Cardiac incoordination induced by left bundle branch block: its relation with left ventricular systolic function in patients with and without cardiomyopathy

Abstract

Background: Although left bundle branch block (LBBB) alters the electrical activation of the heart, it is unknown how it might change the process of myocardial coordination (MC) and how it may affect the left ventricular (LV) systolic function. The present study assessed the effects of LBBB on MC in patients with LBBB with and without dilated (DCMP) or ischemic cardiomyopathy (ICMP).

Methods: Tissue Doppler echocardiography (TDE) was performed in 86 individuals: 21 with isolated LBBB, 26 patients with DCMP + LBBB, 19 patients with ICMP + LBBB and in 20 healthy individuals (Controls). MC was assessed analyzing the myocardial velocity profiles obtained from six basal segments of the LV using TDE. The LV systolic function was assessed by standard two-dimensional echocardiography and by TDE.

Results: Severe alterations in MC were observed in subjects with LBBB as compared with controls (P < 0.01 for all comparisons); these derangements were even worse in patients with DCMP and ICMP (P < 0.001 for comparisons with Controls and P < 0.01 for comparison with individuals with isolated LBBB). Some parameters of MC differed significantly between DCMP and ICMP (P < 0.01). A good or very good correlation coefficient was found between variables of MC and variables of LV systolic function.

Conclusion: LBBB induces severe derangement in the process of MC that are more pronounced in patients with cardiomyopathies and that significantly correlates with the LV systolic function. The assessment of MC may help in the evaluation of the etiology of dilated cardiomyopathy.

Figure 1

a. Echocardiographic image showing the apical four-chamber view in a subject of the control group. The image shows the myocardial velocity profile obtained in the basal segment of the left ventricular lateral wall. The time intervals identified by figures indicate: 1 = Electromechanical delay time (EMDT); 2 = Isovolumic contraction time (IVCT); 3 = Electro hemodynamic delay time (EHDT); 4 = Ejection time (ET); 5 = Isovolumic relaxation time (IVRT). A' = Late diastolic (A-wave) velocity); E' = Early (E-wave) diastolic velocity; PSV = Peak systolic velocity. b, represent the same image in a patient with isolated LBBB; c in a patient with dilated cardiomyopathy and LBBB; d in a patient with ischemic cardiomyopathy and LBBB.

Figure 2

Scatter plot of the correlation coefficient (r = -0.74) between a variable expressing the left ventricular systolic function, (PSV = peak systolic velocity) and a variable expressing the left ventricular myocardial coordination (IVRT = the isovolumic relaxation time).