Introduction: Regional myocardial work by echocardiography was recently introduced as a clinical method. Since work incorporates load it may be superior to strain imaging to identify myocardial dysfunction. We hypothesized that myocardial work identifies preclinical myocardial dysfunction in patients with left bundle branch block (LBBB).
Purpose: To compare the echocardiographic modalities myocardial work and strain in the evaluation of systolic function in patients with LBBB.
Methods: 28 non-ischaemic LBBB patients were divided into three groups based on left ventricular (LV) ejection fraction (EF): Group EFnormal (n=8) with EF>50%, group EFmid (n=10) with EF 36–50% and group EFlow (n=10) with EF≤35%. Furthermore, we included a group of 10 healthy control subjects. All subjects were examined by speckle-tracking echocardiography to calculate peak longitudinal strain in the septum and LV lateral wall. Using a previously validated method for non-invasive estimation of LV pressure, segmental work was calculated by pressure-strain analysis.
Results: There were no significant differences in LVEF between controls and EFnormal LBBB patients (60±4 vs. 58±5%, NS) suggesting normal systolic function. This was also true for septal shortening (21.8±2.8 in controls vs. 21.5±2.2% in EFnormal, NS). Septal work, however, was substantially reduced (2346±280 in EFnormal vs. 4565±1233 mmHg·% in controls, p<0.001). This indicates markedly reduced septal function in LBBB patients despite normal EF (figure). There were further reductions in septal work in the EFmid and EFlow groups consistent with gradually increasing dysfunction. LV lateral wall shortening and work did not change between controls, EFnormal and EFmid, which indicates preserved LV lateral wall function in LBBB patients despite reduced global systolic function.
Conclusions: Myocardial work was more sensitive than strain to identify myocardial dysfunction in patients with LBBB and normal LVEF. This probably reflects that work incorporates loading conditions which are often abnormal in the septum of LBBB patients. These results suggest a role for myocardial work to identify preclinical LV dysfunction. Future studies should investigate whether reduced myocardial work has prognostic value on top of strain.