CMR and MPS better than NICE guidelines for stable angina?

RAPID REVIEWS

CMR and MPS better than NICE guidelines for stable angina?

By Ahmed Adlan
05 September 2016


ABBREVIATIONS 

CCT, cardiac computed tomography; CHD, coronary heart disease; CI, confidence interval; CMR, cardiac magnetic resonance imaging; NICE, National Institute for Health and Care Excellence; MACE, major adverse cardiovascular events; MPS, myocardial perfusion scintography;


Study title Effect of Care Guided by Cardiovascular Magnetic Resonance, Myocardial Perfusion Scintography, or NICE Guidelines on Subsequent Unnecessary Angiography Rates [1]
Background Minimising "unnecessary angiography" rates in stable angina patients potentially reduces cost and patient risk.
Objective To compare rates of "unnecessary angiography" in stable patients using CMR v MPS v NICE guidelines guided care.
Design Multicentre randomised control trial including 1202 patients randomised into 3 arms including CMR (N=481) v MPS (N=481) v NICE guideline (N=240) in 2:2:1 ratio
Inclusion Typical angina symptoms, age >= 30 yrs, CHD pretest probability 10-90 %
Exclusion Non anginal symptoms, normal MPS or CCT within 2 yrs, unstable, previous MI or coronary revascularisation.
Follow up 1 year.
Primary Outcome "Unnecessary angiography" defined as normal fractional flow reserve >0.8 or quantitative coronary angiography showing no stenosis >= 70% (1 view) or >=50% in 2 orthogonal views in all coronary vessels (>=2.5 mm diameter).
Secondary Outcomes Positive angiography, MACE and procedural complications
Results 265 patients (22 %) underwent angiography Fewer angiography in CMR (17.7 %) and MPS (16.2 %) v NICE guidelines (42.5 %). Fewer unnecessary angiography in CMR (7.1 %) and MPS (7.5 %) compared to NICE guidelines (42.5 %). Fewer positive angiography in CMR and MPS v NICE. Higher MACE in CMR and MPS v NICE. Adjusted hazard ratio CMR v NICE 1.37, 95 % confidence interval (CI) 0.52-3.57 p=0.52; adjusted hazard ratio CMR v MPS 0.95, 95 % CI 0.46-1.95.
Study investigators' conclusions In suspected angina CMR has lower probability of unnecessary angiography within 12 months compared to NICE guidelines. No statistically significant difference between CMR and MPS. No statistically significant differences in MACE.
Pubmed URL http://www.ncbi.nlm.nih.gov/pubmed/27570866

Commentary

NICE guidelines [2] recommends that patients suspected to have angina should be assessed and a pretest probability of CHD calculated. Further investigations are recommended based on the pretest probability as follows: cardiac CT (10-29 %), functional imaging including MPS, stress echocardiography (30-60 %) and invasive coronary angiography (61-90 %). Coronary angiography is deemed unnecessary for diagnostic purposes in patients with a pretest probability >90 %. 

The pretest probability is calculated based on a number of factors including chest pain features (typical angina, atypical angina, non anginal), age, gender and presence of risk factors (high risk including any of diabetes, smoking or hyperlipidaemia; low risk have none). A pre-test probability of 61-90 % is present in high risk men aged 65 years with non-anginal chest pain; low risk men aged 65 years with atypical angina; high risk men aged 45 years with atypical angina; low risk men aged 55 years with typical angina; high risk men aged 35 years with typical angina; and high risk women aged 35 yrs with typical angina. A pre-test probability of >90 % is present in low risk men aged 65 years or high risk men aged 35 years with typical angina.

This well designed study looked to address the hypothesis that CMR guided assessment of angina would reduce the rate of unnecessary angiography but not at the expense of increased cardiovascular risk. While the results do support the former it is not clear whether the latter is true. Greenwood et al., demonstrated that NICE guided care resulted in more coronary angiograms (a greater proportion of which were negative for significant coronary disease) but fewer adverse events compared to CMR. Unfortunately it appears the study may be underpowered (due to low MACE rates) which may explain the lack of statistical significance.

Perspective

This study highlights an important distinction between the diagnostic and prognostic benefit of coronary angiography. A coronary angiogram demonstrating non-obstructing coronary artery disease may be deemed as "unnecessary" from a diagnostic point of view, however the prognostic value for patients must not be underestimated. The ability to reassure patients with coronary artery disease that they carry a low risk may be immensely valuable, and given the relatively low risks associated with diagnostic coronary angiography a frank and open conversation with patients should be undertaken upfront when deciding management strategy.

A second interesting finding of this study was that CMR did not add any diagnostic or prognostic benefit compared to MPS. The superiority of CMR in delineating cardiac anatomy is clear and widely accepted. However it may be reassuring for physicians and cardiology units worldwide that in patients with suspected angina, the less expensive, longer standing and more readily available functional imaging modality of MPS appears to have held its own against CMR.

References


1. Greenwood JP, Ripley DP, Berry C,. et al. Effect of care guided by cardiovascular magnetic resonance, myocardial perfusion scintography, or NICE guidelines on subsequent unnecessary angiography rates: The CE-MARC 2 randomized clinical trial. JAMA 2016; Epub ahead of print.

2. National Institute for Health and Clinical Excellence. Chest pain of recent onset: assessment and diagnosis of recent onset chest pain or discomfort of suspected cardiac origin. Clinical guideline CG95. London NICE; 2010. http://www.nice.org.uk/guidance/cg95/resources/guidance-chest-pain-of-recent-onset-pdf (accessed 05 Sep 2016)