Extracardiac Findings on Echocardiography: Blissful Ignorance or a Call to Improve Our Training?

Noninvasive cardiac imaging is one of the pillars of clinical cardiology, with echocardiography being the most widely used imaging modality for assessing cardiovascular anatomy and function. In the United States alone, >20 million echocardiographic studies are performed annually. Virtually all cardiovascular trainees receive instruction in transthoracic echocardiography (TTE), with many receiving level II training, qualifying them to interpret transthoracic echocardiographic studies independently. Recommendations for such training include instruction in the “basic aspects and physical principles of ultrasound, instrumentation, cardiovascular anatomy, physiology and pathophysiology, and appropriateness.” The Core Cardiology Training Symposium guidelines also include a minimum number of studies trainees should perform: ≥150 examinations and 300 transthoracic echocardiographic interpretations for level II training.

As expected, the National Board of Echocardiography examination content is equally focused on cardiovascular issues, with content covering “physical principles of ultrasound, valvular heart disease, ventricular size and function, coronary artery disease, cardiomyopathies, congenital heart disease, cardiac masses, pericardial disease, and myocardial contrast.” Although the 2002 American Society of Echocardiography (ASE) recommendations for a standardized report for adult TTE include reporting of ascites and pleural effusions, the subsequent 2011 ASE recommendations for quality echocardiography laboratory operations do not include mention of these findings in the report. Thus, conspicuously absent from fellowship training guidelines, the 2011 ASE guidelines, and the National Board of Echocardiography’s Examination of Special Competence in Adult Echocardiography is training and reporting of noncardiac findings or extracardiac findings (ECFs).

In contrast to echocardiographic training in cardiology, and likely because of medicolegal issues related to “failure to diagnose,” radiologists have long professed the mantra “I am responsible for everything in the image.” Thus, a patient with a possible aortic dissection referred for chest computed tomographic angiography will also undergo an assessment of the lung parenchyma, breast tissue, mediastinal lymph nodes, superior segments of the liver and spleen, and neck structures such as the thyroid and thymus. Radiologists already have protocols for managing incidental findings in other imaging modalities. The American College of Radiology has issued a series of reports outlining a protocol for reporting incidental findings on abdominal and pelvic computed tomographic and magnetic resonance imaging scans. These give specific instructions to radiologists for classifying the severity of the findings, recommending follow-up imaging if necessary, and communicating this information to ordering providers.

As a result of radiologists’ general responsibility beyond the specific area of interest, there are considerable published data regarding incidental findings or ECFs on epicardial coronary calcium or coronary computed tomographic angiography and cardiac magnetic resonance imaging, two noninvasive cardiac imaging modalities often interpreted by radiologists (and cardiologists). The incidence of ECFs for these two modalities may exceed 40%.

A large determinant of ECF identification is likely to be the skills of the image reviewer, with a higher yield if the images are reviewed by a physician trained in noncardiac pathology, such as a radiologist trained in chest or body imaging. If you are not trained to see an abnormality, your detection sensitivity is likely to be lower. Image interpretation is largely pattern recognition. It helps to “see many” in order to later “find one!”

There are precious few data regarding ECFs on TTE and none that we are aware of regarding ECFs on transesophageal echocardiography (TEE). Even the definition is not established. Although most would agree that a liver abnormality or a lung or mediastinal mass would constitute a noncardiac finding or an ECF, many may argue that a dilated aorta and an aorta with thrombus or atheroma on TEE is within the purview of clinical TEE and is not a noncardiac finding or ECF. Some ECFs are of uncertain clinical relevance or importance, such as a hiatal hernia. Reporting these ECFs often leads to additional imaging studies and even biopsies. This consumes health care resources and causes unnecessary anxiety, as the majority of these findings are ultimately found to be benign.

Alkhouli et al . are congratulated for highlighting and advancing our knowledge of ECFs seen on TTE and TEE. In their retrospective review of >40,000 transthoracic and transesophageal echocardiographic reports from a single institution, they identified 1,797 ECFs, a rate of 4.4%. ECFs were more common on TEE (22.2% vs 3.6% on TTE), although the vast majority (98%) of ECFs seen on TEE were aortic atheromas, aortic thrombi or ulcers, or pleural effusions. Similarly for TTE, 93% of ECFs were pleural effusions, ascites, or descending aortic dilation.

Recognizing the discrepancy between ECFs that are reported and ECFs that can be identified on the images, the authors undertook a sensitivity analysis in which they analyzed the images from a representative sample of 55 transthoracic echocardiographic examinations with and 295 without ECFs. The overall agreement with the original findings was 89%, although those with ECFs had a lower agreement rate (75%) than those without ECFs (95%).

The authors also used the electronic medical records to assess patient follow-up regarding these ECFs and whether the ECFs were novel findings. Eighty percent of patients had adequate follow-up (met with physicians as either inpatients or outpatients within 6 months). Interestingly, only 34% of these patients underwent further imaging studies to confirm the findings on echocardiography.

Consistent with prior studies in both echocardiography and magnetic resonance imaging, the prevalence of ECFs in the study of Alkhouli et al . was much lower when data were extracted from the clinical reports compared with direct review of the source images. In the present study, 5% of the subset of 295 transthoracic echocardiographic reports that did not include ECFs were found to have ECFs on image review, suggesting that more than half of these findings were missed or were felt not to be worthy of reporting. This concept was elucidated by Khosa et al ., who reported on noncardiac findings among 1,008 comprehensive transthoracic echocardiographic studies (443 inpatients, 565 outpatients). Subcostal images were reviewed by a radiologist with fellowship training in cardiovascular and abdominal radiology. Noncardiac findings were identified in 69 patients (7.5%), including 20 benign (e.g., simple hepatic cysts, hemangioma, cholelithiasis), 52 indeterminate (pleural effusions, ascites, cholecystitis), and five worrisome (metastases and venous thromboses) noncardiac findings. This is double the incidence of ECFs noted on TTE reported by Alkhouli et al . Indeed, in the study of Khosa et al ., only 22% of noncardiac findings had been included in the clinical report. As in the study of Alkhouli et al ., pleural effusion and ascites were common, and higher risk findings were rare but more often led to changes in clinical management.

Finally, the sensitivity and specificity of TTE and TEE for noncardiac findings are likely highly variable. Although the sensitivity of TEE is excellent for the diagnosis of descending aortic atheroma and dilation, the sensitivity of TTE for these pathologies is much lower. Both TTE and TEE likely have very poor sensitivity for hiatal hernia, as Alkhouli et al . found only 14 hiatal hernias in >40,000 studies, despite epidemiologic data suggesting that up to 50% of individuals aged ≥50 years have hiatal hernias. Similarly, a transthoracic echocardiographic (and a transesophageal echocardiographic) protocol would not be expected to have the same sensitivity as a dedicated abdominal ultrasound for liver ECFs. Specificity is also an issue, such as the misinterpretation of a benign hiatal hernia as a more concerning extracardiac “mass.”

So what should we do? It is reassuring to know that the incidence of important or management-changing ECFs on TTE and TEE is very low. Thus, it is unlikely that cardiology and radiology coreading of transthoracic or transesophageal echocardiograms would be cost effective or efficient. At the same time, some ECFs do lead to management changes. What may be needed is focused training of both sonographers and physician echocardiographers on noncardiac pathology, specifically emphasizing management-altering liver and mediastinal pathology. At our institution, we recommend that our imaging fellows rotate through the Department of Radiology services to gain this experience (and we offer echocardiography rotations to our radiology residents). As the leading echocardiographic physician and sonographer organization, the ASE should take the lead in developing these training guidelines and make recommendations for their interpretation. Following the lead of the American College of Radiology, the ASE should develop a protocol describing important ECFs that may be found on TTE and TEE and the appropriate action for each category of risk. In addition to echocardiographic training, echocardiographic board certification should include knowledge testing of these ECFs and the recommended practices.

If you don’t see it, it is still there, and it may make a difference. So let’s improve our training!

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May 31, 2018 | Posted by in CARDIOLOGY | Comments Off on Extracardiac Findings on Echocardiography: Blissful Ignorance or a Call to Improve Our Training?

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