Causes of right bundle branch block
Right bundle branch block (RBBB) is a not uncommon pattern seen on the
"Electrocardiographic interpretation of right bundle branch block"
The incidence of RBBB increases with age. In one prospective study of 855 men
followed for 30 years, the incidence was 0.8 percent in subjects at age 50,
9.9 percent by age 75 and 11.3 percent by age 80 (show
There was no significant association with risk factors for or the presence of
ischemic heart disease, myocardial infarction, or cardiovascular deaths,
suggesting that RBBB is usually a marker of a slowly progressive degenerative
disease that also affects the myocardium. Similar observations apply to left
bundle branch block [1
RBBB can rarely occur in an otherwise normal heart [2,3
In a study of 237,000 airmen under age 30, for example, 394 cases of complete
RBBB were found, representing an incidence of 0.2 percent [3
Ninety four percent of these subjects had a normal cardiovascular examination
and the course was benign, with only one subject requiring a pacemaker in 10
There is, however, a subgroup of patients with RBBB and no structural heart
disease who develop potentially fatal ventricular arrhythmias [4
The QT interval is normal in this syndrome, but there are persistent ST
segment abnormalities in leads V1 through V2 or V3.
CAUSES OF RBBB
¡ª The right bundle branch is
vulnerable to stretch and trauma for two-thirds of its course when it is near
the subendocardial surface. Thus, conduction in the right bundle can be
compromised by the following settings:
• Chronically increased right ventricular
pressure, as in cor pulmonale, which may also be associated with
electrocardiographic findings of right ventricular hypertrophy (show
• A sudden increase in right ventricular pressure
with stretch, as in pulmonary embolism.
• Myocardial ischemia, infarction, or
inflammation (as in myocarditis).
Other causes include hypertension, cardiomyopathies, congenital heart disease,
and mechanical damage, as may occur during right-sided cardiac catheterization
or with the placing of a pacing catheter in the right ventricle. RBBB can also
result from fibrosis of the skeleton of the heart; this disorder is called
Lev's disease with involvement of the left heart skeleton and Lenegre's
disease without such involvement [3,5,6
There are also settings in which RBBB may be transient. Examples include
pulmonary embolism, hyperkalemia, chest trauma, and, in following thrombolytic
therapy in occasional patients with an acute myocardial infarction and new
PROGNOSIS OF RBBB
¡ª The prognosis of RBBB
is related largely to the type and severity of the underlying heart disease.
As an example, patients who also have type II second degree atrioventricular
(AV) block or multifascicular block generally have diffuse myocardial disease
and a guarded prognosis. (See
"Second degree atrioventricular block: Mobitz type II"
"Course and treatment of chronic bifascicular and trifascicular
There are also issues that are discussed elsewhere including the development
of multifascicular block (including RBBB) during acute myocardial infarction
and the pre- and perioperative management of patients with RBBB. (See
"Conduction abnormalities after myocardial infarction"
"Temporary cardiac pacing"
RBBB in patients undergoing noncardiac surgery
In patients undergoing noncardiac surgery, the presence of a RBBB is not
associated with an increase in postoperative cardiac complications or
¡ª Patients with isolated chronic
RBBB are generally asymptomatic and do not require a pacemaker. However, this
recommendation may change if syncope occurs, particularly if it reflects the
concurrent presence of other conduction disturbances, such as third degree or
type II second degree AV block or block in other fascicles.