[Transesophageal echocardiography on the intensive care unit]

Transesophageal echocardiography is an important diagnostic tool available to the critical care physician. Indications for the use of transesophageal echocardiography in the intensive care unite include: critical illness and circulatory shock, thoracic aortic dissection, pulmonary embolism and endocarditis. Probe insertion is easy and is successful in 98% of intensive care patients. Further information concerning 44% of the patients was obtained with transesophageal as compared to transthoracic echocardiography. Transesophageal echocardiography is particularly helpful in evaluating cardiac size and function in patients with circulatory shock. When these patients are on multiple positive inotropic and vasopressor drugs, transesophageal echocardiography is useful in assessing left ventricular preload. In these patients, hemodynamic estimation of left ventricular filling may be misleading. More difficult is the assessment of hemodynamic events in patients requiring mechanical ventilation with increasing positive end-expiratory pressure (PEEP). This ventilation mode develops its own pathophysiology which superposes the effects of the underlying disease. Transesophageal examination of the heart after application of PEEP up to 16 cm H2O demonstrated an acute decrease in size of the right and left ventricle (Figure 1). Cardiac index was affected by the decrease in right ventricular dimension by external compression. The addition of positive and expiratory pressure to a level of 8 cm H2O did not depress cardiac index in patients with severe left ventricular dysfunction. PEEP ventilation is associated with abnormal filling patterns characterized by a significant reduction in peak early filling velocity, acceleration and deceleration rate of early filling and peak early to atrial filling velocity ratio (Figures 2a and 2b). Stoddard et al. showed, that these findings of transmitral Doppler flow indices are associated with abnormal left ventricular relaxation. Analysis of regional wall motion under different PEEP levels demonstrated a distinct transmission of increased intrathoracic pressure on the left ventricular wall. We found significant changes in systolic wall motion, in particular a decrease in systolic shortening of the septum and an increase of the lateral wall. Thus, increased intrathoracic pressure under PEEP ventilation is associated with nonuniform regional changes in systolic contraction and abnormal left ventricular relaxation. Both factors are responsible for the decrease in cardiac index under PEEP ventilation. Right ventricular infarction: The transgastric view is usefull in detecting right ventricular wall motion abnormalities and dilatation. Hemodynamically significant right ventricular infarction occurs in the posterior wall, which makes the transesophageal approach ideal. We studied a group of 39 patients with right ventricular infarction.(ABSTRACT TRUNCATED AT 400 WORDS)