Description
Echocardiography is a widely used non-invasive imaging modality which provides real-time dynamic information on cardiac structures of interest. Transoesophageal echocardiog-raphy (TOE) is remarkable for its superior image quality and has served the cardiac surgeons in the perioperative setting since the 1980s. Its initial role was monitoring of left ventricular (LV) function, which, over time has expanded to encompass the complex assessment of the anatomy and function of all heart chambers, valves and the great vessels [ 1 ]. Introduction of real time three dimensional (3D) echo-cardiography has made a revolutionised the history of echo-cardiography by transforming it into a highly competitive and comprehensive imaging modality.
Transthoracic echocardiographic (TTE) assessment is rou-tinely performed before any cardiac surgical procedure. Preoperative TOE is recommended when TTE is non- diagnostic or more detailed evaluation of cardiac structures is needed. TOE has also secured its place in the perioperative setting and is recommend in:
• All open heart (valvular) and thoracic aortic surgical procedures;
• Some (high risk) coronary artery bypass graft cases;
• Non-cardiac surgery when patients have known or suspected cardiovascular pathology which may negatively impact outcomes [ 2 ].
Standard Echocardiographic Assessment
Comprehensive echocardiographic assessment provides a surgeon with information on cardiac chambers, valves and the great vessels. In this chapter, we will highlight the applica-tions of echocardiography on the following topics, most rele-vant for cardiothoracic surgeons:
Left ventricular (LV) function assessment Right ventricular (RV) function assessment Mitral valve (MV) assessment
Aortic valve assessment
Prosthetic valves
Myectomy
Postoperative Complications
LV Function Assessment
Evaluation of LV function is essential for the preoperative assessment of the patient. The degree of LV impairment and dilatation are important parameters when timing valvular surgery. Quick ‘eyeballing’ of the overall systolic function by an experienced observer in the operating room is a good cor-relate to quantitative measurements of LV ejection fraction which is performed by the Simpson method or recently intro-duced 3D LV volumetric reconstruction (Fig. 1.1 ). Assessment of LV regional wall motion abnormalities (RWMA) allows detection of areas of myocardial asynergy and identifies cor-onary territories in compromise. New RWMA in the periop-erative setting may indicate native coronary artery (accidental ligation) or early graft failure, inadequate myocardial preser-vation during cardioplegia or off-pump surgery. This is par-ticularly important in the right coronary artery territory as, due to its anterior and superior location, air embolism may Figure 1.1 Left ventricular volume and ejection fraction assessment by three-dimensional reconstruction on transthoracic echocardiog-raphy. There is evident left ventricular dilatation (end-diastolic and end-systolic volumes are 163 ml and 137 ml, respectively) and severely reduced global left ventricular systolic function (EF 16 %). A semiautomatic algorithm assesses both global (EF) as well as regional LV volumes with the LV segmented into 16 regions (colour coding of the LV) occur. Occasionally, the left circumflex artery (supplying blood to the lateral wall) may become compromised as there is a risk of accidental ligation of the artery in the atrioven-tricular groove while applying sutures in the posterior mitral annular area. TOE assists the surgeon while weaning-off the patient from cardiopulmonary bypass (CPB) and helps ensure complete de-airing of the cardiac chambers by provid-ing visualisation of residual air bubbles in the LV cavity, thus, reducing the risk of coronary air embolism and subsequent RV or LV dysfunction. Perioperative LV dimensions help to assess systemic volume status. While assessing the LV func-tion in the operating room, it is useful to take the following tips into consideration:
• CPB unloads both ventricles and LV function may appear better than it really is;
• Systemic volume underfilling status may falsely ‘shrink’ the LV;
• At a slow heart rate, the LV appears ‘sluggish’ and the increase in heart rate may improve the systolic function in such case;
• Paradoxical anterior systolic motion of the interventricular septum is a common finding after pericardiotomy and, when • observed in isolation, does not indicate new myocar-dial ischemia.
To avoid possible pitfalls in LV assessment, its volumes and function should be assessed, not only while coming off bypass, but also at the very end of the surgery (fully off-bypass).