By Mark Favot, MD, FACEP and Scott Sparks, MD, FACEP
Transthoracic Echocardiography in Chest Pain and Dyspnea
Have you ever had this sign out, “I have this guy with PE that I am admitting. Just keep an eye on him. He is a little hypoxic, but 99% on 2 L nasal cannula.” You dutifully listen to the sign out but remember an older article that you read where the authors found that a room air pulse oximetry <95% was associated with a worsened in-hospital outcome for patients with acute PE and that vital signs change only when the patient has a greater than 50% pulmonary artery occlusion (1). And you also recall a newer article you read just last month that looked at the different echocardiographic findings in patients with acute PE’s (2).
Fans of Social Media and old school print media are more frequently picking up the ultrasound, but when do we use it to diagnose or aid PE diagnosis? Remember VQ scans? If not, then CT angiography for PE diagnosis. What if they have crappy renal function? We also need options for the hemodynamically unstable patient and those at high risk for PE.
Sometimes we have to convince the doubters about POCUS and start with “what if we had a tool at the bedside to help diagnose PE?” It takes time and experience to convince the nonbelievers.
In the September issue of The Journal of the American Society of Echocardiography, Kurnicka et al. conducted a retrospective analysis of 511 consecutive patients with acute PE (diagnosed on CTA with the presence of a segmental pulmonary artery or larger thrombus in patients with symptoms for <14 days) with the goal to assess the frequency of right ventricular dysfunction (RVD) and the supposedly more specific typical echocardiographic signs (TES) of acute PE. They defined RVD as the presence of BOTH RV free wall hypokinesis & a ratio of the RV end diastolic diameter (EDD) to the left ventricular (LV) EDD > 0.9. They identified three TES that they hypothesized would be more specific for the diagnosis of PE: 1) McConnell sign (hypokinesis of the RV with sparing of the RV apex), 2) the 60-60 sign (shortened pulmonary ejection time, <60ms with mid systolic velocity deceleration & tricuspid valve regurgitation with peak systolic gradient >60 mm Hg) & 3) a right heart thrombus. Lastly the authors had a third category called RV overload consisting of any one of the following: RV enlargement, moderate RV free wall hypokinesis, interventricular septum (IVS) flattening, tricuspid regurgitation pressure gradient >30 mm Hg, RVOT acceleration time <80ms, or a distended IVC (greater than 2.1cm in diameter with <50% respiratory collapse. There were 2 main hypotheses: 1) the TES would primarily be present only in patients with massive PE’s (hypotensive) and far less frequently in patients with stable PE’s & 2) echocardiography would identify “incidental” lesions (severe LV systolic dysfunction, moderate to severe aortic valve stenosis or regurgitation, moderate to severe mitral valve regurgitation and significant pericardial disease) that would potentially reduce the likelihood of a physician pursuing the diagnosis of PE when one exists. To date this is the only comprehensive analysis describing the echocardiographic findings in a large number of unselected patients with acute, confirmed PE.
Only 16 of the 511 patients studied were found to be unstable. At least one TES was found to be present in all 16 unstable patients: McConnell’s sign 75% (12/16), 60/60 sign 31.6% (5/16), & right heart thrombus 18.8% (3/16). The rest of the studied cohort was deemed to be stable and at least one TES was found in 24% (119/495) of the patients: McConnell’s sign 18% (89/495), 60/60 sign 12.3% (61/495), and right heart thrombus 1.2% (6/495). Refer to Table 1 for further detail.
Table 1: Frequency of Echocardiographic Findings
|Echo Finding||Stable (n=495)||Unstable (n=16)|
|McConnell’s sign||89 (18%)||12 (75%)|
|60/60 sign||61 (12.3%)||5 (31.2%)|
|Right heart thrombi||6 (1.2%)||3 (18.8%)|
|RVD||89 (18%)||13 (81.3%)|
The authors predefined important incidental findings as the following: severe LV systolic dysfunction (LVEF)
Now it is time to head back to the bedside and figure out what to do with all of this information. First, the data presented in this article support the use of echocardiography as a diagnostic tool in unstable patients presenting with a suspected PE. All 16 patients in this study had at least one TES of PE. McConnell’s sign and right heart thrombi are generally fairly easy to visualize with the naked eye on standard 2-dimensional images. The 60/60 sign requires some skill with Doppler (the RVOT acceleration time <60ms finding in our experience is a bit more challenging to identify than significant TR with gradients >60 mm Hg) but can also be learned with practice. Importantly, the presence of RVD described by the authors was not universally present in the unstable patient cohort as 3 of the 16 patients did not meet both criteria. Each of these 3 patients failed to meet the criteria b/c of severe LV enlargement due to pre-existing left heart disease which led to an RV:LV ratio <0.9.
However, our patient is stable (at least for now), so how does this study help us? The two key points from this study that can be helpful in caring for the hemodynamically stable PE patients are: 1) 7.5% of the stable patients in this study had potentially misleading findings involving the LV or the mitral or aortic valve that could cause the physician to prematurely conclude the work-up if they had use echocardiography as the primary diagnostic tool, 2) 34.5% of the stable patients had completely normal RV morphology with preserved function. The major take home point for the astute emergency physician (i.e. you, because you are reading this) is that in stable patients there are much better diagnostic tools than echocardiography to detect the presence of PE (Well’s score, Geneva score, PERC, gestalt, etc) and echocardiography is best reserved to evaluate stable patients AFTER they have been diagnosed with a PE, because RVD or TES along with other features (elevated troponin, elevated natriuretic peptides, hypoxemia, ECG changes) portend a worsened outcome (3,4). In the unstable patient, the presence of a TES should prompt strong consideration for the initiation of therapy for acute massive PE without definitive diagnostic testing (CT angio). Now that we know the frequency of common PE echo findings, the history and physical exam may aid a PE diagnosis for the unstable and for patients intolerant of CT angiography. This study may also give us a tool to use in those who cannot get a CT due to poor renal function. Just food for thought.