Is stress cardiac magnetic resonance (CMR) imaging able to reclassify risk in patients with suspected coronary artery disease (CAD), across American College of Cardiology/American Heart Association guideline-based risk categories?
The role of stress CMR imaging in clinical decision-making by the reclassification of risk across these categories has not yet been established. A team of researchers from medical institutions in the United States and Switzerland conducted a study to examine the utility of stress CMR imaging for risk reclassification in patients without a history of CAD who presented with suspected myocardial ischemia.
Can stress CMR provide net reclassification improvement?
CAD is the leading cause of death and disability worldwide, with more than 700 000 patients developing a new myocardial infarction (MI) each year in the US alone. The high burden of heart failure and mortality and projected healthcare costs associated with CAD make the evaluation of the clinical use and performance of diagnostic strategies more relevant.
While stress CMR imaging is recognized as valuable and cost-effective in CAD diagnosis and risk stratification of cardiac events, it is under-used in the US, representing less than 0.1% of all imaging tests performed in 2018. Furthermore, the role of CMR imaging in appropriately reclassifying cardiac risk across guideline-recommended categories has not been established.
This multicenter study investigated whether stress CMR imaging provides net reclassification improvement (NRI) across cardiac risk categories recommended by the American College of Cardiology/American Heart Association (ACC/AHA) guidelines in a cohort of patients with no history of CAD.
Patient population and design
The study based its patient population and design on the Stress CMR Perfusion Imaging in the United States study in the Society for Cardiovascular Magnetic Resonance Registry. This multicenter study was specifically designed to evaluate the long-term performance of stress CMR imaging in risk stratification of patients presenting with suspicion of myocardial ischemia.
A retrospective, multicenter cohort study with a median follow-up of 5.4 years (interquartile range, 4.6-6.9) was conducted at 13 centers across 11 US states. Participants included 1698 consecutive patients aged 35 to 85 years with 2 or more coronary risk factors but no history of CAD who presented with suspected myocardial ischemia to undergo stress CMR imaging.
Risk for CV death and MI “significantly reclassified”
It was found that stress CMR imaging significantly reclassified patient risk for cardiovascular (CV) death and myocardial infarction across ACC/AHA guideline-based risk categories. The addition of stress CMR imaging parameters to each baseline model significantly improved reclassification metrics for CV death, nonfatal MI and major adverse cardiovascular events (MACE).
Overall, stress CMR reclassified 33.5% (568 of 1698) of the overall cohort to a more appropriate post-test risk group for CV death, and nonfatal MI. Risk reclassification showed the most substantial changes in patients at intermediate pretest risk. For CV death/nonfatal MI, stress CMR imaging reclassified 60.3% (432 of 716) of patients at intermediate pretest risk (52.4% reclassified to low risk, 7.9% to high risk).
Detailed reclassification tables for events and nonevents, together with an assessment of the weighted NRI and positive and negative predictive values of each model at the event rate can be viewed in these tables.
Value of stress CMR for clinical decision-making ‘supported’
The study presented its main finding as the suggestion that “stress CMR imaging can provide risk reclassification for CV death and nonfatal MI, incremental to established risk factors, across current ACC/AHA-recommended risk categories, especially for patients considered at intermediate risk”. These results, the researchers believe, “expand on previous work and support the value of stress CMR imaging for clinical decision-making in a current practice setting in the US”.
Another major finding of the study was the importance of appropriate reclassification of patients initially categorized in the intermediate-risk group where clinical uncertainty about optimal management is highest. Results showed stress CMR imaging appeared to show the highest NRI in intermediate-risk patients, reclassifying up to 60% of them to a different post-test risk category.
Stress CMR reclassified patient risk beyond clinical risk factors
In a multicenter cohort of patients with no history of CAD presenting with suspected myocardial ischemia, the study found that stress CMR reclassified patient risk beyond clinical risk factors across established ACC/AHA risk categories.
This reclassification was noted most in patients considered at intermediate pretest risk for CV death and nonfatal MI who experienced low event rates when reclassified by stress CMR imaging to a low post-test risk category, and relatively high event rates when reclassified to a high post-test risk category.
Stress CMR to assume a ‘gate-keeping role’?
The study pointed to further evidence that stress CMR imaging may be well poised to assume the role of a gate-keeping noninvasive test, especially in patients in the low-to-intermediate pretest risk category for CV death and nonfatal MI”.