Background:
Patients with severe coronary artery disease (CAD) and coronary artery bypass graft have a higher risk of major adverse cardiac events (MACE). High-dose dobutamine-stress cardiac magnetic resonance imaging (CMR) is a well-established method to identify functional significant CAD. However, prognostic value and safety of this modality in patients with severe CAD has not been investigated. 

Objectives:
We aimed to determine the safety of dobutamine-stress cardiac magnetic resonance imaging in patients with coronary artery bypass graft and its prognostic value.

Methods:
We retrospectively studied patients after coronary artery bypass grafting who underwent dobutamine-stress CMR between November 2008 and July 2018. Follow-up consisted of clinical visits as part of usual care, by contact of primary care physician or by direct contact with the patient. Primary endpoint was defined as the occurrence of a major cardiovascular event (MACE), including cardiac death, non-fatal myocardial infarction, hospitalization for heart failure, percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery. As results of CMR examination may have triggered revascularization, early revascularization procedures within 90 days after dobutamine-stress CMR were excluded.

Results:
296 predominantly male patients (69±9 years, 85% men) with coronary artery bypass grafts were identified. Most patients suffered from a 3-vessel disease (92%) and had three (41%) or four (24%) distal anastomoses. 

Complications occurred in thirty-six patients (12%). Minor symptoms were reported in eighteen patients (6.1%) including chest pain (13 patients), dyspnea (3 patients), dizziness and nausea in one patient each. Non-severe complications occurred in twenty patients (6.8%) including drop in systolic blood pressure (SBP) (>40 mmHg) (4 patients), non-sustained ventricular tachycardia (4 patients), increase in SBP (>200mmHg) (3 patients), tachycardiac paroxysmal atrial fibrillation (3 patients), bradycardia, supraventricular tachycardia, monomorphic ventricular premature complexes, couplets, triplets, left bundle-branch block and sinus arrhythmia in one patient each. No severe complications occurred. Twenty-seven (9.2%) examinations were terminated, because of either chest pain, dyspnea, nausea, dizziness, decrease of blood pressure, arrhythmias, or non-sustained ventricular tachycardia.The median follow-up time was 4.4 years (1.7–6.5 years). 159 MACE occurred during the follow-up time. 50 early revascularization occurred. 44 patients died during the follow-up period, 19 patients because of cardiovascular disease. 50 patients suffered from non-fatal myocardial infarction. 104 patients underwent PCI and 4 patients recurrent bypass surgery. 43 patients were hospitalized for heart failure. 9 patients survived resuscitation and 1 patient experienced an adequate shock delivery by implantable defibrillator.

Using logistic regression analysis, inducible wall motion abnormalities or perfusion deficits during dobutamine-stress CMR was the strongest independent variable for MACE (hazard ratio 2.2, 95% confidence interval: 1.4–3.6, p<0.01).

Dobutamine-stress CMR can identify patients who are at risk for cardiac death, myocardial infarction, and hospitalization, with severe CAD and coronary artery bypass grafts. No severe complications occurred during the stress examination. However, indication for dobutamin-stress CMR should be considered carefully.