There is a role if there is a long pr interval. 

We consider it only in some well selected candidates with several signs of dyssynchrony on ECHO (usually if they have RBBB with LAHB) or delayed PQ interval and expected benefit from optimizing AV delay.

I am a registrar and certainly not an expert, but in patients with RBBB it probably would make more sense to have a CRT with dedicated RV pacing (preferably a septal position to reduce the QRS duration. LV lead pacing can be used after assessment of QRS duration and use of dyssynchrony assessment to see benefit of LV pacing. I would think that this route has not been assessed yet in randomized controlled trials.  

According to ESC guidelines (2013) CRT can be considered in HFrEF patient if EF150ms and nonLBBB ECG patern; NYHA II-III, IV (ambulatory) status and optimal medical therapy. QRS 120-150ms no benefits with CRT according last studies

It was suggested that the combination of RBBB with LAHB and or prolonged PR may define a subgroub of RBBB responders. However a retrospective subanalysis of the MADIT CRT, if I am not mistaken, did not support this view!  

Indeed. That means that we cannot recommend that indication at large. However, it does not mean that we cannot implant some well selected cases with such condition, specially if we have some clues from echo or EP study that they have some degree of correctable  dyssynchrony. This was my message.

I would agree. Although there is strong data that would imply the use of CRT only in patients with LBBB, there are some patients with notable dyssynchrony (echo, EP) who would benefit from CRT especially with additional AV- an VV- interval modifications after implantation.

We all are aware that echo failed to make it as a reason or criteria for crt.large observer variation in the data , poor reproducibility. We know echo is always operator dependent..for now one can only stick to the guidelines and be wise otherwise it becomes difficult

Yes, if mechanical dyssynchrony with a delay of vital myocardium can be documented by imaging, and if these delayed segments are accessible by the device leads.

Otherwise: no

It's true that echo seems to be a rather blunt instrument at assessing dyssynchrony without LBBB. The benefits of CRT do however seem associated with maximum regional variations in the myocardium. I don't think this has been studied yet - however it may be interesting to look at regional dispersion of mIBG uptake (on SPECT scan not planar image H/M ratio) and see if that correlated with results from CRT.

The best way to determine a possible positive effect of CRT in these patients would be evaluating the acute hemodynamic and acute dyssynchrony response as can be measured by usage of LV pressure-volume analysis.

De Roest GJ et al. Prediction of long-term outcome of cardiac resynchronization therapy by acute pressure-volume loop measurements. Eur J of Heart Failure 2013;15299-307

Mafi Rad et al. The role of acute invasive haemodynamic measurements in cardiac resynchronization therapy looping towards prediction of long-term response and therapy optimization. Eur J of Heart Failure 2013;15:247-249.

David, there is a study recently published from MADIT-CRT by me and our group suggesting that patients with non-LBBB and prolonged baseline PR interval derive significant benefit from implantation of a CRT-D.

http://www.ncbi.nlm.nih.gov/pubmed/24963007

These findings imply that there may be patients potentially benefiting from CRT. Let me know if you find this answer helpful. Thanks

Thank you Valentina, I have already read your excellent article as prof. Olshansky (co-author) already suggested PR interval could also be a focus of "resynchronization" in HF patients with wide QRS but nonLBBB morphology. 

Yes, Brian Olshansky is a very knowledgeable collaborator of ours. What do you think, David, do we need a prospective randomized trial to answer this question?

Valentina, the study also has some strong clinical implications since the selection of patients that could benefit from CRT is somehow narrowing. Do you maybe have any data or publications comparing response of LBBB patients with normal PR interval and prolonged PR > 230ms?

I would def. agree. There is a need of prospective randomized study since as I already stated the selection of pts that benefit from CRT is narrowing. But on the other hand there are consistent reports of 30% of nonresponders. Every little bit that would increase the number of responders to this expensive and invasive therapy is very helpful.

The issue of "resynchronization of a prolonged PR interval" and Valentina's analysis from the MADIT-CRT data is very important and should remind us, that the whole issue of pacing in heart failure started in the early 1990's with RV pacing in patients with different types of conduction disturbance. In the study by Hochleitner et al. from Austria, most patient had EITHER LBBB OR A MODERATELY PROLONGED PR-INTERVAL.

http://www.ncbi.nlm.nih.gov/pubmed/2371951

For those patients even RV (!) pacing with AV-delay optimization produced some (moderate) clinical benefit. The subsequent studies which could NOT reproduce the initial positive findings from the austrian group mostly included patients with less conduction delay.

The other issue is the discussion about the usefulness of echo. Echo is stil the best technique to visualize the negative impact of the electrical delay on cardiac mechanics and hemodynamics. However, it becomes difficult to use in large multicenter trials, because it has to be applied with knowledge and care and in a very individualized manner. Of course we will also see dyssynchrony which can not be resynchronized (ischemia, scar) and we may miss e.g. the AV dyssynchrony due to a prolonged PR interval (see above) if we only concentrate on the ventricle. It is not the techique "echo" that failed in the studies, it is our inappropriate analysis and interpretation which fails.