Our objective was to determine whether the development of a computed tomography coronary angiogram (CTCA) service has improved the yield of significant coronary artery disease (CAD) and subsequent referral for revascularisation following conventional invasive coronary angiography (ICA).
A retrospective audit comparing angiographic findings in a cohort of 2,094 patients investigated between 2007 and 2012 with findings from a cohort of 554 patients investigated in 2014 and 2015 during which time a CTCA service had been established. Cases included were those patients undergoing elective angiography for the assessment of possible coronary disease without any history of previous revascularisation.
In the pre-CTCA and CTCA cohorts the rates of one-vessel, two-vessel, three-vessel and left main stem disease were 20% vs. 18%, 14% vs. 14%, 10% vs. 11%, 2% vs. 3%, respectively, with overall yield of obstructive CAD of 46% in both cohorts (p>0.05 for all groups).
In conclusion, the availability of a CTCA service has not had any significant effect on the diagnostic yield of ICA. We propose that, adherence to current guidelines, results in a potential underuse of CTCA in the investigation of suspected stable CAD because a sizeable proportion of patients undergoing ICA have non-significant disease.
Introduction
Computed tomography coronary angiography (CTCA) is an established and validated alternative to invasive coronary angiography (ICA).1 The extent to which CTCA can replace ICA is controversial.2 The low diagnostic yield from ICA suggest there is ample scope to select patients more efficiently for investigation.3 In 2010, in the UK, the National Institute for Health and Care Excellence (NICE)4 published new guidelines for the investigation of patients with suspected coronary artery disease (CAD), which incorporated CTCA as a first-line investigation.5 In keeping with these guidelines, we ceased to use exercise testing as a primary test in the assessment of suspected CAD in favour of CTCA, stress imaging and ICA. The purpose of this study is to assess the impact of the CTCA service on the diagnostic yield from ICA, comparing five years of data with two years of data, at a time when a CTCA service was fully established.
Methods
Subjects eligible for inclusion were all patients undergoing elective ICA for suspected CAD. Patients with a history of previous revascularisation or being investigated for valvular heart disease were excluded. All procedures were performed in a single cardiac catheter laboratory based in a district general hospital (DGH). The extent of underlying CAD was reported at the time of angiography and a management plan recorded by the responsible cardiologist. We compared angiography findings and planned referral for revascularisation rates in a previously audited cohort investigated between 2007 and 2012,6 with a cohort of patients investigated in 2014 and 2015 during which time a CTCA service was fully established.
Results
In 2014 and 2015 there were 266 and 272 CTCAs performed, respectively. The average age of the CTCA cohort was 60 years. Scans were either performed on Toshiba 124 or Toshiba 320 scanners. In the pre-CTCA cohort (2,094 cases with average age 66 years) and the post-CTCA cohort (554 cases with average age 68 years) arteries were normal in 34% versus 33%, showed non-significant disease in 20% versus 21%, single-vessel disease in 20% versus 18%, two-vessel disease in 14% versus 14%, three-vessel disease in 10% versus 11% and left main stem disease in 2% versus 3% (p>0.05 for all groups). The overall detection of obstructive CAD was, therefore, 46% in both cohorts. There was also no significant difference in referral rate for revascularisation 28% versus 25% (p>0.05).
Discussion
The NICE guidelines for the investigation of chest pain of recent onset,4 published in 2010, incorporated CTCA (depending on calcium score) as a cost-effective modality for diagnosis in patients at low risk of having coronary heart disease (CHD). The Diamond-Forrester (DF) algorithm that makes up the basis of the recommendation has been controversial.7 The guideline recommends that CTCA is for just low-risk patients, it is, therefore, not surprising that the presence of CTCA has not changed the diagnostic yield from ICA at our institution. The results of the Prospective Multicenter Imaging Study for Evaluation of Chest Pain (PROMISE) study8 suggest that CTCA could be used more widely in the diagnosis of CAD, and the SCOT-HEART9 study suggests that this may lead to better use of resources. Indeed, in that study, the rate of non-obstructive CAD at ICA was just 5% (54% in this study). However, the population in which CTCA should be used in preference to ICA or other modes of investigation remains controversial.10 In this study, the cohort of patients undergoing CTCA were younger than those undergoing ICA (60 years vs. 68 years, respectively). There is potential concern that using CTCA in older or higher-risk patients with higher calcium scores might lead to inconclusive scans and subsequent further investigations. This, however, has not been our experience. We suggest that CTCA is probably underused in the investigation of suspected CAD and the guidelines for investigation of patients with stable chest pain require revision to allow for advances in this technique.
Conflict of interest
None declared.
Funding
This research did not receive any funding.
Key messages
- In current practice, less than 50% of invasive coronary angiograms reveal significant coronary artery disease
- The advent of computed tomography (CT) angiography has, using current guidelines, had no effect on the diagnostic yield from invasive coronary angiography
- Recent studies suggest that CT angiography is underused in the investigation of patients with suspected coronary artery disease
References
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