RESUMEN
The two features of off-pump coronary artery bypass (OPCAB) grafting that lead to haemodynamic instability are, transient occlusion of the coronary arteries during distal anastomosis construction and displacement of the heart to provide access to the distal coronary arteries. The position of the heart as seen by trans-oesophageal echocardiography (TOE) can often provide an indication as to how much compression of the right or left ventricle has occurred. If either chamber is not filling, repositioning of the heart will be necessary. Close observation of the heart with TOE during periods of coronary occlusion may facilitate detection of worsening cardiac function as evidenced by weakening contraction, ventricular dilatation, or increasing mitral or tricuspid regurgitation. Haemodynamic change are more pronounced with displacement of the heart to access posterior than the anterior coronary arteries. Cardiac manipulations along with transient occlusion of coronary arteries during distal anastomosis may cause transient hypotension with increased filling pressures. TOE is helpful in this scenario as it helps to differentiate between cardiac dysfunction secondary to myocardial ischaemia (in which regional wall motion abnormalities will be present) from a much more common scenario where the increase in filling pressure is secondary to extra-cardiac compression and provides the ability to detect mitral regurgitation with a colour flow Doppler as well as assess the right heart function.