Simultaneous assessment of coronary flow reserve and left ventricular function during vasodilator stress evaluated by 13N-ammonia hybrid PET/MRI

Abstract

Aim: To explore changes in left ventricular (LV) function and the relationship of these changes with myocardial blood flow (MBF) evaluated by ¹³N-ammonia hybrid positron-emission tomography (PET)/magnetic resonance imaging (MRI) during vasodilator stress in patients with suspected coronary artery disease (CAD).

Materials and methods: Fifty-two consecutive patients with suspected CAD, who underwent ¹³N-ammonia PET/MRI, were enrolled. Vasodilator stress was induced by intravenous injection of adenosine. MBF and coronary flow reserve (CFR) were calculated from dynamic acquisition of ¹³N-ammonia PET. LV function was evaluated by MRI both at rest and during vasodilator stress. An abnormal perfusion on myocardial images was defined as a summed difference score of ≥4.

Results: MRI showed that the LV end-diastolic volume, LV end-systolic volume, and LV ejection fraction (LVEF) remained unchanged during vasodilator stress in all patients (n=52) as well as in the patients with CFR of <2 (n=27), stress MBF of <1.3 ml/g/min (n=28), abnormal myocardial perfusion (n=30), and more than one diseased vessel (n=46). In only four patients, the LVEF measured by MRI decreased by >5% during vasodilator stress. In these four patients, CFR was lower (1.57 ± 0.12 versus 2.18 ± 0.86, p<0.01) and the number of diseased vessels was higher (2.75 ± 0.50 versus 1.48 ± 0.92, p<0.01) than in patients without post-stress LV dysfunction.

Conclusion: The LV volume and systolic function evaluated by cardiac MRI remained unchanged during vasodilator stress; however, LV dysfunction during vasodilator stress may occur in patients with severe CAD.