informa
Scandinavian Cardiovascular Journal, 2014; 48: 262-264
h e a lth c a re
EDITORIAL
C oron ary C T an g io g ra p h y in clin ica l p ractice: E x p erien ces from D en m a rk
BJARNE L IN D E N 0R G A A R D Department of Cardiology B, Aarhus University Hospital Skejby, Aarhus C, Denmark
Coronary multislice computed tomography angiog raphy (CTA) is increasingly used for non-invasive visualization of the coronary arteries. More than 100 single-center studies, numerous meta-analyses, and 4 prospective multicenter trials have documented consistently high sensitivities (90-99%) and negative predictive values (93-99%) of coronary CTA in detecting significant coronary artery disease (CAD) (1,2). Accordingly, in clinical practice, coronary CTA is often used as a gatekeeper for invasive coro nary angiography (ICA). However, the worldwide expansion of coronary CTA has been a subject of controversy (3). Because of a suboptimal specificity of coronary CTA in quantifying CAD and the lack of functional assessment of lesions, it has been sug gested that this technology will add unnecessary invasive diagnostic testing and coronary interven tions in the workup of patients suspected of stable CAD (3). Another concern following the introduc tion of coronary CTA has been associated with the inherent exposure to ionizing radiation and the potential association with cancer risk (4). In the event of a well-indicated investigation, cancer risk relative to the diagnostic information obtained by coronary CTA may be small. However, with the increasing use of coronary CTA in low-risk patients, especially in younger women, and when repeated procedures are being performed, this risk should be acknowledged (5). Several radiation dose-saving techniques together with an increased awareness of physicians in these matters have the potential of sig nificantly reducing the radiation exposure associated with coronary CTA (6). In this issue of the Scandinavian Cardiovascular Journal, two Danish reports on local experiences
related to the use of coronary CTA in routine clinical practice are presented (7,8). Both reports show an impressive decline over a 4-year time span in the effective radiation dose associated with “real-world” coronary CTA, both by using conventional 64-slice CT technology (from >17 to -5 mSv) (8) and by using a more recent CT scanner technology (from > 4 to ~ 2 mSv) (7). Of note, this reduction in radi ation dose has developed without sacrificing image quality and thus the diagnostic performance of coro nary CTA. With the most recent CT technology, coronary CTA may be performed in large subsets of patients with a sub-mSv radiation dose. Accordingly, the radiation dose associated with contemporary coronary CTA is substantially lower than that associated with SPECT or ICA. It must be anticipated that these improvements in coronary CTA practice, together with faster acquisition times, and higher spatial as well as temporal resolution may influence indications for coronary and cardiac CT in the future. From registry data, Norgaar et al described the consequences of frontline coronary CTA assessment of patients suspected of CAD on downstream utiliza tion of ICA and revascularization procedures. The fact that data were consecutively provided over a 4-year observation period, and thus, the study cohort was large, comprising > 3000 patients, is noteworthy. One interesting finding was a reduction in referrals to ICA during the observation period irrespective of unchanged patient characteristics. However, the authors did not provide information on symptoms (temporal changes in proportions of individuals with or without non-anginal, atypical, or anginal symp toms). Probably, symptoms are the most important
Correspondence: Bjarne Linde Norgaard, Department of Cardiology B, Aarhus University Hospital Skejby, 8000 Aarhus C, Denmark. E-mail: bnorgaard@ dadlnet.dk (Received 17 A ugust 2014; accepted 17 A ugust 2014)
ISSN 1401-7431 print/ISSN 1651-2006 online © 2014 Informa Healthcare DOI: 10.3109/14017431.2014.956329
Coronary C T angiography in clinical practice “patient characteristic” driver for ICA in patients suspected of stable CAD. One might interpret the reduction in referrals to ICA during the observation period as a result of the introduction of coronary CTA. However, this would be a flawed conclusion since the authors did not compare their findings with patient flows during the standard diagnostic practice before the introduction of coronary CTA. Of note is the relatively high ICA rate ranging between 21 and 24% following coronary CTA assessment during the first three years of the observation period. The drop off in referrals to ICA in 2013 to around 11% may, as suggested by the authors, be explained by the addition of myocardial perfusion imaging (MPI) testing in patients with a positive coronary CTA result before referring patients to ICA. Accordingly, several studies have documented increasing diagnos tic specificity of coronary CTA by adding functional information from either M PI or coronary CT-derived fractional flow reserve. Moreover, it was shown by Norgaard et al. that the proportion of patients having revascularization performed during follow-up was reduced from 2010 until 2013. However, this is not surprising since group observation times were not truncated (e.g., observation time was substantially longer for the “2010” versus the “2013” cohort). Thus, from the study by Norgaard et al., it cannot be concluded that coronary CTA leads to “less inva sive angiography or less revascularization.” Rather, this study underscores two important issues regard ing frontline coronary CTA testing in patients sus pected of CAD: 1. an inherent risk of subsequent “unnecessary” ICA even in a low-intermediate pre test risk cohort, that is, between 2010 and 2012, ICA following coronary CTA was performed in more than 20% of the patients (of whom less than 30% were revascularized); 2. in patients with a positive coronary CTA result, the diagnostic performance of the test may be improved by adding the information from M PI testing (although data on subsequent clin ical events were not reported in the study by Nor gaard et al.), that is, in 2013 after the introduction of MPI, the ICA referral rate after coronary CTA was reduced to 10% (of whom approximately 40% were revascularized). Expanding the study by N or gaard et al. with information from a matched stan dard diagnostic practice (historical or parallel) cohort for comparison of the real-world influence of front line coronary CTA with M PI testing on subsequent resource utilization and costs relative to clinical out comes would be highly relevant. It is well known that contrast (e.g., in relation to ICA or CT) is well tolerated. Serious short-term complications such as “real” allergic reactions and nephropathy occur very rarely. In the report by Pedersen et al. comprising 416 consecutive patients
263
suspected of stable CAD, the renal function observation time was extended to 2 months. As expected in this rather low-risk cohort, contrast was well tolerated using estimated glomerular filtration rate (eGFR) as the reference standard. Rather paradoxically, eGFR improved at follow-up in the small subcohorts with diabetes mellitus or impaired pre-test renal function. Although this change in eGFR was statistically sig nificant, it seems to have limited clinical relevance. Even with the highest temporal resolution CT technology, the best image quality in coronary CTA is achieved in heart rates of
Scandinavian Cardiovascular Journal, 2014; 48: 262-264
h e a lth c a re
EDITORIAL
C oron ary C T an g io g ra p h y in clin ica l p ractice: E x p erien ces from D en m a rk
BJARNE L IN D E N 0R G A A R D Department of Cardiology B, Aarhus University Hospital Skejby, Aarhus C, Denmark
Coronary multislice computed tomography angiog raphy (CTA) is increasingly used for non-invasive visualization of the coronary arteries. More than 100 single-center studies, numerous meta-analyses, and 4 prospective multicenter trials have documented consistently high sensitivities (90-99%) and negative predictive values (93-99%) of coronary CTA in detecting significant coronary artery disease (CAD) (1,2). Accordingly, in clinical practice, coronary CTA is often used as a gatekeeper for invasive coro nary angiography (ICA). However, the worldwide expansion of coronary CTA has been a subject of controversy (3). Because of a suboptimal specificity of coronary CTA in quantifying CAD and the lack of functional assessment of lesions, it has been sug gested that this technology will add unnecessary invasive diagnostic testing and coronary interven tions in the workup of patients suspected of stable CAD (3). Another concern following the introduc tion of coronary CTA has been associated with the inherent exposure to ionizing radiation and the potential association with cancer risk (4). In the event of a well-indicated investigation, cancer risk relative to the diagnostic information obtained by coronary CTA may be small. However, with the increasing use of coronary CTA in low-risk patients, especially in younger women, and when repeated procedures are being performed, this risk should be acknowledged (5). Several radiation dose-saving techniques together with an increased awareness of physicians in these matters have the potential of sig nificantly reducing the radiation exposure associated with coronary CTA (6). In this issue of the Scandinavian Cardiovascular Journal, two Danish reports on local experiences
related to the use of coronary CTA in routine clinical practice are presented (7,8). Both reports show an impressive decline over a 4-year time span in the effective radiation dose associated with “real-world” coronary CTA, both by using conventional 64-slice CT technology (from >17 to -5 mSv) (8) and by using a more recent CT scanner technology (from > 4 to ~ 2 mSv) (7). Of note, this reduction in radi ation dose has developed without sacrificing image quality and thus the diagnostic performance of coro nary CTA. With the most recent CT technology, coronary CTA may be performed in large subsets of patients with a sub-mSv radiation dose. Accordingly, the radiation dose associated with contemporary coronary CTA is substantially lower than that associated with SPECT or ICA. It must be anticipated that these improvements in coronary CTA practice, together with faster acquisition times, and higher spatial as well as temporal resolution may influence indications for coronary and cardiac CT in the future. From registry data, Norgaar et al described the consequences of frontline coronary CTA assessment of patients suspected of CAD on downstream utiliza tion of ICA and revascularization procedures. The fact that data were consecutively provided over a 4-year observation period, and thus, the study cohort was large, comprising > 3000 patients, is noteworthy. One interesting finding was a reduction in referrals to ICA during the observation period irrespective of unchanged patient characteristics. However, the authors did not provide information on symptoms (temporal changes in proportions of individuals with or without non-anginal, atypical, or anginal symp toms). Probably, symptoms are the most important
Correspondence: Bjarne Linde Norgaard, Department of Cardiology B, Aarhus University Hospital Skejby, 8000 Aarhus C, Denmark. E-mail: bnorgaard@ dadlnet.dk (Received 17 A ugust 2014; accepted 17 A ugust 2014)
ISSN 1401-7431 print/ISSN 1651-2006 online © 2014 Informa Healthcare DOI: 10.3109/14017431.2014.956329
Coronary C T angiography in clinical practice “patient characteristic” driver for ICA in patients suspected of stable CAD. One might interpret the reduction in referrals to ICA during the observation period as a result of the introduction of coronary CTA. However, this would be a flawed conclusion since the authors did not compare their findings with patient flows during the standard diagnostic practice before the introduction of coronary CTA. Of note is the relatively high ICA rate ranging between 21 and 24% following coronary CTA assessment during the first three years of the observation period. The drop off in referrals to ICA in 2013 to around 11% may, as suggested by the authors, be explained by the addition of myocardial perfusion imaging (MPI) testing in patients with a positive coronary CTA result before referring patients to ICA. Accordingly, several studies have documented increasing diagnos tic specificity of coronary CTA by adding functional information from either M PI or coronary CT-derived fractional flow reserve. Moreover, it was shown by Norgaard et al. that the proportion of patients having revascularization performed during follow-up was reduced from 2010 until 2013. However, this is not surprising since group observation times were not truncated (e.g., observation time was substantially longer for the “2010” versus the “2013” cohort). Thus, from the study by Norgaard et al., it cannot be concluded that coronary CTA leads to “less inva sive angiography or less revascularization.” Rather, this study underscores two important issues regard ing frontline coronary CTA testing in patients sus pected of CAD: 1. an inherent risk of subsequent “unnecessary” ICA even in a low-intermediate pre test risk cohort, that is, between 2010 and 2012, ICA following coronary CTA was performed in more than 20% of the patients (of whom less than 30% were revascularized); 2. in patients with a positive coronary CTA result, the diagnostic performance of the test may be improved by adding the information from M PI testing (although data on subsequent clin ical events were not reported in the study by Nor gaard et al.), that is, in 2013 after the introduction of MPI, the ICA referral rate after coronary CTA was reduced to 10% (of whom approximately 40% were revascularized). Expanding the study by N or gaard et al. with information from a matched stan dard diagnostic practice (historical or parallel) cohort for comparison of the real-world influence of front line coronary CTA with M PI testing on subsequent resource utilization and costs relative to clinical out comes would be highly relevant. It is well known that contrast (e.g., in relation to ICA or CT) is well tolerated. Serious short-term complications such as “real” allergic reactions and nephropathy occur very rarely. In the report by Pedersen et al. comprising 416 consecutive patients
263
suspected of stable CAD, the renal function observation time was extended to 2 months. As expected in this rather low-risk cohort, contrast was well tolerated using estimated glomerular filtration rate (eGFR) as the reference standard. Rather paradoxically, eGFR improved at follow-up in the small subcohorts with diabetes mellitus or impaired pre-test renal function. Although this change in eGFR was statistically sig nificant, it seems to have limited clinical relevance. Even with the highest temporal resolution CT technology, the best image quality in coronary CTA is achieved in heart rates of
