Abstract 4135061: Myocardial work in different patients with electrical dysynchrony due to left bundle branch block

Left bundle branch block (LBBB) in patients with dilated cardiomyopathy (DCM) is defined by huge wasted work and decreased myocardial constructive work. The aim of this study is to assess the myocardial work in patients in LBBB and other clinical situations. Materials and methods: The echocardiographic study was performed in 25 patients with LBBB and DCM (LBBB-DCM); 20 patients with DCM and narrow QRS complex (nonLBBB-DCM group); 15 patients with LBBB developed after transcatheter aortic valve implantation (TAVI group); 12 patients with idiopathic LBBB, normal systolic LV function and excluded cardiovascular pathology (LBBB group); 27 patients with right ventricular pacing due to atrioventricular block of high grade (RVP group) and 20 healthy volunteers (HV group). In all of them global longitudinal strain (GLS) and myocardial work parameters including global constructive work (GCW), global wasted work (GWW), global work index (GWI) and global work efficiency (GWE) were assessed. In all patients the segments with maximum and minimum GWI value were determined. Results: GLS, GWI and GCW values were comparable in LBBB and RVP groups, whereas in TAVI and in both DCM groups they was significantly lower than in HV (p = 0.049, 0.006, 0.025; p < 0,001 respectively, (Fig.1A,B,C)). Patients from LBBB, TAVI, RVP and LBBB-DCM groups were characterized by increased amount of GWW (261 [203.5; 291.5], 273 [184.8; 385,3] and 237 [149.5; 445.3] vs 108 [74.3; 137.3] mmHg%, p = 0.033, 0.006, < 0.001, < 0.001 respectively). GWW value in LBBB-DCM group was the highest (346.5 [255.5; 437.8] mmHg% (Fig.1D). There was moderate strength of relation between GWW and QRS duration (ρ=0.456, p<0.001). A huge amount of wasted work affected the GWE value and led to its considerable reduction in LBBB, TAVI, RVP and LBBB-DCM groups compared to HV (p = 0.033, 0.007, 0.023, < 0,001, respectively, Fig.1E). The zone of maximum GWI localized in posterolateral wall, the zone of minimum GWI was in interventricular septum in most LBBB patients (Fig.1F). At the same time, these zones turned out to be very variable in RVP group. Conclusion: Although all patients with LBBB pattern of electrical activation are characterized by significant amount of wasted work, its contribution to global myocardial work manifested only in DCM patients. Wasted work doesn’t lead to reduced constructive work in patients with idiopathic LBBB and RVP and normal systolic function probably due to compensatory mechanisms.