Vasodilator Stress Cardiac Magnetic Resonance Imaging Shows Promise in the Identification of Fatal Heart Disease Prognostic Value of A Multicenter Study With 48 000 Patient-Years of Follow-up

The findings of a study by Heitner et al. published online on February 8  in JAMA cardiology has provided a foundational motivation to study the comparative effectiveness of stress CMR (Cardiac Magnetic Resonance) against other modalities. The study found that clinical vasodilator stress CMR is associated with patient mortality in a large, diverse population of patients with known or suspected CAD as well as in multiple subpopulations defined by a history of CAD and left ventricular ejection fraction. Although the utility of MRI to determine heart function has been slow to catch on, this study performed by Duke Health researchers showcased how stress cardiac MRI not only diagnosed disease but could also predict which cases would be potentially fatal. 

Findings from several previous reports and meta-analyses have reflected that stress cardiac magnetic resonance imaging (CMR) is more accurate for the diagnosis of CAD compared with conventional stress imaging methods, yet CMR represents less than 0.1% of all imaging-based stress tests performed in the USA. Stress cardiac magnetic resonance imaging (CMR) is not widely used in current clinical practice, and its ability to predict patient mortality is unknown. However, with escalating costs associated with the use of advanced imaging methods, there has been a fundamental shift from a simple focus on test accuracy to a broader focus on the patient outcome. John F. Heitner and his colleagues strived to determine whether the results of vasodilator stress cardiac magnetic resonance imaging could be associated with subsequent patient mortality.  The design of the study was such that real-world evidence from consecutive clinically ordered CMR examinations was taken to conduct a multicenter study of patients undergoing clinical evaluation of myocardial ischemia. The patient population included those with known or suspected coronary artery disease (CAD) who underwent clinical vasodilator stress CMR at 7 different hospitals. An automated process was used to gather data from the finalized clinical reports, de-identify and aggregate the data, and mortality was estimated using the US Social Security Death Index. All-cause patient mortality was the primary outcome to be measured.

The investigators noted that of the 9151 patients, the median (interquartile range) patient age was 63 (51-70) years, 55%were men, and the median (interquartile range) body mass index was 29 (25-33) (calculated as weight in kilograms divided by height in meters squared). In addition to this, the multicentre automated process yielded 9151 consecutive patients undergoing stress CMR, with 48,615 patient-years of follow-up. Of these patients, 4408 had a normal stress CMR examination, 4743 had an abnormal examination, and 1517 died during a median follow-up time of 5.0 years. Using multivariable analysis, addition of stress CMR improved prediction of mortality in 2 different risk models (model 1 hazard ratio [HR], 1.83; 95%CI, 1.63-2.06; P < .001; model 2: HR, 1.80; 95%CI, 1.60-2.03; P < .001) and also improved risk reclassification (net improvement: 11.4%; 95%CI, 7.3-13.6; P < .001). For patients without any history of heart disease and at low risk based on traditional clinical criteria, those with an abnormal CMR scan were 3.4 times more likely to die compared to patients with a normal CMR scan. For the entire patient population, the researchers found a strong association between an abnormal stress CMR and mortality, even after adjusting for patient age, sex, and cardiac risk factors. Thus, Heitner et al. concluded that in this multicenter study of 9151 patients followed up for up to 10 years, stress cardiac magnetic resonance imaging was strongly associated with patient mortality, both in the overall patient population as well as in a total of 14 different subpopulations, implying that stress cardiac magnetic resonance imaging could be considered as another noninvasive indicator of prognosis.

“Noninvasive cardiac stress testing is a cornerstone in the clinical management of patients with known or suspected coronary artery disease,” senior author Robert Judd, Ph.D., co-director of the Duke Cardiovascular Magnetic Resonance Center stated, noting that CMR works as well or better than other exams at identifying heart wall motion, cell death and the presence of low blood flow. In addition, the technology does not require any radiation exposure, which is essential in nuclear stress tests that are by far the most commonly used in the U.S. “There are a number of reasons for the limited use of stress CMR, including availability of good quality laboratories, exclusion of patients who cannot undergo magnetization, and a lack of data on patient outcomes,” Judd noted. “With the findings from this study suggesting that stress CMR is effective in predicting mortality, we provide a strong basis for a head-to-head study between stress CMR and other modalities.” While one of the impediments to broader use has been a lack of data on its predictive value — something competing technologies have, the investigators firmly believe that their study provides some clarity, although direct comparisons between CMR and other technologies would be definitive.