Myocardial Strain Analysis in Anaesthetized Coronary Artery Disease Patients During Hyperoxia and Normoxaemia

Myocardial Strain Analysis in Patients With Coronary Artery Disease at Hyperoxia and Normoxaemia Prior to Coronary Artery Bypass Graft Surgery - a Randomized Crossover Study

The purpose of this study is to investigate the impact of supraphysiologic oxygen (hyperoxia) on myocardial function in anaesthetized patients with coronary artery disease.

Up to 106 patients with coronary artery disease undergoing elective coronary artery bypass graft (CABG) surgery will be recruited to undergo this single visit study. In the timeframe shortly after the induction of anaesthesia and prior to the start of surgery, myocardial strain as a marker of cardiac function will be measured by transesophageal echocardiography (TEE). Echocardiography measurements will be acquired at two different oxygen states for each patient. The fraction of inspired oxygen (FiO2) will be adjusted to reach a normoxaemic state (FiO2=0.3) and a hyperoxic state (FiO2=0.8). Patients will be randomized to which oxygen level is investigated first. Thereafter, the study intervention is completed and anaesthesia and surgery will be performed as planned by the treating team. Echocardiography images will be analyzed in a blinded manner for cardiac function and systolic and diastolic strain parameters. The results will help anaesthesiologists to better weigh risks and benefits when selecting an inspired oxygen fraction in such patients, and will help to evaluate hyperoxia as a risk factor for myocardial injury.

Inclusion Criteria:

• Elective CABG surgery (with or without other cardiac surgery)
• Ability to give and sign informed consent
• Age >18 years.

Exclusion Criteria:

• Absolute contraindication for TEE
• Emergency surgery, including but not limited to patients with instable CAD: ST- and Non-ST-elevation myocardial infarction (STEMI, NSTEMI) and instable angina (instable AP)
• Atrial fibrillation or significant arrhythmia
• Pacemaker, CRT, left bundle branch block
• Severe-grade valvular disease
• Pericardial disease
• Previous cardiac or thoracic aortic surgery
• Previous chest radiation therapy or cardiotoxic or bleomycin chemotherapy
• Severe pulmonary hypertension, cor-pulmonale, or right ventricular dysfunction, i.e., where high FIO2 might reduce pulmonary vascular resistance and right ventricular afterload
• Patients where study explanation and informed consent cannot been performed/obtained at the latest on the day before scheduled surgery
• Females of child-bearing potential