Left bundle branch block: prevalence, incidence, follow-up and outcome

In a randomly selected population screening study of 8450 men and 9039 women 33 to 71 years of age conducted in Iceland in 1967-1977, 27 men and 17 women were found to have left bundle branch bock (LBBB). The prevalence of LBBB at that time was 0-43 % for men and 0-28 % for women. The incidence of LBBB was 3-2 per 10 000 per year for men and 3-7 per 10 000 per yearfor women. AH except one of 37 alive patients with LBBB were examined in 1984 including chest X-ray, echo-cardiography and exercise testing (Bruce protocol). Eight men had had myocardial infarction (P<0-05), 12 had angina pectoris, 15 had hypertension, 7 had cardiomyopathy, 13 had primary conduction disease, and 3 had pacemakers. Five men and two women had died in comparison with 18 men and 1 woman in an age-matched control group of 176 people (P • ns). Three of 5 decreased LBBB men had cardiomyopathy at autopsy. Three men died suddenly. The two women died of noncardiac causes. Only one patient in the control group had cardiomyopathy (P < 001). There was no significant difference in other cardiac diagnoses between the groups. Eleven LBBB women out of thirteen had a normal exercise duration (~^6 min) and 11/17 men exercised normally ( ^ 7 min). In comparison with the control group, the LBBB patients had an increased LV diameter 2-85 ± 0-38 vs 2-58 ±0-38 cm m'1 body surface area (P < 0-01). There was no difference between the groups in left atrial diameter or LV wall thickness