Introduction: Cardiac resynchronization therapy (CRT) is generally contraindicated in QRS duration <130 msec due to previously proven mortality increase. However, certain narrow QRS (nQRS) patients exhibit overt dyssynchrony.

Methods: We present the case of a 54 year-old (y/o) female with non-compaction cardiomyopathy (LVNC) and narrow QRS (110 msec) favorably responding to CRT. Clinical evaluation, transthoracic echocardiogra-phy (TTE), Holter ECG followed by cardiac magnetic resonance (CMR) were performed. Electrophysiologi-cal study and radiofrequency ablation (RFA) of PVCs were performed after 6 months of premature ventricu-lar contractions (PVC) suppression by antiarrhythmic therapy. Subsequently a cardiac resynchronization de-fibrillator (CRT-D) was implanted and the patient was monitored for 3 years.

Results: A 54 y/o female patient, with maternal sud-den cardiac death history, presented for NYHA class heart failure (HF) symptoms. History revealed a 5 y/o diagnosis of non-ischemic dilated cardiomyopathy with severe (but stationary) LV systolic dysfunction (LV ejection fraction (LVEF) ~20%) and frequent mo-nomorphic PVCs (40%) currently treated with Sotalol (no reverse remodeling 6 months after PVC suppressi-on). ECG exhibited a fragmented nQRS of 110 msec. TTE revealed a diffusely hypokinetic dilated LV (end-diastolic volume (EDV) ~240 mL) with EF ~20% with marked dyssynchrony (septal to posterior wall motion delay (SPWMD) ~290 msec). LVNC criteria were met in CMR evaluation. RFA targeting septal right ventri-cular outflow tract (RVOT) was performed after anti-arrhythmic withdrawal. A multipoint (MP) CRT-D de-vice was implanted and programed by optimal fusion resynchronization (OFu) protocol. Even though post-procedural QRS duration was 120 msec, ventricular dyssynchrony was mechanically corrected (SPWMD ~80 msec). The patient remained asymptomatic 3 years after CRT-D implant and reverse remodeled througho-ut the 1st year of monitoring (LVEF ~45% and EDV ~160 mL). The particularities of this case that must be addressed are the presence of pathologically fragmen-ted nQRS with marked dyssynchrony, the decision of CRT in nQRS and the subsequent choice of OFu resyn-chronization delivery protocol.

Conclusions: Tailored CRT in non-compaction pa-tients exhibiting nQRS, but with overt mechanical dyssynchrony, may provide reverse remodeling.