery disease (CAD) in 405 patients who underwent coronary arteriography. In the 102 patients with either single right or left circumflex (LC) CAD, inferior segment defects (anterior view) were associated with right CAD, and both lateral segment defects (40’ left anterior oblique view) and posteroinferior defects (00” teft anterior oblique view) were associated with LC CAD. In all 405 patients, inferior segment defects had a sensitivity of 65 %, a specificity of 92 %, and a predictive accuracy of 69% for right CAD, and lateral segment defects had a sensitivity of 52 %, a specificity of 96%) and a predictive accuracy of 90% for LC CAD. Posteroinferior defects had a low predictive accuracy
for narrowing in either artery. The presence or absence of concomitant anterior defects did not alter these results. Narrowing in both right and LC coronary arteries was best identified by a combination of inferior and lateral segment defects (sensitivity 30 % , specificity 96 %, predictive accuracy 72 % ). Narrowing in only 1 of these 2 arteries was best identified by a combination of inferior segment without lateral segment defects for right CAD (sensitivity 63 %, specificity 66 %, predictive accuracy 55%) and lateral segment without inferior segment defects for LC CAD (sensitivity 45%, specificity 92%, predictive accuracy 57 % ). Thallium scanning identifies significant narrowing in the right and LC coronary arteries, and these may be separated by the pattern of defects.
Thallium-201 myocardial perfusion scanning may help both to diagnose coronary artery disease (CAD) and to localize the area of ischemia.l-lo Thallium perfusion defects in the anterior wall of the heart strongly suggest significant narrowing of the left anterior descending coronary artery,6-10 but defects in the inferior and lateral walls may result from obstruction in either the right or the left circumflex (LC) coronary artery.srO This study examines the distribution of thallium defects within the inferior and lateral walls to predict whether the right or the LC coronary artery was obstructed.
were excluded. The mean age of the patients was 51 years (range 2’7to 70). Exercise thallium scanning was performed within 6 months of coronary arteriography in all but 12 patients, in whom arteriography preceded thallium scanning by 6 to 24 months. Exercise thallium-201 myocardial scanning: The patients performed maximal exercise on an upright bicycle ergometer or on a treadmill using a graded multistage, continuous protocol” until they experienced chest pain, breathlessness, or fatigue. A 12-lead electrocardiogram was recorded before and during each minute of exercise and recovery. At peak exercise, 1.5 to 2.0 mCi of thallium-201 was injected intravenously, and the patients exercised for another minute. Scanning was begun 5 minutes after the administration of thallium-201. Four views were obtained: anterior, 40’ left anterior oblique, 60’ left anterior oblique, and left lateral, using a Searle PHO-Gamma mobile camera and low-energy all-purpose parallel-hole collimator, as previously described.3 The scans were interpreted at the time of study from the original Polaroid scintiphotographs without computer enhancement or background subtraction, by the consensus of 3 experienced observers, who had no knowledge of the patients. Each of the 4 views was diagrammatically divided into 3 segments, as shown in Figure 1, and analyzed for the presence or absence of a thallium defect. The interconsensus variability for this technique is 7%.* Defects in the inferior and lateral walls (Fig. 1) were defined as defects in 1 or more of the following segments: inferior in the anterior view, lateral in the 40” left anterior
Methods The study group included 405 consecutive patients (364 men and 41 women) who underwent exercise thallium scanning and coronary arteriography to assess CAD. Patients with a clinical diagnosis of valvular heart disease or cardiomyopathy and patients who had previous coronary bypass surgery
From the Hallstrom Institute of Cardiology and Department of Nuclear Medicine, Royal Prince Alfred Hospital, Sydney, Australia. This study was supported in part by grants from the National Heart Foundation of Australia and the Postgraduate Foundation of the University of Sydney, Sydney, Australia. Manuscript received July 1, 1982, accepted December 22, 1982. Address for reprints: Professor David T. Kelly, Hallstrom Institute of Cardiology, Royal Prince Alfred Hospital, Missenden Road, Camperdown, N.S.W. 2050, Australia.
1052
April 1983
TABLE I
Relation of Defects in inferior and Lateral Walls and Specific Coronary Artery Disease
Diseased Coronary Arteries
Patients (n)
Defects in Inferior and Lateral Walls
THE AMERICAN JOURNAL OF CARDIOLOGY
Volume 51
ANTERIOR
40’
1053
LAO
\
No Defects in inferior and Lateral Walls SEPT
Si;g;;horonary
artery
61
LC LAD Two coronary arteries Right + LC $g”: lAFD
41 95
:z3
922
40
37 22 16
3
LAT
6
z;
AP 40
60’
::
LAO
LEFT
LATERAL
Three coronary arteries Right Normal+ LC + LAD Total
67 4::
55 23:
:; 173
LAD = left anterior descending; LC = left circumflex; coronary arteries normal or insignificant narrowing.
i ANT SEPT
normal = POST
TABLE II
Incidence of Thallium Defects in Patients With Single Right and Left Circumflex Coronary Narrowing Patients (n) With Thallium Defects Right (n = 61)
Thallium Segments
n
%
n
Anterior view ANT LAT APEX INF
3; 47
6: 77
2:
4OgELpApview APEX LAT
12 46 3
10 70 5
60;;;;kTw APEX POST INF Left lateral APEX ANT POST
3”:
;:
0 f”2
3: 69
:;
1:
19
4
10
NS
6”:
7 6; 57
;:
2
AP
FIGURE 1. Location of inferior and lateral segments (black) in the 4 views of the thallium scan. ANT = anterior; ANT LAT = anterolateral; ANT SEPT = anteroseptal; AP ANT = apical, anterior view; AP LL = apical, left lateral view; AP 40 = apical, 40’ LAO view; AP 60 = apical, 60“ LAO view; INF = inferior segment; LAO = left anterior oblique; LAT = lateral; POST = posterior; POST INF = posteroinferior; SEPT = septal.
p Value
a
;:
2
%
:--y AP 60
INF
17 rz
:: <0.005
:: 71
is” NS
ANT = anterior; ANT LAT = anterolateral; ANT SEPT = anteroseptal; LAO = left anterior oblique; LAT = lateral segment; LC = left circumflex coronary artery: NS = not significant; POST = posterior; SEPT = septal.
branches. All patients with left main coronary narrowing also i had significant narrowing of the right coronary artery and were classified as 3-vessel disease. Data analysis: Data were analyzed using the Yates-corrected chi-square test and the McNemar test.” Sensitivity was defined as the ratio of true positives to the sum of true positives and false negatives. Specificity was the ratio of true negatives to the sum of true negatives and false positives. Predictive accuracy of a positive test was the ratio of true positives to the sum of true positives and false positives. Patients with single right and LC CAD were analyzed first to see which defect was most closely associated with narrowing in these 2 arteries. Then, all patients were analyzed to determine the predictive accuracy of defects in the inferior and lateral walls for narrowing of the right and LC coronary arteries.
Results oblique view, posteroinferior in the 60” left anterior oblique view, and posterior in the left lateral view.* Anterior defects were defined as defects in 1 or more of the following segments: anterolateral in the anterior view, septal in the 40’ left anterior oblique view, anteroseptal in the 60” left anterior oblique view, and anterior in the left lateral view.8 Defects in the inferior, lateral, and anterior walls usually extended into the apical segments, which were defined as nonspecific. Coronary arteriography: Selective coronary arteriography was performed in multiple projections using the Judkins or Sones techniques. Each study was reviewed by 2 experienced angiographers. The maximal luminal diameter narrowing for each major coronary artery was estimated visually, and mean measurements were used if the angiographers’ opinions differed. Significant narrowing was defined as obstruction of at least 70% in the distribution of the left anterior descending, right, or LC coronary arteries or their major
The distribution of CAD and the incidence of defects in the inferior and lateral walls in the 405 patients are shown in Table I. Isolated right and left circumflex narrowing (Table II): In the 61 patients with isolated right CAD, thallium defects were most frequent in the inferior segment (77%), posterior segment (69%), and posteroinferior segment (57%). Apical defects also were frequent, whereas defects in the anterolateral, septal, anteroseptal, anterior, and lateral segments were uncommon. The typical pattern of thallium defects associated with isolated right CAD is shown in Figure 2. When the 41 patients with isolated LC CAD were compared with patients with isolated right CAD, defects were more frequent in the lateral segment (68%, p
1054
DIFFERENTIATIONOF RIGHT AND CIRCUMFLEX CORONARY ARTERY DISEASE
ANTERIOR
60’
LAO
409
LEFT
ANTERlOR
LAO
BOC
LATERAL
FIGURE2. Exercise thallium scan of a patient with single-vessel right coronary artery disease. Perfusion defects are present in the inferior and apical segments in the anterior view, posteroinferior and apical segments in the 60’ left anterior oblique view, and posterior and apical segments in the left lateral view, and are represented as black areas on the diagrams. Abbreviations as in Figure 1.
and were less frequent in the inferior segment (19%, p
AD
scending, LC, and right CAD and have little localizing value.5-g The relation between inferior thallium defects and right CAD is shown in Table III. Inferior defects had a sensitivity of 65% and a specificity of 92%. The predictive accuracy of inferior defects for right CAD was 89%, whereas in the absence of inferior defects there was still a 28% probability of right CAD (that is a predictive accuracy for absence of right CAD of 72%). The relations between the lateral and posteroinferior defects and LC CAD are shown in Tables IV and V. The sensitivity of lateral defects for LC CAD was 52Y0, the specificity was 96%, and the predictive accuracy was 90%. Absence of lateral defects had a predictive accu-
Sensitivity, Specificity, and Predictive Accuracy of Thallium Defect in Lateral Segment (LAT) for Left Circumflex (LC) Coronary Artery Disease (CAD) LC CAD (n = 180)
Right CAD (n = 203) INF Thallium Defect (n = 149)
+
132
17
Predictive Accuracy for Presence of Right CAD
LAT Thallium Defect (n = 103)
f
+
-
93
10
I-
=!$=89% 71
Sensitivity
= g
= 65 %
185
LATERAL
left circumflex coronary artery disease. Perfusion defects are present in the apical segment in the anterior view, lateral and apical segments in the 40 left anterior oblique view, posteroinferior and apical segments in the 60” left anterior oblique view, and posterior segment in the left lateral view, and are represented as black areas on the diagrams. Abbreviations as in Figure 1.
Sensitivity, Specificity, and Predictive Accuracy of Thallium Defect in inferior Segment (INF) for Right Coronary Artery Disease (CAD)
-I
LEFT
LAO
FIGURE 3. Exercise thallium scan of a patient with single-vessel
TABLE IV TABLE ill
1
4o”
=&go%
-
Predictive Accuracy for Absence of Right CAD
Specificity
= g
= 92 %
Predictive Accuracy for Presence of LC CAD
Sensitivity
= +$
215
= 52%
Predictive Accuracy for Absence of LC CAD
Specificity
= 2
= 96%
1058
DIFFERENTIATION
OF RIGHT AND CIRCUMFLEX CORONARY ARTERY DISEASE
single artery narrowed. Defects in the inferior segment were significantly more common in patients with right CAD and defects in the lateral and posteroinferior (60° left anterior oblique view) segments were significantly more common in patients with LC CAD. Previous studies have shown that inferior defects are common in right CAD, but too few patients with single-vessel LC CAD have been studied to determine the incidence of lateral segment defects. s,8,gIn our study, there were 41 patients with single LC CAD; 28 (68%) had a perfusion defect in the lateral segment, whereas only 5% of patients with single right CAD had a similar defect. After correlating scan defects in patients with single right CAD and LC CAD, defects in all 405 patients were analyzed and compared with the coronary anatomy. Inferior segment defects predicted right CAD (predictive accuracy 89%, specificity 92%). In contrast, lateral segment defects predicted LC CAD (predictive accuracy 90%, specificity 96%). Posteroinferior segment defects, although more common in LC CAD, occurred also in right CAD and did not predict either accurately. Although defects in the inferior and lateral segments accurately predicted right and LC CAD, normal thallium uptake in these segments did not exclude narrowing of that artery. Approximately 30% of patients without inferior or lateral defects had significant narrowing of the right and LC coronary arteries. This poor predictive accuracy for the absence of significant narrowing is related to the low sensitivity of each of these segments for the presence of narrowing. Only 65% of patients with right CAD had inferior segment defects and only 52% of patients with LC CAD had lateral defects. These sensitivities are, however, similar to previous reports that have used visual interpretation of thallium scans.6T7JoJ2J3 Such interpretation does not detect narrowing in all significantly obstructed arteries.s,7J2-14 As thallium defects represent relative abnormalities in myocardial perfusion, only the most ischemic vascular area will appear abnormal, and ischemia in another vascular territory may not be apparent. The vascular supply to a specific myocardial segment may vary in different patients, and overlap in an individual patient. Also, the severity of obstruction at angiography may be difficult to determine. Quantitative computer-assisted analysis improves interpretation.13a14 Perfusion defects in the inferior wall may be either underestimated or overestimated in the presence of anterior perfusion defects. Rigo et al’* found that significant right and LC CAD may be missed if anterior defects are present, but there have been no previous studies to determine if inferior wall defects are overestimated in the presence of anterior defects. This study indicates that the predictive accuracies of inferior defects for right CAD and lateral defects for LC CAD did
not significantly differ whether or not anterior defects were present. However, defects in the posteroinferior segment better predicted LC CAD when anterior defects were present and had a similar accuracy in defects in the lateral segment. Previous studies have suggested that right CAD and LC CAD are difficult to separate on thallium scanningsJO because the vascular territories may vary. We found that inferior defects predicted right CAD and lateral defects predicted LC CAD; we analyzed combinations of defects to try to separate right from LC CAD. As expected, defects in the inferior without lateral defects were most common in right CAD but also occurred in 32% of patients with both right and LC CAD. Similarly, defects in the lateral without inferior defects were most common in LC CAD, but occurred in 38% of patients with CAD of both arteries. Defects in both the inferior and lateral segments occurred only occasionally ;n right and LC CAD and were suggestive of CAD in both. References 1. Bailey IK, Griffith SC, Rouieau J, Strauss HW, Pitt B. Thallium-201 myocardial perfusion imaging at rest and during exercise. Comparative sensitivity to electrocardiography in coronary artery disease. Circulation 197755: ?Q_A7 2. Ritchie JL, Trobaugh GB, Hamilton GW, Gould K, Narahara KA, Murray JA, Williams DL. Myocardial imaging with thallium-201 at rest and during exercise. Comparison with coronary arteriography and resting and stress electrocardiography. Circulation 1977;56:66-71. 3. Dunn RF, Kelly DT, Bailey IK, Uren R, McLaughlin A. Serial exercise thallium myocardial perfusion scanning and exercise electrocardiography in the diagnosis of coronary artery disease. Aust N Z J Med 1979;9:547553 4. Bodenheimer MM, Banka VS, Fooshee CM, Heifant RH. Comparative sensitivity of the exercise electrocardiogram, thallium imaging and stress radionuciide an iography to detect the presence and seventyof coronary heart disease. E rrculabon 1979:60:1270-1278. 5. Becker LC. Diagnosis of cwona& artery disease with exercise radionuclide imaging: state of the art. Am J Cardiol 1980;45:1301-1304. 6. Rigo P, Bailey IK, Grifilth LSC, Pitt 6, Burow RD, Wagner HN, Becker LC. Value and limitations of segmental analysis of stress thallium myocardial imaging for localization of coronary artery disease. Circulation 1980;61: 973-981. 7. Massie BM, Botvinick EH, Brundage BH. Correlation of thallium-201 scintigrams with coronary anatomy: factors affecting region by region sensitivity. Am J Cardioi 1979;44:616-622. 6. Dunn RF, Freedman 8, Bailey IK, Uren RF, Kelly DT. Exercise thallium imaging: location of perfusion abnormalities in single vessel coronary disease. J Nucl Med 1980;21:717-722. 9. Lenaers A, Block P, Van Thiei E, Lebedelle M, Becquevort P, Erbsmann F, Ermans AM. Segmental analysis of TI-201 stress myocardial scintigraphy. J Nucl Med 1977;18:509-516, 10. Eikavam U, Weinstein M, Berman D, Maddahi J, Staniioff H, Freeman M, Waxman A, Swan HJC, Forrester J. Stress thallium-201 myocardiai scintigraphy and exercise technetium ventriculography in the detection and location of chronic coronary artery disease. Comparison of sensitivity and specificity of these non-invasive tests alone and in combination. Am Heart J 1981;101:657-666. 11. McNemar, Q. Note on the sampling error of the differences between correlated proportions of percentages. Psychometrika 1947;12:153-157. 12. Rigo P, Balley IK, Grlfflth LSC, Pitt B, Wagner HN, Becker LC. Stress thallium-201 myocardial scintigraphy for the detection of individual coronary arterial lesions in patients with and without previous myocardial infarction. Am J Cardiol 1981;48:209-216, 13. Maddahi J, Garcia EV, Berman DS, Waxman A, Swan HJC, Forrester J. Improved noninvasive assessment of coronary artery disease by quantitative analysis of regional stress myocardial distribution and washout of thailium-201. Circulation 1981;64:924-935. 14. Gibson RS, Taylor GJ, Watson DD, Stebbins PT, Martin RP, Cramptom RS, Bever GA. Predicting the extent and location of coronary artery disease during the early postinfarction period by quantitative thallium-201 scintigraphy. Am J Cardiol 1981;47:1010-1019.
Thallium defects in the inferior and lateral walls of the heart were correlated with right and circumflex coronary artery disease (CAD) in 405 patients who underwent coronary arteriography. In the 102 patients with either single right or left circumflex (LC) CAD, inferior segment defects (anterior view) were associated with right CAD, and both lateral segment defects (40’ left anterior oblique view) and posteroinferior defects (00” teft anterior oblique view) were associated with LC CAD. In all 405 patients, inferior segment defects had a sensitivity of 65 %, a specificity of 92 %, and a predictive accuracy of 69% for right CAD, and lateral segment defects had a sensitivity of 52 %, a specificity of 96%) and a predictive accuracy of 90% for LC CAD. Posteroinferior defects had a low predictive accuracy
for narrowing in either artery. The presence or absence of concomitant anterior defects did not alter these results. Narrowing in both right and LC coronary arteries was best identified by a combination of inferior and lateral segment defects (sensitivity 30 % , specificity 96 %, predictive accuracy 72 % ). Narrowing in only 1 of these 2 arteries was best identified by a combination of inferior segment without lateral segment defects for right CAD (sensitivity 63 %, specificity 66 %, predictive accuracy 55%) and lateral segment without inferior segment defects for LC CAD (sensitivity 45%, specificity 92%, predictive accuracy 57 % ). Thallium scanning identifies significant narrowing in the right and LC coronary arteries, and these may be separated by the pattern of defects.
Thallium-201 myocardial perfusion scanning may help both to diagnose coronary artery disease (CAD) and to localize the area of ischemia.l-lo Thallium perfusion defects in the anterior wall of the heart strongly suggest significant narrowing of the left anterior descending coronary artery,6-10 but defects in the inferior and lateral walls may result from obstruction in either the right or the left circumflex (LC) coronary artery.srO This study examines the distribution of thallium defects within the inferior and lateral walls to predict whether the right or the LC coronary artery was obstructed.
were excluded. The mean age of the patients was 51 years (range 2’7to 70). Exercise thallium scanning was performed within 6 months of coronary arteriography in all but 12 patients, in whom arteriography preceded thallium scanning by 6 to 24 months. Exercise thallium-201 myocardial scanning: The patients performed maximal exercise on an upright bicycle ergometer or on a treadmill using a graded multistage, continuous protocol” until they experienced chest pain, breathlessness, or fatigue. A 12-lead electrocardiogram was recorded before and during each minute of exercise and recovery. At peak exercise, 1.5 to 2.0 mCi of thallium-201 was injected intravenously, and the patients exercised for another minute. Scanning was begun 5 minutes after the administration of thallium-201. Four views were obtained: anterior, 40’ left anterior oblique, 60’ left anterior oblique, and left lateral, using a Searle PHO-Gamma mobile camera and low-energy all-purpose parallel-hole collimator, as previously described.3 The scans were interpreted at the time of study from the original Polaroid scintiphotographs without computer enhancement or background subtraction, by the consensus of 3 experienced observers, who had no knowledge of the patients. Each of the 4 views was diagrammatically divided into 3 segments, as shown in Figure 1, and analyzed for the presence or absence of a thallium defect. The interconsensus variability for this technique is 7%.* Defects in the inferior and lateral walls (Fig. 1) were defined as defects in 1 or more of the following segments: inferior in the anterior view, lateral in the 40” left anterior
Methods The study group included 405 consecutive patients (364 men and 41 women) who underwent exercise thallium scanning and coronary arteriography to assess CAD. Patients with a clinical diagnosis of valvular heart disease or cardiomyopathy and patients who had previous coronary bypass surgery
From the Hallstrom Institute of Cardiology and Department of Nuclear Medicine, Royal Prince Alfred Hospital, Sydney, Australia. This study was supported in part by grants from the National Heart Foundation of Australia and the Postgraduate Foundation of the University of Sydney, Sydney, Australia. Manuscript received July 1, 1982, accepted December 22, 1982. Address for reprints: Professor David T. Kelly, Hallstrom Institute of Cardiology, Royal Prince Alfred Hospital, Missenden Road, Camperdown, N.S.W. 2050, Australia.
1052
April 1983
TABLE I
Relation of Defects in inferior and Lateral Walls and Specific Coronary Artery Disease
Diseased Coronary Arteries
Patients (n)
Defects in Inferior and Lateral Walls
THE AMERICAN JOURNAL OF CARDIOLOGY
Volume 51
ANTERIOR
40’
1053
LAO
\
No Defects in inferior and Lateral Walls SEPT
Si;g;;horonary
artery
61
LC LAD Two coronary arteries Right + LC $g”: lAFD
41 95
:z3
922
40
37 22 16
3
LAT
6
z;
AP 40
60’
::
LAO
LEFT
LATERAL
Three coronary arteries Right Normal+ LC + LAD Total
67 4::
55 23:
:; 173
LAD = left anterior descending; LC = left circumflex; coronary arteries normal or insignificant narrowing.
i ANT SEPT
normal = POST
TABLE II
Incidence of Thallium Defects in Patients With Single Right and Left Circumflex Coronary Narrowing Patients (n) With Thallium Defects Right (n = 61)
Thallium Segments
n
%
n
Anterior view ANT LAT APEX INF
3; 47
6: 77
2:
4OgELpApview APEX LAT
12 46 3
10 70 5
60;;;;kTw APEX POST INF Left lateral APEX ANT POST
3”:
;:
0 f”2
3: 69
:;
1:
19
4
10
NS
6”:
7 6; 57
;:
2
AP
FIGURE 1. Location of inferior and lateral segments (black) in the 4 views of the thallium scan. ANT = anterior; ANT LAT = anterolateral; ANT SEPT = anteroseptal; AP ANT = apical, anterior view; AP LL = apical, left lateral view; AP 40 = apical, 40’ LAO view; AP 60 = apical, 60“ LAO view; INF = inferior segment; LAO = left anterior oblique; LAT = lateral; POST = posterior; POST INF = posteroinferior; SEPT = septal.
p Value
a
;:
2
%
:--y AP 60
INF
17 rz
:: <0.005
:: 71
is” NS
ANT = anterior; ANT LAT = anterolateral; ANT SEPT = anteroseptal; LAO = left anterior oblique; LAT = lateral segment; LC = left circumflex coronary artery: NS = not significant; POST = posterior; SEPT = septal.
branches. All patients with left main coronary narrowing also i had significant narrowing of the right coronary artery and were classified as 3-vessel disease. Data analysis: Data were analyzed using the Yates-corrected chi-square test and the McNemar test.” Sensitivity was defined as the ratio of true positives to the sum of true positives and false negatives. Specificity was the ratio of true negatives to the sum of true negatives and false positives. Predictive accuracy of a positive test was the ratio of true positives to the sum of true positives and false positives. Patients with single right and LC CAD were analyzed first to see which defect was most closely associated with narrowing in these 2 arteries. Then, all patients were analyzed to determine the predictive accuracy of defects in the inferior and lateral walls for narrowing of the right and LC coronary arteries.
Results oblique view, posteroinferior in the 60” left anterior oblique view, and posterior in the left lateral view.* Anterior defects were defined as defects in 1 or more of the following segments: anterolateral in the anterior view, septal in the 40’ left anterior oblique view, anteroseptal in the 60” left anterior oblique view, and anterior in the left lateral view.8 Defects in the inferior, lateral, and anterior walls usually extended into the apical segments, which were defined as nonspecific. Coronary arteriography: Selective coronary arteriography was performed in multiple projections using the Judkins or Sones techniques. Each study was reviewed by 2 experienced angiographers. The maximal luminal diameter narrowing for each major coronary artery was estimated visually, and mean measurements were used if the angiographers’ opinions differed. Significant narrowing was defined as obstruction of at least 70% in the distribution of the left anterior descending, right, or LC coronary arteries or their major
The distribution of CAD and the incidence of defects in the inferior and lateral walls in the 405 patients are shown in Table I. Isolated right and left circumflex narrowing (Table II): In the 61 patients with isolated right CAD, thallium defects were most frequent in the inferior segment (77%), posterior segment (69%), and posteroinferior segment (57%). Apical defects also were frequent, whereas defects in the anterolateral, septal, anteroseptal, anterior, and lateral segments were uncommon. The typical pattern of thallium defects associated with isolated right CAD is shown in Figure 2. When the 41 patients with isolated LC CAD were compared with patients with isolated right CAD, defects were more frequent in the lateral segment (68%, p
1054
DIFFERENTIATIONOF RIGHT AND CIRCUMFLEX CORONARY ARTERY DISEASE
ANTERIOR
60’
LAO
409
LEFT
ANTERlOR
LAO
BOC
LATERAL
FIGURE2. Exercise thallium scan of a patient with single-vessel right coronary artery disease. Perfusion defects are present in the inferior and apical segments in the anterior view, posteroinferior and apical segments in the 60’ left anterior oblique view, and posterior and apical segments in the left lateral view, and are represented as black areas on the diagrams. Abbreviations as in Figure 1.
and were less frequent in the inferior segment (19%, p
AD
scending, LC, and right CAD and have little localizing value.5-g The relation between inferior thallium defects and right CAD is shown in Table III. Inferior defects had a sensitivity of 65% and a specificity of 92%. The predictive accuracy of inferior defects for right CAD was 89%, whereas in the absence of inferior defects there was still a 28% probability of right CAD (that is a predictive accuracy for absence of right CAD of 72%). The relations between the lateral and posteroinferior defects and LC CAD are shown in Tables IV and V. The sensitivity of lateral defects for LC CAD was 52Y0, the specificity was 96%, and the predictive accuracy was 90%. Absence of lateral defects had a predictive accu-
Sensitivity, Specificity, and Predictive Accuracy of Thallium Defect in Lateral Segment (LAT) for Left Circumflex (LC) Coronary Artery Disease (CAD) LC CAD (n = 180)
Right CAD (n = 203) INF Thallium Defect (n = 149)
+
132
17
Predictive Accuracy for Presence of Right CAD
LAT Thallium Defect (n = 103)
f
+
-
93
10
I-
=!$=89% 71
Sensitivity
= g
= 65 %
185
LATERAL
left circumflex coronary artery disease. Perfusion defects are present in the apical segment in the anterior view, lateral and apical segments in the 40 left anterior oblique view, posteroinferior and apical segments in the 60” left anterior oblique view, and posterior segment in the left lateral view, and are represented as black areas on the diagrams. Abbreviations as in Figure 1.
Sensitivity, Specificity, and Predictive Accuracy of Thallium Defect in inferior Segment (INF) for Right Coronary Artery Disease (CAD)
-I
LEFT
LAO
FIGURE 3. Exercise thallium scan of a patient with single-vessel
TABLE IV TABLE ill
1
4o”
=&go%
-
Predictive Accuracy for Absence of Right CAD
Specificity
= g
= 92 %
Predictive Accuracy for Presence of LC CAD
Sensitivity
= +$
215
= 52%
Predictive Accuracy for Absence of LC CAD
Specificity
= 2
= 96%
1058
DIFFERENTIATION
OF RIGHT AND CIRCUMFLEX CORONARY ARTERY DISEASE
single artery narrowed. Defects in the inferior segment were significantly more common in patients with right CAD and defects in the lateral and posteroinferior (60° left anterior oblique view) segments were significantly more common in patients with LC CAD. Previous studies have shown that inferior defects are common in right CAD, but too few patients with single-vessel LC CAD have been studied to determine the incidence of lateral segment defects. s,8,gIn our study, there were 41 patients with single LC CAD; 28 (68%) had a perfusion defect in the lateral segment, whereas only 5% of patients with single right CAD had a similar defect. After correlating scan defects in patients with single right CAD and LC CAD, defects in all 405 patients were analyzed and compared with the coronary anatomy. Inferior segment defects predicted right CAD (predictive accuracy 89%, specificity 92%). In contrast, lateral segment defects predicted LC CAD (predictive accuracy 90%, specificity 96%). Posteroinferior segment defects, although more common in LC CAD, occurred also in right CAD and did not predict either accurately. Although defects in the inferior and lateral segments accurately predicted right and LC CAD, normal thallium uptake in these segments did not exclude narrowing of that artery. Approximately 30% of patients without inferior or lateral defects had significant narrowing of the right and LC coronary arteries. This poor predictive accuracy for the absence of significant narrowing is related to the low sensitivity of each of these segments for the presence of narrowing. Only 65% of patients with right CAD had inferior segment defects and only 52% of patients with LC CAD had lateral defects. These sensitivities are, however, similar to previous reports that have used visual interpretation of thallium scans.6T7JoJ2J3 Such interpretation does not detect narrowing in all significantly obstructed arteries.s,7J2-14 As thallium defects represent relative abnormalities in myocardial perfusion, only the most ischemic vascular area will appear abnormal, and ischemia in another vascular territory may not be apparent. The vascular supply to a specific myocardial segment may vary in different patients, and overlap in an individual patient. Also, the severity of obstruction at angiography may be difficult to determine. Quantitative computer-assisted analysis improves interpretation.13a14 Perfusion defects in the inferior wall may be either underestimated or overestimated in the presence of anterior perfusion defects. Rigo et al’* found that significant right and LC CAD may be missed if anterior defects are present, but there have been no previous studies to determine if inferior wall defects are overestimated in the presence of anterior defects. This study indicates that the predictive accuracies of inferior defects for right CAD and lateral defects for LC CAD did
not significantly differ whether or not anterior defects were present. However, defects in the posteroinferior segment better predicted LC CAD when anterior defects were present and had a similar accuracy in defects in the lateral segment. Previous studies have suggested that right CAD and LC CAD are difficult to separate on thallium scanningsJO because the vascular territories may vary. We found that inferior defects predicted right CAD and lateral defects predicted LC CAD; we analyzed combinations of defects to try to separate right from LC CAD. As expected, defects in the inferior without lateral defects were most common in right CAD but also occurred in 32% of patients with both right and LC CAD. Similarly, defects in the lateral without inferior defects were most common in LC CAD, but occurred in 38% of patients with CAD of both arteries. Defects in both the inferior and lateral segments occurred only occasionally ;n right and LC CAD and were suggestive of CAD in both. References 1. Bailey IK, Griffith SC, Rouieau J, Strauss HW, Pitt B. Thallium-201 myocardial perfusion imaging at rest and during exercise. Comparative sensitivity to electrocardiography in coronary artery disease. Circulation 197755: ?Q_A7 2. Ritchie JL, Trobaugh GB, Hamilton GW, Gould K, Narahara KA, Murray JA, Williams DL. Myocardial imaging with thallium-201 at rest and during exercise. Comparison with coronary arteriography and resting and stress electrocardiography. Circulation 1977;56:66-71. 3. Dunn RF, Kelly DT, Bailey IK, Uren R, McLaughlin A. Serial exercise thallium myocardial perfusion scanning and exercise electrocardiography in the diagnosis of coronary artery disease. Aust N Z J Med 1979;9:547553 4. Bodenheimer MM, Banka VS, Fooshee CM, Heifant RH. Comparative sensitivity of the exercise electrocardiogram, thallium imaging and stress radionuciide an iography to detect the presence and seventyof coronary heart disease. E rrculabon 1979:60:1270-1278. 5. Becker LC. Diagnosis of cwona& artery disease with exercise radionuclide imaging: state of the art. Am J Cardiol 1980;45:1301-1304. 6. Rigo P, Bailey IK, Grifilth LSC, Pitt 6, Burow RD, Wagner HN, Becker LC. Value and limitations of segmental analysis of stress thallium myocardial imaging for localization of coronary artery disease. Circulation 1980;61: 973-981. 7. Massie BM, Botvinick EH, Brundage BH. Correlation of thallium-201 scintigrams with coronary anatomy: factors affecting region by region sensitivity. Am J Cardioi 1979;44:616-622. 6. Dunn RF, Freedman 8, Bailey IK, Uren RF, Kelly DT. Exercise thallium imaging: location of perfusion abnormalities in single vessel coronary disease. J Nucl Med 1980;21:717-722. 9. Lenaers A, Block P, Van Thiei E, Lebedelle M, Becquevort P, Erbsmann F, Ermans AM. Segmental analysis of TI-201 stress myocardial scintigraphy. J Nucl Med 1977;18:509-516, 10. Eikavam U, Weinstein M, Berman D, Maddahi J, Staniioff H, Freeman M, Waxman A, Swan HJC, Forrester J. Stress thallium-201 myocardiai scintigraphy and exercise technetium ventriculography in the detection and location of chronic coronary artery disease. Comparison of sensitivity and specificity of these non-invasive tests alone and in combination. Am Heart J 1981;101:657-666. 11. McNemar, Q. Note on the sampling error of the differences between correlated proportions of percentages. Psychometrika 1947;12:153-157. 12. Rigo P, Balley IK, Grlfflth LSC, Pitt B, Wagner HN, Becker LC. Stress thallium-201 myocardial scintigraphy for the detection of individual coronary arterial lesions in patients with and without previous myocardial infarction. Am J Cardiol 1981;48:209-216, 13. Maddahi J, Garcia EV, Berman DS, Waxman A, Swan HJC, Forrester J. Improved noninvasive assessment of coronary artery disease by quantitative analysis of regional stress myocardial distribution and washout of thailium-201. Circulation 1981;64:924-935. 14. Gibson RS, Taylor GJ, Watson DD, Stebbins PT, Martin RP, Cramptom RS, Bever GA. Predicting the extent and location of coronary artery disease during the early postinfarction period by quantitative thallium-201 scintigraphy. Am J Cardiol 1981;47:1010-1019.