Significance of Cardiac Computed Tomography Incidental Findings in Acute Chest Pain
Article Outline
- Abstract
- Materials and Methods
- Results
- Discussion
- Study Strengths and Weaknesses
- Clinical Implications
- Conclusions
- References
- Copyright
Abstract
Background
Coronary computed tomography angiography might improve the management of patients presenting to the emergency department with acute chest pain; however, noncoronary incidental findings are frequently detected. The prevalence and clinical significance of these findings have not been well described.
Methods
Consecutive patients presenting to the emergency department with acute chest pain and inconclusive initial evaluation between May 2005 and May 2007 underwent 64-slice coronary computed tomography angiography before hospital admission with noncoronary incidental findings immediately reported. An expert panel adjudicated which incidental findings changed in-hospital patient management, and projections for additional testing were based on standard medical practice.
Results
Among 395 patients (37.0% were female, mean age 53 ± 12 years), incidental findings were detected in 44.8% (n = 177): noncalcified pulmonary nodules (n = 94, 23.8%), simple liver cysts (n = 26, 6.6%), calcified pulmonary nodules (n = 16, 4.1%), and contrast-enhancing liver lesions (n = 9, 2.3%). In-hospital management was changed because of incidental finding reporting in 5 patients (1.3%), and a potential alternative diagnosis was offered in another 16 patients (4.1%). Subsequent diagnostic imaging tests were recommended in 81 patients (20.5%), including 74 chest computed tomography scans. After 6 months, biopsy was performed in 3 patients, revealing cancer in 2 (0.5%) who underwent successful tumor resection.
Conclusion
Clinically important findings are detected in up to 5% of patients with a lead symptom of acute chest pain and low to intermediate likelihood of acute coronary syndrome, but only few directly change patient management; 21% are recommended for further imaging tests, resulting in invasive procedures and detection of cancer in few patients.
Keywords: Chest pain, Computed tomography, Incidental findings
The management of patients with acute chest pain is inefficient and associated with a significant economic burden.1, 2, 3, 4, 5 Recent data indicate that cardiac computed tomography (CT) might facilitate early triage of these patients.6, 7, 8 The nature of CT image acquisition allows reconstruction of data sets similar to standard chest CT.9 Thus, this technique routinely permits high-resolution imaging of structures adjacent to the heart and thorax. There has been an ongoing debate regarding the medical and legal implications of reporting incidental findings.10, 11
Retrospective reports indicate that the incidence of incidental findings ranges from 8% in asymptomatic patients undergoing noncontrast chest CT for the detection of coronary artery calcium12 to 58% in symptomatic patients with known or suspected coronary artery disease undergoing contrast-enhanced cardiac CT,13 with up to 22% of these findings requiring follow-up testing. Moreover, in patients with undifferentiated acute chest pain, using CT protocols designed to encompass the coronary arteries, pulmonary arteries, and thoracic aorta, pulmonary embolism or aortic dissection has been observed in 2% of patients.14 However, there are no data available regarding the prevalence and clinical significance of incidental findings not detected during standard care in consecutive patients undergoing a standard coronary CT protocol for the exclusion of acute coronary syndrome.
The aims of our study were to determine the prevalence and nature of incidental findings detected in patients presenting to the emergency department with acute chest pain using a standard coronary CT acquisition protocol; determine the effect on in-hospital patient management; and project subsequent diagnostic testing.
Materials and Methods
Patients
The Rule-Out Myocardial Infarction using Computer Assisted Tomography study is a prospective, double-blinded, observational cohort study of consecutive adult patients presenting to the emergency department with acute chest pain and suspected acute coronary syndrome. Patients were recruited on weekdays from 7 am to 7 pm from May 2005 to May 2007. Patients were included if they had been entered into a rule-out myocardial infarction pathway on clinical grounds in the emergency department, were in sinus rhythm, documented normal initial cardiac biomarkers, and had a normal or nondiagnostic electrocardiogram. Exclusion criteria were the presence of atrial fibrillation, renal function impairment, and hemodynamic instability.
All patients underwent contrast-enhanced cardiac CT in addition to standard care before hospital admission. Clinical history was obtained through a structured questionnaire that included details regarding cardiovascular risk factors, other medical conditions, and history of smoking. A history of smoking was defined by current or previous regular cigarette smoking. The institutional review board of the Massachusetts General Hospital approved the study.
Cardiac Computed Tomography: Data Acquisition
A dedicated cardiac CT was performed with a 64-slice CT scanner (Sensation 64, Siemens Medical Solutions, Forchheim, Germany) using a standardized coronary CT angiography protocol as described previously.6 Typically, 80 to 100 mL contrast agent (320 mg/cm3, Visipaque, General Electrics Healthcare, Princeton, NJ) was administered as a bolus at a flow rate of 5 mL/sec during a single breath-hold in inspiration to acquire the cardiac CT data set (64 × 0.6-mm slice collimation, gantry rotation time: 330 ms, tube voltage: 120 kV, effective tube current: 850 mA). Raw data were reconstructed with a wide field of view encompassing the entire thorax in xy axis and the volume from the carina to the upper abdomen with a slice thickness of 3 mm.
Reading and Reporting of Incidental Findings
While caregivers and patients remained blinded to findings related to coronary atherosclerosis and plaque, the CT data sets were immediately reviewed for the presence of noncoronary incidental findings by a board-certified radiologist in all patients. The report was entered into the patient's electronic medical record. In cases with a potentially significant finding, emergency department caregivers were immediately notified. In all other cases, the report was sent to the primary care physician or, if the primary care physician was unknown, directly to the patient.
Consequences of Incidental Findings Reporting for Patient Management During Index Hospitalization
On the basis of the medical records and all other prospectively collected information pertaining to the index hospitalization, an outcomes committee consisting of 2 experienced clinicians (1 emergency department physician and 1 cardiologist: JTN, SJL) assessed whether the CT report changed in-hospital management, that is, whether management decisions such as ordering additional diagnostic testing or treatments were made specifically on the basis of the incidental findings report, independently of the standard of patient care. For this analysis, we excluded all incidental findings that had been documented in the patient's medical record or were already identified during the initial emergency department evaluation.
Projected Subsequent Diagnostic Testing
Reports of incidental findings also were assessed to project subsequent diagnostic testing. For pulmonary nodules, recommendations for follow-up were based on the guidelines of the Fleischner Society.15 Briefly, recommendations for subsequent testing are determined by the size of the nodule and the smoking history of the patient. For example, a 55-year-old smoker with a 5-mm noncalcified pulmonary nodule should undergo repeated noncontrast chest CT at 6 to 12 months and then at 18 to 24 months if there is no interval change. For all other findings, projections were based on the expert opinion of the reporting radiologist. We also determined the number and results of invasive procedures performed as a result of the incidental finding reporting based on a review of the patient medical records at Massachusetts General Hospital 6 months after enrollment.
Statistical Analysis
Absolute data are presented as means with standard deviation, and relative data are presented as percentages.
Results
Patient Population
There were 395 patients (mean age: 53 years, 63.0% were male, 48.1% were current or former smokers) who successfully completed the CT study (Table 1).
Table 1. Baseline Characteristics of 395 Patients Who Presented with Acute Chest Pain to the Emergency Department and Underwent Cardiac Computed Tomography
Age (mean ±SD) | 53±12 y |
| Male n (%) | 249(63.0%) |
| Smoking history n (%) | 190(48.1%) |
| Diabetes n (%) | 47(11.9%) |
| Hypertension n (%) | 166(42.0%) |
| Hypercholesterolemia n (%) | 154(39.0%) |
| History of CAD n (%) | 49(12%) |
| Previous PCI n (%) | 34(9%) |
| Previous CABG n (%) | 15(4%) |
Prevalence and Type of Incidental Finding
Overall, 215 noncoronary incidental finding were detected in 44.8% of patients (177/395) with more than 1 incidental finding detected in 18.6% (33/177) (Table 2). The most common findings were noncalcified pulmonary nodules (23.8%, n = 94), liver cysts (6.6%, n = 26), hiatal hernia (3.5%, n = 14), contrast-enhancing liver lesions (2.3%, n = 9), and mediastinal lymph nodes (2.3%, n = 8) (Figure 1, Figure 2). Thoracic aortic aneurysm and pneumonia were seen in 3 patients (0.8%) each. Findings such as chronic aortic dissection, sinus of Valsalva aneurysm, and penetrating aortic ulcer also were detected. Notably, 79.5% of incidental findings (n = 171/215) were previously unknown and also not detected during standard care of the patients. There were no findings of pulmonary embolism or acute aortic dissection in our cohort.
Table 2. Nature, Prevalence, and Location of Incidental Findings in 395 Patients Who Presented with Acute Chest Pain to the Emergency Department and Underwent Cardiac Computed Tomography
| Prevalence in the Cohort (n=395) in % | Fraction of New Findings n (%) | |
|---|---|---|
| Pulmonary Incidental Finding | ||
| Noncalcified pulmonary nodule | 94(23.8%) | 86/94(91.5%) |
| Calcified pulmonary nodule | 16(4.1%) | 14/16(87.5%) |
| Pulmonary infiltrate | 7(1.8%) | 3/7(42.9%) |
| Emphysema | 7(1.8%) | 4/7(57.1%) |
| Atelectasis | 5(1.3%) | 2/5(40.0%) |
| Pleural effusion | 3(0.8%) | 0/3(0.0%) |
| Enlarged hilar or mediastinal lymph node | 9(2.3%) | 5/9(55.6%) |
| Pneumothorax | 1(0.3%) | 1/1(100.0%) |
| Abdominal Incidental Finding | ||
| Liver cyst | 26(6.6%) | 24/26(92.3%) |
| Contrast-enhancing liver lesion | 9(2.3%) | 8/9(88.9%) |
| Fatty liver | 1(0.3%) | 1/1(100.0%) |
| Hiatus hernia | 14(3.5%) | 12/14(85.7%) |
| Contrast-enhancing splenic lesion | 1(0.3%) | 1/1(100.0%) |
| Gallstones | 1(0.3%) | 1/1(100.0%) |
| Aortic Incidental Finding | ||
| Aneurysm | 3(0.8%) | 3/3(100.0%) |
| Dissection | 1(0.3%) | 0/1(0.0%) |
| Penetrating aortic ulcer | 1(0.3%) | 0/1(0.0%) |
| Cardiac incidental finding | ||
| Sinus of Valsalva aneurysm | 1(0.3%) | 1/1(100.0%) |
| Pericardial effusion | 1(0.3%) | 1/1(100.0%) |
| Other Incidental Finding | ||
| Hemangioma of the spinal column | 1(0.3%) | 1/1(100.0%) |
| Thyroid mass | 1(0.3%) | 1/1(100.0%) |
| Chest wall mass | 1(0.3%) | 1/1(100.0%) |
| Hemangioma | 1(0.3%) | 1/1(100.0%) |
| Overall | 215 | 171/215(79.5%) |
Figure 1.
Pulmonary incidental findings. A, Nine-millimeter noncalcified pulmonary nodule (arrow) in the right lower lobe. Biopsy of this lesion demonstrated adenocarcinoma. B, Patchy areas of opacity (circles) in the lingual and superior segment of the left lower lobe, suggestive of bronchopneumonia. C, Pneumothorax with the lung borders (arrows).
Figure 2.
Nonpulmonary incidental findings. A, Aneurysm of the descending thoracic aorta, measuring 41 mm in short axis. B, Right anterior mass of the chest wall (arrows). The mass was histologically classified as hypertrophied internal thoracic muscle after biopsy. C, Thyroid mass (arrowheads) in a patient with coronary bypass grafts. Biopsy of the lesion demonstrated follicular carcinoma. D, Contrast-enhancing lesion of the right lobe of the liver (circle).
In-Hospital Patient Management
Per adjudication, in-hospital patient management was changed in 5 patients (1.3%) with new incidental findings of pneumonia (n = 3), pneumothorax (n = 1), and gallstones in a patient with cholecystitis (n = 1). In addition, findings with the potential to change future patient management were detected in 16 patients (4.1%), including hiatus hernia in 12 patients (3.0%), thoracic aortic aneurysm in 3 patients, and sinus of Valsalva aneurysm in 1 patient. The standard “rule out myocardial ischemia” protocol was performed all patients except the patient with pneumothorax (99.8%).
Projection of Subsequent Diagnostic Testing
Overall, further diagnostic imaging tests were recommended in 81 patients (20.5%). The majority of these tests were recommended for the further evaluation of noncalcified pulmonary nodules (n = 65), contrast-enhancing liver lesions (n = 8), mediastinal lymph nodes (n = 4), thoracic aortic aneurysm (n = 3), and sinus of Valsalva aneurysm (n = 1) (Table 3). The majority of these recommendations included noncontrast chest CT for a follow-up of pulmonary nodules in 69 of 81 patients (85.1%), contrast-enhanced magnetic resonance or CT for a follow-up of liver lesions in 8 of 83 patients (9.6%), and follow-up for aortic disease by contrast-enhanced chest CT in 4 of 81 patients (4.9%).
Table 3. Recommendation for Further Diagnostic Imaging Tests per Radiologist
| Incidental Finding | Recommendation for Further Diagnostic Imaging Tests Made n (%) |
|---|---|
| Noncalcified pulmonary nodule | 65(16.5%) |
| Contrast-enhancing liver lesion | 8(2.0%) |
| Mediastinal lymph node | 4(1.0%) |
| Aortic aneurysm | 3(0.8%) |
| Sinus of Valsalva aneurysm | 1(0.3%) |
| Total | 81(20.5%) |
At 6 months, 3 patients had undergone biopsy as a result of incidental finding reporting. In 2 of these patients, a cancer (follicular carcinoma of the thyroid, adenocarcinoma of the lung) was diagnosed and later successfully removed surgically (Figure 1, Figure 2). In a third patient, the suspected mass was diagnosed as a hypertrophied internal thoracic muscle.
Discussion
Main Findings
Noncoronary incidental findings were detected in approximately half of the patients with a lead symptom of acute chest pain and low to intermediate likelihood of acute coronary syndrome who underwent cardiac CT before hospital admission. Report of these findings significantly changed in-hospital patient management in 1.3% of patients and provided a potential alternative cause of chest pain in 4.1% of patients, although neither pulmonary embolism nor acute aortic dissection occurred. The “rule out myocardial ischemia protocol” was performed as planned in all but 1 patient. Subsequent diagnostic testing was recommended in 20.5% of patients, with noncalcified nodules accounting for the majority of them (65/81). Within 6 months, 3 patients underwent biopsies with 2 of the lesions diagnosed as cancers.
In Context to the Literature
At 44.8%, the prevalence of noncardiac findings detected by contrast-enhanced cardiac CT in our population is lower than in patients with stable chest pain (58%) but higher than in asymptomatic patients undergoing coronary calcium scanning (8%-41%).12, 13, 16, 17, 18, 19 The lower incidence of incidental findings compared with a clinical population of patients with stable chest pain can be explained by the demographics of our study population, which was slightly younger, had a higher proportion of women, had a lower proportion of smokers, and excluded patients with a creatinine level greater than 60 mg/kg/min. As expected, the incidence was higher than in noncontrast examinations because of a higher spatial resolution and the ability to visualize vascular structures after contrast administration.
In contrast with previous studies that reported other life-threatening findings such as aortic dissection or pulmonary embolism in patients with acute chest pain,20, 21, 22, 23 our study did not detect such findings as new diagnoses. However, our population did not include patients with undifferentiated chest pain, a lead symptom of shortness of breath, or an elevated D-dimer, with a primary suspicion of pulmonary embolism. Patients with a primary suspicion of aortic dissection also were not included in the study. In addition, unlike “triple rule-out” CT acquisition protocols, the standard CT coronary angiography protocol used in our study only allows visualization of approximately 70% of the chest volume.9 Although triple rule-out protocols may have improved the ability for the diagnosis of aortic dissection and pulmonary embolism, they come at the expense of additional contrast and radiation exposure.
As found in other studies, pulmonary nodules presented the majority of incidental findings (43.7%), followed by simple liver cysts (12.1%). The frequency of pulmonary infiltrate in our cohort (1.8%), however, was lower than previously reported (9%) and likely represents different reporting thresholds.13
We defined the clinical significance of incidental findings not previously known or detected during routine evaluation on the basis of whether such findings changed in-hospital or long-term patient management as adjudicated by 2 clinicians. An alternative cause for chest pain with a subsequent change in patient management was found in 1.3% of patients, whereas in another 4.1% an incidental finding was discovered that could provide an alternative explanation for the chest pain (eg, hiatal hernia for gastroesophageal reflux disease). However, in the acute situation the latter findings did not justify a change in immediate patient management, and standard care to “rule out myocardial ischemia” was performed in all but 1 patient.
Recommendations for follow-up imaging also were driven by the detection of noncalcified pulmonary nodules (80.2%) based on the established Fleischner Society guidelines.15 There is general agreement that pulmonary nodules are the major source of subsequent testing. Although there have been many studies demonstrating that the rate of lung cancer detection and surgical resection is significantly increased through systematic lung cancer CT screening,24 there is no evidence that lung cancer screening prolongs life.25 Clarification as to whether such practice would save lives is expected to be given by the USA National Lung Screening Trial, with results anticipated for between 2009 and 2012.25
Finally, a review of medical records revealed that 3 patients underwent biopsies leading to the detection of cancer in 2 patients (0.5%), similar to previous reports of patients with stable chest pain (0.8%) or after coronary bypass surgery (0.4%).13, 26
Study Strengths and Weaknesses
The strengths of our study include the prospective assessment and consecutive enrollment of a well-defined population, in whom cardiac CT has been suggested to be an appropriate diagnostic tool improving patient management. Thus, our results provide essential information to determine the efficiency and cost-effectiveness of cardiac CT in this clinical setting. The observational nature of the study allowed us to assess information obtained from CT in addition to standard of care, thus allowing estimation of incremental value. Furthermore, our definition of the significance of incidental findings was strictly based on changes in patient management and was adjudicated independently by a dedicated committee of clinicians. Weaknesses of the study include that the resulting diagnostic imaging test burden was projected rather than observed. However, for the majority of incidental findings, most notably pulmonary nodules, these projections are based on established guidelines and thus may be reliable and generalizable. Further, we did not perform an analysis as to whether reporting of incidental findings is cost-effective.
Clinical Implications
There is growing availability of advanced CT technology in emergency departments across the United States and mounting evidence that coronary CT angiography may improve the management of patients who present with acute chest pain.6, 7, 8 The impact of incidental noncoronary findings on patient management and additional diagnostic testing constitutes important information to enable an objective assessment of the risk/benefit ratio of coronary CT in the emergency department. Although few findings directly change the management of patients with a primary suspicion of acute coronary syndrome, reporting of incidental findings remains medico-legally warranted.
Conclusions
Clinically important findings are detected in up to 5% of patients with a lead symptom of acute chest pain and low to intermediate likelihood of acute coronary syndrome, but few directly change patient management and 21% are recommended for further imaging tests, resulting in invasive procedures and detection of cancer in few patients.
References
- . National Hospital Ambulatory Medical Care Survey 2003 (Emergency Department Summary: Advance Data from Vital and Health Statistics, No. 358). Hyattsville, MD: National Center for Health Statistics; 2005;
- . Evaluation of the patient with acute chest pain. N Engl J Med. 2000;342:1187–1195
- . Value and limitations of chest pain history in the evaluation of patients with suspected acute coronary syndromes. JAMA. 2005;294:2623–2629
- . Care of patients with a low probability of acute myocardial infarction (Cost effectiveness of alternatives to coronary-care-unit admission). N Engl J Med. 1984;310:1301–1307
- . Cost-effectiveness of a coronary care unit versus an intermediate care unit for emergency department patients with chest pain. Circulation. 1996;94:143–150
- Coronary multidetector computed tomography in the assessment of patients with acute chest pain. Circulation. 2006;114:2251–2260
- Usefulness of 64-slice cardiac computed tomographic angiography for diagnosing acute coronary syndromes and predicting clinical outcome in emergency department patients with chest pain of uncertain origin. Circulation. 2007;115:1762–1768
- A randomized controlled trial of multi-slice coronary computed tomography for evaluation of acute chest pain. J Am Coll Cardiol. 2007;49:863–871
- Coronary artery imaging with contrast-enhanced MDCT: extracardiac findings. AJR Am J Roentgenol. 2006;187:105–110
- Ethics (Incidental findings in brain imaging research). Science. 2006;311:783–784
- . Incidentalomas—clinical correlation and translational science required. N Engl J Med. 2006;354:2748–2749
- . Prevalence of significant noncardiac findings on electron-beam computed tomography coronary artery calcium screening examinations. Circulation. 2002;106:532–534
- Noncardiac findings in cardiac imaging with multidetector computed tomography. J Am Coll Cardiol. 2006;48:402–406
- . Evaluation of a “triple rule-out” coronary CT angiography protocol: use of 64-section CT in low-to-moderate risk emergency department patients suspected of having acute coronary syndrome. Radiology. 2008;248:438-436
- Guidelines for management of small pulmonary nodules detected on CT scans: a statement from the Fleischner Society. Radiology. 2005;237:395–400
- . Non-cardiac findings on coronary computed tomography and magnetic resonance imaging. Eur Radiol. 2007;17:2038–2043
- Prevalence and clinical significance of accidental findings in electron-beam tomographic scans for coronary artery calcification. Eur Heart J. 2001;22:1748–1758
- Non-cardiac findings on coronary electron beam computed tomography scanning. J Thorac Imaging. 2004;19:82–86
- Incidental findings on cardiac multidetector row computed tomography among healthy older adults. Arch Intern Med. 2008;168:756–761
- Chest pain evaluation in the emergency department: can MDCT provide a comprehensive evaluation?. AJR Am J Roentgenol. 2005;185:533–540
- ECG-gated 64-MDCT angiography in the differential diagnosis of acute chest pain. AJR Am J Roentgenol. 2007;188:76–82
- . Multi-detector row computed tomography: imaging in acute aortic syndrome. Clin Radiol. 2005;60:1256–1267
- . 64 slice cardiovascular CT in the emergency department: concepts and first experiences. Radiol Med (Torino). 2006;111:481–496
- Survival of patients with stage I lung cancer detected on CT screening. N Engl J Med. 2006;355:1763–1771
- Computed tomography screening and lung cancer outcomes. JAMA. 2007;297:953–961
- Cardiac CT angiography after coronary bypass surgery: prevalence of incidental findings. AJR Am J Roentgenol. 2007;189:414–419
Funding: Dr Lehman is supported by grants from the National Heart Foundation of Australia and the Royal Australian College of Physicians.
Conflict of Interest: None.
Authorship: All authors had access to the data and played a role in writing.
PII: S0002-9343(08)01263-1
doi:10.1016/j.amjmed.2008.10.039
© 2009 Elsevier Inc. All rights reserved.
