the study will assess the impact of intraoperative dexmedetomidine infusion on myocardial performance by investigating the left ventricular (LV) systolic and diastolic function and right ventricular (RV) fraction area change (which reflect RV systolic function) using two-dimensional trans-esophageal echocardiography (TEE) in patients undergoing elective first-time isolated off-pump coronary artery bypass (OPCAB) grafting. LV Systolic function will be measured by the TEE via the fractional area change, fraction shortening, and ejection fraction.

Off pump coronary revascularization is an old technique performed first in St Petersburg in 1964, Off pump coronary artery surgery has been developed following two different approaches. Minimally invasive direct-access coronary artery bypass (MIDCAB) that consists of anastomosing the left internal mammary artery to the left anterior descending coronary artery through small anterior left thoracotomy, The second approach is multi-vessel grafting without CPB performed through standard median sternotomy. Dexmedetomidine (Dex), a highly selective α2-adrenergic receptor agonist, is widely used for sedation and analgesia in the ICU or as an anesthetic adjuvant.

This study will be a prospective comparative controlled randomized double blinded clinical trial on 36 patients divided into control ,and dexmedetomidine group.

Inclusion Criteria:

• Patients undergoing elective first-time off-pump isolated coronary artery bypass graft (OPCAB) surgery
• Patients with good ventricular functions.
• Patients with normal levels of cardiac troponin I and myocardial enzymes
• Patients of Body Mass Index (BMI) more than 20 and less than 34.

Exclusion Criteria:

• Severe functional liver or kidney disease.
• Diagnosed HF (NYHA class >3).
• Arrhythmia or received treatment with anti-arrhythmic drugs.
• Severe bradycardia (HR < 45 bpm) and AV block.
• Pathologic esophageal lesion (esophageal stricture or varix )
• Pregnancy.