This prospective, observational study was conducted in an academic emergency department with a residency training program. The institutional review board approved this study (HUM00113390, 2016). Participation in this study was voluntary and no compensation was offered. Patients were verbally consented prior to inclusion in the study. Patient data were gathered over a 2-month time period. All sonographic images were obtained by Mindray® M9 ultrasound machines (Mindray Ltd., Shenzhen, China) available to the emergency department for regular patient care use. A Mindray phased array (P4-1c) probe was used for obtaining all images.
Patients were selected via a sample of patients who presented to the ED with a chief complaint of chest pain or dyspnea. Patients older than 18 years of age were eligible for the study. When the initial ED provider deemed that FOCUS was necessary in the ED for further aid with narrowing the differential diagnosis, the EM-based ultrasound team was consulted. This team consisted of an ultrasound fellow, along with an EM resident. This team was available for 8-h blocks in the ED, from the hours of 12:00 P.M. to 8 P.M., on weekdays. This availability was based on the point of care ultrasound rotation for EM resident education.
Basic demographic information, including the patient’s age, weight, and BMI, was gathered. This team then performed FOCUS, and attempted to obtain parasternal long (PSLA), parasternal short (PSSA), apical five-chamber, and subxiphoid views. A gross visual interpretation of the systolic ejection fraction, right ventricular systolic heart strain pertaining to visual interpretation of abnormal ventricular septal movement in the PSSA and apical views, and visual assessment of pericardial effusion was made by the performing resident/fellow. Following this, left ventricular outflow tract (LVOT) diameter in a PSLA, and the VTI in the apical view were obtained, for calculation of stroke volume. Finally, the E and E′ values were obtained in the apical five-chamber view, for measurement of possible diastolic heart failure. The interpretations and measurements were recorded, and reported back to the EM provider. Given that patients were evaluated in real time within the emergency department, while also undergoing further work-up with laboratory studies and other possible imaging studies, only either the resident or fellow performed the ultrasound on the individual patient.
These measurements were chosen as they represent advanced cardiac measurements that require advanced training in FOCUS, yet can potentially aid EM physicians in obtaining complex diagnoses. The time needed to perform LVOT, VTI, E, and E′ was the primary outcome of this study.
Prior to performing the study, residents were given a 20-min didactics on performance of LVOT/VTI and diastolic measurements. They were then allowed to practice on a standardized model prior to performance of any FOCUS on patients with cardiopulmonary complaints. The residents were given hands-on instruction from the fellow on obtaining the advanced cardiac measurements on the standardized model. All residents, varying from Post Graduate Year (PGY) 1–4, had varying amounts of experience with both FOCUS and point of care ultrasound. All residents involved in this study were rotating through a month-long point of care ultrasound rotation as part of their EM residency training. The images and measurements on a patient made by residents were independent from the fellow on the team. Similarly, the ultrasounds performed by the fellows did not have interpretations by the resident.
The cardiac window images and LVOT/VTI and E/E′ images were then over-read by multiple ultrasound-fellowship trained EM physicians, to determine if images were of suitable quality, as this is the primary outcome of the study. The interpretation and image acquisition had to be complete to be considered adequate. Recorded images were deemed adequate/inadequate based on image gain, depth, appropriate LVOT diameter measurement, appropriate doppler placement for VTI, E, and E′ images, and appropriate doppler waveforms for VTI, E, and E′ images. All criteria for LVOT/VTI/E/E′ needed to be deemed adequate to be considered of appropriate quality. The studies deemed of appropriate quality for use with clinical decision making with regard to LVOT/VTI and E/E′ measurements, by an ultrasound expert were included in the data analysis. These ultrasound-fellowship trained physicians currently practice at the institute performing the study. They did not collect individual data on any patients or assist with any collection of data. The collected data from the residents/fellows was then analyzed by a statistician using a Test of Between-Subjects Effect to evaluate for significance.