User:Mr. Ibrahem/Left bundle branch block

Left bundle branch block (LBBB) is a type of electrical conduction abnormality of the heart seen on the electrocardiogram (ECG). In and of itself, it results in no symptoms. The condition is generally permanent.

Causes include dilated cardiomyopathy, such as may occur following a heart attack, valvular heart disease, or heart failure and amyloidosis. Though some cases occurs without any specific cause. The underlying mechanism involves abnormal conduction down both anterior and posterior left fascicles of the His-Purkinje system.

Diagnosis requires four conditions: the rhythm is supraventricular, the QRS is greater than 120 ms, lead V1 has a QS or a small r with a large S wave, and lead V6 has a notched R and no Q wave. When the QRS duration is less than 120 ms, but the other criteria are present, it is called an incomplete LBBB. New onset LBBB together with chest pain was previously, but is no longer considered, a STEMI equivalent. Rather it is recommended the Sgarbossa criteria be applied.

No specific treatment is generally required. Management is directed at the underlying cause, which determines the outcomes. LBBB is common, affected about 1 in 1,000 people. About 33% of those with heart failure are affected. Those affected are not permitted to fly an aircraft in the United States or United Kingdom.