Longitudinal study of heart disease in a Jamaican rural population. 3. Factors influencing changes in serial electrocardiograms.

A longitudinal survey of heart disease in adults in a representative rural population in Jamaica provided an opportunity to study factors influencing the progression and incidence of electrocardiographic abnormalities in serial tracings taken at a 5-year interval. An analysis of changes occurring in those with ECG abnormalities compatible with ischaemia at the first survey showed that progression from a less severe to a more severe category was greater in men than in women, in hypertensive than in normotensive subjects, and, among men, in those with the amplitude criteria of left ventricular hypertrophy. The incidence of abnormal Q/QS patterns was greater in men than in women, and that of all abnormalities suggesting ischaemia was greater in hypertensive than in normotensive persons; in men, it was greater in those with high amplitude R waves. The incidence cases showed S-T and T wave abnormalities, the great majority of which were classified as showing features compatible with ischaemia rather than with strain secondary to hypertrophy. These findings, which are discussed in terms of their possible causes, seem to confirm that much of the heart disease in this Jamaican community has features of myocardial ischaemia despite other evidence that extramural coronary vessels tend to be spared from such severe occlusive atheromatous disease as is found in many other populations.