Incidental findings on computed tomography coronary angiography and its impact on respiratory services in a United Kingdom district general hospital [version 1; peer review: awaiting peer review]

Background: Computed tomography coronary angiography is used to assess for coronary artery disease but can also pick up non-cardiac pathology. Previous studies have assessed the frequency of noncardiac pathology. We investigated the non-cardiac findings and resulting follow up in a District General Hospital. Methods: All computed tomography coronary angiography scans for 1 year were retrospectively collected. Basic demographics and the non-cardiac findings were recorded from electronic health records. The significant respiratory findings and the respiratory follow up of these non-cardiac findings were recorded. Results: A total of 503 scans were carried out in one year. Of these scans, 24% had non cardiac findings present. Older patients were more likely to have non cardiac findings. The most common non cardiac findings were lung nodules, emphysema and hiatus hernias. Significant respiratory findings were present in 35 cases, which generated 24 episodes of respiratory follow up. Some patients who met criteria for follow up had not been referred. Conclusions: Non cardiac findings are common on computed tomography coronary angiography and in our hospital these findings led to significant follow up in respiratory services.


Introduction
Computed tomography coronary angiography (CTCA) is used to assess for coronary artery disease in patients with chest pain and in preprocedural planning. In the United Kingdom the National Institute for Health and Care Excellence (NICE) guidelines 2016 have recommended CTCA as the first-choice imaging modality in patients with chest pain 1 . Aside from imaging the coronary arteries, CTCA will also image surrounding structures and can pick up non-cardiac findings (NCF). Some of the NCF will need follow up and further investigation, which has cost and service delivery implications 2 .
The British thoracic society guidelines and the Fleischner society have guidelines of the follow up of lung nodules 17,18 .
In this study of a district general hospital we assessed the frequency of NCF on CTCA, their significance and the follow up requested. The hospital provides secondary care services for cardiology, respiratory, gastroenterology and orthopaedics among other services.

Methods
Ethical approval for data collection and analysis was received from our institution's clinical effectiveness team and all patient data has been anonymised. As the data was retrospectively collected and did not affect the included patients care no further ethical approval was required.
All CTCA performed for one year (2018) were collected retrospectively. Data were reviewed on electronic health records with demographics of patient's age and sex recorded in an Excel spreadsheet. The CTCA's had been performed on a Toshiba Acquillion One using the standard protocol and the images reported by consultant radiologists. NCF were recorded and divided by speciality. Patients with respiratory NCF had their notes reviewed for significance of findings, initial referral and follow up.Findings were assessed as significant if they required further investigation, follow up or treatment. For lung nodules significance was determined by whether they met criteria for further follow up according to British Thoracic Society Guidelines 18 .If a significant finding had not been followed up the primary careprovider for the patient involved was informed.

Statistical analysis
Statistical analysis was performed using Jamovi (version 1.2.22) 19 . Normally distributed data are presented as means and standard deviations. Statistical significance was assessed by t-test or chi squared test, as appropriate. A p value <0.05 was deemed significant.

Results
A total of 503 CTCA were requested in 12 months with nearly all being requested by cardiology and 3 by primary care. There were 284 scans on females and 219 scans on males. The average age of the patients was 60.
NCF were identified in 120 (24%). NCF were more frequent in older patients with statistical significance. For gender there was no statistically significant difference in likelihood to have NCF ( Table 1). Details of all CTCA and resultant NCF are available as Underlying data 20 .
Of the NCF identified, 95 were respiratory with the majority being lung nodules ( Table 2). The respiratory NCF were judged to be significant in 35 cases (7% of total scans). Other NCF were found in gastroenterology, orthopaedic and endocrine specialties which we did not assess for significance.
Onward referral for imaging (all CT Chest) was requested in 18 patients with results followed up by the respiratory team (Table 3). In addition to this, 5 patients were reviewed in the respiratory clinic without further imaging and 1 in a multidisciplinary team meeting.
There were 16 patients who had significant respiratory findings not referred for secondary care follow up, of these 9 were emphysema or parenchymal changes, 5 were nodules and 1 was a pleural effusion.

Discussion
NCF on CTCA are common, but the majority of these are not significant. If the use of CTCA increases, this will lead to significant downstream effects on other specialties, especially respiratory. In our hospital, one year's worth of CTCA led to 24 respiratory follow ups in terms of imaging and clinic appointments.   Even non-significant findings may lead to referrals and investigations if the ordering clinician is unsure of the current guidelines.
Other similar studies show a large variability in proportion of NCF in CTCA, likely due to variability in study populations, equipment and protocols used. Our results are similar to the most recent large UK dataset from the SCOT HEART trial with NCF more frequent as age increases and the most common findings being lung nodules, emphysema and hiatus hernia 2 . These additional data from a single district general hospital should inform other healthcare providers of possible service provision consequences from the use of CTCA.
We identified several patients who would have met criteria for follow up with lung nodules but did not receive this follow up. For some of the NCF such as emphysema and hiatus hernia the patients primary care practitioner will be the correct route of follow up and so they should be informed of the result. As these patients are all symptomatic enough to warrant a CTCA optimising their treatment for NCF seems prudent particularly as these may be the underlying cause of the symptoms. Not correctly following up lung nodules can have significant implications for the patient and in our data set some patients were not followed up according to guidelines.
Cardiologists may not be familiar with the follow up of NCF and so should be cautious when interpreting scan reports. As NCF are common in CTCA a standardised method of reviewing scans and referring findings could be considered with the aim to reduce unnecessary follow up requests and missed significant findings.

Conclusion
NCF are frequent on CTCA and will lead to downstream follow up which will have implications in terms of cost, service provision and patient's time. This project contains details of each computed tomography coronary angiography procedure performed, including a description of the non-cardiac findings, where applicable. To anonymise the data patient age and date of birth is not included.

Data availability
Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).