This randomized controlled study aims to evaluate the effects of Remote Ischemic Preconditioning (RIPC) on diastolic function in patients undergoing coronary artery bypass grafting (CABG). The study will compare diabetic and non-diabetic patients to determine whether RIPC improves myocardial relaxation and reduces diastolic dysfunction, as assessed by the E/e' ratio at multiple time points during the surgery.

Inclusion Criteria:

• All adult patients scheduled for elective isolated on-pump CABG surgery for two- to three-vessel coronary artery disease.
• Both males and females will be included.
• In the diabetic groups: Type II diabetes currently requiring and adhering to insulin therapy for at least the past 3 months
• During cardiopulmonary bypass, the temperature will range from 28-33°C using an esophageal temperature probe.
• Antegrade warm cardioplegia will be given by the cardiovascular perfusionist.
• Baseline diastolic function will be obtained preoperatively using transthoracic echocardiography done within the six months prior to the surgery

Exclusion Criteria:

• Combined CABG and valve surgery, emergency CABG.
• Type I diabetes, Type 2 diabetes managed with oral hypoglycemic agents without insulin in the past 3 months
• Peripheral vascular disease (PVD) affecting the upper limbs.
• Acute coronary syndrome (ACS); acute or recent myocardial infarction.
• Left ventricular ejection fraction ≤30%.
• Serious pulmonary disease necessitating oxygen supplementation or mechanical ventilation.
• Renal failure, defined as eGFR < 30 mL/min/1.73 m² or requiring renal replacement therapy (dialysis).
• Liver failure, including Child-Pugh Class B or C cirrhosis, severe hepatocellular dysfunction, or listed for liver transplantation.