Download Coronary Artery Anatomy in Left Bundle Branch Block

Coronary Artery Anatomy in Left
Bundle Branch Block
By HENRY DE MOTS, M.D., JOSEF ROSCH, M.D.,
AND
SHAHBUDIN H. RAHIMTOOLA, M.B., F.R.C.P.
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SUMMARY
It has previously been reported that the length of the left main coronary artery is short in
patients with left bundle branch block (LBBB) and that an unexpectedly large number of LBBB
patients had dominant left coronary arterial distribution. The present coronary arteriographic
study of 13 patients with LBBB revealed a mean length of the left main coronary artery (+ 1 SD)
of 10.9 + 6.0 mm, a measurement which was not significantly different (P > 0.5) from that of the
left coronary arteries in 78 patients in a control group (10.0 + 3 mm). The arterial distribution
patterns showed a contribution of the right coronary artery to the posterior descending artery in
12 of the 13 patients with LBBB. Coronary artery anatomy does not appear related to the presence of LBBB.
Additional Indexing Words:
Coronary arteriography
Left main
coronary
artery
LEFT BUNDLE BRANCH BLOCK (LBBB) is
found in association with a variety of cardiac
lesions including coronary artery disease, hypertension, valvular heart disease, myocarditis, and
various cardiomyopathies.1 Fibrosis of the conducting system has been found by most investigators to
be the histologic abnormality in patients with
LBBB. Ischemia is a possible common pathogenetic
mechanism producing fibrosis.2 4
Lewis et al. found that the length of the left main
coronary artery (LMCA) was less than 6 mm in all
but one of 12 patients with LBBB and was longer
than 7 mm in a control group of 25 patients.5 This
data suggest that the cardiac diseases associated
with LBBB were not etiologically important or that
they were important only when the LMCA was
short. Because significant etiologic and prognostic
implications are raised by these observations we
studied a group of patients with LBBB in whom
coronary arteriography had been performed. We
were unable to confirm their findings.
Materials and Methods
The electrocardiograms of patients studied consecutively with coronary arteriography were examined for
the presence or absence of LBBB. LBBB was diagnosed
if the QRS interval was 0.12 sec or longer and there
was a broad R wave not preceded by a Q wave in I,
aVL and V6 with secondary ST and T wave
abnormalities.6 The patients had been studied because
of suspected or known coronary artery disease, in some
as a screening procedure prior to valve replacement.
Coronary arteriography was carried out using the
Judkins technique7 and radiographs made in the right
anterior oblique (RAO) projection were used to
measure the length of the LMCA. In each instance, the
radiograph showing the longest length was chosen to
obviate the problem of shortening during systole. The
length of the LMCA was corrected for X-ray
magnification by comparing the actual and projected
catheter widths. The arterial distribution pattern and
the presence or absence of coronary artery disease was
noted.
Thirteen patients with LBBB were identified. Seven
were women and six were men. Their mean age was 54
years (range 44-71). Five of the patients had only
coronary artery disease. Of the remaining eight, two
had isolated valve disease, one had combined coronary
and valvular disease, two had hypertensive heart
disease, two had cardiomyopathy, and one patient had
no demonstrable abnormality at cardiac catheterization
and coronary arteriography. The control group of 78
patients was drawn from 13 groups of six patients each.
The three patients immediately before and the three
From the Division of Cardiology, Department of Medicine
and the Department of Radiology, University of Oregon
Medical School, Portland, Oregon.
Supported in part by Cardiology Training Grant HL
05791 and Cardiovascular Program Project Grant HL 06336
from the National Heart and Lung Institute.
Reprint requests to: Henry DeMots, M.D., Division of
Cardiology, University of Oregon Medical School, 3181 S.W.
Sam Jackson Park Road, Portland, Oregon 97201.
Received April 9, 1973; accepted April 25, 1973.
Circulation, Volume XLVIII, September 1973
Coronary arterial distribution pattern
605
DEMOTS, ROSCH, RAHIIMTOOLA
606
after the index patient with LBBB comprised these
groups.
Results
The left coronary artery of a patient with a long
LMCA and LBBB is shown in figure 1. Figure 2
demonstrates a patient with normal conduction and
a very short LMCA. The distribution of lengths of
the LMCA in all patients is shown in figure 3. The
mean length (±+ 1 SD) of the LMCA in patients
with LBBB was 10+ 6 mm and in the control
group was 10.9 ± 3.6 mm. The difference between
the two groups was not statistically significant
(P > 0.5). The right coronary artery was dominant
in nine, the left in one7 and a balanced system was
found in three patienits.
Discussion
There was no significant difference in the lengths
of left main coronary artery (LMCA) in patients
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Figure 1
This long (18 mm) left main coronary artery was present in a man with coronary artery disease and aortic
valvular disease. The patient developed left bundle branch block at a time remote from his surgery following a progressively severe intraventricular conduction delay associated with left ventricular hypertrophy.
Circulation, Volume XLVIII, September 1973
CORONARY ARTERY ANATOMY IN LBBB
607
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Figure 2
This radiograph taken in the RAO projection demonstrates the very short left main coronary artery in
a patient with normal conduction.
with and without left bundle branch block
(LBBB). The arterial distribution pattern of patients in our series does not differ from those
described by other workers.8 10 In contrast to the
patients described by Lewis et al., all of the patients with no discernable LMCA or a common
ostium were in the control group rather than the
group with LBBB.
We are unable to confirm the previously described angiographic patterns.4 Though the mean
values of the lengths of the LMCA in patients in the
two control groups were similar, the distribution
curve differs in the complete absence of short
LMCA in patients in their control series. The small
number of patients in their group may explain this
difference. There is no apparent reason for the
difference in length between the two LBBB groups
though each group is relatively small.
Correction for X-ray magnification by measurement of catheter diameters is not entirely satisfactory. However, our study was a retrospective one
designed to compare the LMCA length distribution
curve in patients with LBBB and a group of
controls rather than to establish standards for the
Circulation, Volume XLVIII, September 1973
length of the LMCA. Because the ratio of tube to
film distance was constant and that of image to
film distance varied only a little, the error
introduced by this factor was small and should not
affect the results in a systematic fashion. Further,
because a similar method was used in the work
referred to above, a difference in techniques cannot
explain the differences in the observed lengths of
the LMCA.
Lewis et al. speculated that the association
between a short LMCA and LBBB could be
explained by greater shearing forces imposed
during systole in the short arteries. This, in turn,
might compromise flow through the early septal
branches of the left coronary system and thus
produce ischemia and fibrosis of the left bundle
branch. However, in patients with LBBB, disease of
the left bundle is diffuse rather than accelerated
and well localized in a portion of the conducting
system as would be expected if only flow through
the small septal arteries were compromised.
Frink and James1' reported a dual blood supply
to the anterior half of the left bundle in four of ten
hearts. In these same hearts, the posterior division
DEMOTS, ROSCH, RAHIMTOOLA
608
by a congenital predisposition associated with the
length of the LMCA or the distribution pattern of
the coronary arterial system.
Patients With LBBB
References
0
2 3 4
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19202122232425262728
Patients With Normal Conduction
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2 3 4 5 6 7 8 9 10.11 12 13 14 15 16 17 18 19 20 21 22 2324 25262728
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Length of Left Main Coronory Artery (mm)
Figure 3
The distribution of 13 patients with LBBB according to
length of the LMCA is shown on the upper graph and of
78 control patients on the lower graph. There is no statistical
difference between the two groups.
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the left bundle branch system and their relationship
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Coronary arteriographic appearances in patients with
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of the left bundle was supplied completely either by
the right coronary or by both the right and left
coronary arteries in nine of ten. Therefore, a
mechanism involving only the left coronary system
would not be expected to produce LBBB unless
there were no contribution to septal flow by the
right coronary artery, a circumstance found in only
one of our 13 LBBB patients.
It is therefore likely that the presence or absence
of LBBB in a given patient is related to apparently
random and unpredictable localization of lesions
occurring in a number of clinical entities. The
etiology of LBBB does not appear to be influenced
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Circulation 47: 8, 1973
Circulation, Volume XLVIII, September 1973
Coronary Artery Anatomy in Left Bundle Branch Block
HENRY DE MOTS, JOSEF RÖSCH and SHAHBUDIN H. RAHIMTOOLA
Circulation. 1973;48:605-608
doi: 10.1161/01.CIR.48.3.605
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