3-D Myocardial Perfusion Cardiac MRI Detects Functionally Significant CAD

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Use of 3-D whole heart myocardial perfusion cardiac magnetic resonance imaging (MRI) accurately predicts the presence of ischemia-producing stenosis as measured by fractional flow reserve (FFR). The findings, published online July 18, 2012, ahead of print in the Journal of the American College of Cardiology, support the feasibility of noninvasive guidance for therapy and risk stratification in patients with coronary artery disease (CAD).

Investigators led by Sven Plein, MD, PhD, of Kings College (London, United Kingdom), examined the diagnostic accuracy of 3-D whole heart myocardial perfusion cardiac MRI vs. FFR measured during coronary angiography to detect flow-limiting coronary artery stenosis in 53 patients (mean age 63 years).

Good Values, Correlation with Standard Scoring

Overall disease prevalence in the study population was 64%. FFR was measured in 64 of 159 coronary vessels, with 39 having an FFR < 0.75. In all, there were 47 vessels with significant stenosis: 24 cases of single-vessel disease, 7 cases of 2-vessel disease, and 3 cases of 3-vessel disease.

Average examination time per patient with 3-D cardiac MRI was 51 ± 4 minutes, and image quality was considered good. Main artifacts seen were subendocardial dark rim-related artifacts in 7 patients (13%) and breathing artifact in 8 patients (15%), although the overall quality was deemed sufficient to make a diagnosis in all of these cases.

MRI images yielded good sensitivity, specificity, and positive and negative predictive values on a per patient and per territory basis with diagnostic accuracy of 90.6% and 88.1%, respectively (table 1).

Table 1. Diagnostic Accuracy of 3-D Cardiac MRI

In addition, there was a strong correlation (r = 0.82; 95% CI 0.70-0.89) between the Duke Jeopardy Score and ischemic volume as assessed by cardiac MRI (P < 0.0001).

3-D Overcomes Limitations of Cardiac MRI

“This study demonstrates excellent agreement between FFR and 3-D whole heart myocardial perfusion [cardiac MRI],” Dr. Plein and colleagues conclude.

Several prior studies, including the recent prospective CE-MARC (Clinical Evaluation of MAgnetic Resonance imaging in Coronary heart disease) trial, have found MR imaging to be more accurate than single-photon emission computed tomography (SPECT) in detecting stable CAD. But as good as cardiac MRI is, the study authors say 3-D methods may be able to overcome some of the remaining limitations of the technology, namely that it is unable to provide complete myocardial coverage. “Furthermore, 3-D acquisition is more signal-to-noise efficient than 2-D imaging; in addition, because all data are acquired in one shot, all images are acquired in the same cardiac phase,” they write.

The study also had the novel aspect of using FFR rather than angiography as the reference standard for assessing the hemodynamic significance of lesions, Dr. Plein and colleagues add.

Increasingly Useful, But Validation Required

This method is one of a few new applications of cardiac MRI “that looks like it’s going to be an increasingly useful tool,” said Matthew J. Budoff, MD, of Harbor-UCLA Medical Center (Torrance, CA), in a telephone interview with TCTMD, adding that the current study moves things “further in the right direction.”

“This represents a very positive study even though it is small and from a single center,” he said. “This type of validation is really critical, particularly to validate against a gold standard—and I don’t know of any better gold standard than fractional flow reserve.”

Dr. Budoff commented that FFR is a better comparison than angiography in this type of study because the newer test correlates so well with need for revascularization. “MR has been subject to some criticism because of other single-center studies that didn’t pan out when multicenter trials were done with better blinding and a more rigorous process,” he noted, “so I think the next step is to replicate this study in a large, multicenter trial where they can really see the accuracy of the technology in multiple users’ hands.”

In an editorial accompanying the study, Jens Vogel-Claussen, MD, of Hannover Medical School (Hannover, Germany), similarly notes that future trials need to show that the technique is robust and can be applied using equipment made by different manufacturers. “Also, the feasibility and potential clinical application of quantitative 3-D MRI perfusion measurements in ischemic and nonischemic heart disease—as already shown with 2-D perfusion MRI and PET—has to be evaluated in future research,” he added.

Study Details

All subjects were scanned on a 3-T magnetic resonance scanner (Achieva, Philips Healthcare, Best, The Netherlands). For perfusion imaging, a 3-D spoiled turbo gradient-echo sequence was used. Stress perfusion cardiac MRI was followed by cine imaging covering the left ventricle in 10 to 12 short-axis sections and a rest perfusion scan performed 15 minutes later using the same concentration and volume of contrast agent as for stress perfusion.

 

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Sources:
1. Jogiya R, Kozerke S, Morton G, et al. Validation of dynamic 3-dimensional whole heart magnetic resonance myocardial perfusion imaging against fractional flow reserve for the detection of significant coronary artery disease. J Am Coll Cardiol. 2012;Epub ahead of print.

2. Vogel-Claussen J. Will 3D at 3-T make myocardial stress perfusion magnetic resonance imaging even more competitive? J Am Coll Cardiol. 2012;Epub ahead of print.

 

 

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• Noninvasive Functional Imaging Satisfactory for Detecting, Stratifying Obstructive CAD
• Perfusion Imaging Guidance for Revascularization Improves Outcomes
• Noninvasive MR Perfusion Testing Matches FFR in Identifying Ischemic Lesions

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