Causes of right bundle branch block

May 19, 2000

Right bundle branch block (RBBB) is a not uncommon pattern seen on the electrocardiogram (show ECG 1). (See "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 figure 1) [1]. 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 years.

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 — 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 ECG 2).

  •  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 RBBB [7].

PROGNOSIS OF RBBB — 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" and see "Course and treatment of chronic bifascicular and trifascicular block").

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" and see "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 mortality [8].

TREATMENT — 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.