Mid-Q Response Study

Inclusion Criteria: * Subject is willing to sign and date the study Informed Consent Form (ICF). * Subject is indicated for a CRT device according to local guidelines. * Subject has sinus rhythm at time of enrollment * Subject has a moderately wide intrinsic QRS duration ≥120 ms and \<150 ms * Subject has Left Bundle Branch Block (LBBB) as documented on an ECG (preferably within 30 days prior to enrollment but up to 50 days is accepted) with Qs or rS in leads V1 and V2, and Mid-QRS notching or slurring in ≥2 of leads V1, V2, V5, V6, I, and aVL * Subject has intrinsic, normal AV conduction as documented on an ECG by a PR interval ≤200 ms (preferably within 30 days prior to enrollment but up to 50 days is accepted). * Subject has left ventricular ejection fraction ≤35% (documented within 180 days prior to enrollment). * Subject has NYHA class II, III, or IV (documented within 30 days prior to enrollment) despite optimal medical therapy. Optimal medical therapy is defined as maximal tolerated dose of Beta-blockers and a therapeutic dose of ACE-I, ARB or MRA. Exclusion Criteria: * Subject is less than 18 years of age (or has not reached minimum age per local law if that is higher). * Subject is not expected to remain available for at least 1 year of follow-up visits. * Subjects has permanent atrial arrhythmias for which pharmacological therapy and/or cardioversion have been unsuccessful or have not been attempted. * Subject is, or previously has been, receiving cardiac resynch…