The story of left bundle branch block from interesting anomaly to a electrophysiologic fixable condition

In the beginning the EKG pattern of LBBB was an interesting phenomenon . William Einthoven in 1925 presented a case with a tracing that had also been recorded 31 earlier in the same patient. No one knew what the tracing signified and Dr. Einthoven remarked that the patient with this finding seemed to not be bothered by any heart symptoms.

As time went on it was realized that the pattern represented a "block" or conduction delay in the left branch of the Bundle of His and became established as a reliable sign of heart disease, it being often associated with ischemic heart disease,hypertensive heart disease and various cardiomyopathies.

Occasionally LBBB was noted in patients without obvious structural heart disease and the effect(s) of the cases of "lone "LBBB  on cardiac function was not initially appreciated.

 However, as early as  1979  physiologic studies  (1) on "lone LBBB" demonstrated significant septal and left ventricular  wall motion abnormalites associated with decreased left ventricular function and impaired relaxation. Later numerous studies on LBBB have detailed  the pathophysiology of the electrical and mechanical dyssynchrony of LBBB as well as molecular perturbations and deleterious ventricular remodeling.

In 2005 and 2013 reports from France described a cardiomyopathy that occurred with variable latency periods from the onset of LBBB that was to varying degrees reversible by cardiac resynchronization therapy (CRT) . Think about that for minute. LBBB may cause a cardiomyopathy that is possibly reversible by CRT.

Recognition of the role of a prolonged QRS and decreased cardiac function and the role of ventricular dyssynchrony in HF lead to idea of cardiac resynchronization therapy (CRT) in which there was pacing of  both the right ventricle and the left ventricle( with a pacing lead in  a coronary vein accessed via the coronary sinus)  in an effort to restore synchrony between the septum and the ventricular free wall.

From 2001 through 2009 there were several randomized clinical trials that demonstrated the efficacy of CRT in improving cardiac function, lessening  symptoms and in reducing mortality in heart failure patients.

As CRT was increasingly used to treat refractory heart failure (HR) it was realized that patients with a LBBB pattern were more likely to respond favorably and that CRT was essentially a treatment for LBBB.

Risum has published data from speckle tracking echo studies that suggest that the LBBB patients with HF who  respond favorably to CRT are those with a particular contraction pattern consisting of early septal activation and bulging of the lateral left ventricle followed by contracting of the LV with peak contraction occurring after aortic valve closure.