Despite the growing use of computed tomographic angiography (CTA), the effect on patient management is less clear. We sought to determine the perceived usefulness of the results provided by CTA and to assess whether and how it influences patient management. Comprehensive prospective data were collected from 184 consecutive patients who presented for clinical CTA for the evaluation of coronary artery disease from March to July 2008. In addition, a detailed survey was sent to each referring physician for each patient examined to assess whether they found the results of the CTA useful and whether it had any influence on subsequent patient management. Of 184 CTA examinations, which had been ordered by 82 different providers, 108 surveys (59%) were completed by 53 different physicians. No significant differences were found in either the patient or provider characteristics for the completed versus noncompleted surveys. Of the 184 CTA examinations, the severity of coronary disease detected by CTA was severe for 26%, mild to moderate in 47%, and not present in 27% of the patients. Clinicians considered the test results to be useful in virtually all cases and thought the results led to significant risk reclassification in 58% of the patients. If CTA had not been available, the clinicians indicated that they would have ordered an invasive test for 46% of the patients and noninvasive tests for 32%. After CTA, changes in medical therapies were made for 31%, invasive angiography was planned for 19%, and noninvasive testing was scheduled for 6% of the patients. In conclusion, of 53 different referring clinicians from different medical specialties, CTA was considered to almost always be useful; however, the effect on subsequent medical management was more variable.
To use computed tomographic angiography (CTA) efficiently, it is important to determine that it does not merely result in yet another test in our diagnostic algorithm but rather has a significant effect on patient management or that it prevents the use of additional testing. Although most computed tomographic angiographic studies to date have examined the technical advancements and diagnostic accuracy of this modality, the value of CTA and whether it is a useful test in patient management remain unknown. Thus, the aim of our study was to describe physicians’ perceptions of the utility of CTA and its effect on patient management.
Methods
From March 2008 to July 2008, data were prospectively collected for all consecutive patients referred for CTA at the Massachusetts General Hospital. Before each examination, information, including demographics, baseline cardiac history, results of previous cardiac testing, symptoms, and the indication for the examination were obtained from the medical records, a self-administered questionnaire that had been completed by each patient, and from an interview conducted by a physician performing the computed tomographic angiographic examination.
Within 1 week after CTA, all referring physicians were contacted by e-mail and were provided with an electronic copy of the final examination report. At that time, they were asked to complete a brief on-line questionnaire that was designed to assess the usefulness of the results of the cardiac computed tomographic examination in the treatment of the given patient (see Appendix 1 ). The survey was administered using secure, on-line, survey software (SurveyMonkey; available at: www.SurveyMonkey.com ). To encourage participation, the referring physicians were promised a small token of appreciation (a Starbucks gift certificate) for each survey they completed. The clinicians who did not respond to the initial e-mail were sent a follow-up reminder e-mail. Those who failed to respond to the reminder e-mail were then sent a printed copy of the survey by United States postal mail, together with the printed final report. As a part of each survey, information relating to the referring physician’s specialty and training was obtained.
No patient underwent more than one CTA; thus, the comparisons among patient populations included no duplicate subjects; however, several physicians had ordered more than one CTA (average 2.2 per provider). The clinical characteristics of the patients with and without completed surveys were compared to determine whether the patients for whom survey data were available might differ from the overall study population.
The pretest probability of coronary artery disease (CAD) was calculated by choosing the most appropriate risk score according to the presence or absence of symptoms. For asymptomatic patients, the Framingham risk score was calculated. Although this score is intended to determine a patient’s risk of developing coronary heart disease events, it has also been shown to correlate with the burden of clinical or subclinical atherosclerosis. It was thus an appropriate risk score for predicting the presence of CAD in asymptomatic patients.
After calculating the Framingham risk score for each patient, their risk level was reclassified using 2 methods. First, using the Adult Treatment Panel III criteria, any patient who had a known coronary heart disease risk equivalent (ie, history of known CAD, coronary artery bypass grafting surgery, percutaneous coronary intervention, diabetes mellitus, peripheral vascular disease, or stroke) was reclassified as being at high risk. Any patient who had had abnormal myocardial perfusion imaging findings was also reclassified as being at high risk. This second reclassification was determined from data showing that patients with abnormal myocardial perfusion imaging findings have an annualized hard event rate equivalent to high Framingham risk (ie, >2% annually).
For symptomatic patients, the estimated pretest probability of significant CAD was calculated using the Duke clinical score. Typical angina was defined as chest discomfort that was (1) precipitated by physical exertion or emotion and (2) relieved with rest or nitroglycerin. Atypical angina was defined as chest discomfort that was associated with either physical exertion or emotion or relieved with rest or nitroglycerin, but not both, or by having dyspnea on exertion that was clinically suspected to represent the patient’s anginal equivalent. Nonanginal chest pain was characterized as chest discomfort that lacked any of these associations. The pretest probability of significant CAD was calculated using the previously validated Duke Clinical Score model integrating the type of chest pain, together with clinical variables of age, gender, history of myocardial infarction, smoking, hyperlipidemia, and diabetes. The model used for this calculation is given in Appendix 2 . From the calculated pretest probability of significant CAD, each patient was then categorized as having low risk (<30%), intermediate risk (30% to 70%), or high risk (>70%).
CTA was performed using the Definition dual-source computed tomography scanner (Siemens Medical Systems, Munich, Germany) with a gantry rotation time of 330 ms and standard detector collimation of 2 × 32 × 0.6 mm. To reduce the patient’s radiation exposure, tube current modulation was used whenever possible. In addition, for younger patients (eg, age <50 years), axial acquisition using prospective electrocardiographic triggering (Siemens sequential scanning) was selected, when appropriate.
Axial and double-oblique images viewed in thin, maximal intensity projections and multiplannar reformation settings were used for image analysis. Clinical reporting was then used to categorize each vessel as normal (no CAD), mild to moderate CAD (visually estimated at <70% stenosis), or severe CAD (visually estimated at >70% stenosis for any coronary artery or >50% stenosis for the left main coronary artery). The disease extent was determined by the number of vessels with severe disease (1, 2, or 3 vessels). Left main coronary artery disease was classified as equivalent to 2-vessel disease.
Statistical analysis was performed using Stata IC, version 10.0 (StataCorp LP, College Station, Texas). All continuous variables are expressed as the mean ± SD, and categorical variables are expressed as percentages. Differences in continuous variables were assessed using Student’s unpaired t tests. Differences in dichotomous variables were assessed using the chi-square test or Fisher’s exact test. For ordinal variables, the rank sum test was performed to assess for significance. A 2-tailed p value of <0.05 was considered statistically significant.
Results
Clinical data were obtained from 184 consecutive computed tomographic angiographic examinations that had been ordered by 82 different physicians for an evaluation of CAD as the primary indication. Of the 184 examinations, the follow-up survey was completed for 108 (59%) Of these 108 surveys, 85 (79%) were completed by cardiologists and the rest were completed predominantly by primary care physicians.
Table 1 lists the baseline patient characteristics, primary indication for CTA, frequency of previous cardiac imaging studies, and the results of the computed tomographic angiographic examination for all 184 patients and the 108 for whom the provider survey was completed. A comparison of the patient and provider characteristics for examinations with completed versus noncompleted surveys ( Supplement Tables 1 and 2 ) did not detect any significant differences between the 2 groups.
| Variable | Patients With Indication for CAD Evaluation (n = 184) | Patients With Indication for CAD Evaluation and Completed Survey (n = 108) |
|---|---|---|
| Clinical characteristics | ||
| Women | 73 (40%) | 36 (33%) |
| Age (years) | 57.2 ± 14.3 | 58.5 ± 15.1 |
| Coronary heart disease risk equivalent ⁎ | 65 (35%) | 39 (36%) |
| Coronary heart disease risk equivalent † ‡ | 86 (47%) | 47 (44%) |
| Diabetes mellitus | 28 (15%) | 15 (14%) |
| Hypertension § | 106 (58%) | 58 (54%) |
| Hyperlipidemia § | 115 (63%) | 71 (66%) |
| Smoker | 21 (11%) | 13 (12%) |
| Patient symptoms | ||
| Asymptomatic | 52 (28%) | 26 (24%) |
| Dyspnea only | 2 (1%) | 2 (2%) |
| Chest pain syndrome | 132 (72%) | 82 (76%) |
| Dyspnea thought to represent angina pectoris | 29 (16%) | 23 (21%) |
| Nonanginal chest pain | 47 (26%) | 26 (24%) |
| Atypical chest pain | 27 (15%) | 16 (15%) |
| Typical chest pain | 29 (16%) | 17 (16%) |
| Previous testing (within 6 months) | ||
| Echocardiography | 53 (29%) | 31 (29%) |
| Stress test | ||
| Nuclear stress test | 78 (42%) | 42 (39%) |
| Stress echocardiography | 6 (3%) | 5 (5%) |
| Exercise electrocardiographic stress test | 16 (9%) | 8 (7%) |
| Cardiac catheterization | 9 (5%) | 6 (6%) |
| Primary indication | ||
| Native coronary artery disease evaluation | 153 (83%) | 89 (82%) |
| Bypass graft/stent evaluation | 31 (17%) | 19 (18%) |
| Computed tomographic angiographic results | ||
| Normal | 49 (27%) | 29 (27%) |
| Mild to moderate coronary artery disease | 87 (47%) | 48 (44%) |
| Severe coronary artery disease | 48 (26%) | 31 (29%) |
⁎ Coronary heart disease risk equivalent included history of known CAD, myocardial infarction, coronary artery bypass grafting surgery, percutaneous coronary intervention, diabetes, peripheral vascular disease, and/or cerebrovascular accident.
† Coronary heart disease risk equivalent expanded to also include all patients with abnormal findings from single photon emission computed tomographic myocardial perfusion imaging.
‡ Included abnormal findings from nuclear stress testing.
§ Patients classified as having hypertension or hyperlipidemia if diagnosis present on medical record or if they had been told by physician that they had the condition.
Of the 184 patients referred for CTA, 132 (72%) were symptomatic and 52 (28%) were asymptomatic ( Table 2 ). CTA showed that 48 (26%) had no evidence of CAD and 73% had CAD. These proportions did not vary between the patients who were symptomatic and asymptomatic.
| Variable | Total (n = 184) | Symptomatic (n = 132) | Asymptomatic (n = 52) | p Value |
|---|---|---|---|---|
| Clinical characteristics | ||||
| Women | 73 (40%) | 58 (44%) | 15 (29%) | 0.06 |
| Age (years) | 57.2 ± 14.3 | 56.9 ± 14.9 | 57.9 ± 12.9 | 0.68 |
| Diabetes | 28 (15%) | 24 (18%) | 4 (8%) | 0.07 |
| Coronary heart disease risk equivalent ⁎ | 65 (35%) | 45 (34%) | 20 (38%) | 0.58 |
| Coronary heart disease risk equivalent † ‡ | 86 (47%) | 60 (45%) | 26 (50%) | 0.58 |
| Hypertension § | 106 (58%) | 80 (61%) | 26 (50%) | 0.19 |
| Hyperlipidemia § | 115 (63%) | 83 (63%) | 32 (62%) | 0.87 |
| Previous testing (within 6 months) | ||||
| Any previous noninvasive testing | 116 (63) | 88 (67%) | 28 (54%) | 0.11 |
| Any previous stress testing | 95 (52%) | 75 (57%) | 20 (38%) | 0.03 |
| Stress echocardiography | 6 (3%) | 4 (3%) | 2 (4%) | 0.78 |
| Exercise electrocardiographic stress test | 16 (9%) | 13 (10%) | 3 (6%) | 0.38 |
| Nuclear stress test | 78 (42%) | 62 (47%) | 16 (31%) | 0.045 |
| Echocardiography | 53 (29%) | 37 (28%) | 16 (31%) | 0.71 |
| Cardiac catheterization | 9 (5%) | 7 (5%) | 2 (4%) | 0.68 |
| Pretest probability of significant coronary artery disease ¶ | 0.64 | |||
| Low | 53 (29%) | 37 (28%) | 16 (31%) | |
| Intermediate | 24 (13%) | 17 (13%) | 7 (13%) | |
| High | 107 (58%) | 78 (59%) | 29 (56%) | |
| Framingham risk score ∥ | 0.68 | |||
| <6% | 59 (45%) | 42 (45%) | 17 (46%) | |
| 6–10% | 22 (17%) | 15 (16%) | 7 (19%) | |
| 10–20% | 43 (33%) | 31 (33%) | 12 (32%) | |
| ≥20% | 7 (5%) | 6 (6%) | 1 (3%) | |
| Reclassification of risk by addition of Adult Treatment Panel III coronary heart disease risk equivalents ⁎ ∥ | 0.60 | |||
| <6% | 46 (35%) | 33 (35%) | 13 (35%) | |
| 6–10% | 14 (11%) | 10 (11%) | 4 (11%) | |
| 10–20% | 17 (13%) | 15 (16%) | 2 (5%) | |
| ≥20% | 54 (41%) | 36 (38%) | 18 (49%) | |
| Reclassification of risk by addition of nuclear imaging results † ‡ ∥ | 0.31 | |||
| <6% | 34 (26%) | 25 (27%) | 9 (24%) | |
| 6–10% | 11 (8%) | 8 (9%) | 3 (8%) | |
| 10–20% | 14 (11%) | 13 (14%) | 1 (3%) | |
| ≥20% | 72 (55%) | 48 (51%) | 24 (69%) | |
| Computed tomographic angiographic results | 0.46 | |||
| Coronary artery disease severity | ||||
| Normal | 49 (27%) | 36 (27%) | 13 (25%) | |
| Mild to moderate | 87 (47%) | 64 (48%) | 23 (44%) | |
| Severe | 48 (26%) | 32 (24%) | 16 (31%) | |
| Number of coronary arteries with stenosis | 0.32 | |||
| 0 | 136 (73%) | 100 (76%) | 36 (69%) | |
| 1 | 25 (14%) | 18 (14%) | 7 (13%) | |
| 2 | 17 (9%) | 10 (8%) | 7 (13%) | |
| 3 | 6 (3%) | 4 (3%) | 2 (4%) |
⁎ Coronary heart disease risk equivalent included history of known coronary artery disease, myocardial infarction, coronary artery bypass grafting surgery, percutaneous coronary intervention, diabetes, peripheral vascular disease, and/or cerebrovascular accident.
† Coronary heart disease risk equivalent expanded to include all patients with abnormal findings from single photon emission computed tomographic myocardial perfusion imaging.
‡ Included abnormal findings from nuclear stress testing.
§ Patients classified as having hypertension or hyperlipidemia if diagnosis present on medical record or if they had been told by physician that they had the condition.
¶ Duke clinical scoring system.
∥ Framingham risk score calculated for 131 of 184 patients with lipid panel findings available.
Figure 1 illustrates the perceived usefulness of the computed tomographic angiographic examination results as assessed by the referring physician. Most respondents (106 of 108) indicated that the test results were helpful; and 85% rated it ≥8 on a scale of 1 to 10, with 1 indicating “not helpful” and 10, “extremely helpful.” The reasons for the unhelpful category included a “technically limited study” and when the “results did not lead to any change in practice because the test did not add any new information.”
Of the survey respondents, 46% indicated they would have ordered an invasive test and 32% indicated they would have ordered a noninvasive test if CTA was hypothetically not available (ie, responded “yes” or “probably yes”; Figure 2 ).
Comparing the characteristics of the symptomatic versus asymptomatic patients ( Table 2 ), no difference was found in age, prevalence of hypertension, or prevalence of hyperlipidemia; however, a nonsignificant trend was seen toward a greater proportion of women as symptomatic patients. Symptomatic patients were more likely to be current smokers and to have undergone a stress test in the previous 6 months.
No significant difference was found between the symptomatic and asymptomatic patients in the pretest probability of CAD using either the Duke clinical score or the Framingham risk score. Also, no difference was found in the extent or severity of CAD identified by CTA between the symptomatic and asymptomatic patients.
When assessing the effect of the computed tomographic angiographic results for symptomatic versus asymptomatic patients ( Table 3 ), a trend was seen for the test to more often be considered “helpful” for the symptomatic patients. Although the presence or absence of symptoms had no influence on the post-test probability of CAD, significantly more clinicians indicated that they would have ordered invasive angiography if CTA was hypothetically not available for symptomatic patients than for asymptomatic patients (51% vs 31%, p = 0.05). In contrast, given the same scenario of CTA not being available, no difference was seen in the clinician predicted use of a noninvasive stress test between these 2 groups. Furthermore, although the presence or absence of symptoms did not have any influence on the planned changes to medical therapy after CTA, a trend was seen such that symptomatic patients were more likely to be referred for invasive angiography after CTA (23% vs 8%, p = 0.08).
