Assessment of left ventricular ejection fraction using an ultrasonic stethoscope in critically ill patients

Abstract

IntroductionAssessment of cardiac function is key in the management of intensive care unit (ICU) patients and frequently relies on the use of standard transthoracic echocardiography (TTE). A commercially available new generation ultrasound system with two-dimensional imaging capability, which has roughly the size of a mobile phone, is adequately suited to extend the physical examination. The primary endpoint of this study was to evaluate the additional value of this new miniaturized device used as an ultrasonic stethoscope (US) for the determination of left ventricular (LV) systolic function, when compared to conventional clinical assessment by experienced intensivists. The secondary endpoint was to validate the US against TTE for the semi-quantitative assessment of left ventricular ejection fraction (LVEF) in ICU patients.MethodsIn this single-center prospective descriptive study, LVEF was independently assessed clinically by the attending physician and echocardiographically by two experienced intensivists trained in critical care echocardiography who used the US (size: 135 × 73 × 28 mm; weight: 390 g) and TTE. LVEF was visually estimated semi-quantitatively and classified in one of the following categories: increased (LVEF > 75%), normal (LVEF: 50 to 75%), moderately reduced (LVEF: 30 to 49%), or severely reduced (LVEF < 30%). Biplane LVEF measured using the Simpson's rule on TTE loops by an independent investigator was used as reference.ResultsA total of 94 consecutive patients were studied (age: 60 ± 17 years; simplified acute physiologic score 2: 41 ± 15), 63 being mechanically ventilated and 36 receiving vasopressors and/or inotropes. Diagnostic concordance between the clinically estimated LVEF and biplane LVEF was poor (Kappa: 0.33; 95% CI: 0.16 to 0.49) and only slightly improved by the knowledge of a previously determined LVEF value (Kappa: 0.44; 95% CI: 0.22 to 0.66). In contrast, the diagnostic agreement was good between visually assessed LVEF using the US and TTE (Kappa: 0.75; CI 95%: 0.63 to 0.87) and between LVEF assessed on-line and biplane LVEF, regardless of the system used (Kappa: 0.75; CI 95%: 0.64 to 0.87 and Kappa: 0.70; CI 95%: 0.59 to 0.82, respectively).ConclusionsIn ICU patients, the extension of physical examination using an US improves the ability of trained intensivists to determine LVEF at bedside. With trained operators, the semi-quantitative assessment of LVEF using the US is accurate when compared to standard TTE.

Evaluation of a new pocket echoscopic device for focused cardiac ultrasonography in an emergency setting

“…In a perioperative setting, Frederiksen and colleagues [18] confirmed that PUD was well suited for performing a focus-assessed TTE in a surgery setting with a good image quality. More recently, Amiel and colleagues [16] demonstrated that PUD was able to assess LVEF with a good agreement in 94 critically ill patients.…”

“…Its true portability, ease of use, and relative low cost make this device adequately suited for routine use in strategies of focused US examination. At present, only a few studies evaluating its feasibility and clinical usefulness have been published [16-20]. However, none of them has compared its diagnostic accuracy with that of standard echocardiography in emergency settings.…”

Year in review 2012: Critical Care - cardiology

“…There was a good agreement between both techniques for all items examined. Similar results were obtained in 94 critically ill patients [23]. In that trial left ventricular ejection fraction (LVEF) was independently assessed clinically by the attending physician and echocardiographically by two experienced intensivists trained in critical care echocardiography who used the pocket ultrasound and a fully featured device (CX50, Philips Healthcare, Eindhoven, The Netherlands).…”

Impact of point-of-care ultrasound on the hospital length of stay for internal medicine inpatients with cardiopulmonary diagnosis at admission. – Study protocol of a randomized controlled trial: the IMFCU-1 (Internal Medicine Focused Clinical Ultrasound) study

“…(5) Its use has become very common in some medical specialties such as emergency medicine, anesthesia and critical care. Several prior studies have demonstrated validity and reliability (6)(7)(8)(9)(10)(11)(12)(13)(14).…”