Electrocardiographic measurements in a coherent sample of healthy adult urban africans in Kenya
Background: Electrocardiogram (ECG) measurements (intervals, amplitudes, heart rate, and QRS axis) are known to differ with age and sex. Most available data have been collected in Caucasian populations, yet evidence exists for racial differences in ECG findings. Studies of ECG parameters in the black African population are few and have their limitations such as those perfomed in hypertensive, HIV/AIDs, ischaemic heart disease and heart failure patients. This study describes changes in major ECG measurements with normal ageing in a population of healthy adult Africans. Objective: To determine the ECG parameter differences with age and gender in a sample of healthy adult urban Africans in Kenya. Design: Descriptive cross-sectional study. Setting: The city of Nairobi and its environs. Subjects: The study included 151 men and 224 women, all apparently healthy, with a relatively even spread of ages between 18 and 90 years. Methods: Standard 12-lead ECGs were recorded and manually processed using digital callipers in and around Nairobi, Kenya. Volunteers were recruited from the University of Nairobi and from the surrounding estates of Nairobi city. ECGs were reviewed to exclude any that were technically unsatisfactory and others that had an unexpected abnormality. Data was empirically divided into six age groups; Group 1 (18-30 years), Group 2 (31-40 years), Group 3 (41-50 years), Group 4 (51-60 years), Group 5 (61-70 years) and Group 6 (70 years and above). The medians, lower limits (2nd percentile) and upper limits (98th percentile) of various ECG measurements were determined and age and sex comparisons examined. Data were expressed as mean (SO). Results: Significant differences in numerical ECG values based on age and sex were observed. Heart rate was higher in women than men in all age groups (P<0.05) and did not differ with age. The other study findings were as follows when the young, middle and older age groups, median (2nd and 98th percentile) were compared, Group 1 (18-30 years), Group 3 (41-50 years) and Group 5 (61-70 years)) were compared: P duration: Group 1,110 (78,136) ms vs. Group 3,114 (96,136) ms and Group 5,125 (105,145) ms, P<0.001, respectively. PR interval: Group 1,171 (125,213) ms vs. Group 3,187 (135,247) ms and Group 5, 199 (149,216) ms P<0.001, respectively. ORS duration: Group 1, 63 (52, 84) ms vs. Group 3, 70 (47, 93) ms P<0.01; Group 1, 63 (52, 84) ms vs. Group 5, 98 (65,117) ms P<0.001. OT interval: Group 1, 362 (364, 458) ms vs. Group 3, 386 (320,429) ms P<0.01; Group 1, 362 (364, 458), vs. Group 5, 403 (342,469) ms, P<0.001. The mean QRS axis in degrees: Group 1, 62 (-72,108) vs. Group 3,30 (-7, 82), P<0.01; Group 1,62 (-72,108) vs. Group 5, 11 (-35,89), P<0.001. Moreover, there were marked sex differences in the PR and QT intervals whereby men had higher mean PR interval (199 vs.192, P<0.01) than women and on the other hand women had higher QT intervals than men (397 vs.403, P<0.05). Conclusions: The study showed marked age and sex difference-s in the ECG parameters measured in the black African population. This merits the definition and use of age- and sex-specific ECG criteria for the African population. Keywords: Electrocardiogram; Age; Sex; African population; Developing countries.