Hemodynamic assessment of critically ill patients using a miniaturized transesophageal echocardiography probe

Abstract

Introduction: Hemodynamic management in intensive care patients guided by blood pressure and flow measurements often do not sufficiently reveal common hemodynamic problems. Trans-esophageal echocardiography (TEE) allows for direct measurement of cardiac volumes and function. A new miniaturized probe for TEE (mTEE) potentially provides a rapid and simplified approach to monitor cardiac function. The aim of the study was to assess the feasibility of hemodynamic monitoring using mTEE in critically ill patients after a brief operator training period.

Methods: In the context of the introduction of mTEE in a large ICU, 14 ICU staff specialists with no previous TEE experience received six hours of training as mTEE operators. The feasibility of mTEE and the quality of the obtained hemodynamic information were assessed. Three standard views were acquired in hemodynamically unstable patients: 1) for assessment of left ventricular function (LV) fractional area change (FAC) was obtained from a trans-gastric mid-esophageal short axis view, 2) right ventricular (RV) size was obtained from mid-esophageal four chamber view, and 3) superior vena cava collapsibility for detection of hypovolemia was assessed from mid-esophageal ascending aortic short axis view. Off-line blinded assessment by an expert cardiologist was considered as a reference. Inter-rater agreement was assessed using Chi-square tests or correlation analysis as appropriate.

Results: In 55 patients, 148 mTEE examinations were performed. Acquisition of loops in sufficient quality was possible in 110 examinations for trans-gastric mid-esophageal short axis, 118 examinations for mid-esophageal four chamber and 125 examinations for mid-esophageal ascending aortic short axis view. Inter-rater agreement (Kappa) between ICU mTEE operators and the reference was 0.62 for estimates of LV function, 0.65 for RV dilatation, 0.76 for hypovolemia and 0.77 for occurrence of pericardial effusion (all P<0.0001). There was a significant correlation between the FAC measured by ICU operators and the reference (r=0.794, P (one-tailed)<0.0001).

Conclusions: Echocardiographic examinations using mTEE after brief bed-side training were feasible and of sufficient quality in a majority of examined ICU patients with good inter-rater reliability between mTEE operators and an expert cardiologist. Further studies are required to assess the impact of hemodynamic monitoring by mTEE on relevant patient outcomes.

Figures

Figure 1

Difficulty of acquiring mTEE views. Difficulty of acquisition and image quality of three different transverse views obtained using the mTEE probe in 148 examinations of 55 patients with hemodynamic compromise. Difficulty of acquiring the views was rated by the ICU mTEE operator. ICU, intensive care unit; ME 4 chamber, mid-esophageal four chamber view; ME asc aortic SAX, mid-esophageal ascending aortic short axis view; mTEE, miniaturized trans-esophageal echocardiography; TG mid SAX, trans-gastric mid-esophageal short axis view.

Figure 2

Quality of mTEE views. Percentage of all attempted views that were acquired stratified by the three standard mTEE views (TG mid SAX, ME 4 Chamber, ME asc aortic SAX) and proportion of all attempted loops and acquired loops with sufficient quality as assessed by a trained cardiologist. ME 4 chamber, midesophageal four chamber view; ME asc aortic SAX, mid-esophageal ascending aortic short axis view; mTEE, miniaturized trans-esophageal echocardiography; TG mid SAX, trans-gastric mid-esophageal short axis view

Figure 3

Accuracy of measurements of left ventricular systolic function. Assessment of the accuracy of measurements of left ventricular systolic function using the mTEE probe in 148 examinations of 55 patients with hemodynamic compromise. Measurements of left ventricular function fractional area change (FAC) by ICU operators were repeated by a trained cardiologist blinded to the patients and the mTEE operator's identity and to the results of the operator's examination. Correlation analysis revealed substantial inter-rater reliability of LV FAC measurements (r = 0.794, P (one-tailed) < 0.0001). ICU, intensive care unit; LV FAC, fractional area change of left ventricle; mTEE, miniaturized trans-esophageal echocardiography