Use of cardiac MRI for low gradient aortic stenosis

Introduction

Low gradient aortic stenosis (AS) is a challenging problem. Low dose dobutamine (LDD) to seperate low gradient AS with myopathic etiology from true severe aortic stenosis is the gold standard practice today.

Purpose

This initial small cohort will try to compare LDD to cardiac MRI with delayed enhancement (CMR-DE) imaging for the evaluation of contractile reserve.

Methods

7 patients (pts) with mean gradient < 30 mm Hg and LVEF < 30% underwent LDD and CMR-DE before aortic valve replacement (AVR). Increase in stroke volume > 20% by LDD up to 20 micrograms/kg/min was considered indication of the presence of myocardial reserve.

Results

From the CMR-DE images: 3 pts had completely viable myocardium, 1 pt had intra-myocardial scar and 3 had subendocardial scar suggestive of concomitant coronary artery disease. Only 3 pts had evidence of contractile reserve by LDD. 2 pts with viable myocardium by CMR-DE did not show response to dobutamine. Pts with scar had mixed response.

Conclusion

The absence of response to dobutamine may not be enough to preclude the presence of myocardial reserve in low flow/low gradient aortic stenosis. This small cohort raises the question that CMR-DE may be needed in pts that do not respond to LDD since the presence of myocardial reserve may affect the management of these pts and has prognositic implications.