Left bundle branch block.

A RECENT STUDY of the prognosis of patients with left bundle branch block (L.B.B.B.) suggested that life expectancy was extremely short (Smith and Hayes 1965). While in general L.B.B.B. has a sinister reputation, we have been struck by a few individuals who have survived many years with L.B.B.B., and we thought an analysis of some of the material available at the Royal Victoria Hospital, Belfast, would be of value. MATERIAL In the years 1956 and 1957, 111 of the patients who attended the electrocardiographic department of the Royal Victoria Hospital had L.B.B.B. In all cases the hospital records were studied, and additional data were obtained from the family doctors. Where possible, survivors were examined personally by the authors. In eight cases complete data were not available (a loss to follow-up of 7 per cent). Electrocardiographic criteria for L.B.B.B. were those of the New York Heart Association (1964). "The QRS interval is 0.12 seconds or more and the components of the QRS are notched and slurred. In leads I, aVL, sometimes aVF, and in leads from the extreme left side of the precordium and the left side of the thorax, the initial deflection is usually an R wave or one of its prominent notches occurs relatively late in the QRS interval. The ST segment is most often displaced in a direction opposite to the principal QRS deflection and the T wave also points in this direction. The appearance of QRS in other leads depends principally on the average direction of the electrical axis of QRS". In all cases where statistical testing of significance was required the "chi-square" method was used. All differences mentioned in the text were significant at the 1 in 20 level (P(0.05). RESULTS incidence During the years 1956-57, 9,469 electrocardiographs were recorded at the Royal Victoria Hospital. The 111 patients with L.B.B.B. represent about 1 per cent of this total. Age and Sex The age and sex distribution of the patients are shown in Table I. The majority of patients (87 per cent) were aged 50 years or over, and about one-third (34 per cent. were aged 70 years or more. Approximately half (45 per cent) the series were male, and there was no significant difference in the sex incidence between different age groups. TABLE I Age and sex distribution Age (years) Male Female Total 28-49 6 (43%) 8 (57%/) 14 50-69 31 (53%) 28 (47%) 59 70-87 14 (37%) 24 (63O/,) 38 Total 51 (46%) 60 (54%) 111