Effect of the isolated left bundle branch block on systolic and diastolic functions of left ventricle

Background: We planned this study to evaluate the effects of left bundle br anch block (LBBB) on systolic and diastolic functions of left ventricle (LV ) that have not previously been investigated in detail. Material and Methods. Forty-five cases diagnosed as isolated LBBB according to the standard electrocardiographic criteria (group I, mean age: 60 +/- 1 2 years) were taken as the case group and 65 cases with normal conduction s ystem (group II, mean age 58 +/- 14 years) were taken as the control group. Echocardiography was performed to all patients and coronary angiography wa s performed to 21 patients in group I and 35 patients in group II. In addit ion to standard systolic and diastolic function parameters, isovolumetric r elaxation time (IRT), isovolumetric contraction time (ICT), and ejection ti me (ET) were measured by echocardiography, and the myocardial performance i ndex (MPI) [(IRT+ICT)/ET] was calculated. IV end-diastolic pressure was cal culated for the patients undergoing coronary angiography. Results: In group I, IV end-systolic diameter was greater (3.1 +/- 0.4 cin vs 2.8 +/- 0.4 cm, P < .001) and ejection fraction was lower (64% +/- 6% vs 68% +/- 6%, P < .001) than those of group II. Rapid filling deceleration t ime and rate was markedly different in group I (respectively, 133 +/- 50 ms vs 166 +/- 24 ins, P < .001; 608 +/- 291 cm/s(2) vs 383 +/- 116 cm/s(2), P < .001). In addition, it was found that LBBB caused shortening of IV diast olic period and ET markedly (respectively, 347 +/- 116 ins vs 394 +/- 106 m s, P = .03; 255 +/- 40 ms, vs 294 +/- 21 ms, P < .001) and prolongation of IRT and ICT (respectively; 124 +/- 36 ins vs 91 +/- 16 ms, 96 +/- 35 in vs 38 +/- 9 ins, P < .001). The MPI was predominantly higher in group I (0.89 +/- 0.29 vs 0.40 +/- 0.06, P < .001). Invasively determined IV end-diastoli c pressure was found higher in group I (14 +/- 3 min Hg vs 10 +/- 3 mm. Hg, P < .001). Conclusion: A marked elevation of the IV MPI and end-diastolic pressure, pa rallel to changes of conventional echocardiographic parameters, in patients with isolated LBBB points out that LBBB causes marked deterioration on IV systolic and diastolic functions.