Predictors of normal coronary arteries at coronary angiography

doi:10.1016/j.ahj.2013.07.030

American Heart Journal

Volume 166, Issue 4, October 2013, Pages 694-700

https://doi.org/10.1016/j.ahj.2013.07.030 Get rights and content

Background

Coronary angiograms are important in the diagnostic workup of patients with suspected coronary artery disease. However, little is known about the clinical predictors of normal angiograms and whether this rate varies across different cardiac centers in Ontario.

Methods

We conducted a study using the Cardiac Care Network Variations in Revascularization Practice in Ontario database of 2,718 patients undergoing an index cardiac catheterization for an indication of stable angina between April 2006 and March 2007 at one of 17 cardiac hospitals in Ontario. We determined predictors of normal coronary angiograms (0% coronary stenosis) and compared rates of patients with normal catheterizations across centers.

Results

Overall, 41.9% of patients with stable angina had a normal catheterization. A multivariate model demonstrated female gender to be the strongest predictor of a normal angiogram (odds ratio 3.55, 95% CI 2.93-4.28). In addition, atypical ischemic symptoms or no symptoms, the absence of diabetes, hyperlipidemia, smoking history, peripheral vascular disease, and angiography performed at a nonteaching site were associated with higher rates of normal catheterization. The rate of normal angiograms studied varied from 18.4% to 76.9% across hospitals and was more common in community compared with academic settings (47.1% vs 35.4%, P < .001).

Conclusions

The absence of traditional cardiac risk factors, female gender, and lack of typical angina symptoms are all associated with a higher frequency of normal cardiac catheterizations. The wide variation in Ontario in the frequency of normal angiograms in patients with stable angina suggests that there are opportunities to improve patient case selection.

Section snippets

Background

Coronary angiography plays an integral role in the diagnosis and management of patients with coronary artery disease (CAD) and is the criterion standard test for identification of CAD. However, it is associated with a small risk of serious complications estimated at <1% and vascular complications at 2% to 4%.1, 2

Some proportion of coronary angiograms are anticipated to be normal; but it is important that this proportion be minimized, given the invasive nature of angiography and the associated

Data source

The VRPO study involved a retrospective medical record review of a random sample of 8,972 patients undergoing coronary angiography in Ontario at Cardiac Care Network (CCN) member hospitals (17 total) between April 2006 and March 2007. The original study included patients who had a primary indication for cardiac catheterization for suspected CAD. All patients who had undergone a cardiac procedure in the preceding year were excluded from the study. The research ethics boards at each participating

Study population

A total of 8,972 patients were included in the CCN VRPO study (Figure 1). A total of 6,254 patients were excluded because they had presented with an ACS (55.1%) or had a previous myocardial infarction (35.2%). Only a small proportion of patients were excluded because of previous CABG or valve surgery. A total of 2,718 patients (30.2% of the total VRPO registry) were used for this analysis.

Prevalence of normal coronaries

Patients with normal angiograms were found in 41.9% of all cardiac catheterizations for the indication of

Discussion

Approximately 40% of patients undergoing diagnostic coronary angiography for an indication of stable angina have normal coronary angiograms in Ontario. This finding is consistent with previous studies in the United States and other Canadian provinces looking at similar study populations.3, 7 These findings highlight the limitations of current methods of risk stratifying patients for coronary angiography. The 4-fold variation in the proportion of normal angiograms across cardiac centers in

Limitations

Our study has a few limitations. First, it has been estimated that as many as 20% of cardiac events occur in the absence of cardiac risk factors.¹⁵ It is possible that some of the patients who had a normal angiogram went on to have cardiac events at a later point and therefore were justified being followed more closely by their physicians. Second, we do not have any information on the large population of patients who were evaluated but did not undergo cardiac catheterization. Third, the

Conclusions

Despite most patients having positive noninvasive stress test results, there continue to be a substantial number of patients with suspected stable angina referred for cardiac catheterization in Ontario who do not have angiographic evidence of CAD. Using risk score models such as FRS and eliciting better histories of patient symptoms may help discern those who might benefit more from invasive angiography and might limit unnecessary referrals. Our study also highlights the need to develop better

Contributions

All authors made substantial contributions to the conception and design of this project, and participated in the acquisition of data and in the analysis and interpretation of the data. Dr Levitt drafted the article, and Dr Tu and the other coauthors revised it. Dr Tu had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Acknowledgements

We acknowledge that the clinical data used in this publication are from the CCN of Ontario and its member hospitals under a project funded by the Ontario Ministry of Health and Long-Term Care and carried out in collaboration with the Institute for Clinical Evaluative Sciences. Additional support for this project was provided by operating grants (MOP111035, TCA118349) from the Canadian Institutes of Health Research. The results and conclusions are those of the authors and should not be

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Citation Excerpt :
This study showed that nearly 60% of angiograms had results showing <50% stenosis or normal findings.1 Despite lower population rates of angiography in Canada, rates of normal (0% stenosis in major epicardial arteries) approaches 42%.2 Current rates of nonobstructive CAD in Ontario, Canada (defined as <70% stenosis in major epicardial vessels or <50% stenosis of the left main artery) in patients undergoing elective angiography are approximately 53% (CorHealth QPMM Quarterly Reports, unpublished data, 2020).
Conventional clinical risk scores and diagnostic algorithms are proving to be suboptimal in the prediction of obstructive coronary artery disease, contributing to the low diagnostic yield of invasive angiography. Machine learning could help better predict which patients would benefit from invasive angiography vs other noninvasive diagnostic modalities.
To reduce patient risk and cost to the healthcare system by improving the diagnostic yield of invasive coronary angiography through optimized outpatient selection.
Retrospective analysis of 12 years of referral data from a provincial cardiac registry, including all patients referred for invasive angiography of more than 1.4 million individuals in Ontario, Canada. Stable outpatients undergoing coronary angiography during the study period were included in the analysis. The training set (80% random sample, n = 23,750) was used to develop 8 prediction models in Python using grid-search cross-validation. The test set (20% random sample, n = 5938), evaluated the discrimination performance of each model.
The machine-learning model achieved a substantially better performance (area under the receiver operating characteristics curve: 0.81) than existing models for predicting obstructive coronary artery disease in patients referred for invasive angiography. It significantly outperformed both the reference model and current clinical practice with a net reclassification index of 27.8% (95% confidence interval [CI]: [24.9%–30.8%], P value <.01) and 44.7% (95% CI: [42.4%–47.0%], P value <.01), respectively.
This prediction model, when coupled with a point-of-care, online decision support tool to be used by referring physicians, could improve the diagnostic yield of invasive coronary angiography in stable, elective outpatients, thus improving patient safety and reducing healthcare costs.
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Routine inpatient transthoracic echocardiography (TTE) for patients with unstable angina is common, but it anecdotally adds little value to clinical care. A practice audit at our academic hospital demonstrated that 61.5% of patients with troponin-negative chest pain (TNCP) had normal left ventriculography (LVG) during coronary angiography and normal TTE on the same admission (duplicate testing).
We developed the Reducing Non-Invasive Testing (RUNIT) protocol, a clinical algorithm applied by clinical nurses to patient with TNCP. We performed a prospective assessment of rate of duplicate testing before and after intervention. If patients met certain simple clinical criteria, their TTE was cancelled (RUNIT positive). Patients then proceeded to have either coronary angiography with LVG or noninvasive risk stratification. We aimed to reduce duplicate testing by 25% over a 1-year period. Balancing measures included pathology on ordered TTEs, 30-day readmission, length of stay, and number of LVG.
Among 254 patients admitted with TNCP over 12 months, we reduced duplicate testing from 61.5% (before intervention) to 34% (P = 0.001). There was no clinical difference in 30-day readmission (0.9% vs 0.7%), and length of stay was significantly shorter in RUNIT positive (3.48 vs 4.16 days, P = 0.02). The majority of duplicate TTEs did not reveal any management-informing pathology. RUNIT-positive patients underwent more LVG than RUNIT-negative patients (78.3% vs 62.8%, P = 0.008).
We achieved a sustained reduction in reflexive TTE ordering in patients with TNCP, and we discuss the potential of nursing-led interventions to address other areas of low value care in cardiology.
La réalisation systématique d’une échocardiographie transthoracique (ETT) chez les patients hospitalisés pour angine instable est une pratique courante, qui n’apporte toutefois qu’une valeur anecdotique aux soins cliniques. Un audit des pratiques en vigueur dans l’hôpital universitaire auquel nous sommes rattachés a révélé que 61,5 % des patients ayant une douleur thoracique sans élévation de la troponine (DTST) présentaient une ventriculographie gauche (VGG) normale à la coronarographie et une ETT normale lors de la même admission (tests effectués en double).
Nous avons mis au point le protocole RUNIT (Reducing Non-Invasive Testing, réduction des tests non invasifs), un algorithme clinique appliqué par le personnel infirmier clinicien aux patients présentant une DTST. Nous avons ensuite mené une évaluation prospective du taux de réalisation de tests en double avant et après l’intervention. Si les patients répondaient à certains critères cliniques simples, l’ETT n’était pas effectuée (score RUNIT positif). Les patients ont par la suite été soumis soit à une coronarographie et à une VGG, soit à une stratification du risque associé aux méthodes non invasives. Notre objectif était de réduire de 25 % la réalisation de tests en double sur une période de 1 an. Les mesures de compensation comprenaient une évaluation pathologique des résultats des ETT demandées, la réadmission à 30 jours, la durée de l’hospitalisation et le nombre de VGG. Résultats : Parmi les 254 patients admis en raison d’une DTST sur une période de 12 mois, nous avons réduit la réalisation de tests en double de 61,5 % (avant l’intervention) à 34 % (p = 0,001). Il n’y avait pas de différence clinique quant au taux de réadmission à 30 jours (0,9 % vs 0,7 %), et l’hospitalisation a été beaucoup plus courte chez les patients ayant obtenu un score RUNIT positif (3,48 vs 4,16 jours, P = 0,02). La majorité des ETT réalisées en double n’ont mis au jour aucune caractéristique pathologique permettant d’éclairer la prise en charge. Les patients qui ont obtenu un score RUNIT positif ont par ailleurs subi un plus grand nombre de VGG que ceux qui ont obtenu un score négatif (78,3 % vs 62,8 %, p = 0,008).
Nous avons réussi à réduire de manière soutenue la réalisation systématique d’ETT chez les patients présentant une DTST, et nous traitons de la possibilité de mettre en place des protocoles à appliquer par le personnel infirmier afin de réduire l’exécution d’autres interventions n’apportant que peu de valeur aux soins en cardiologie.
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However, a previous study showed that it is used with considerably lower frequency than other imaging techniques like radionuclide myocardial perfusion imaging (MPI) and stress echocardiography [1]. This is despite a number of studies suggesting that CCTA is superior to the other two as the initial choice for clinicians when CAD is suspected [2-18]. CCTA is a considerably newer technique than MPI and stress echocardiography, and Current Procedural Terminology, version 4 codes have only been available for CCTA since 2006.
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Citation Excerpt :
This result corresponds to the 61% of patients with a nonocclusive coronary atherosclerosis in our study population. In the Canadian study, the nonocclusive coronary atherosclerosis was found in 42% of hospitalized patients [13]. Cardiovascular mortality and population risk in the developed countries is decreasing.
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^h: For the Cardiac Care Network of Ontario Variations in Revascularization Practice in Ontario Working Group.

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Clinical InvestigationInterventional CardiologyPredictors of normal coronary arteries at coronary angiography

Background

Methods

Results

Conclusions

Section snippets

Background

Data source

Study population

Prevalence of normal coronaries

Discussion

Limitations

Conclusions

Contributions

Acknowledgements

Am J Cardiol

J Cardiovasc Comput Tomogr

Int J Cardiol

J Am Coll Cardiol

J Nucl Cardiol

J Nucl Cardiol

Complications of cardiac catheterization

Clinical Investigation
Interventional Cardiology
Predictors of normal coronary arteries at coronary angiography