Redefining the ECG in urban South Africans: electrocardiographic findings in heart disease-free Africans.

BACKGROUND: The 12-lead electrocardiogram (ECG) represents an important diagnostic tool for detecting heart disease, but the "normal" ECG in those of African descent has yet to be definitively described.

METHODS: We systematically analysed 12-lead ECGs from 387 urban South Africans determined to be heart disease free (using the Minnesota code) following advanced cardiologic assessment, including echocardiography, at the Baragwanath Hospital in Soweto, South Africa.

RESULTS: 123 males (32%, 41.2 ± 14.5 years) and 264 females (37.4 ± 14.2 years) were studied. Most were in sinus rhythm (87%) and had normal axis (89%). Mean interval data were: PR interval (156 ± 28 ms; 95% CI: 153-159 ms), QRS duration (82 ± 16 ms; 95% CI: 80-84 ms), QT interval (379 ± 48 ms; 95% CI: 374-384 ms) and QTc interval (426 ± 32 ms; 95% CI: 423-429 ms). Overall, 199 (51%; 95% CI: 46.0% to 56.0%) subjects had an ECG "abnormality" or normal variant and 67 ECGs (17%; 95% CI: 13.3% to 20.7%) had major and minor abnormalities. ECG changes normally ascribed to myocardial ischaemia were: i) ST elevation (9.3%; 95% CI: 6.2 to 11.9%), ii) Q waves (7.4%; 95% CI: 4.4 to 9.5%) and iii) ST depression (2.3%; 95% CI: 0.8 to 3.8%). Sokolow-Lyon Index voltage exceeding 38 mm indicative of left ventricular hypertrophy was more prominent in males than females (23.6% vs. 6.4%; OR=4.5; 95% CI: 2.3-8.5).

CONCLUSIONS: These data provide a contemporary reference to the 12-lead ECG in urban South Africans found to be heart disease free, with both major and minor abnormalities detected.