1. Department of Cardiology, University Hospital of Brazzaville, BP 32, Brazzaville, Congo
2. Department of Medecine, Faculty of Health Science, Marien Ngouabi University, BP 2672, Brazzaville, Congo
3. Department of Pediatrics, University Hospital of Brazzaville, BP 32, Brazzaville, Congo
4. Faculty of Health Science, Walter Sisulu University, Mthatha, P.O. Box 5117, Eastern Cape, South Africa