Bundle branch blocks usually do not cause symptoms. They are not considered to be irregular heartbeats or arrhythmias.
A block in the right bundle branch can occur in people who otherwise seem normal. If it happens with a heart attack, it can be a sign of serious heart muscle damage.
A block of the right bundle branch may cause an electrocardiogram to be distorted. The distortion usually is not enough to make diagnosing a heart attack difficult. It may be a sign of worsening heart conditions. It can also appear after an embolism in the lung.
A block in the left bundle branch can sometimes be benign and not cause problems. However, it always interferes with using an electrocardiogram to diagnose heart disease.
Causes and Risk Factors
Bundle branch block is a common disorder. It occurs in many medical conditions.
A right bundle branch block only occurs in medical conditions that affect the right side of the heart or lungs. Finding a right bundle branch block is a signal to your doctor to look for other conditions, including blood clots to the lung, chronic lung disease, cardiomyopathy and defects of the wall between the upper chambers or lower chambers of the heart (atrial and ventricular septal defects). However, right bundle branch block can also occur in normal, healthy individuals, so an examination may reveal no cause.
A left bundle branch block usually is a sign of an underlying heart disease, including dilated cardiomyopathy, hypertrophic cardiomyopathy, high blood pressure, aortic valve disease, coronary artery disease and other heart conditions. While left bundle branch block can appear in healthy people, it most often does not.