Prospective, observational study of the reliability of achieving diagnostic quality transthoracic echocardiograpy images in critically ill adult patients

Introduction

Echocardiography is often requested in the management and diagnosis of hemodynamically unstable critically ill patients [1]. Transoesophageal echocardiography (TOE) is often considered the echocardiographic test of choice in the general ICU patient population. This is based on studies in which transthoracic echocardiography (TTE) commonly offered inadequate images [2]. The aim of this study is to assess the quality and quantity of images obtained in critically ill patients.

Methods

Patients were recruited from February 2006 to December 2007, when the attending consultant requested a TTE on clinical grounds. A single operator carried out all of the TTE procedures. Each study was performed in the 45° head-up, left lateral position. Left ventricular function was assessed either using Simpson's biplane model or the 16-segment Wall motion score index (WMSI). All studies and changes in management were recorded in the patient's notes. Demographic, diagnostic and severity scoring data were collected.

Results

Sixty-six TTE procedures were performed. Mean age of patients was 69 ± 13 years. Eighteen out of 66 studies lacked one or more basic views. The commonest request was for left ventricular function, 45% were normal studies, and the commonest changes in management were fluid boluses, inotrope changes, and commencement of ACE inhibitor therapy. Five TOE procedures were requested. The Simpson biplane method was obtained in 65% of the patients. The WMSI was obtained in 73% of studies. In ventilated patients, the mean positive end-expiratory pressure (PEEP) in the full studies was 7.7 cmH₂O. The mean PEEP was 11.5 cmH₂O in the inadequate studies. The parasternal windows were impaired by high PEEP settings.

Conclusion

In 73% of the patients a full study was performed. Studies may be impaired in patients where their respiratory support requires PEEP > 10 cmH₂O. Changes in management occurred in 60% of the patients within 48 hours. TTE should therefore be considered the initial and principal echocardiographic investigation in critically ill patients. In a minority of cases, inadequate views may require progression to TOE.