Cardioprotective effect of propofol in cardioplegia compared to systemic propofol in heart valves surgery; a randomized controlled trial

INTERVENTION: Placebo in 50 patients will be as a controlled group. Propofol in cardioplegia Propofol in the aortic line before and after aortic cross clamp CONDITION: ; Surgery Surgery PRIMARY OUTCOME: Cardiac troponin T level SECONDARY OUTCOME: Echocardiography,liver function test,renal function test,cross clamp time,total bypass time, reperfusion time, recovery time,need for defibrilator, ICU stay and morbidty. INCLUSION CRITERIA: The study will include all patients subjected to valve replacement or repair due to rheumatic affection. Those patients will be categorized into three groups: *Group 1(patients with propofol in the cardioplegia and placebo injection in the aortic line). *Group 2(patients with propofol injection in the aortic line before and after the aortic cross clamp and placebo injection in the cardioplegia). *Group 3(patients with placebo injection either in the cardioplegia and aortic line).