Download Right Bundle-Branch Block and Left Anterior

Right Bundle-Branch Block and Left Anterior
Fascicular Block (Left Anterior Hemiblock)
Following Tricuspid Valve Replacement
By V. ARAVINDAKSHAN, M.D., MARCELO V. ELIZARI, M.D.,
AND
MAURIcIo B. ROSENBAUM, M.D.
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SUMMARY
Right bundle-branch block occurred in 42.8% and left anterior hemiblock in 35% of
14 patients after surgical replacement of the tricuspid valve. The combination of RBBB
with left anterior hemiblock is caused by injury to the branching portion of the bundle
of His or more likely, by a lesion involving the pseudobifurcation. This study provides
further proof that left anterior hemiblock may be produced by a "central" lesion of
the conduction system. An attempt was made to re-define the relationships of the
bundle of His and bundle branches to the membranous septum and septal leaflet of
the tricuspid valve and to correlate the site of surgical injury with the type of conduction disturbances produced.
Additional Indexing Words:
Atrioventricular block
Bundle of His
Pseudobifurcation
Tricuspid valves are being replaced with
increasing frequency for rheumatic and
traumatic disease as well as for Ebstein's
anomaly. 1-15 However, comprehensive studies
of conduction disturbances following tricuspid
valve replacement have not been reported.
The purposes of this study were threefold:
The first was to assess the overall incidence of
the different conduction disturbances resulting
from tricuspid valve replacement; the second
was to correlate the type of conduction
disturbance with the site of injury, and the
third was to clarify why the anterior division
of the left bundle branch (LBB), which is a
left ventricular structure, may be injured in a
surgical procedure done from the right side of
the heart.
T HE frequent occurrence of conduction
disturbances following intracardiac surgery is well documented.1-4 Appreciation,
early in the era of open heart surgery, of the
close relationship of the conduction system to
the postero-inferior margin of the membranous septum resulted in a rapid diminution
of the incidence of postoperative atrioventricular (A-V) block following repair of high
ventricular septal defects.5 The incidence of
right bundle-branch block (RBBB), however,
remains high,6 and recently, it has been shown
that left anterior hemiblock7-9 may also occur
after repair of high ventricular defects.6 10
From the Cardiovascular Division, Department of
Medicine, University of Kentucky College of
Medicine, Lexington, Kentucky.
Supported by Cardiology Training Grant HE 05771
from the National Institutes of Health, U. S. Public
Health Service. Work was done during Dr.
Aravindakshan's tenure of a research fellowship from
the Kentucky Heart Association and during Dr.
Rosenbaum's visiting professorship at the University
of Kentucky.
Received June 9, 1970; accepted for publication
July 23, 1970.
Circulation, Volume XLII, November 1970
Surgical heart block
Methods
The case records and ECGs of 15 patients who
survived tricuspid valve replacement at the
University of Kentucky Medical Center between
the years 1966 and 1968 were analyzed. There
were eight females and seven males. Two patients
had traumatic tricuspid insufficiency. The
remaining 13 had rheumatic heart disease. In the
895
ARAVINDAKSHAN ET AL.
896
Table 1
Incidence of Conduction Disturbances
Type of conduction disturbance
No. of patients
Comments
Complete A-V block
1
Temporary complete A-V block and
subsequent I-V conduction disturbance
2
Patient died 3 days after operation.
Presence or absence of I-V conduction disturbances undetermined.
I-V conduction disturbances present on
ECGs taken after recovery of A-V
conduction
I-V conduction disturbances only
No conduction disturbances
Total
6
6
15
Table 2
Cases Showing I-V Conduction Disturbances Following Tricuspid Valve Replacement
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Case
Age (yr)
1
2
3
4
5
6
7
8
44
44
29
29
38
59
35
17
Sex
Valves replaced
F
M
F
F
M
F
F
M
M, T
M, T
A, M, T
A, M, T
T
M, T
M, T
A,M,T
Mean QRS axis
Preoperative
Postoperative
+900
Indeterminate
Indeterminate
-800
+1050
- 600
+600
- 600
+30°
-100°
+1050
+1000
+1000
+1000
+300
+450
Conduction disturbances
Preoperative
Postoperative
IRBBB
IRBB
None
RBBB
None
None
None
IRBBB
Abbreviations: A = aortic valve; M = mitral valve; T = tricuspid valve; RBBB
IRBBB - incomplete right bundle-branch block: LAH = left anterior hemiblock.
two patients with traumatic tricuspid incompetence only the tricuspid valve was replaced. In
eight, both mitral and tricuspid, and in five,
mitral, tricuspid, and aortic valves were replaced.
One patient with complete A-V block died
without recovering A-V conduction; therefore,
intraventricular (I-V) conduction disturbances
(RBBB and left anterior hemiblock) could be
evaluated in only 14 patients.
Criteria for RBBB were a slow terminal QRS
force directed anteriorly and to the right, and a
QRS duration of 0.12 sec or more. Block was
termed "incomplete" when QRS duration was less
than 0.12 sec. Left anterior hemiblock was diagnosed when the AQRS became -450 or more.7-9
Left anterior hemiblock in the presence of RBBB
wvas recognized when the axis of the QRS deflection (AQRS) became oriented superiorly between
-60 and -120°, with a q1-S3 pattern and a very
small r/S ratio in lead II.7 10, 16, 17
Results
The incidence of conduction disturbances in
the 15 patients are listed in table 1. Three of
the 15 patients (20%) developed complete A-V
=
LAH and IRBBB
LAH and RBBB
LAH and IRBBB
LAH and RBBB
LAH and RBBB
IRBBB
IRBBB
RBBB
right bundle-branch block;
block during operation and were paced. Two
of these recovered A-V conduction a few
hours later; the third patient died after 3 days
without recovering A-V conduction. An
immediate postoperative tracing was not
available to determine the width of the QRS
complex of the idioventricular beats in any of
these three cases. Eight patients developed IV conduction disturbances, and in the
remaining six patients neither A-V nor I-V
conduction disturbances were observed in the
postoperative ECGs.
The I-V conduction disturbances are listed
in table 2. Five patients developed left
anterior hemiblock and six RBBB (incomplete
in three). In all instances of left anterior
hemiblock RBBB was also present (fig. 1).
However, in two (cases 1 and 4), the degree
of RBBB was not appreciably greater than
before opeartion (fig. 2), and in one (case 3),
left anterior hemiblock was transient and
lasted less than 2 weeks (fig. 3). In case 1,
Circalation, Volume XLIl
November 1970
:>*_;fm+4s
RBBB AND LEFT ANTERIOR FASCICULAR BLOCK
O*W
897
t
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A
4
41W
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Figure 1
Case 2. T:he preoperative tracings showc an indeterminate mnean QRS axis, severe right ventricular hypertrophy, and a small degree of incomplete RBBB. The postoperative ECG is characteristic of RBBB with left anterior hemiblock. Note the change in the direction of the initial
(HRS forces, with the appearance of a Q wave in leads I and aV1J, and the disappearance of q
front leads III and aVF. These ECG changes have persisted.
B.J.C.
[I,41
Pre-o p
ftt
TIN
Vil
If-fllf --1,11M
1 t;
INH110 11
Jill ttluLl1,
1-IR
II .111 -
eiI.,t
on
fl
1111
ft'
I
-tl
4ii
|. W
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Post-op
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I
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..1-T"
+R:I
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.Ir.
HI$. f-t
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llt4'IlTV t1+
li 1,;uI XM~~~~~~~~~~~~~~~~
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Figure 2
Case 4. The preoperative tracings show an AQRS about +60', left ventricular hypertrophy,
and RBBB with a QRS interval of 0.12 sec. The postoperative ECG shows, in addition, a high
degree of left anterior hemiblock with deep S waves in leads II and IIl (as commonly seen
i7i the presence of severe left ventricuilar hypertrophy). The AQRS has shifted to -60°. The
degree of RBBB has nIot chaniged appreciably. These ECG changes have persisted.
at
Circulation, Volume XLII, November 1970
898
ARAVINDAKSHAN ET AL.
E.B.
Pre-op
1
I
..
III
.....
....
aVR
aVL
dVF
VI*I
Vnax
W2
3
V
V17
4
VA
'TY
VI
01
V4
V5
V6
V4
V5
V6
+H+UH+H44++il
H H4i-+
2days
Rost-op
........
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I
2weeks
Pbst-op
11
Ni
aVR c/L
dVF
V1
V2
11
111
aVL
aVR
dVF
V1
V2
1~~~~~~~~~~~~~~~
I
V3
Figure 3
Case 3. The preoperative tracings show an AQRS at about +105° and biventricular hypertrophy. ECGs taken on the first and second postoperative days were characteristic of RBBB
with left anterior hemiblock. The AQRS shifted to -60°. However, left anterior hemiblock
was transient, and a third ECG on the 13th postoperative day showed ontly incomplete RBBB.
The AQRS shifted back to about +1200. The patient died the next day.
complete heart block occurred in the
immediate postoperative period, and the left
anterior hemiblock pattern emerged when
normal A-V conduction was restored. In case
6, incomplete RBBB was seen after recovery
from complete A-V block which lasted a day.
In case 7, incomplete RBBB appeared in the
immediate postoperative tracing but was not
present in the ECGs taken 1 mo and 2 mo
later. However, complete RBBB was seen in
the tracing taken after 9 mo.
Discussion
Involvement of the anterior division of the
LBB during tricuspid valve replacement may
seem enigmatic, but appreciation of the
anatomic relationships of the conduction
system provides a reasonable explanation. The
relationships of the conduction system to the
tricuspid valve are illustrated in figures 4 and
5. The bundle of His comprises two segments:
"penetrating" and "branching."4 7,17 21 The
penetrating portion is protected within the
rigid structure of the central fibrous body and
is only a few millimeters superior to the
insertion of the septal leaflet of the tricuspid
valve. The branching portion extends from the
point where the most posterior fibers of the
LBB originate from the main bundle to the
point marking the origin of the RBB and the
most anterior fibers of the LBB. This segment
of the bundle is precisely at the level of
insertion of the septal leaflet of the tricuspid
valve. There is no true bifurcation of the
bundle of His in the human heart, but rather a
branching segment from which the RBB and
the two divisions of the LBB arise. The bundle
Circulation, Volume XLII, November 1970
RBBB AND LEFT ANTERIOR FASCICULAR BLOCK
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Figure 4
Relationships of tricuspid valve to the conduction system in the human heart. Photograph taken from the
right side, under the dissecting microscope (reduced
from x10). The membranous septum (MS) has been
separated from the muscular septum and the tricuspid
valve has been removed, except for the insertion of
the septal leaflet (T). The conduction system has been
dissected. The right bundle branch (RBB) appears as
direct contin-uation of the bundle of His, which is
from the oval-shaped structure of the
A-V node (AVN). HB indicates the penetrating portion of the butndle. The two arrows indicate the limits
of the branching portion, from which the left bundle
branch (LBB) is given ofF. The inferior arrow also
points to the pseudobifurcatiotn of the bundle of His
into a right bu-ndle branch and anterior part of the
left bundle branch
a
seen to arise
of His gives off the fibers of the LBB almost
perpendicularly in an orderly and sequential
fashion. After the posterior fibers have been
given off, the bundle contains only the fibers
of the RBB and the anterior division of the
LBB. What appears in some microscopic
sections as a bifurcation (fig. 5) is in fact the
point at which the RBB separates from the
most anterior fibers of the LBB. This
"pseudobifurcation"0'17,22 is only a few
millimeters below the insertion of the septal
leaflet of the tricuspid valve. A small lesion at
this site may produce RBBB and left anterior
hemiblock simultaneously. It should be
stressed that the RBB is a direct continuation
of the bundle of His after all the fibers of the
LBB have been given off. The, initial segment
of the RBB is located a few millimeters below
the insertion of the septal leaflet of the
tricuspid valve. Although the RBB is
Circulation, Volume XLII, November 1970
899
considered a right ventricular structure and
the LBB and its two divisions are considered
left ventricular structures, all three are
centrally located in the upper part of the
muscular septum and within the thin fibrous
sheath of the membranous septum and,
therefore, can be involved in pathologic
processes stemming from either side of the
heart.
Depending upon the site and extent of
injury (fig. 6) to the conducting system, five
types of conduction disturbances may be
expected after tricuspid valve replacement:
(1) Monofascicular complete A-V block with
a narrow QRS complex due to a lesion of
the penetrating portion of the bundle of His.
(2) Complete A-V block with a wide QRS
complex due to an extensive lesion of the
branching portion. This has been termed a
"proximal" form of bifascicular block.22 Un
fortunately, no postoperative tracings of
our cases with complete A-V block showing
idioventricular beats were available to test
these two possibilities. (3) RBBB with left
anterior hemiblock due to a lesion limited to
the branching portion after the posterior fibers
of the LBB have been given off, or more
likely, to a lesion of the pseudobifurcation
(site 3 and 3' of fig. 6). This occurred in five
of our 14 cases. (4) RBBB alone due to a lesion
of the initial segment of the RBB and this was
seen in three of our cases, and (5) left anterior hemiblock alone due to a lesion of the proximal end of the anterior division of the LBB.
An example of left anterior hemiblock alone,
however, was not seen in our cases. This type
of correlation of the site of injury to the ECG
manifestations is an oversimplification because
surgical injury is often diffuse and involves
more than one area, but nonetheless our data
are consistent with such correlations.
Condorelli23 obtained RBBB in canine
hearts by partial transection of the bundle of
His (probably at the level of the branching
portion). Sciacca and Sangiorgi24 demonstrated conduction disturbances which we
would classify as left anterior hemiblock after
partial transection of the bundle of His in the
area of insertion of the septal leaflet of the
900
ARAVINDAKSHAN ET AL.
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Figure 5
Serial sections of the conducction system in a normal human heart. The diagram at bottom
right shows the level of sections 1 to 5; the solid black indicates the A-V node, bundle of His,
main LBB, and the thin anterior division and thicker posterior division. The parallel interrutpted lines correspond to the RBB. (1) The arrow points to the penetrating portion of the
bundle within the central fibrous body. (2) Branching portion (upper arrow). The fibers given
off toward the left (left arrow) correspond to the posterior part of the LBB. On the right, insertion of the septal leaflet of the tricuspid valve. (3) Pseudobifurcation of the bundle of His
into the RBB and most anterior part of the LBB, just atop the summit of the muscular septum.
(4) Terminal part of the pseudobifurcation. (5) Distal portion of the RBB.
tricuspid valve (fig. 3A and 3B of reference
24). The site of injury in these canine
experiments23'24 was comparable to those in
our surgical cases, and thus the work of Sciacca
and Sangiorgi24 supports our thesis that left
anterior hemiblock was caused by a central
lesion in our cases.
It has been suggested that fibers destined
to form the RBB and LBB are already
differentiated in the lower third of the bundle
of His.23-23 This early differentiation and a
lesion of the main bundle need not be invoked
to explain RBBB and left anterior hemiblock
in our cases since both fascicles have a short
common pathway where a localized lesion
(site 3', fig. 6) would cause RBBB and left
anterior hemiblock. Injury to the distal portion
of the anterior division of the left bundle is
unlikely to have been the cause of left anterior
hemiblock in our cases.
Conduction disturbances were a common
and significant complication of tricuspid valve
replacement even in our retrospective study in
which the true increase was probably
underestimated because complete ECGs were
not always available early in the postoperative
period.
C:rculation, Volume XL11! Nov ember 1970
RBBB AND LEFT ANTERIOR FASCICULAR BLOCK
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Figure 6
Diagriammatic representation of the conduction sysand the five sites which may be injured durinig
tricuspid valve replacement. A lesion at 1 will callse
monofascicuilar complete heart block with a n2arrotw
QRS complex; at 2, complete heart block with a wide
3', RBBB w;ith left anterior
QRS complex; at 3
tem
or
hemiblock;
at
4, RBBB alone, and
at
5, left
hemiblock alone. For fturther descr iption
T
insertion
of
the
septal leaflet
of
the
anterior
see
text.
tricuspid
valve.
It may be argued that injury of the
conduction system was associated with aortic
or mitral valve replacement and not tricuspid
valve replacement. Conduction disturbances
as a result of mitral valve replacement alone
are virtually unknown. A high incidence of
complete A-V block was repo rted in the early
experience of aortic valve replacement.28
Subsequently, the incidence diminished because of improved appreciation of the
relationships of the bundle of His to the
commissure between the right coronary and
noncoronary aortic cusps. In two of our five
cases in which RBBB and left anterior
hemiblock occurred, the aortic valve also had
been replaced, and it is possible that left
anterior hemiblock resulted from the trauma
of this procedure. In the two cases in which
both mitral and tricuspid valves were
replaced, and in the case in which only the
tricuspid valve was replaced, it is hard to
conceive that RBBB and left anterior
hemiblock resulted from anything other than
Circulation, Volume XLII, November 1970
901
direct injury of the conduction system during
tricuspid valve replacement.
Complete A-V block produced at the time
of surgery adversely affects the surgical result.
Block of the RBB alone or in combination
with block of the anterior division of the LBB
causes no immediate concern, but the longterm prognosis has yet to be determined. Left
anterior hemiblock and RBBB may lead, in
time, to complete A-V block.7'17 22, 27, 28 This
progression has not been documented in
surgical RBBB with left anterior hemiblock,
but total dependence of A-V conduction upon
the posterior division of the LBB may increase
the risk of complete heart block in later life.
Therefore, surgical attention should be
directed not only to the avoidance of damage
to the main bundle, but also the right bundle
and left anterior division.
Acknowledgment
The authors gratefully acknowledge the helpful
critical review of the manuscript by Drs. Ralph
Shabetai and Leonard Gettes.
References
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Circulation, Volume XLII, November 1970
Right Bundle-Branch Block and Left Anterior Fascicular Block (Left Anterior
Hemiblock) Following Tricuspid Valve Replacement
V. ARAVINDAKSHAN, MARCELO V. ELIZARI and MAURICIO B.
ROSENBAUM
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Circulation. 1970;42:895-902
doi: 10.1161/01.CIR.42.5.895
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