Myocardial function in cardiac resynchronization therapy and factors significant for its improvement

Aim. To analyze myocardial work in cardiac resynchronization therapy (CRT) and to determine the factors influence its positive dynamics. Materials and methods. 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 analyzed in addition to standard transthoracic echocardiography (TTE) in 60 patients (mean age 61±10 years, 36 male) with left bundle branch block (LBBB), chronic heart failure (HF 2 [2; 3] FC (NYHA), decreased left ventricular ejection fraction (LF EF=28 [23; 31] %) before and 6 months after CRT implantation.. In all patients the segments with maximum and minimum WI value were determined and the difference in segments with maximal and minimal WI (Max-Min WI), as the indicator of myocardial work asymmetry was calculated. Results. CRT led to reverse cardiac remodeling in 44 (73.3%) patients; clinical stabilization without positive TTE dynamics – in 11 (18.3%) patients, worsening or death – in 5 (8.3%) patients. In both groups of reverse remodeling and clinical stabilization CRT resulted in GWW reduction and thus GWE and GWI enhancement. However, the decrease in GWW in these patients is not accompanied by an increase in GCW and GLS, in contrast to patients with reverse remodeling, who developed statistically significant change in GCW and GLS during CRT. Patients with worsening or death were characterized by a minimal decrease in GWW in CRT (62,0 [9,7; 133,7] vs 149,5 [92.8; 206,2] mmHg% in patients with reverse remodeling and clinical stabilization; p=0,035). Max-Min WI turned out to be directly related to the LV EF change in CRT (rxy=0,336; p=0,017) that makes this value to be one of possible predictors of reverse remodeling during CRT. Conclusion. Wasted myocardial work can serve a contractile reserve, which represent a target for CRT. Its mobilization and decrease can lead to stable clinical status in patients even in the absence of reverse myocardial remodeling.