Splenic Switch-Off for Determining the Optimal Dosage for Adenosine Stress Cardiac MR in Terms of Stress Effectiveness and Patient Safety.

Background: Adenosine stress MRI is well established for the evaluation of known and suspected coronary artery disease. However, a proportion of patients might be "under-stressed" using the standard adenosine dose.

Purpose: To compare three different adenosine dosages for stress MRI in terms of stress adequacy based on splenic switch-off (SSO) and limiting side effects.

Study Type: Prospective.

Population: In all, 100 patients were randomized in group 1 (33 pts), group 2 (34 pts), and group 3 (33 pts), receiving dosages of 140 μg/kg/min, 175 μg/kg/min, or 210 μg/kg/min, respectively. SSO was evaluated visually and quantitatively.

Sequence: Stress perfusion was performed using a 1.5T scanner in three short axes using a standard single-shot, saturation recovery gradient-echo sequence.

Assessment: Three blinded experienced operators evaluated SSO on stress and rest perfusion acquisitions in the three groups. The signal intensity of the spleen and myocardium and the presence of inducible ischemia and late gadolinium enhancement were assessed.

Statistical Analysis: T-test, analysis of variance (ANOVA), chi-squared test, and Pearson's correlation coefficient.

Results: SSO was present more frequently in patients receiving 175 μg/kg/min and 210 μg/kg/min (31/33 [94%] and 27/29 [93%], respectively) compared to those receiving the standard dose (19/33 [58%], P < 0.05). A positive stress result was noted in 3/33 (9%) patients receiving 140 μg/kg/min vs. 9/33 (27%) patients receiving 175 μg/kg/min and 10/31 (33%) patients receiving 210 μg/kg/min (P < 0.05 for all, P < 0.05 for group 1 vs. groups 2, 3). The relative decrease of splenic signal intensity at hyperemia vs. baseline was significantly lower in group 1 compared to groups 2 and 3 (-33% vs. -54%, -56%, respectively; P < 0.05). No adverse events during scanning were noted in groups 1 and 2, whereas in group 3 four examinations were stopped due to severe dyspnea (n = 2) and AV-blockage (n = 2).

Data Conclusion: A dosage of 175 μg/kg/min adenosine results in a higher proportion of SSO, which may be an indirect marker of adequate coronary vasodilatation and simultaneously offers similar safety compared to the standard 140 μg/kg/min dosage.

Level Of Evidence: 1 TECHNICAL EFFICACY STAGE: 2 J. MAGN. RESON. IMAGING 2020;52:1732-1742.