Strategies to Improve Selection of Patients Without Typical Left Bundle Branch Block for Cardiac Resynchronization Therapy.

Cardiac resynchronization therapy (CRT) is becoming increasingly controversial in patients without typical left bundle branch block (LBBB). Yet, several recent studies displayed that a distinct subpopulation of patients with non-LBBB does benefit from CRT. Patients with non-LBBB should, therefore, not as a group be withheld from a potentially very beneficial therapy. Unfortunately, current clinical practice lacks validated selection criteria that may identify possible CRT responders in the non-LBBB subgroup. Consequently, clinical decision making in these patients is often challenging. A few studies, strongly differing in design, have proposed additive selection criteria for improved response prediction in patients with non-LBBB. There is accumulating evidence that more sophisticated echocardiographic dyssynchrony markers, taking into account the underlying electrical substrate responsive to CRT, can aid in the selection of patients with a non-LBBB who may benefit more favorably from CRT. Furthermore, it is important that cardiologists are aware of the shortcomings of current electrocardiographic selection criteria for CRT. Whereas these criteria provide an evidence-based approach for selecting patients for CRT, they do not necessarily guarantee the most optimal strategy for patient selection. Parameters obtained with vectorcardiography, such as QRS area, show potential to overcome the shortcomings of conventional electrocardiographic selection criteria and may improve response prediction regardless of QRS morphology.