Margaret Wolf, PGY1
Article: Nazerian, Peiman, et al. “Integration of transthoracic focused cardiac ultrasound in the diagnostic algorithm for suspected acute aortic syndromes.” European Heart Journal, vol 40, 2019, pp. 1925-1960, doi:10.1093/eurheartj/ehz356.
Background: Acute aortic syndromes (AAS) affect 4-6/100,000 individuals per year. The diagnosis of AAS is challenging as symptoms are often non-specific. This leads emergency providers to overuse computed tomography angiography (CTA) in patients suspected of having an AAS. Despite this, misdiagnosis of AAS reaches 39%. This is why many physicians use diagnostic algorithms to better calculate pretest probability. The aortic dissection risk score (ADD-RS) can be used to define if the pre-test probability of AAS is low or high. For patients at a low probability, further evaluation is necessitated. The authors of this study wanted to validate the use of transthoracic focused cardiac ultrasound (FoCUS) as a first-line tool allowing rapid bedside assessment of the aorta. In particular, they hypothesized that FoCUS can help to rapidly identify patients requiring CTA despite having a low pretest probability and that the combination of a negative FoCUS, low pretest probability, and negative d-dimer can safely rule-out AAS.
Study Design: This paper is based off of a prespecified subanalysis of the ADvISED study, a prospective multicenter study from five hospitals in four countries. A total of 864 patients were enrolled from 2014-2016 with 839 patients included in the final analysis. Patients with suspected AAS underwent FoCUS in order to detect direct and indirect signs of AAS. FoCUS was performed by both cardiologists (20% of the time) and non-cardiologists. Direct signs included presence of an intimal flap, intramural aortic hematoma, or penetrating aortic ulcer. Indirect signs included thoracic aorta dilation >4cm, pericardial effusion, and aortic valve regurgitation. All patients received a FoCUS exam followed by definitive imaging including a CTA or TEE. If patients did not receive definitive imaging they were followed up with in 14 days to see if they had any events following their ED visit.
Inclusion criteria: >18 years old and experiencing one or more of the following symptoms over the past 14 days: chest/abdominal/back pain, syncope, signs/symptoms of a perfusion deficit
Exclusion criteria: primary trauma or unwillingness to participate
Results: Of the 839 patients analysed, 17.4% had an AAS. Any FoCUS sign of AAS was detected in 36.6% of patients. Of these, 177 cases were false positives and 16 were false negatives. Presence of direct FoCUS signs had a sensitivity of 45.2% and specificity of 97.4% for AAS. Presence of any FoCUS sign had a sensitivity and specificity of 89% and 74.5%. In patients who were low risk by AAD-RS, direct FoCUS signs were identified in 40 (4.8%) of patients, 29 of which had AAS on definitive imaging. Patients who were low risk by ADD-RS and had a negative FoCUS for AAS had a failure rate of 1.9% with a sensitivity of 93.8%. The addition of a negative d-dimer led to a failure rate of 0%.
Limitations: FoCUS exams were performed at tertiary care centers with experienced physicians. As ultrasound is operator-dependent, these results may not apply to less experienced physicians. Likewise, 20% of operators were cardiologists and not emergency physicians, making the study less applicable to bedside use in the ED. Another limitation was that only half of patients received definitive diagnostic imaging (CTA or TEE). Despite following these patients up in 14 days, some cases of AAS may have been missed. Finally, this was not a blinded study and some degree of selection bias may have been present.
Take Home: FoCUS is a useful tool for providing bedside data in the diagnostic approach to suspected AAS. It is most useful in the identification of direct signs of AAS as opposed to indirect signs as these have a higher false positive rate. For patients with low clinical probability of AAS, FoCUS can be used to further risk stratify them for definitive imaging and prevent both misdiagnosis and over-testing. FoCUS should not be used as a standalone test, but is best used in conjunction with risk stratification such as the ADD-RS and d-dimer. In combination, these lead to exceptionally safe and efficient rule-out criteria.