Eighteen patients with isolated left bundle branch block (LBBB) were compared with 10 normal control subjects. Apexcardiograms, phonocardiograms, electrocardiograms, two-dimensional and dual M-mode echocardiograms, and radionuclide ventriculograms (RNV) were performed. There were no differences in the timing of right ventricular events between LBBB and normal subjects; however, striking delays in left ventricular systolic and diastolic events were apparent in the LBBB group. The delay was associated with shortening of left ventricular diastole and resultant increase in the ratio of right to left ventricular diastolic time in LBBB (1.2 ±0.08) compared with normal (1.0± 0.06), p <0.0001. First heart sound (S1) amplitude, expressed as the ratio S11S2, was decreased in LBBB compared with normal (0.67±0.2 compared with 1.34+0.25, p<0.01), in part due to wide separation of the valvular contributors to S1. The abnormal interventricular septal motion in LBBB corresponded to periods of asynchrony in contraction, ejection, end systole, and end diastole between right and left ventricles. Radionuclide ventriculograms revealed decreased regional ejection fraction of the septum in LBBB (40±16o) compared with 67±7% in normal subjects (p<0.001), while the apical and lateral regional ejection fractions were similar in the two groups. This loss of septal contribution resulted in a reduction in global ejection fraction in LBBB compared to normals (54+7% compared with 62±5%, p<0.005). The magnitude of systolic septal motion (echocardiography) and septal ejection fraction (RNV) were closely correlated to the ratio of right to left ventricular diastolic time (r=-0.86 and -0.85, respectively). Thus, isolated LBBB caused global ventricular abnormalities manifested by abnormalities in diastolic filling times, heart sounds, interventricular septal motion, and left ventricular ejection fraction. (Circulation 1989;79:845-853

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This document was developed by a consensus conference initiated by Kristian Thygesen, MD, and Joseph S. Alpert, MD, after formal approval by Lars Rydén, MD, President of the European Society of Cardiology (ESC), and Arthur Garson, MD, President of the American College of Cardiology (ACC). All of the participants were selected for their expertise in the field they represented, with approximately one-half of the participants selected from each organization. Participants were instructed to review the scientific evidence in their area of expertise and to attend the consensus conference with prepared remarks. The first draft of the document was prepared during the consensus conference itself. Sources of funding appear in Appendix A. The recommendations made in this document represent the attitudes and opinions of the participants at the time of the conference, and these recommendations were revised subsequently. The conclusions reached will undoubtedly need to be revised as new scientific evidence becomes available. This document has been reviewed by members of the ESC Committee for Scientific and Clinical Initiatives and by members of the Board of the ESC who approved the document on April 15, 2000.*

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