[1] Putri Bidadari Gen Hosp, Langkat, North Sumatera, Indonesia
[2] Bidadari Gen Hosp, Binjai, North Sumatera, Indonesia
[3] Murni Teguh Mem Hosp, Medan, North Sumatera, Indonesia
[4] Univ Sumatera Utara, Haji Adam Malik Gen Hosp, Dept Cardiol & Vasc Med, Fac Med, North Sumatera, Indonesia