Transoesophageal echocardiography in critically ill patients. A comprehensive approach

European Journal of Anaesthesiology 1997, 14, 350–358

REVIEW

Transoesophageal echocardiography in critically ill patients. A comprehensive approach J. Poelaert, C. Schmidt∗, H. Van Aken∗ and F. Colardyn Department of Intensive Care Medicine, University Hospital, Gent, Belgium and ∗Department of Anesthesiology and Surgical ICU, Westfalisches Wilhelmus-Universitat, Munster, Germany

Introduction Monitoring has become a progressively more important part of the management of the critically ill patient over the last decade. However, the wide selection of available techniques offers a range of applicability and invasiveness, and the need to contain costs has contributed a significant extra economic dimension to the purely medical problems of choosing a monitoring system. Since its development, the pulmonary artery catheter has been widely used as a diagnostic and monitoring tool [1]. If current recommendations are followed, the risk-benefit ratio remains very low although, even in the most experienced hands, mishaps and failures can occur [2]. However, owing to alterations in compliance of the left ventricle and the risk of incorrectly estimating left heart filling from measured pressures, less indirect assessments of flows and volumes appear to allow better evaluation of preload [3–5]. More recently, automated technology has simplified haemodynamic assessment and it is relatively non-invasive. Echocardiography was first introduced in cardiological practice for determining pressure gradients in patients with mitral stenosis, but its use as a diagnostic tool has grown over the years. In particular, the introduction of echocardiography during and immediately after cardiac anaesthesia and surgery has led to a revolution in bedside diagnosis and monitoring. However, its role in other settings has still not been fully established. Lack of widespread experience Accepted February 1997 Correspondence: J. Poelaert, Department of Cardiac Surgical ICU, University Hospital, de Pintelaan 185, B-9000 Gent, Belgium.

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and advanced training partly accounts for the reluctance to use the technique more widely. This review aims at a comprehensive coverage of the applications and usefulness of transoesophageal echocardiography and colour Doppler (TOE) for diagnosis and assessment of cardiac function in critically ill patients.

Anatomy and images Separate authors have described the anatomy and related echocardiographic images. Standard views consist of cross-sectional imaging in the transverse plane [6,7]; the three major views are the short axis of the left ventricle at the level of the mid-papillary muscles (Fig. 1), the four-chamber and the short-axis view through the superior mediastinum. In addition, as much as possible of the aorta should be evaluated in order to complete the whole TOE investigation. At each level, various flows can be measured by means of colour flow examination and Doppler assessment. Biplanar and, subsequently, multiplanar imaging have made visualization of cardiac structures possible from different views, sometimes inaccessible from the transverse plane [8,9].

Determination of ventricular function Short-axis imaging in the transverse plane allows optimal visualization of both the left (LV) and right ventricle [6,7] and is the first image to be brought into view. The view gives immediate and relevant information about global contractility, LV ejection fraction and a first estimation of LV filling. Myocardial contractility can be evaluated in relation to the first three major areas of coronary perfusion. A correlation  1997 European Academy of Anaesthesiology

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Fig. 1. Standard view at the transgastric level (short axis) of both the left (right side) and the right (left side) ventricle. Besides evaluation of global and regional contractility, an immediate idea of LV filling can be obtained. Right: systole; left: diastole.

coefficient of 0.96 has been shown between the fractional area contraction (reduction in cross-sectional area of ventricular cavity) and the ejection fraction obtained by radionucleide angiography [10]. A hyperkinetic LV with a small end-systolic area and unenlarged end-diastolic area is indicative of hypovolaemia [11,12], although increased inotropic activity of the LV (e.g. after administration of inotropes) should be excluded [12]. Global and segmental wall movement can be routinely monitored intraoperatively at the level of the mid-papillary muscle [13–15], and these measurements help to predict post-operative morbidity and mortality [13]. The means for more concise evaluation of segmental wall motion have become available with the introduction of multiplane probes [8,9]. The longitudinal plane allows visualization of the apex of the LV and enables thrombi to be excluded; the whole posterior wall can be inspected in order to detect hypokinesis or an aneurysmal region. The zone perfused by the main left anterior descending artery – just beneath the mitral valve – is another part of the myocardium that can only be assessed in the longitudinal plane. Some appreciation of right ventricular contractility may also be obtained from the short-axis transverse plane, but a four chamber view is needed for a proper assesment of the contractility of the right ventricular free wall, from which hypokinesis can be distinguished or excluded. Acute overload of the right heart may

also be characterized by hypokinesis of the free wall and dilatation of the right chamber (Table 1).

Evaluation of the valvular apparatus Mitral valve Imaging of the mitral valve and the subsequent assessment of the function of the valvular apparatus is one of the most valuable adjuncts of TOE in critically ill patients. Morphological abnormalities (such as insufficient closure of one or both of the mitral valve leaflets, myxomatous degeneration and calcification) can be discerned. Abnormalities in the motility of one or both leaflets (bulging, prolapse or flail) can be concisely evaluated by analysis of multiplanar images [8,9]. Colour flow mapping provides insights into the width [16], length [17], direction of regurgitant jets and into the extent of mitral regurgitation into the left atrium. The next step in the evaluation of mitral valve function is Doppler assessment (Fig. 2). The Doppler pattern comprises an early filling wave and an atrial contraction wave [18]. Transmitral spectral Doppler analysis of the flow pattern offers insight into both early and late filling of the LV in various critical situations (Table 2). Doppler flow recordings are easy to obtain, but they need to be interpreted with due allowance for recognized modifying influences such as age [19],

 1997 European Academy of Anaesthesiology, European Journal of Anaesthesiology, 14, 350–358

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Table 1. Evaluation of hypotension in the critically ill patient using TOE Diagnosis Hypovolaemia Cardiogenic shock Septic shock Septic-cardiogenic shock Tamponade RV infarction Pulmonary embolism Restr./constr. filling abnormalities Hypertrophic cardiomyopathy

LVEDA

LVESA

LVFAC

− +

− + −

+ − +

− (+) (+)

+ − var

−/+

−/+ − − −

−

−

−

+

−

RV dilation E/A

S/D

RWMA

References