Identification of High-Risk ACS Patients Using POC Echo

Background

Current American Heart Association (AHA) recommendations suggest that high-risk patients with unstable angina or NSTEMI should undergo early invasive intervention. Risk stratifying these patients generally relies on serial EKGs and troponins, which can delay findings and subsequent intervention as these tests require time and do not have optimal sensitivity or specificity.

Though not a traditional part of the Emergency Department (ED) workup, point of care (POC) echocardiography can be used to stratify high-risk patients. In patients with clinically significant NSTEMIs, prior studies have shown that regional wall motion abnormalities (RWMA) seen on ultrasound may be visualized before the patient develops concerning EKG findings. RWMA represent large areas of the myocardium at risk during acute ischemia. Typically those performing echocardiography studies are either cardiologists or echocardiography technicians with formal training. It is unclear if EM physicians are able to obtain the same images and make similar clinical interpretations.

Primary Results

Three cases where POC echocardiography identified regional wall motion abnormality during ED work-up, which raised concern for a significant acute occlusive coronary lesion.

Patient 1: 55 yo man with HTN and HLD presents with retrosternal chest pain and non-specific EKG findings. He has continued pain despite two sublingual nitroglycerins. In the ED, patient had continued pain and dynamic T waves on EKG. POC echo performed by an ED physician found large anterior and lateral RWMA. As such, patient was taken emergently to the catheterization lab despite only having a mildly positive troponin of 1.2 ng/L and non-diagnostic EKG. He was later found to have a 99% occlusion of his LAD.

Patient 2: 37 yo man with HTN and HLD presents with left sided chest pressure for 1 week with associated nausea and diaphoresis. His initial EKG showed new ST depressions and T wave inversions in the lateral leads. Upon pain resolution, his repeat EKG returned to his baseline and no longer showed the new changes. POC echo found a hypokinetic inferior wall, and his initial troponin was mildly positive (1.05 ng/L). He was ultimately taken to the catheterization lab several hours later from the inpatient floor and found to have 99% of his right coronary artery.

Patient 3: 64 yo man with DM and HLD presents with 6 hours of retrosternal chest pressure with associated dyspnea. His EKG showed sinus bradycardia and lateral ST depressions and inferior T wave inversions. POC echo was performed, showing inferior RWMA. Initial troponin was 0.6 ng/L. Cardiology initially recommended medical management. However many hours later when his repeat troponin resulted at 15.9, he was taken to the catheterization lab, which diagnosed significant stenosis of his right coronary and circumflex arteries.

Strengths

For this article, we are discussing the strengths and weaknesses of the modality (POC Echo) and not the article itself.

• POC echo can be performed rapidly in patient management
• Results are more immediately available than lab data
• Echocardiography shows real-time cardiac function

Limitations

• Patient body habitus may result in difficulty to obtain views
• Interpretation of images may vary from provider to provider
• Difficult to distinguish new vs. old occlusion

Other Issues

There were only three ultrasound fellowship trained emergency physician performing POC echoes in this series. The training was described as watching a brief 10-minute video on focused assessment of wall motion abnormalities. It is unclear how the 3 cases were chosen, as there were 15 cases available to chose from overall.

Author's Conclusions

“Based on these cases, we hypothesize that, in patients without prior history of coronary atherosclerosis, trained ED providers can identify large RWMAs and help prognosticate large areas of myocardium at risk… Additional studies are also needed to better delineate the sensitivity and specificity of bedside echocardiography performed by ED physicians for patients with UA/NSTEMI in comparison with more traditional methods of evaluating risk.”

Our Conclusions

Though POC echo found RWMA in each of the three cases, many could argue that these patients were “high-risk” based on their clinical pictures and EKGs alone, and that POC echo findings did not greatly alter management. Patients 1 and 2 both had risk factors for coronary disease in addition to EKGs with dynamic changes over a short period of time, suggesting clinically significant coronary disease. However it is possible that in more ambiguous patients, POC echo can be better used as an adjunctive test in risk stratification. Additionally more studies should investigate the disparity of echo findings between cardiologists vs. EM physicians, and how to minimize them.

Potential Impact To Current Practice

Performing bedside ultrasounds assessing for general cardiac function is within the scope of Emergency Medicine, but current training does not teach assessment for RWMA. Emergency providers trained in this technique can use RWMA findings in conjunction with troponin and EKG, to further risk stratify patients presenting with unstable angina/NSTEMI.

Bottom Line

Those trained in POC echocardiography should consider assessing for RWMA to identify high-risk NSTEMI patients who may benefit from an early invasive intervention.

Read More

Jneid H et al. 2012 ACCF/AHA Focused Update of the Guideline for the Management of Patients with Unstable Angina/Non-ST Elevation Myocardial Infarction (Updating the 2007 Guideline and Replacing the 2011 Focused Update). Circulation. 2012;126:875-910. PMID: 22800849