1. Al Neelain University, Faculty of Medicine, Khartoum, P.O. Box 12702, Sudan
2. University of Khartoum, Faculty of Medicine, Khartoum, P.O. Box 102, Sudan
3. Almaarefa University, Faculty of Medicine, Riyadh, Saudi Arabia
4. University of Khartoum, Faculty of Nursing Sciences, Khartoum, P.O. Box 102, Sudan
5. Cardiology Department, Al-Shaab Teaching Hospital, Khartoum, Sudan