Introduction: Left ventricular non-compaction (LVNC) is a structural cardiomyopathy (SC) with a high probability of LV systolic dysfunction. Left bundle branch block (LBBB) frequently occurs in SCs.

Objective: We sought to analyse the evolution of LVNC-CRT (LC) patients in general and compare it with the non-LVNC-CRT group (nLC).

Methods: We analysed 40 patients with contrast-MRI documented LVNC (concomitant positive Petersen and Jacquier criteria) implanted with CRT devices in CEHB. The follow-up included 7 hospital visits for each patient (between baseline and 3 years). Demogra-phics, risk factors, usual serum levels, pre-procedural planning factors, clinical, ECG, TTE and biochemical markers were recorded. Statistical analysis was perfor-med using SPSS® and Microsoft Excel® software. Nota-ble differences were reported as either p-values from crosstabs (discrete) or mean differences, p-values and confidence intervals from t-tests (continuous). A p-va-lue of 0.05 was chosen for statistical significance (SS).

Results: Subjects in LC were younger (-7.52 ys; p<0.000; (-3.617; -11.440)), with no sex predominance, more obese (45.9 vs. 28.3%; p<0.24) and had less is-chaemic disease (17.9 vs. 39.7%; p<0.007). LC implants were usually CRT-Ds (91 vs. 49.5%; p<0.000) and more frequently MPP-ready (35.8 vs. 8.4%; p<0.000). At ba-seline, sinus rhythm was predominant in LC (97.4 vs. 79.8%; p<0.007) and permitted frequent use of opti-mal fusion CRT (75.5 vs. 46.6%; p<0.002). Although initial LVEFs were similar, LCs had much larger EDVs (+48.91 ml; p<0.020; (+7.705; +90.124)) and ESVs (+34.91; p<0.05; (+1.657; +71.478)). After an initi-al encouraging ear evolution the LC-CRT group crashed its performance in terms of both LVEF and volumes. Thus, at 1 year follow-up, when compared to nLCs, LVEFs were far lower (-22.02%; p<0.000; (-32.29; -11.76)) while EDVs and ESVs much higher – (+70.8 ml; p<0.037; (+49.27; +189.65)) and (+100.13; p<0.039; (+5.25; +195)) respectively – in LCs in spite of similarly corrected dyssynchrony. The mean mitral regurgitation (MR) degree at 1 year was much higher in LCs (+1.8 classes; p<0.002; (+0.69; +2.97)) certainly contributing to the poor results. The cumulated super-responder/ responder (SR/R) rates were constantly lower and de-creasing at both 1 year (37.5 vs. 72.4; p<0.040) and 2 years of follow-up (10.1 vs. 80%; NS).

Conclusions: CRT candidates with LVNC are signi-ficantly more severe at the time of implant. After an initial short-term improvement (probably due to acute correction of dyssynchrony) most patients fail to res-pond in the long term. Severe dilation with important secondary MR probably plays an important role.