2089557 High Body Mass Index is Strongly Correlated With Decreased Image Quality in Focused Bedside Echocardiography

Abstract

We sought to correlate obesity as measured by Body Mass Index (BMI) with image quality of focused bedside echocardiography (FOCUS) performed by emergency physicians. We conducted a prospective observational study between Nov. 2012 and Mar. 2014 in patients presenting to two academic emergency departments and an affiliated bariatric surgery outpatient clinic, in a convenience sample of emergency and ambulatory adult patients. 20 patients were enrolled in each of three BMI categories: < 30, 30-39, and ≥ 40. FOCUS was performed on each patient by an ultrasound fellowship-trained EP in the supine and left lateral decubitus positions. The heart was imaged in the subxiphoid, parasternal long axis, and parasternal short axis views. The resulting video clips were interpreted by a second ultrasound fellowship-trained EP who was blinded to BMI. Each clip was assigned two scores on a scale from 1 to 5 for image quality, one score for the ability to discern the myocardial/pericardial interface and another for the ability to visualize global left ventricular function. Scores of 1-2 were considered technically limited (TLS) and would be insufficient for diagnosis. 23 males and 37 females were enrolled. The median age was 49 years and the median BMI was 35.6. There was a significant difference in the percentage of TLS examinations between BMI categories for both image quality scores. For the pericardial interface, there were 10% TLS in the BMI < 30 category, 10% in the BMI 30-39 category, and 50% in the BMI ≥ 40 category (p=0.0069). For left ventricular function there were 10% TLS in the BMI < 30 category, 25% in the BMI 30-39 category, and 55% in the BMI ≥ 40 category (p=0.0107). Additionally, there was an overall negative linear correlation between BMI and image quality for the pericardial interface (r = –0.65, p<0.0001) and left ventricular function (r = –0.60, p<0.0001). Our findings suggest that there is a decrease in the quality of FOCUS images as BMI increases for both the myocardial/pericardial interface and left ventricular function. Emergency physicians should be aware of the potential limitations of focused bedside echocardiography in this patient population.