Risk Stratification of Chest Pain Patients in the Emergency Department by Assessing Diastolic Function Using Tissue Doppler Imaging: A Feasability Study
Zach Achen1,2, Jonathan Morales1, Elitz Leal-Alegria1, Cyrus Nguyen3, Carlos Basaure, MD, Manpreet Singh, MD, MS4, Alan Chiem, MD, MPH5
1David Geffen School of Medicine at UCLA, 2UCLA Department of Emergency Medicine, 3UCR School of Medicine, 5Harbor-UCLA Emergency Department
DGSOM Short Term Training Program
Chest pain is a common complaint encountered by emergency physicians. Differentiating ischemic from non-ischemic chest pain cause can be challenging, time consuming, and costly. Utilization of Tissue Doppler Imaging (TDI) with echocardiography can assess myocardial tissue motion to provide better insight into overall cardiac function. More specifically, it can detect impaired relaxation during the early phase of diastole in the initial stages of the ischemic cascade 1, 2, 3. A proof-of-concept study demonstrated that TDI performed in the ED has the potential to increase the sensitivity of chest pain patient work-ups by enabling early detection of those at high risk for ischemic damage 4. The study demonstrated that TDI measurements can in fact provide accurate and reliable detection of cardiac ischemia through diastolic function assessment with a lower risk of generating false negatives. The study measured left ventricular filling velocity at the medial and lateral mitral annulus through the apical 4 chamber view. They also measured the anterior and posterior ventricular walls through the apical 2 chamber view. A lower than normal tissue velocity in at least one of the walls measured indicated abnormal diastolic function. Through a sample of 56 patients, they showed that TDI values predicted true ischemic chest pain with 100% sensitivity and 81.82% specificity.
The goal of this project is to demonstrate the feasibility of training emergency medicine residents this TDI protocol for evaluating patients presenting with chest pain.
The study consists of recruiting Emergency Medicine Physicians, gaining a baseline assessment of their knowledge and training of ultrasound and TDI, conducting a didactic intervention that includes in-person learning on volunteer models along with an instructional video, and then re-assessing the residents’ competency using ultrasound and their comfort with assessing diastolic cardiac function using TDI.
Recruitment of EM physicians took place at the Harbor-UCLA Emergency Department, Olive View Emergency Department, and Ronald Reagan Emergency Department. A total of 26 residents have been enrolled and 14 have completed the testing and didactic training.
Subjects are asked to interpret diastolic function based on TDI measurements, and assess risk of ischemic damage based upon ultrasound images and TDI measurements in 10-15 modules prior to and after training as a measurement of improvement and learning of the material. A Wilcoxon signed rank test will be used to compare pre and post-test results for both image acquisition and interpretation portions. Effect size will be calculated using Cohen’s d statistic.
Intervention consists of 2 hours of didactics and 4 hours of hands-on instruction. The study protocol involves training residents in obtaining four chamber (A4C) and two chamber (A2C) apical windows. They are trained to use TDI to measure tissue velocity of the lateral and septal walls (in A4C) and anterior and inferior walls in A2C. The definition for normal tissue velocity will be >9 cm/s for lateral, anterior and inferior walls, and >7cm/s for septal wall.
For the image acquisition portion, we estimate that residents will correctly obtain 2 of 4 views necessary pre-intervention and 4 of 4 views necessary post-intervention. A sample size of 30 will have 99% power to detect a difference in means of 1.5 (with first condition 2.5 and second condition 4.0), assuming a standard deviation of differences of 1.5, using a paired t-test with a 0.05 two-sided significance level.
For the image interpretation portion, we estimate that residents will accurately assess abnormal from normal diastolic function in 25% of cases pre-intervention, and in 90% of cases post-intervention. A sample size of 30 will have 99% power to detect a difference in means of 0.15 (with first condition mean of 0.75 and second condition mean of 0.90), assuming a standard deviation of differences of 0.15, using a paired t-test with a 0.05 two-sided significance level.
The average pre-intervention evaluation based on amount of passed checklist requirements was 21.71%.
After intervention, the average evaluation based on amount of passed checklist requirements was 88.88%.
The average pre-intervention multiple choice test score was 58.1%.
As of right now, although not complete, the average post-intervention multiple choice test score was 93.3%.
Based on physician competency of using TDI post-intervention, it seems feasible that EM physicians could utilize this imaging modality to assess low risk chest-pain patients. With a successfully made online podcast that can explain the use and techniques involved with TDI, our module can be used to train future physicians and make TDI a more prominent tool in chest-pain work-ups in the ED. Future studies can evaluate the accuracy of emergency medicine physicians performing this TDI protocol on patients presenting to the ED, as well as its effect on outcomes like ED length of stay and patient satisfaction.