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Clinical and Pathologic Features of Obstructive
Disease in the Predominant Right and Left
Coronary Circulations in Man
ROBERT J. BOUCEK, M.D., RENZO ROMANELLI, M.D., WILLIAM H. WILLIS, JR., M.D.,
AND WINSTON A. MITCHELL, M.D.
SUMMARY The clinical features and the location and severity of obstructive coronary artery disease are
contrasted in 98 patients with predominant left and 99 patients with predominant right coronary circulations.
A significantly higher incidence of ventricular conduction disturbances and a greater incidence and severity of
obstructive coronary artery disease (>70% cross-sectional narrowing in the proximal left anterior descending,
circumflex and right coronary arteries and their major branches) distinguish the predominant left from the
predominant right coronary circulation. The results suggest an anatomically disadvantaged status for the
predominant left compared with the predominant right coronary circulations with respect to ventricular conduction disturbances and to coronary atherogenesis in man.
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predominant right circulation. These results suggest
an anatomically disadvantaged status for the predominant left coronary circulation with respect to ventricular conduction abnormalities and to coronary
atherosclerosis.
ANATOMIC VARIATIONS of the coronary
arteries around the crux of the heart were first
described by Banchil and later used by Schlesinger2 to
divide the coronary circulation into three general
types. In the most common, the predominant right,
the right coronary artery (RCA) provides branches to
the posterior right and left ventricles and to the
posterior one-third of the ventricular septum, while in
the least common, the predominant left, the left coronary artery (LCA) supplies all of the branches to the
posterior regions of the ventricular septum and left
ventricle. In the third type, the balanced circulation,
both the RCA and the circumflex division of the LCA
provide branches to the posterior heart. Of the three
coronary circulations, Schlesinger2 suggested that the
predominant left is the most vulnerable to the effects
of pathologic changes; however, no evidence supporting this hypothesis has appeared in the literature. To
test the Schlesinger hypothesis, we studied the clinical
and pathologic findings of patients with predominant
right and left coronary circulations established by coronary arteriography.
Although the presenting symptoms of patients with
obstructive coronary artery disease in the two coronary circulations are similar, the frequency of conduction disturbances through the ventricular septum is
significantly greater in the predominant left than in
the predominant right circulation. Additionally, more
advanced obstructive disease occurs in the proximal
regions and in the major branches of the three major
coronary arteries in the predominant left than in the
From the Department of Medicine, Division of Gerontology,
University of Miami School of Medicine, Miami, Florida; University of Pisa, Pisa, Italy; and the Departments of Medicine and
Radiology, Loma Linda Universi-ty School of Medicine, Loma Linda, California.
Supported in part by USPHS Research grants HL-17909 and
HL-17865 from the NHLBI.
Address for correspondence: Robert J. Boucek, M.D., University
of Miami School of Medicine, Department of Medicine R127, P.O.
Box 016960, Miami, Florida 33101.
Received October 29, 1979; revision accepted February 11, 1980.
Circulation 62, No. 3, 1980.
485
Materials and Methods
The clinical records, including ECGs, coronary
arteriograms, left ventricular cineangiograms and
myocardial perfusion scintigrams of 197 patients
studied at Loma Linda University Medical Center
during a 4-year interval, were analyzed. The patients
were referred for diagnostic work-up because of
recurring chest pain.
A 12-lead ECG recorded on high-sensitivity paper
was examined by two experienced electrocardiographers for absent q waves in leads 1, aVL, V6 and
V,, and for evidence of myocardial ischemia and infarction. Patients who had absent q waves in the left
precordial leads due to leftward and clockwise rotation, which placed these electrodes perpendicular to
the direction of the initial septal depolarization vector,
were excluded. One hundred seven of the 178 patients
exercised on a computer-controlled treadmill, with 3minute work loads, beginning with 1.7 mph at a 5%
grade and increasing to 1.7 mph at a 10% grade, 2.5
mph at a 12% grade, 3.4 mph at a 14% grade and 4.2
mph at a 16% grade. The exercise was continued to the
point of fatigue, chest pain or dyspnea. A positive
response was horizontal ST-segment depression or
elevation > 1 mm in lead 1, > 1.5 mm in leads 2 and 3
and >2 mm in the precordial leads; the appearance of
diphasic or inverted T waves in leads I and 2 or over
the left precordium; or the appearance of bundle
branch block or hemiblock or bigeminy.
The criteria for left septal block were an absent q
wave in leads 1, aVL, V5 and V6 and a normal QRS
duration; for left anterior hemiblock, a Q,S3 pattern,
left axis deviation of the QRS (> - 400) and
prolongation of the QRS (.0.02 second); for left
posterior hemiblock, an S wave in lead 1 and a tall R
wave in leads 2, 3 and aVF, right axis deviation (QRS
axis . 1200) and prolongation of QRS (>0.2 second);
486
CIRCULATION
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for left bundle branch block (LBBB), an absent or embryonic q wave in leads 1, aVL, V, and V,, QRS duration of 0.08-0.12 second, delayed onset of the intrinsicoid deflection in lead V6 (>0.045 second); for right
bundle branch block (RBBB), an rsR' in V1 and V2
and a qRS complex in V, and V,, with a QRS > 0.12
second; and for bilateral bundle branch block, a
RBBB plus anterior or posterior hemiblock.
Selective coronary arteriography was performed
using the Judkins technique.3 The coronary arteries
were imaged in the anteroposterior, 200 right anterior
oblique, 700 left anterior oblique, lateral and left
anterior oblique craniocaudad projections using 35
mm cineradiography. Some of the studies included
large cut films. Ventriculography was performed and
recorded in the 20° right and left anterior oblique
projections using biplane cineradiography.
The extent of arterial narrowing was estimated
from multiple views of the coronary arteries and was
expressed as a percentage of the cross-sectional
diameter.
To analyze the topography of obstructive coronary
artery disease, the major coronary arteries were
divided into proximal, middle and distal regions. For
the left anterior descending coronary artery (LAD),
the region from the origin to the take-off of the first
septal perforator was designated proximal, from the
first septal perforator to the take-off of the second
anterior left ventricular branch (second diagonal) as
the middle and the remaining artery, the distal region.
The proximal region of the circumflex artery extended
from its origin to the take-off of the obtuse marginal
artery; the middle region, from the obtuse marginal to
the posterior lateral left ventricular artery or posterior
descending artery (PDA); and the distal segment, the
remaining posterior continuation(s) of the circumflex.
The proximal region of the RCA extends from the
take-off to the acute marginal artery, the middle
region from the acute margin to the PDA and the
PDA as the distal region.
Seventy-four patients with predominant right and
75 patients with predominant left coronary circulations had myocardial scintigrams after coronary
arteriography. Technetium-99m microspheres (2.63.4 1£Ci) were injected into the LCA in all of the
patients; 34 predominant right and 28 predominant
left circulations received iodine-131 macroaggregated
albumin 131-150 ,uCi injected into the RCA. In the
remaining patients, differing amount of technetium99m microspheres were injected into the RCA. At the
end of the injections, the patient was taken to the
Nuclear Medicine Section, and multiple views with an
Anger camera were integrated in a data acquisition,
storage, processing and display system developed by
Adams et al.4 The images were photographed
separately as a series of 10 color-coded isocount contours in spectral sequence. The channel with the maximal counts was arbitrarily assigned the color red and
each 10% change in counts resulted in a different
color. The scintigrams of the left and right coronary
circulations appeared separately, in combination and
in color. Heparin (2500-5000 units) was given intraarterially at the beginning of the study and was
VOL 62, No 3, SEPTEMBER 1980
reversed by Protamine intravenously at the end of the
procedure.
Differences between the data for the two circulations were determined statistically by t test and
chi-square analysis.'
Results
The angiographic features of the predominant right
and left coronary circulations are shown in figure 1.
Principal differences between the two circulations concern the origin of the PDA and the length of the LCA.
In the predominant right coronary circulation, the
PDA is a continuation of the RCA (fig. IA), whereas
in the predominant left circulation (fig. 1 B), the PDA
arises from the circumflex artery. Additionally, the
LCA is usually shorter in the predominant left than in
the predominant right coronary circulation.
Eighty-eight patients with a predominant left coronary circulation were matched for age, sex, duration
of angina pectoris and blood pressure with 90 patients
with a predominant right coronary circulation; all
patients had obstructive (>70%) coronary artery disease (table 1). The incidence, duration and referral of
angina pectoris chest pain were similar in the two circulations. The incidence of a positive exercise stress
response was similar for the two groups: 40 out of 53
patients (75%) with the predominant left circulation
and 39 out of 54 (72%) with the predominant right circulation.
Of the 88 patients with a predominant left circulation and obstructive coronary artery disease, 57 (65%)
showed conduction disturbances on the ECG, ranging
from the ECG syndrome of septal fibrosis" or left septal block7 (absence of q waves in leads 1, aVL, V5 and
V6) to left anterior hemiblock, right bundle branch
and bilateral bundle branch block (table 2), as contrasted with 28 (31 %) of the 90 patients with the
predominant right circulation with similar conduction
disturbances (p < 0.001). Even without obstructive
coronary artery disease, left anterior hemiblock occurred in three of 10 hearts with the predominant left
circulation, compared with none of nine hearts with
the predominant right circulation.
The number of coronary arteries with significant
cross-sectional diameter narrowing (estimated at
.70%) in one, two or three vessels was similar for the
two coronary circulations (table 3), but the distribution of the obstructive lesions differed. The predominant left circulation had a higher incidence of significant obstruction of the LAD and the circumflex
artery, while the predominant right circulation had a
higher incidence of single artery obstruction of the circumflex or RCA alone and two-artery involvement of
the circumflex artery and the RCA. Of 616 branch
arteries* in the predominant left circulation, 142
*The intermediate, first septal perforating and first and second
anterior ventricle (diagonal) from the LAD, the obtuse marginal,
posterior left ventricle and posterior descending branches from the
circumflex and the acute marginal and posterior descending
branches from the RCA.
CORONARY ARI ERY PREDOMINANCE AND OBSTRUCTIVE CAD/Boucek et al.
LCA
AP
RCA
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FIGURE 1. Distiniguishing features of the predominant
right (A) fromn the predominant left (B) coronary circulatiotns are a shorter leJt coronary artery (LCA), the
posterior descending artery (PDA) arising Jrom the circumflex artery (Cirx.) and (tnot shown in figure JB) a
diminutive right coroniary artery (RCAj in the predominant
left circulation. Other vessels ideictifed are the left anterior
descending artery (LAD) and Lth - -btusc iinarginal (MO)Jfr
the
circulations. The large arrow directed toward the
LAD in both circulations identtifies the take-off oj'the first
septal perforating artery. Both circulations are imaged in the
right anterior oblique projection.
two
487
(23%) had significant narrowings, whereas of 720
branch arteries in the predominant right circulation,
95 (13%) had significant narrowings (table 3)
(p < o.001).
Differences between the two circulations are seen in
the topology of obstructive coronary artery disease as
well. In the predominant left circulation, a
significantly greater frequency of obstructive lesions
occurred in the proximal LAD and in the proximal
PDA (distal circumflex, table 4) than in the predominant right circulation. In the predominant right circulation, a significantly greater frequency of obstructive lesions occurred in the proximal circumflex, the
middle RCA and the proximal PDA (distal RCA,
table 4) than in the predominant left circulation.
The estimated severity of obstructive coronary
artery disease (expressed as percentage narrowing,
table 4) was greater in the proximal segments of the
LAD, circumflex and RCA in the predominant left
compared with the predominant right circulation. The
mean for all lesions in this region of the LAD, circuinflex artery and RCA is 87%, 86% and 88%, respectively, in the predominant left, compared with 75%,
76% and 79%, respectively, in the predominant right
circulation. The mean narrowing in the proximal
segments was 87% in the predominant left circulation
and 77% in the predominant right circulation.
No differences in the incidences of myocardial infarction (ECG changes) or abnormal myocardial perfusion (scintigraphy) between right and left coronary
circulations were found (table 5).
Discussion
Three important distinguishing features of the
predominant left contrasted with the predominant
right circulation emerge from this study. The incidence of ventricular septal conduction disturbances,
the frequency of significant narrowings of the LAD
plus circumflex and branch arteries, and the extent of
obstructive disease in the proximal regions of the
LAD, circumflex artery and RCA are all greater in
the predominant left than in the predominant right
coronary circulation.
The relatively high incidence of left septal and
anterior hemiblock in the predominant left compared
with the predominant right circulations, with or
without obstructive coronary artery disease, suggests
anatomic variations in the geometry of the left bundle
branch or in the blood supply to the upper third of the
ventricular septum in the two circulations. Demoulin
and Kulbertus described the varying left bundle
branch geometry in 49 normal human hearts,8 but did
not correlate these variations with the blood supply to
the ventricular septum. Probably no relationship
would be found, because the region of the ventricular
septum, which contains the proximal portions of the
left bundle branch, is supplied chiefly by branches of
the LAD and by the "ramus septi fibrosi" from the
PDA. In the absence of significant obstructive disease
in the LAD, RCA or the circumflex artery, the higher
incidence of ventricular conduction disturbances in the
predominant left circulation (table 2) may reflect the
.
VOL 62. No 3, SEPTEMBER 1980
CIRCULATION
488
TABLE 1. Clinical Features of Patients With Predominant Left and Right Coronary Circulations and Obstructive
(> 70%) Coronary Artery Disease
Duration of
Treadmill stress test
Blood pressure
Sex
angina
Age
m
(mm Hg)
Negative Positive %
F
(months)
n
(years)
75
40
13
136 - 2.5*
34.9 +4.69
73
13
38.3 - 0.85
88
Left
78 - 1.2t
Right
90
57.0
-
0.93
76
14
32.2 = 4.97
75
Values are mean - SEM.
*Systolic pressure.
tDiastolic pressure.
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more common development of luminal narrowings of
intramural ventricular septal arteries in the predominant left than in the predominant right coronary circulation. Yater9 reported a 63-year-old patient with
intraventricular conduction disturbances and fibrous
replacement of the atrioventricular node and left bundle branch with a predominant left coronary circulation: "The small arteries in the ventricular septum
were thickened here and there, markedly in places,
and the lumen was greatly reduced at these points.
TABLE 2. Ventricular Conduction Disturbances in Predominant Left and Right Coronary Circulations with and
Without Obstructive Coronary Artery Disease
Left
llight
Obstructive coronary artery disease
Without
With
Without
With
(n = 88) (ii = 10) (n - 90) (ii - 9)
Left septal
1
20
44
block
Left anterior
3
3
7
hemiblock
Left bundle
1
branich block
Right bundle
4
branich block
5
Bilateral bundle
1
branch block
p < 0.001 (chi-square atialysis), comparinig left vs right
with coronary artery disease.
2.4*
128
-
15
39
72
1.2t
These arterial changes were most notable about the
middle of the septum and were most pronounced
nearer the left side."9 Perhaps other anatomic features
common to the predominant left coronary circulation,
i.e., a short LCA'0 or muscle bridging over the LAD,1'
may accelerate obstructive disease in the intramural
ventricular septal arteries; this possibility is currently
being investigated in our laboratory. The more frequent and more severe obstructive lesions of the proximal LAD in the predominant left compared with the
predominant right coronary circulations, when
superimposed upon possible disease of small, intramural coronary arteries, probably provide an optimal background for intraventricular conduction disturbances.`2
In 1956, Burch6 first described the ECG changes in
ventricular septal fibrosis, the absence of q waves in
leads 1, V5 and V, in hearts without LBBB or
clockwise rotation, and referred to these changes as
the ECG syndrome of septal fibrosis (or left septal
block). Then, in 1960, Burch and DePasquale'3 found
127 hearts with histologic evidence of septal fibrosis
from 1184 consecutive autopsies; 101 of these hearts
had absent q waves in leads 1, aVL, V, and V6.
Witham,14 in analyzing the vectorcardiograms of
patients with the ECG syndrome of septal fibrosis,
reported an abnormal initial vector in the horizontal
and sagittal planes extending beyond the expected
time for completion of transseptal depolarization and
considered these changes indicative of septal infarction. Romanelli et al.'5 recently reviewed the coronary
arteriograms and the myocardial scintigrams
TABLE 3. Obstrulctive Coronary Lesions (> 70of7) in Predominant Left and Right Coronary Circulations
Arterv
LAD
Cirx
+
RCA
Inivolvement
Branches
RCA
Cirx
LAI)
5
34
2
Left
17
2
0
73
(11= 88)
69
(1 = 90)
15l
8
6
4
Rlight
19
37
27
8
49
LAD) + circuiciflex iyivolvemeiit of predomiiianit left vs right circutlationi--p < 0.05; RCA with LAD or
cir ctumflex iiivolvemeiit of predominiaiit right vs left circulation-p < 0.05; branch inivolvemient of predormiinant
left vs right circulation p < 0.001 (all comparisons by chi-square analysis).
Abbreviations: LAI) = left anterior descending; Cirx circumflex; RCA right coronary artery.
LAD
Cirx
25
12
RCA
Cirx
Cirx
3
=
RCA
RCA
=
CORONARY ARTERY PREDOMINANCE AND OBSTRUCTIVE CAD/Boucek et al.
489
TABLE 4. Regional Differences in Obstructive Coronary Artery Disease in 88 Patients With Predominant Left
and 90 Patients With Predominant Right Coronary Circulations
Narrowing (%)
Number of lesions (. 70%/ narrowing)
Left vs right
Right
Left
Left vs right
Left
Right
LAD
< 0.01*
Proximal
< 0.01°t
47
29
87 - 2
75
3
30
36
84 2
< 0.05t
Middle
78 3
NSI
4
NS
10
Distal
69 7
NS
74 7
Cirx
Proximal
Middle
Distal
14
11
12
27
19
2
< 0.05*
NS
< 0.01
86
81
86
-
4
5
4
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RCA
Proximal
28
39
NS
88 2
Middle
21
8
83 - 4
< 0.05*
Distal
13
*Chi-square analysis.
tt test analysis.
tNot significant.
Abbreviations: LAD = left anterior descending coronary artery; Cirx
RCA = right coronary artery.
(technetium-99m microspheres alone or combined
with iodine- 131 macroaggregated albumin) of 65
angina pectoris patients with obstructive coronary
artery disease (.70% narrowing) with the ECG syndrome of septal fibrosis and compared the findings
with those in 113 patients matched for age, sex, and
duration of symptoms. Patients with the ECG syndrome of septal fibrosis had significantly higher incidences of .70% narrowing, greater overall severity
of proximal LAD involvement and more extensive
ventricular septal hypoperfusion than patients without
the syndrome.
The higher frequency of disease and greater narrowing of the LAD and circumflex arteries in the
predominant left than in the predominant right coronary circulation suggests an anatomic basis for
locating and determining the severity of occlusive
atherosclerotic coronary artery disease. That the coronary anatomy affects the locations of coronary
atherosclerotic lesions was suggested more than a century ago by Von Rokitansky.1' Later, M6nkeberg,17
Kirsch,'8 Levine and Brown'9 and Saphir et al.20 identified the proximal 2-4 cm of the LAD as the region
where the most extensive atherosclerotic narrowing or
TABLE 5. Incidence of Mlyocardial Infarction and Abnormal
Left Ventricular Scintigram in Predomiinant Left and Right
Coronary Circulations with Obstructive Coronary Artery Disease
Left vs
Left
Right
right
(n = 88) (n = 90)
NS
33
29
Myocardial infarction
Abnormal left
NS
43
52
ventricular scintigram
3
5
21
76
80
58
79
87
80
4
-
4
3
5
<
0.05t
NS
<
<
0.02t
0.02t
NS
circumflex coronary artery;
thrombotic occlusion occurs in the coronary arteries.
Kronzon et al.10 reported a shorter LCA in the
predominant left coronary circulation, and Gazetopoulos et al.2' found an inverse relationship
between the length of the LCA and the severity of coronary atherosclerosis in a postmortem series of more
than 204 hearts. Lewis et al.22 found a high incidence
of the predominant left coronary circulation in 12
patients with LBBB, 11 of whom had a short LCA.
Whatever the anatomic contribution in localizing
atherosclerosis, the more advanced obstructive disease
in the proximal LAD and circumflex artery and in the
major branch arteries implies a greater vulnerability
to coronary atherosclerosis in the predominant left
than in the predominant right circulation. One would
think that an increased vulnerability would be
reflected by a higher ECG incidence of myocardial infarction or abnormal myocardial scintigrams.
However, the similar ECG incidence of myocardial infarction and the frequency of abnormal scintigrams in
the two coronary circulations (table 5) may be explained by sampling bias (higher mortality with acute
myocardial infarction in the predominant left than
right circulation, as suggested by Schlesinger2), or a
lack of positive correlation between the severity of
proximal coronary artery disease and the frequency of
myocardial infarction. Although the evidence is strong
for a positive relationship between severe proximal
obstructive coronary artery disease and increased
mortality,23 the relationship between the severity of
proximally located coronary artery disease and the incidence of recurring myocardial infarction is not established. The findings presented in the above report,
however, are highly suggestive of a disadvantaged
status for fatal myocardial infarction in the predomi-
ClIRCULATION
490
nant left compared with the predominant right coronary circulation, but confirmation of Schlesinger's2
theory must await the results of contrasting studies of
the natural history of subjects with the predominant
left and right circulation.
Acknowledgment
11.
12.
13
The authors thank Dr. John E. Peterson and Dr. Roy V. Jutzy for
their continued interest and cooperation.
14.
References
15.
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Clinical and pathologic features of obstructive disease in the predominant right and left
coronary circulations in man.
R J Boucek, R Romanelli, W H Willis, Jr and W A Mitchell
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Circulation. 1980;62:485-490
doi: 10.1161/01.CIR.62.3.485
Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
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