Download Excess mortality and morbidity associated with right bundle branch

JAM COLL CARDIOL
1983,1(5): 1207~ 12
1207
Excess Mortality and Morbidity Associated With Right Bundle Branch
and Left Anterior Fascicular Block
MICHAEL B. PINE, MD, FACC, MICHA OREN, MD, FAce, RUSSELL CIAFONE, MD, FACC,
BERNARD ROSNER, PhD, YUZO HIROTA, MD, BURTON RABINOWITZ, MD, FACC,
WALTER H. ABELMANN, MD, FACC
Boston, Massachusetts
Excess mortality and morbidity associated with right
bundle branch and left anterior fascicular block were
evaluated in 108 patients with block (age 74 ± 10 years,
69% male) and 108 age- and sex-matched control patients with normal conduction. Clinical characteristics
were similar initially except for more congestive heart
failure in patients with block. Life table analysis revealed
a higher 12year mortality with block, evenafter omitting
patients with moderate or severe congestive heart failure
(risk ratio 1.47, P < 0.05). Compared with control sub-
Disturbances of intraventricular conduction are associated
with distinct electrocardiographic abnormalities (1,2), but
the clinical significance of these abnormalities remains unclear. Intraventricular conduction defects can be a marker
of underlying clinically significant heart disease and may
have independent prognostic importance as a precursor of
complete heart block, cardiac syncope or sudden death (110). However, the significance of right bundle branch block
is highly dependent on the clinical characteristics of the
patients in whom it is found. In generally healthy adults,
bifascicular block may have a benign prognosis, but in patients with coexisting disease, its prognosis can be ominous
with a 1 year mortality rate as high as 17% (11-14).
Previous studies have described the clinical features and
progress of patients with intraventricular conduction disturbances, but have given little information about the characteristics and fate of the population from which the study
sample was drawn. In the present study, 108 patients with
right bundle branch and left anterior fascicular block are
compared with an age- and sex-matched group of patients
From the Harvard-Thorndike Laboratory of Beth Israel Hospital, Department of Medicine, Beth Israel Hospital and Harvard Medical School,
Boston, Massachusetts. Manuscript received September 22, 1982; revised
manuscript received December 22, 1982, accepted December 23, 1982.
Address for reprints: Michael B. Pine, MD, Chief, Cardiology Section,
VA Medical Center, 3200 Vine Street, Cincinnati, Ohio 45220.
© 1983 by the Amencan College of Cardiology
jects, the group of patients with block had more sudden
death and deaths of unknown cause, but a similar number of noncardiac and diagnosed cardiac deaths. More
patients with block developed new second and third degree atrioventricular block or new overt coronary artery
disease, but this finding did not support prophylactic
pacing in asymptomatic patients. The importance of internal controls in assessingthe natural history of clinical
and electrocardiographic abnormalities is emphasized.
with intact intraventricular conduction. A 12 year followup of these patients revealed excess mortality and morbidity
that was independentof recognized coexistent cardiac disease.
Methods
Study patients. All electrocardiograms performed on
inpatients and outpatients at the Beth Israel Hospital between
January 1, 1964 and December 31, 1968 were reviewed.
One hundred and eight patients were found to have right
bundle branch block and left anterior fascicular block, diagnosed by the following criteria: 1) a QRS duration of 120
ms or greater with a qR, rSR' or tall R wave in lead V I,
and 2) a counterclockwise frontal plane QRS vector with a
mean axis during the first 80 ms negative more than - 30°.
Patients with electrocardiograms consistent with "pseudoleft axis deviation" as described by Pryor and Blount (15)
were not included in this study.
A matched series of patients (control subjects) was obtained asfollows: beginning with each study patient's electrocardiogram reference number, tracings were reviewed
going backward 100 numbers and then forward 100 numbers
until a patient was found who was of the same sex and age
(± 2 years) as the study patient and who had an electrocardiogram obtained between 1964 and 1968 in which no
intraventricular block (left, right, anterior fascicular or pos0735-1097/83/0501207-6$03 00
1208
PINE ET AL
J AM COLL CARDIOL
1983;1(5) 1207-12
terior fascicular) was present. Study and control patients
were subsequently evaluated in an identical fashion (Table
I).
Follow-up. A profile of each patient at the time of the
index electrocardiogram included the patient's presenting
complaints, cardiovascular symptoms and diagnoses, other
major medical diseases, roentgenographic and electrocardiographic findings and cardiac medications . History relating to the development of any conduction disturbance was
also recorded . Patients were followed up by reviewing hospital charts and office records. When complete records were
not available, patients, relatives and physicians were contacted directly. A complete patient profile was repeated for
the next available follow-up examination 2 years after a
previous profile or whenever a significant change in status
occurred . A complete profile was also prepared for the last
available follow-up. Patients with electrocardiograms that
revealed complete atrioventricular (A V) dissociation with a
ventricular rate of less than 60 beat s/min were considered
to have developed third degree heart block. Autopsy data
were obtained whenever possible. Patients who were not
known to have died and for whom follow -up data could not
be obtained through January I, 1978 were considered lost
to follow-up after their last evaluation .
Data analysis. The prevalences in study and control patients of each patient characteristic at the time of the index
electrocardiograms were compared using the Yates' corrected chi-square statistic (16) . Mortality in the two groups
was compared using life table analysis . The Yates ' corrected
chi-square statistic was also used to compare the incidence
rates of various conditions over time between the study and
control patients who initially did not have these conditions.
The log-rank test (17) was used to compare the life table
experiences of study and control patients, again restricting
the analysis to those who were initially negative for the
condition being considered. This latter method offers the
advantage of taking into account when as well as whether
the conditions developed .
Table 1. Presenting Complaints in 108 Patients With and 108
Patients Without Bifascicular Block
With Block
(no.)
Routine physical examination
Acute cardiac problem (no pre vious
cardiac history)
Acute cardiac problem (with previous
cardia c history)
Follow -up of chronic cardiac cond ition
Syncope . unknown cause
Noncardiac complaint
Total
3
Without Block
(no .)
II
5
9
14
14
4
6
I
2
74
108
73
108
Results
Patient characteristics. At entry into the study , the 108
patients with bifascicular block ranged in age from 32 to
102 years (mean ± standard deviation == 74 ± 10). Seventy-five (69%) were men . In 6% of patients, bifascicular
block was found to have developed in conjunction with an
acute myocardial infarction.
Initial diagnoses and electrocardiographic abnormalities
are presented in Table 2. Congestive heart failure was mild
or completely compensated in 20 patients, moderate in 9
and severe in 7. Of the eight patients with syncope, four
had cardiac syncope, three had syncope of unknown cause
and one had noncardiac syncope. Of the 24 patients with
ventricular arrhythmia, 12 had rare unifocal, 11 had frequent
unifocal, 1 had multi focal and no patient had paired premature ventricular complexes . In 58% of patients, no evidence of organic heart disease was found to be associated
with bifascicular block.
Comparisons of patients with bifascicular block and control patients (Table I and 2) revealed similar distributions
of presenting complaints and electrocardiographic abnormalities, and similar prevalences of all diagnoses except
congestive heart failure , which was nearly twice as common
in patients with bifascicular block (probability [p] < 0.05 ).
This was reflected by a higher proportion of patients with
bifascicular block having roentgenographic evidence of
moderate or severe cardiomegaly (67 versus 51%, P < 0.05) .
Survival. Of the 2 16 patients in this study, 7% had only
an initial contact, 17% were lost to follow-up examination
before the end of the follow-up per iod and 76 % were followed up either until they died or to the end of the followup period. Patients who were evaluated after initial contact
and were alive at last contact were followed up for an
average 7.6 years, with no significant difference in length
of follow-up for control patients and those with bifascicular
block.
Life table analysis (Fig. I) revealed a higher mortality
in patients with bifascicular block than in control patients
during the 12 year follow-up per iod (p < 0.02). Because
the increased prevalence of congestive heart failure in patients with bifascicular block at entrance to the study may
have accounted for the poorer survival of patients with bifascicular block , the life table analysi s was repeated omitting
patients with moderate or severe congestive heart failure.
When patients with congestive failure were removed from
the analysis (Fig. 2) , the difference in mortality remained
significant (p < 0.05) with a risk ratio of 1.47.
Patients with bifascicular block and control patients had
similar mortality due to noncardiac and diagnosed nonconduction-related cardiac causes (Table 3). Bifascicular block
was associated with more sudden or conduction-related deaths
and deaths of unknown cause (p < 0.05).
J AM COLL CARDIOL
1983:1(5): 1207-12
NATURAL HISTORYOF BIFASCICULAR BLOCK
1209
Table 2. Initial Diagnoses and Electrocardiographic Abnormalities in 108 Patients With and 108 Patients Without Bifascicular Block
Patients With Block
(%)
Diagnoses
Coronary artery disease
Congestive heart failure
Syncope
Valvular heart disease
Systemic hypertension
Cerebrovascular disease
Pulmonary embolic disease
Cancer
Renal insufficiency
Pulmonary msufficiency
Hepatic insufficiency
Diabetes mellitus
Thyroid disease
Electrocardiographic abnormalities
Atrial fibrillation or flutter
Ventricular premature complexes
10 atrioventricular block
Left ventricular hypertrophy
NS
41
33
7
I
p
Value
Patients Without Block
NS
38
17
7
<
(%)
0.05
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
32
II
4
17
9
6
I
20
5
2
31
10
2
15
10
9
I
14
6
NS
NS
NS
NS
8
22
8
26
10
14
5
30
= not sigruficant; p = probability.
Complications. Study patients with bifascicular block
without coexisting conduction abnormalities other than first
degree AV block had a significantly greater incidence of
subsequent high degree AV conduction disturbances than
did control patients (risk ratio = 13.5, p < 0.001, Fig. 3).
The development of overt coronary artery disease, when
none was recognized at the beginning of the study, was also
greater in patients with bifascicular block (risk ratio = 2.2,
p < 0.05, Fig. 4). Cardiac syncope developed in only four
patients with bifascicular block and three control patients.
The new development of other conditions and abnormalities
during the follow-up period was similar in both groups.
During this study, 66 surgical procedures were performed
in patients with bifascicular block, compared with 75 operations in control patients. There were no surgical complications related to rhythm or conduction disturbances in patients with bifascicular block, and transvenous pacing was
not required during any of these surgical procedures.
Figure 1. Survival of patients with right bundle branch and left
anterior fascicular block and that of control patients. At time 0, n
= 103 for patients with block and n = 98 for control patients.
Mortality was significantly higher in patients with bifascicular
block (p < 0.02).
Figure 2. Survival of patients with right bundle branch and left
anterior fascicular block and that of control patients after people
with moderate or severe congestive heart failure were removed
from the study population. At time 0, n = 88 for patients with
block and n = 94 for control patients. Mortality was significantly
higher in patients with bifascicular block (p < 0.05).
100
100
80
80
60
60
'/-
OJ
>
::;
<t
OJ
40
>
-'
40
<t
•
o
20
CONTROL
BLOCK
20
( I NUMBER REMAINING
o
•
CONTROL
( l
NUMBER REMAINING
0
181
181
BLQCK
0
i
o
i
I
I
I
I
2
4
6
8
10
YEARS
12
I
I
I
0
2
4
i
I
I
t
6
8
10
12
YEARS
J AM COLL CARDIOL
1210
PINE ET AL
1983.1(5) 1207-12
Table 3. Causes of Death of Patients With and Without
(!50)
100
Bifascicular Block
With Block
(no. [%])
Without Block
(no. [%])
(211
-;'EK>
.
(14)
(9)
w
Sudden orconduction-related
Other cardiac-related
Not cardiac-related
Unknown
Total
lJ)
7 (13)
16 (29)
28 (51)
4 (7)
55 (100)
13 (17)
20 (27)
31 (41)
II (15)
75 (100)
w
lJ)
60
(16)
0
>l>:
(4)
2!40
0
l>:
0
u
~zo
•
o
0
....::I:
i
Discussion
Figure 3. Patients with right bundle branch block (RBBB) and
left anterior fascicular block (LAFB) and control patients remainingfree of second andthird degree AV block. 100% = all people
without second and thirddegree AV block at entry intothe study.
At time 0, n = 81 for patients with block and n = 87 for control
patients. The development of second and third degree AV block
was more common in patients with right bundle branch block and
left anterior fascicular block at the beginning of the study (risk
ratio = 13.5; p < 0.001)
100~(74)
(eel
1411
(211I
(19I
(9)
(!lSI
l44l
(0)
(211
~
u
o
...J
II>
~ 40
....
•
o
o
1=
i
CONTROL
LAFS·RBBB
( ) NUMBER
20
o
~)
~
;60
::>
,
o
REMAINING
/;
YEARS
CONTROL
LAFB-R8B8
J NUMBER REMAINING
0
Association with congestive failure. Patients with intraventricular conduction abnormalities tend to be older and
have more serious disease than the general population as
indicated by prevalences of right bundle branch block and
left anterior fascicular block of less than 0.01 % in generally
healthy young military personnel (II). 0.35% in a survey
of Belgian citizens 35 years or older (12) and about I % in
older hospitalized patients (3,4). In the present study, after
the influence of age, sex and the method of screening were
considered, coexisting right bundle branch block and left
anterior fascicular block was independently associated only
with congestive heart failure. The high prevalence of coronary artery disease and hypertension in patients with block
was similar to that found' by other investigators studying
hospital and referral populations (3-10), but data on control
patients indicated that the high prevalence of these conditions was a result of the population sampled rather than
being related to the conduction abnormalities themselves.
eo
(
11
i
i
i
i
i
i
i
0
2
4
6
8
10
12
YEARS
Figure 4. Patients with right bundle branch block (RBBB) and
left anterior fascicular block (LAFB) and control patients remaining free of overt coronary artery disease. At time 0, n = 62 for
both groups. 100% = all people without overt coronary artery
disease at entry intothe study. Thedevelopment of overt coronary
artery disease was more common inpatients with bifascicular block
at the beginning of the study (risk ratio 2.2, p < 0.05).
High prevalence rates of diabetes mellitus and cancer in
both patients with block and control patients indicate that a
high incidence of cardiac and noncardiac disease would be
found in any sample of elderly patients who had electrocardiograms performed in the hospital. The present data do
not explain whether the association of right bundle branch
block and left anterior fascicular block with congestive heart
failure represents a propensity to develop conduction system
disease in patients with more severe myocardial dysfunction, or whether the association of the two conditions indicates a common etiology.
Prognosis: future mortality and AV block. Previous
studies have found varying prognoses in patients with right
bundle branch block and left anterior fascicular block depending on the population from which the patients were
drawn. Coexistent heart disease was found to be a major
factor influencing survival (5-14). One study attempted to
deal with this difficulty by comparing survival with that in
an age-matched control group derived from life tables for
the general population (10), but this analysis did not allow
for the risk of being included in a group that was screened
in a medical setting. The control group in the present study
compensates for the method used to obtain the patients with
bifascicular block, and when patients with moderate to severe congestive heart failure are removed from the analysis,
it clearly indicates that the presence of right bundle branch
block and left anterior fascicular block is associated with
significantly higher future mortality independent of coexisting clinically recognized medical conditions. Not surprisingly, the development of second and third degree block
was much more frequent in patients who entered the study
with intraventricular conduction disturbances than in control
NATURAL HISTORYOF BIFASCICULAR BLOCK
J AM COLL CARDIOL
1983. 1(5) 1207- 12
patients, with an incidence of these conduction disturbances
in the study group of about 2% a year. Other studie s
(1,5,6,8,9,11,12 ,18) have shown similar or higher degree s
of progression to AV block depending on the length of
follow-up and the population being sampled .
In the present study, the incidence of cardiac syncope
and pacemak er insertion was too low to permit statistical
analysis . The safet y of surgical procedures without temporary pacemaker insertion in patients with uncomplicated
intraventricular conduction disturbances was confirmed in
this study , as it has been in others (19-23 ).
Causes of death. An analy sis of the causes of death of
study patients and control patient s revealed that sudden or
conduction-related deaths and deaths of unknown cause were
responsible for most of the exce ss mortality observed in the
patients with bifascicular block . This observation is consistent with a direct causal relat ion between conduction system disease and excess risk of dying in patients with right
bundle bran ch block and left anterior fascicular block , although it is also possible that bifascicular block served as
a marke r of covert myocardial or coronary artery disease
that eventually resulted in excess mortality in patient s with
block. Furthermore, these data do not indicate that compl ete
heart block was important in increasing mortality amon g
study patients because significant ventricular ectopic arrhythmi as have also been associated with intraventricul ar
conduction abnormalities (7,24,25).
Role of His bundle electrograms. A number of investigators have evaluated the usefulne ss of His bundle electrograms in determining which patient s with bifascicular
block are at greater risk of develop ing heart block or dying
suddenly (26-38). The result s of these studies have not been
conclu sive because in only some of the patients studied were
prolonged HV intervals predictive of future difficulties. Even
when His bundle studies produced a statistically significant
differenti ation between high and low risk groups, the incidence of complications appeared too low to justify the
routin e insertion of a prophylactic perman ent pacemaker
even in "high risk" patients.
Indications for pacemaker therapy. In the present study,
His bundle electrograms and othe r electrophysiolog ic studies were not performed to subdivide study patient s. The
increased risk of clinically serious complications, althou gh
substantial, was probabl y not sufficient to ju stify pacemaker
therapy, especially because ventricular arrhythmia rather
than heart block may have been the cause of some of these
difficult ies. Howe ver , the risk ratios derived in this study
provide a first order definition of a population at risk . and
using Bayesian analysis (39), other independently derived
information relating to conduction abnormalities such as
conduction during atrial pacing (40) can be used to modify
the risk ratio for subsequent mortality and morbidity in
subpopulations of patients with bifascicular block. In this
manner, small groups of patients with a risk ratio high
1211
enough to j ustify a trial of prophyl actic pacing may ultimately be identified, similar to the group of patient s with
acute anterior wall myocardi al infarction who developed
tran sient complete heart block (4 1,42) .
Finally, the present study emph asizes the need for internal control groups in studies of the natural history of
clinical and electrocardiographic abnorm alities, and suggests that individual centers dealing with such problems
should develop their own data that would be spec ifically
applicable to their particular patient populations .
We acknowledge the generou s assistance of George Kurland, MD , Director
of the Electrocardiography Laboratory at the Beth Israel Hospital , whose
advice and cooperation in facilitat ing data retrieval were invaluable .
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