Reappraisal of cardiovascular surveys in Jamaica Use of submaximal exercise tests for clinical investigation

Abstract

Assertions that idiopathic cardiomegaly or an obscure form of ischaemic heart disease are common in Jamaica have been based on a high prevalence in community surveys of unexplained electrocardiographic abnormalities and of positive responses to a questionnaire for ischaemic heart pain. Thirty-one men, aged 42-62 years, in whom these abnormalities had been found in a previously surveyed rural community, were recalledfor clinical examination and exercise tests and compared with I8 control subjects. No clinical abnormalities were found. The heart rates during standard work and maximum oxygen uptake of subjects and controls were similar, and indicated, on average, excellent exercise performance consistent with their heavy physical activity in daily life. None complained of chest pain at near maximal exertion, and the previous diagnosis of angina pectoris was judged to have been mistaken. Most of the electrocardiographic abnormalities at rest were minor or isolated and did not change on exercise. Significant changes in exercise occurred in 4 subjects, in whom inverted T waves and ST depression became less obvious than at rest, but the cause of these abnormalities was not found. Though idiopathic cardiomegaly and ischaemic heart disease do occur in Jamaica, their incidence is not known but there is no evidence that they are as widespread as has been previously asserted. Interpretations of answers to questionnaires and of electrocardiograms obtained in population surveys should be made with caution. From this study we have no evidence on whether the electrocardiographic changes were related to ethnic or environmental factors.