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Background Adenosine stress-perfusion cardiovascular magnetic resonance (CMR) is widely used to diagnose coronary artery disease (CAD). However, in patients with heart failure with reduced ejection fraction (HFrEF), attenuated vasodilatory responses to adenosine may impair diagnostic performance. Hence, dobutamine may prove a superior stressor in this population. This study aimed to determine whether dobutamine-stress perfusion CMR provides superior sensitivity compared with adenosine for the detection of severe CAD in patients with HFrEF.Methods Patients with HFrEF (left ventricular ejection fraction ≤40%) prospectively underwent 3-Tesla CMR comprising cine imaging, late gadolinium enhancement and first-pass perfusion imaging at rest and during pharmacological stress with (1) adenosine [140-210μg/kg/min] and (2) dobutamine [10-30µg/kg/min]. Severe CAD was defined at the vessel level as: (1) fractional flow reserve ≤0.80 in vessels ≥2mm if available, or diameter stenosis ≥70% (≥50% for left main stem) on invasive or computed tomography coronary angiography; and (2) the presence of infarction and/or ischaemia on visually-read CMR, assessed by two experienced readers acting in consensus.Results Fifty patients were included in the final analysis (figure 1, table 1). From angiographic analysis, prevalence of severe CAD was 50%. Haemodynamic responses to adenosine and dobutamine are summarised in table 2. Compared with adenosine-stress CMR, dobutamine-stress CMR demonstrated similar per-vessel sensitivity (81.8% vs. 72.7%, respectively; p=0.453), specificity (86.3% vs. 87.2%, respectively; p=0.732) and accuracy (85.3% vs. 84.0%, respectively; p=0.564) (table 3, figure 2).Conclusions In patients with HFrEF, dobutamine and adenosine-stress perfusion CMR demonstrate comparable diagnostic performance for detecting severe CAD, suggesting no incremental benefit of dobutamine over standard adenosine-stress perfusion CMR. In patients with heart failure with reduced ejection fraction, what did this study find regarding dobutamine- versus adenosine-stress perfusion CMR for the detection of severe coronary artery disease.A. Dobutamine-stress CMR demonstrated significantly higher sensitivity and overall diagnostic accuracy than adenosine-stress CMRB. Adenosine-stress CMR demonstrated significantly higher specificity than dobutamine-stress CMRC. Dobutamine-stress CMR demonstrated higher sensitivity, but lower specificity than adenosine-stress CMRD. Dobutamine- and adenosine-stress CMR showed comparable sensitivity, specificity, and diagnostic accuracyE. Both stressors demonstrated poor diagnostic performanceAbstract 11 Table 2Baseline haemodynamics and response to pharmacological stressBaselinePeak stressMean differenceAdenosine Heart rate, bpm72 ± 1290 ± 1418 ± 10 Systolic BP, mmHg133 ± 22133 ± 23-1 ± 18 Diastolic BP, mmHg80 ± 1079 ± 12-2 ± 10Dobutamine Heart rate, bpm73 ± 49120 ± 1547 ± 14 Systolic BP, mmHg135 ± 23148 ± 3213 ± 24 Diastolic BP, mmHg79 ± 1078 ± 16-1 ± 15Data presented as mean ± standard deviationAbbreviations: BP blood pressure; BPM beats per minuteAbstract 11 Table 3Diagnostic performance of adenosine versus dobutamine-stress perfusion CMR for the detection of severe coronary artery diseasePer vessel, n=150Adenosine-stress CMRDobutamine-stress CMRMean difference P valueSensitivity81.8%72.7%-9.1% [-24.2%, 6.1%]0.453Specificity86.3%87.2%+0.9% [-3.4%. 5.1%]0.732Accuracy85.3%84.0%-1.3% [-6.7%, 3.3%]0.564Differences in proportions [95% confidence interval] calculated using the Newcombe-Wilson score method and compared using exact binomial tests.Abstract 11 Table 1Baseline characteristicsParticipants with HFrEF, n=50Demographics Age, years64 ± 10 Male38 (76%) Body mass index, kg/m229.3 ± 5.4Cardiovascular risk factors Current or ex-smoker33 (66%) Hypertension25 (50%) Type II diabetes 12 (24%) Hypercholesterolemia17 (34%) Previous myocardial infarction22 (44%)Medications ACEi/ARB42 (84%) Beta adrenoreceptor antagonist38 (76%) Loop or thiazide diuretic23 (46%) Statin32 (64%)Aspirin24 (48%)Left ventricular structure and function Ejection fraction, %36 ± 10 End-diastolic volume index, ml/m2103 ± 25 End-systolic volume index, ml/m267 ± 24 Mass index, g/m266 ± 15LGE Infarction30 (60%) Non-ischaemic focal fibrosis10 (20%)Coronary angiography* Presence of severe CAD25 (50%) Single-vessel disease20 (40%) Double-vessel disease2 (4%) Triple-vessel disease 3 (6%) Presence of complete occlusion18 (36%)Data presented as mean ± standard deviation or counts and percentage (%).Abbreviations: ACEi/ARB angiotensin-converting enzyme inhibitor/angiotensin receptor blocker; CAD coronary artery disease; LGE late gadolinium enhancement.*Invasive coronary angiography performed in 36 (72%) participants and computed tomography coronary angiography in 14 (28%).Abstract 11 Figure 2DISCORDANCE study overview. Abbreviations: CAD coronary artery disease; CMR cardiovascular magnetic resonance; FFR fractional flow reserve; HFrEF heart failure with reduced ejection fraction; LGE late gadolinium enhancement; LMS left main stem; LVEF left ventricular ejection fractionAbstract 11 Figure 1Study flow diagram. *Residual left ventricular thrombus, recent myocardial infarction, new diagnosis of hypertrophic obstructive cardiomyopathyCorrect answer: D