Clin. Cardiol. 13, 783-788 (1990)
Differentiation Between Left Circumflex and Right Coronary Artery Occlusions: Studies on ST-Segment Deviation During Percutaneous Transluminal Coronary Angioplasty Y. HIASA,M.D..*
s. MORIMOTO,M.D.,*
T.
WADA, M.D..*
K. HAMAI,M.D..* Y.NAKAYA, M.D.." H. MORI,M.D."
*Department of Cardiology,Komatsushima Red Cross Hospital; tSecond Departmentof Internal Medicine, School of Medicine, The University of Tokushima, Tokushima,Japan
Summary: To distinguish between acute occlusion of the right coronary artery (RCA) and the left circumflex artery (LCx) by electrocardiography,we studied ST-segment deviation during balloon inflation in percutaneous transluminal angioplasty. The composite electrocardiographic criteria based on ST-segment deviations increased the diagnostic specificity: that is, the finding of inferior infarction (ST-segment elevation in leads 11, 111, aVF) without lateral infarction (ST-segment elevation in leads v5,6) was highly suggestive of RCA occlusion (sensitivity and specificity: 35 of 43 cases, 81.4%;and 33 of 36 cases, 91.7%), whereas ST-segment elevation in leads v5,6 (LCx: 23 of 36 cases; 63.9%.RCA: 5 of 43 cases; 11.6%)or isolated ST-segment depression in leads V2-4(LCx: 9 of 36 cases; 25.0%, RCA: none of 43 cases) was highly suggestive of LCx occlusion. These results indicated that the composite electrocardiographic criteria were useful in predicting the artery involved in acute myocardial infarction, although any single criterion was not sensitive or specific enough to differentiate right from left circwnflex coronary artery occlusion.
Key words: right coronary artery, left circumflex artery, ST-segment deviation, percutaneous transluminal coronary angioplasty
Address for reprints: Yoshikazu Hiasa, M.D. Department of Cardiology Komatsushima Red Cross Hospital Shinbiraki 2-18, Chuden-cho Komatsushima-city, Tokushima 773, Japan Received: March 14, 1990 Accepted with revision: June 16, 1990
Introduction Prompt accurate diagnosis of acute myocardial infarction is of extreme clinical importance, more so now that various reperfusion procedures seem to offer promise as approaches for reducing the size of infarction. However, acute occlusion in the left circumflex artery does not always produce the electrocardiographic changes typical of acute myocardial infarction. Furthermore, differentiation between occlusions of the left circumflex and right coronary artery from electrocardiographic changes is difficult because both types of occlusion may be associated with an electrocardiographicpattern of inferior myocardial infarction.3-5 Previous studies on the relation of the anatomical location of acute myocardial infarction with the electrocardiogram were mainly based on postmortem findings, or coronary angiograms during myocardial i n f a r c t i ~ n . ~ - ~ Results of these studies were often complicated by the inclusion of patients with multivessel coronary artery diseases, in whom it is difficult to determine the vascular distribution of ischemia. The present study was designed to distinguish between occlusions of the left circumflex and right coronary artery during acute ischemia from the electrocardiographicchange in ST segment. Complete occlusion of the coronary artery in humans can be produced by coronary angioplasty. Therefore, we studied electrocardiographic changes of ST segments during coronary angioplasty for the left circumflex and right coronary arteries. Results indicated criteria for differentiationbetween occlusions of the right and left circumflex artery in patients with electrocardiographicchanges of the inferior and lateral walls.
Subjects and Methods Patients The subjects studied were 79 consecutive patients who underwent percutaneous transluminal angioplasty between
784
Clin. Cardiol. Vol. 13, November 1990
1982 and 1987 at the Department of Cardiology, Komatsushima Red Cross Hospital. The localization of coronary stenosis was evaluated according to the AHA reporting system. l o Patients had an isolated and fixed coronary stenosis 2 75 % in the left circumflex artery (LCx group: 36 patients with a mean age of 55.0 years), or in the right coronary artery (RCA group: 43 patients with a mean age of 53.6 years). All patients underwent coronary angioplasty of either the left circumflex or right coronary artery. In the LCx group, coronary angioplasty was performed to segment 11 (from the origin to the takeoff of the obtuse margin) in 17 patients, to segment 12 (obtuse marginal branch) in 3, and to segment 13 (distal to the takeoff of the obtuse marginal branch) in 16. In the RCA group, coronary angioplasty was performed to segment 1 (the proximal one third of the right coronary artery) in 13, to segment 2 (the middle portion of the right coronary artery) in 19, and to segment 3 (the distal one third of the right coronary artery) in 1 I . Cases of myocardial infarction, complete bundle branch block, or Wolff-Parkinson-White(WPW) syndrome were excluded from this study.
Electrocardiography
Before, during, and after balloon inflation, standard 12lead electrocardiogramswere recorded in all patients with a thermal pen-writing 6-channel electrocardiograph. Translucent carbon electrodes, attached during the procedures, were used to record the electrocardiogram. The magnitudes of ST-segment deviations were measured 80 ms after the J point, and ischemic ST-segment deviations of more than l mm from control were considered as significant. The electrocardiogram leads were grouped into four lead groups: (1) anterior lead, V2-4; (2) lateral limb lead, I and aVL; (3) inferior leads, 11, 111, and aVF; and (4) lateral chest leads, V5+. ST-segment deviation was evaluated using these lead groups. ST-segment deviation was defined as present when at least one of the leads of each group showed significant deviation. These measurements were made by consensus of opinions of two of the investigators. The electrocardiographicchanges during the first balloon inflation were studied. Statistics
The results are expressed as means and standard deviations. Student's unpaired t-test was used to evaluate the statistical significance of differences between values for groups of patients. Proportional differences were analyzed by the chi-square test and Fischer's exact test. Differences were considered as significant when ~ ~ 0 . 0 5 .
Cineangiography and Coronary Angioplasty
Routine multiple view coronary angiography and contrast left ventriculography in the 30" right anterior oblique projection were performed in all patients. Balloon inflation in the left circumflex or right coronary artery was carried out in all patients. Angioplasty was performed by the routine method with balloon catheters of diameter 2.5 to 3.5 mm as appropriate. Balloon inflation was carried out for 60 s at 4 to 8 atmospheric pressure. This procedure was repeated two to four times in each patient. Informed consent was obtained from all patients after a full explanation of the procedure, and of the potential risk of the coronary angioplasty. No patient developed acute myocardial infarction or died suddenly as a result of the procedure.
Results Incidence of ST-Segment Deviation During Coronary Angioplasty
Table I shows the incidence of ST-segment deviation during coronary angioplasty in the LCx and RCA groups. In the inferior lead, ST-segment elevation was observed
TABLEI Incidence of ST-segment deviation in each lead group Lead group ~
LCX (n=36)
RCA (n =43)
20 (55.6%) 2 (5.6%) 3 (8.3%) 30 (83.3%) 23 (63.9%) 0 (0.0%) 2 (5.6%) 13 (36.1 %)
40 (93.0%) 1 (2.3%) 2 (4.7%) 28 (65.1 %) 5 (11.6%) 6 (14.0%) 0 (0.0%) 30 (69.8%)
p Value
~~~
Inferior lead (11, 111, aVF) Anterior lead (V*-4) Lateral chest lead W5,J
Lateral limb lead (1, aVL)
ST t ST I ST t ST I ST t ST 1 ST t ST 1
Abbreviations: LCx, left circumflex artery; RCA, right coronary artery.
p
Differentiation Between Left Circumflex and Right Coronary Artery Occlusions: Studies on ST-Segment Deviation During Percutaneous Transluminal Coronary Angioplasty Y. HIASA,M.D..*
s. MORIMOTO,M.D.,*
T.
WADA, M.D..*
K. HAMAI,M.D..* Y.NAKAYA, M.D.." H. MORI,M.D."
*Department of Cardiology,Komatsushima Red Cross Hospital; tSecond Departmentof Internal Medicine, School of Medicine, The University of Tokushima, Tokushima,Japan
Summary: To distinguish between acute occlusion of the right coronary artery (RCA) and the left circumflex artery (LCx) by electrocardiography,we studied ST-segment deviation during balloon inflation in percutaneous transluminal angioplasty. The composite electrocardiographic criteria based on ST-segment deviations increased the diagnostic specificity: that is, the finding of inferior infarction (ST-segment elevation in leads 11, 111, aVF) without lateral infarction (ST-segment elevation in leads v5,6) was highly suggestive of RCA occlusion (sensitivity and specificity: 35 of 43 cases, 81.4%;and 33 of 36 cases, 91.7%), whereas ST-segment elevation in leads v5,6 (LCx: 23 of 36 cases; 63.9%.RCA: 5 of 43 cases; 11.6%)or isolated ST-segment depression in leads V2-4(LCx: 9 of 36 cases; 25.0%, RCA: none of 43 cases) was highly suggestive of LCx occlusion. These results indicated that the composite electrocardiographic criteria were useful in predicting the artery involved in acute myocardial infarction, although any single criterion was not sensitive or specific enough to differentiate right from left circwnflex coronary artery occlusion.
Key words: right coronary artery, left circumflex artery, ST-segment deviation, percutaneous transluminal coronary angioplasty
Address for reprints: Yoshikazu Hiasa, M.D. Department of Cardiology Komatsushima Red Cross Hospital Shinbiraki 2-18, Chuden-cho Komatsushima-city, Tokushima 773, Japan Received: March 14, 1990 Accepted with revision: June 16, 1990
Introduction Prompt accurate diagnosis of acute myocardial infarction is of extreme clinical importance, more so now that various reperfusion procedures seem to offer promise as approaches for reducing the size of infarction. However, acute occlusion in the left circumflex artery does not always produce the electrocardiographic changes typical of acute myocardial infarction. Furthermore, differentiation between occlusions of the left circumflex and right coronary artery from electrocardiographic changes is difficult because both types of occlusion may be associated with an electrocardiographicpattern of inferior myocardial infarction.3-5 Previous studies on the relation of the anatomical location of acute myocardial infarction with the electrocardiogram were mainly based on postmortem findings, or coronary angiograms during myocardial i n f a r c t i ~ n . ~ - ~ Results of these studies were often complicated by the inclusion of patients with multivessel coronary artery diseases, in whom it is difficult to determine the vascular distribution of ischemia. The present study was designed to distinguish between occlusions of the left circumflex and right coronary artery during acute ischemia from the electrocardiographicchange in ST segment. Complete occlusion of the coronary artery in humans can be produced by coronary angioplasty. Therefore, we studied electrocardiographic changes of ST segments during coronary angioplasty for the left circumflex and right coronary arteries. Results indicated criteria for differentiationbetween occlusions of the right and left circumflex artery in patients with electrocardiographicchanges of the inferior and lateral walls.
Subjects and Methods Patients The subjects studied were 79 consecutive patients who underwent percutaneous transluminal angioplasty between
784
Clin. Cardiol. Vol. 13, November 1990
1982 and 1987 at the Department of Cardiology, Komatsushima Red Cross Hospital. The localization of coronary stenosis was evaluated according to the AHA reporting system. l o Patients had an isolated and fixed coronary stenosis 2 75 % in the left circumflex artery (LCx group: 36 patients with a mean age of 55.0 years), or in the right coronary artery (RCA group: 43 patients with a mean age of 53.6 years). All patients underwent coronary angioplasty of either the left circumflex or right coronary artery. In the LCx group, coronary angioplasty was performed to segment 11 (from the origin to the takeoff of the obtuse margin) in 17 patients, to segment 12 (obtuse marginal branch) in 3, and to segment 13 (distal to the takeoff of the obtuse marginal branch) in 16. In the RCA group, coronary angioplasty was performed to segment 1 (the proximal one third of the right coronary artery) in 13, to segment 2 (the middle portion of the right coronary artery) in 19, and to segment 3 (the distal one third of the right coronary artery) in 1 I . Cases of myocardial infarction, complete bundle branch block, or Wolff-Parkinson-White(WPW) syndrome were excluded from this study.
Electrocardiography
Before, during, and after balloon inflation, standard 12lead electrocardiogramswere recorded in all patients with a thermal pen-writing 6-channel electrocardiograph. Translucent carbon electrodes, attached during the procedures, were used to record the electrocardiogram. The magnitudes of ST-segment deviations were measured 80 ms after the J point, and ischemic ST-segment deviations of more than l mm from control were considered as significant. The electrocardiogram leads were grouped into four lead groups: (1) anterior lead, V2-4; (2) lateral limb lead, I and aVL; (3) inferior leads, 11, 111, and aVF; and (4) lateral chest leads, V5+. ST-segment deviation was evaluated using these lead groups. ST-segment deviation was defined as present when at least one of the leads of each group showed significant deviation. These measurements were made by consensus of opinions of two of the investigators. The electrocardiographicchanges during the first balloon inflation were studied. Statistics
The results are expressed as means and standard deviations. Student's unpaired t-test was used to evaluate the statistical significance of differences between values for groups of patients. Proportional differences were analyzed by the chi-square test and Fischer's exact test. Differences were considered as significant when ~ ~ 0 . 0 5 .
Cineangiography and Coronary Angioplasty
Routine multiple view coronary angiography and contrast left ventriculography in the 30" right anterior oblique projection were performed in all patients. Balloon inflation in the left circumflex or right coronary artery was carried out in all patients. Angioplasty was performed by the routine method with balloon catheters of diameter 2.5 to 3.5 mm as appropriate. Balloon inflation was carried out for 60 s at 4 to 8 atmospheric pressure. This procedure was repeated two to four times in each patient. Informed consent was obtained from all patients after a full explanation of the procedure, and of the potential risk of the coronary angioplasty. No patient developed acute myocardial infarction or died suddenly as a result of the procedure.
Results Incidence of ST-Segment Deviation During Coronary Angioplasty
Table I shows the incidence of ST-segment deviation during coronary angioplasty in the LCx and RCA groups. In the inferior lead, ST-segment elevation was observed
TABLEI Incidence of ST-segment deviation in each lead group Lead group ~
LCX (n=36)
RCA (n =43)
20 (55.6%) 2 (5.6%) 3 (8.3%) 30 (83.3%) 23 (63.9%) 0 (0.0%) 2 (5.6%) 13 (36.1 %)
40 (93.0%) 1 (2.3%) 2 (4.7%) 28 (65.1 %) 5 (11.6%) 6 (14.0%) 0 (0.0%) 30 (69.8%)
p Value
~~~
Inferior lead (11, 111, aVF) Anterior lead (V*-4) Lateral chest lead W5,J
Lateral limb lead (1, aVL)
ST t ST I ST t ST I ST t ST 1 ST t ST 1
Abbreviations: LCx, left circumflex artery; RCA, right coronary artery.
p
