About one third of patients with heart failure (HF) do not benefit appreciably or respond to cardiac resynchronization treatment (CRT). Some other have a clinical benefit with physiological confirmation in the form of echocardiographic demonstration of reduction in heart size and increase in the ejection fraction. A relatively small subset show a marked improvement both symptomatically and in terms of impressive improvement in terms of ejection fraction and reduction in left ventricular size.
Neither EKG nor echocardiographic patterns accurately predict who will respond and to what degree. However, patients with a LBBB EKG pattern -particularly using the new criteria suggested by Strauss (1 )- are much more likely to have a favorable response. In fact CRT basically "treats" the electric and associated mechanical dyssynchrony imposed by the left bundle branch block.Some of the variables influencing response include how much myocardial damage may have already occurred in the patient ( e.g. heart attacks) and the location of the left ventricular lead in relationship to left ventricular scar(s).
The most dramatic example of super responders was reported by Vaillent et al in 2013. (2). They described 6 patients with a diagnosis of LBBB without evidence of coronary or other heart disease and an EJ of greater than 50% at the time of diagnosis. Over a period of five to 21 years all developed heart failure severe enough to warrant referral for CRT. Following CRT, ejection fraction improved greatly , five of the six within 3 months .Mean EJ increased from 31 to 56.In one patient , from 26 to 60.Other cardiac functional indices improved as well
The authors suggest that these cases "strongly support the concept of LBBB-induced cardiomyopathy".This idea was apparently suggested earlier by Blanc et al in 2005 (4)
LBBB induced heart failure represents a vary small percentage of patient who are treated with CRT. Ghani et al (3) report on the predictors of long term outcome of "super-responders to CRT which they define as Left ventricular EF (LVEF) greater than 50% ( mean of 54.9%, +/-6) on follow-up echocardiogram.The group whose EF was between 30 and 50% were labelled as "responders"
They describe 56 patients from a group of 347 patients with primary CRT D indication. The predictors were female sex,nonischemic etiology,higher EF at baseline and wider QRS duration.
Vaillant's patients , when compared to Ghani's patient, perhaps could be considered "super super" responders.
1. Strauss DG et al, Defining Left Bundle Branch block in the Era of Cardiac Resynchronization Therapy. American J Cardiology 2011,Vol 107 pg 927-934
2. Vaillant C et al. Resolution of left bundle branch block induced cardiomyopathy by cardiac resynchronization therapy. J. Amer College of Cardiology 2013,vol 61, p 1089
3. Ghani, S et al Predictors and long term outcome of super-responders to cardiac resynchronization therapy. Clin Cardiology 2017
4.Blanc J et al. Evaluation of left bundle branch lock as a reversible cause of non-ischemic dilated cardiomyopathy with severe heart failure. A new concept of left ventricular dyssynchrony-induced cardiomyopathy. Europace 2005;7,604