Objectives: The objectives of this study were to find the prevalence of third-degree atrioventricular block in representative population sample and to estimate its prognostic significance. Most earlier studies have been performed on hospital patients and some professional groups.
Setting and subjects: In the Reykjavik Study, a prospective cardiovascular population study, 9139 men and 9773 women aged 33-79 years were examined in 1967-91. Electrocardiograms were taken and coded according to the Minnesota code. Third-degree atrioventricular block was found in 11 persons, seven male and four female, an overall prevalence of 0.04%. All of these individuals had signs of dysrhythmia on electrocardiograms taken later, and in addition some other heart disease. The heart block was temporary in seven individuals (64%); six (55%) needed a pacemaker.
Conclusions: The prevalence of third-degree atrioventricular block in this general population was low. The block was temporary in the majority of subjects. All had some underlying heart disease, which may affect the prognosis more than the heart block. Fewer subjects than expected were found to need a pacemaker.