Directed bedside transthoracic echocardiography: preferred cardiac window for left ventricular ejection fraction estimation in critically ill patients

Background: Bedside transthoracic echocardiography (TTE) performed by emergency physicians (EPs) is valuable in the rapid assessment and treatment of critically ill patients. We sought to determine the preferred cardiac window for left ventricular ejection fraction (LVEF) estimation by EP sonographers in a critically ill patient population. Methods: Prospective investigator-blinded study of focused bedside TTE in a convenience sample of surgical intensive care patients. Investigators were faculty, fellows, or residents from an academic emergency medicine department. Five standard cardiac views were performed: parasternal long axis (PSLA), parasternal short axis (PSSA), subxiphoid 4-chamber, subxiphoid short axis, and apical 4-chamber (AFC). LVEF was determined using at least 1 cardiac view. Investigators rated their preference for each cardiac view on a 5-point Likert scale. Results: A total of 70 studies were performed on 70 patients during a 6-month period. Users rated the PSLA as the most useful view for estimation of LVEF (mean 4.23; 95% confidence interval, 3.95-4.51). Pairwise comparisons of cardiac ultrasound views revealed PSLA was preferred over all other views (P < .05) except PSSA (P = .23). Complete 5 view examinations were not achieved in all patients (PSLA in 98%, PSSA in 96%, apical 4-chamber in 74%, subxiphoid 4-chamber in 35%, and subxiphoid short axis in 18%). Interobserver correlation of LVEF estimation was good (r = 0.86, r² = 0.74, P < .0001). Conclusion: Parasternal long axis and PSSA are the preferred echocardiographic windows for EP estimation of LVEF using focused bedside TTE in critical care patients. This may be an important consideration in patients who often have physical barriers to optimal echocardiographic evaluation, are relatively immobile, and have unstable conditions requiring rapid assessment and intervention.