Hot Off the Press: SGEM #276—FOCUS on PE in Patients With Abnormal Vital Signs

Focused cardiac ultrasound (FOCUS) has been studied as an option for rapid, bedside diagnosis of pulmonary embolism (PE) with disappointing results when applied to patients with stable vital signs.1 However, in patients with an elevated heart rate (HR), signs of right ventricular dysfunction due to PE are more prevalent.2 Among signs of right ventricular dysfunction (RVD), tricuspid annular plane systolic excursion (TAPSE), which assesses for RVD using M-mode to measure movement of the tricuspid annulus over the course of a contraction, has been shown to have a higher sensitivity for PE than other signs, particularly in patients with unstable vital signs.2, 3 In this study, the authors sought to investigate the test characteristics of FOCUS in patients with tachycardia and/or hypotension. This was a prospective observational multicenter cohort study of patients undergoing FOCUS for suspected PE. Patients were enrolled who were age 18 or older, presented with hypotension (systolic blood pressure [sBP] < 90 mm Hg) and/or tachycardia (HR ≥ 100 beats/min) and were being evaluated by the treating physician with a computed tomography angiography (CTA) assessing for PE. A convenience sample was enrolled when FOCUS-trained providers were available in the department. FOCUS was used to evaluate for right ventricular dysfunction using TAPSE, RV enlargement compared to the left ventricle, septal flattening, tricuspid regurgitation, or McConnell’s sign. Abnormal TAPSE was defined as ≤ 2.0 cm. Any abnormal finding resulted in an abnormal study. The primary outcomes were the sensitivity of FOCUS for PE in 1) patients with HR ≥ 100 beats/min or sBP ≤ 90 mm Hg and 2) patients with HR ≥ 110. Sensitivity was 92% in the first group, with TAPSE being the most sensitive component of the examination. The sensitivity in those with a HR ≥ 110 was 100%, again with TAPSE as the most sensitive component. This was a study with well-defined assessment criteria and outcomes; however, the combination of two primary outcomes was unusual. It is more typical to define one primary and other secondary outcomes. The selection of patients through a convenience sample could introduce bias. Another source of potential bias was blinding—some aspects of the treatment of individual patients may have clued the investigators into the diagnosis. Training of the ultrasonographers was adequate, but there was a fair amount of heterogeneity among the ultrasonographers. However, inter-rater reliability was very good. The confidence intervals (CIs) around the results are fairly wide, likely due to the small number of patients enrolled in each group. A number of patients were excluded due to technical difficulties, which provides a window into the real-world applicability of FOCUS for PE. One hundred and forty-three patients who underwent CTA were screened. 136 subjects were ultimately enrolled in the study. The mean age was in the mid-50’s, 59% were female, 23% had a previous VTE, 40% had cancer in the previous 6 months and 15% had signs or symptoms of a DVT. Due to large CIs surrounding the primary outcomes, FOCUS cannot be recommended as a primary rule-in or rule-out tool for PE, even in unstable patients. There may be some utility in ED settings where access to CTA is limited. However, in these settings, volumes of patients may be low and skill maintenance may be difficult. Great episode—with a great discussion on pragmatic research design and the nuances of diagnostic and treatment threshold! I think the reason the discussion tends to move beyond just diagnostic performance is because there's a lot more to patient care than just getting the diagnosis right. Patients with hemodynamic compromise from PE are sick—very sick. When working a busy shift (urban or rural), I think it helps to know who needs our attention most (whether that's more frequent vitals, a team huddle to discuss potential deterioration and action planning, or that longer conversation with that vulnerable patient and their family) and any tool that helps identify the cause of illness, anticipate decline, or prognosticate improves our ability to offer the best possible care. I think this study shows that FOCUS can help in these aspects of care and ED management. Other research seems to support the idea that the RV can also tell us a lot about how the patient might do—include predicting mortality (Tricuspid annulus plane systolic excursion (TAPSE) has superior predictive value compared to right ventricular to left ventricular ratio in normotensive patients with acute PE [PMID 27695491]). In EM, we get pulled in many directions. This type of information helps me determine who needs my attention most, and who I can be less worried about. Having had conversations with the sick PE patients—I have had the chance to impress onto them (and their loved ones) the seriousness of the situation right there in the resuscitation room prior to further testing. I have had these same patients cruise through with no trouble, I have seen some of them crash and then respond to lytic therapy, and I have also seen some of them die. In every instance, being able to screen for sinister causes and/or the heart's response to them (something that not too recently we could only guesstimate through indirect measures like ECG, CXR, labs and invasive lines) through FOCUS (and POCUS more broadly) has made a positive contribution to caring for the patient in front of me. Thanks for the insight Paul! I like your point about how we use ECG to screen for things like PE (where the sens/spec LRs are much poorer than FOCUS). Just because a diagnostic test doesn't have the necessary rule in/out stats (i.e. super sensitive), doesn't mean it's not potentially useful. I think it's a great thing to do (as you mention) in the initial workup of the potentially sick patient—if some one has chest pain and tachycardia, I'm heading into the room w/my ultrasound cart to do the history/physical/ECHO all at the same time. Really can help you triage people. Also can help you look for alternative dx (aortic root widening = dissection, I typically look at lungs so it can often ID PNA or PTX). Importantly too for people without a ton of experience—that's okay! just start practicing on those folks who come in and who have had recent echos that you can compare your FOCUS results with. I think it is an invaluable addition to Wells/YEARS + clin judgement in patients who are too sick for CT where urgent decision needed re: lytics. Impt to know FP's and FN's of “RV dysfxn” and limitations of RV:LV size, this goes double for arrested patients esp if long downtime. If access to CTA is limited, consider the use of FOCUS in unstable patients in whom you suspect PE. Become comfortable with the several assessment measures and understand that the most sensitive finding is TAPSE <2.0 cm and the most specific finding is McConnell’s sign. However, the diagnostic characteristics of FOCUS are not adequate to rule in or rule out PE by itself.

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