Left bundle branch block (LBBB) is seen on the ECG when there is failure of the electrical impulse to be conducted via the His-Purkinje fibers.
Patients who present with LBBB may have a congenital heart defect or prior cardiac surgery. The medical history should include symptoms like exercise tolerance, presence of fatigue, dyspnea, syncope, orthopnea and falls. The duration and intensity of symptoms should be recorded.
Physical exam may be unremarkable in some patients with LBBB, but auscultation may reveal a diminished or absent first heart sound and/or reversed splitting of the 2nd heart sound. Patients with heart failure may present with the following features:
In a patient with LBBB, blood work is not essential as it is often noncontributory. However, in symptomatic patients it is important to order cardiac biomarkers to ensure that the patient has not suffered a myocardial infarction. Levels of creatine kinase, troponin and LDH should be serially ordered in symptomatic patients. If the cause of LBBB is due to an infection or an inflammatory process, ESR or CRP levels should be ordered. While not specific for myocarditis, they do help in assessing the effects of treatment. Other blood work will depend on the suspected cause of the LBBB.
Routine blood work that is done includes:
All patients who have been diagnosed with LBBB need a thorough workup of their heart. It is important to treat the underlying cause if found. There is no medical therapy to treat LBBB. In all asymptomatic patients the treatment is an annual ECG.
For patients who have syncope or symptoms of heart failure, a dual chamber cardiac pacemaker is required. While resynchronization therapy may help improve symptoms, survival is not always improved. The improvement in patients is variable and not predictable . Pacemakers can be inserted by the cardiologist or cardiac surgeon under local anesthesia. In most cases, progression to a complete heart block is rare.
Left bundle branch block does not progress to a complete heart block in most cases. The overall prognosis of LBBB depends on coexisting cardiac disease. In patients with heart failure, biventricular pacing can improve symptoms and morbidity. In general, the higher the cardiac morbidity, the poorer is the prognosis in the presence of LBBB. Patients who develop LBB after open heart surgery procedures generally do not have a higher morbidity as long as the primary disorder has been surgically corrected.
LBBB has several causes which include the following:
In children LBBB is usually associated with congenial heart disease and is quite rare in normal healthy children. In adults, LBBB may appear after a variety of open heart surgery procedures on the left ventricular outflow tract such as after aortic valve replacement, surgery on the septum, or aortic annulus. The exact number of people with LBBB is not known but the numbers are not miniscule. Because many patients remain asymptomatic, they never come to medical attention. The disorder can occur in people of all ages and in all races.
Left bundle branch block develops when there is interruption of the electrical impulse in the heart. The conduction from the sinus node is normal until it reaches the bundle of His-Purkinje tissues. At this point the electrical conduction may be delayed or absent. There can be either a complete LBBB or an incomplete left bundle branch block known as a hemiblock. The damage to the electrical conduction may be a result of structural defects in the heart since birth (eg. endocardial cushion defects) or they may be caused during open heart surgery on the left ventricular outflow tract.
Prevention of LBBB is not possible in most cases. For children born with heart defects, it is important to follow up closely with a cardiologist to ensure that the disease is not progressing. If the child becomes symptomatic, pacing may be required. Adults who undergo open heart surgery and develop LBBB generally do not show symptoms as long as surgery corrected the primary disorder. However, symptomatic adults who develop heart failure may need a permanent pacemaker. For patients who developed an LBBB after a myocardial infarction, change in lifestyle is important. This means eating healthy, discontinuing smoking, regular exercise and remaining compliant with medications. Levels of cholesterol and blood sugar should be controlled to prevent progression of atherosclerotic heart disease.
Left bundle branch block (LBBB) is a conduction abnormality seen on the ECG when the regular sequence of electrical impulse is altered in the His-Purkinje fibers. In the majority of cases, this conduction abnormality is seen in people with some type of underling heart disease. However, it must be noted that LBBB may also be seen in people with no symptoms and in the presence of any structural defect in the heart. When LBBB is identified on the ECG it often makes the diagnosis of a myocardial infarction difficult. In addition, this conduction abnormality also interferes with the ECG analysis in patients who undergo exercise testing. Patients who have a low ejection fraction and develop LBBB, generally tend to develop dyssynchronous ventricular beats that eventually results in congestive heart failure. It is important to realize that LBBB may not always cause symptoms but it is not a benign disorder  .
There are many causes of left bundle branch block (LBBB) that include heart disease that developed at birth, open heart surgery procedures and following a heart attack. Patients should be told that LBBB rarely progresses to a complete heart block or cause sudden death and to watch out for other symptoms of heart disease like shortness of breath, swelling of the legs, chest pain or fatigue. They should be encouraged to have annual visits for a physical checkup and undergo a 12 lead ECG if they develop chest pain or dizziness. All symptomatic patients should be told to have more frequent visits with their cardiologist. Patients should be told that there may be a need for a pacemaker if the symptoms of heart failure do not respond to medications. Patients with LBBB need instructions on what types of activities they can carry out. Patients who are symptomatic or have a tendency to develop arrhythmias need to limit themselves from intense physical activity. Those patients without symptoms can perform most daily living activities.