Two studies similar in design, Study E and Study F, evaluated the sensitivity and specificity of gadobutrol injection cardiac MRI (CMRI) for detection of coronary artery disease (CAD) in adult patients with known or suspected CAD. Patients were excluded from study if they had a history of coronary artery bypass grafting, or if it was known in advance that they were unable to hold their breath, or had atrial fibrillation or other arrhythmia likely to prevent electrocardiogram-gated CMRI. The studies were multi-center, open-label, and evaluated 764 subjects for efficacy: 376 in Study E, with an average age of 59 (range 20–84); 69% male; 74% white, 1% black, and 25% Asian; and 388 subjects in Study F, with an average age of 59 (range 23–82); 61% male; 67% white, 17% black, and 12% Asian.

All subjects underwent dynamic first-pass gadobutrol injection imaging during vasodilator stress, followed ~10 minutes later by dynamic first-pass gadobutrol injection imaging at rest, followed ~5 minutes later with imaging during a period of gradual gadobutrol injection washout from the myocardium (late gadolinium enhancement, LGE). Imaging was performed on 1.5 T or 3.0 T MRI devices equipped with multichannel surface coils to support accelerated acquisitions with parallel imaging, T1-weighted, 2D gradient-echo, dynamic acquisition of perfusion with at least 3 slices per heartbeat. Gadobutrol injection was administered intravenously at a rate of ~4 mL/second as two separate bolus injections (0.05 mmol/kg each), the first at peak pharmacologic stress (~3 minutes after start of ongoing adenosine infusion, or immediately after completion of regadenoson administration, at approved doses). No additional gadobutrol injection was administered for LGE imaging.

Images were read by three independent readers blinded to clinical information. Reader detection of CAD depended on visually detecting defective perfusion or scar on gadobutrol injection CMRI (stress, rest, LGE) imaging. Quantitative coronary angiography (QCA) was used to measure intraluminal narrowing and served as the standard of reference (SoR). Computed tomographic angiography (CTA) was used as the SoR if disease could be unequivocally excluded, and no coronary angiography (CA) was available. The left ventricular myocardium was divided into six regions. Readers provided per-region (CMRI, CTA) and per-artery (QCA) interpretations for each subject. Subject-level endpoints reflected each subject’s most abnormal localized finding.

The sensitivity results for gadobutrol injection CMRI to detect CAD defined as either maximum stenosis ≥50% or ≥70% by QCA are presented in Table 12. For each reader, sensitivity of gadobutrol injection CMRI larger than 60% can be concluded if the lower 95% confidence limit of the sensitivity estimate exceeds the pre-specified threshold of 60%.

The specificity results for gadobutrol injection CMRI to detect CAD defined as either maximum stenosis ≥50% or ≥70% by QCA are presented in Table 13. For each reader, specificity of gadobutrol injection CMRI larger than 55% can be concluded if the lower 95% confidence limit of the specificity estimate exceeds the pre-specified threshold of 55%.

In Study E, among the 33 patients with maximum stenosis by QCA between 50% and <70%, the proportion of gadobutrol injection-CMRI positive detections of CAD ranged from 15% to 33%. In Study F, among the 45 patients with maximum stenosis by QCA between 50% and <70%, the proportion of gadobutrol-CMRI positive detections of CAD ranged from 20% to 35%. The results of gadobutrol injection-CMRI reads to detect CAD in patients with maximum stenosis between 50% and <70% are summarized in Table 14.

###  Left Mainstem Stenosis (LMS)

The studies did not include sufficient numbers of subjects to characterize the performance of gadobutrol injection CMRI for detection of LMS, a subgroup at high risk from false negative reads. In Studies E and F, only three subjects had isolated LMS stenosis >50%. In two of the three cases, the CMRI was interpreted as normal by at least two of the three readers (false negative). Sixteen subjects had LMS stenosis >50% (including subjects with isolated LMS stenosis and subjects with LMS stenosis in addition to stenoses elsewhere). In five of these sixteen cases, the CMR was interpreted as normal by at least two of the three readers (false negative).