Background:
Patients with coronary artery bypass grafts (CABG) face an elevated risk of major adverse cardiac events (MACE). High-dose dobutamine-stress cardiovascular magnetic resonance imaging (DCMR) is a well-established technique for detecting hemodynamically significant coronary artery disease (CAD). However, there is a scarcity of data regarding the prognostic value and safety of DCMR for patients with CABG. This study aimed to evaluate the prognostic value and safety of DCMR in patients with CABG.

Methods:
We retrospectively included patients after CABG who subsequently underwent DCMR between November 2008 and July 2018. Complications during DCMR were compared to 200 individuals matched for age, sex and BMI. The primary endpoint was defined as the occurrence of MACE encompassing cardiac death, non-fatal myocardial infarction, hospitalization for heart failure, percutaneous coronary intervention (PCI), or CABG surgery. To account for potential revascularization triggered by the CMR examination results, early revascularization procedures within 90 days after DCMR were excluded.

Results:
336 patients (70±9 years, 85% men) who had undergone CABG and DCMR were identified. Fifty-one early revascularizations occurred. The median follow-up time of the remaining patients was 4.5 years (1.9 – 6.4 years). 161 MACE occurred during follow-up. Fifty-seven patients died, with 24 deaths attributed to cardiovascular disease. Forty-one patients suffered from a non-fatal myocardial infarction. In addition, 103 patients underwent PCI, and three patients recurrent bypass surgery. Thirty-nine patients were hospitalized due to heart failure. Six patients survived resuscitation, and one experienced an adequate shock delivery by an implantable defibrillator. 

The strongest independent variable for MACE were inducible wall motion abnormalities or perfusion deficits during DCMR (hazard ratio 1.97, 95% CI 1.2 – 3.1, p <0.01).

Complications arose in 35 patients (10%) with CABG and 15 controls (7.5%) (p=0.262). A drop of systolic blood pressure (SBP) (>40mmHg) (12 patients), non-sustained ventricular tachycardia (6 patients), increase in SBP (>200mmHg) (5 patients), monomorphic premature ventricular contractions (PVC) (2 patients), bigeminy (2 patients), left bundle-branch block (2 patients), as well as tachycardiac paroxysmal atrial fibrillation, bradycardia, supraventricular tachycardia, couplets/triplets, and sinus arrhythmia in one patient each occurred in the study group. In addition, one patient was hospitalized due to tachycardiac paroxysmal atrial fibrillation and transient ischemic attack. 29 (8.7%) examinations in the study group were aborted because of either chest pain, dyspnea, nausea, dizziness, a drop of SBP, arrhythmias, tachycardiac paroxysmal atrial fibrillation, monomorphic PVCs, or non-sustained ventricular tachycardia. The rate of aborted examination was comparable to the control group (15 (7.5%), p=0.631). Univariable logistic regression analysis revealed that female sex (OR 2.21, 95% CI 1.2 - 4.3, p= 0.017) and inducible ischemia (OR 3.50, 95% CI 2.0 - 6.0, p<0.001) were associated with an increased risk of complications during DCMR. 

Conclusion:
Overall, dobutamine-stress CMR appears to be a safe technique for patients after CABG. Dobutamine-stress CMR can effectively identify patients at risk for cardiac death, myocardial infarction, and hospitalization for heart failure.