Physical and physiological effects of dobutamine stress echocardiography in low-gradient aortic stenosis.

Dobutamine stress echocardiography (DSE) is a useful tool for assessing low-gradient significant aortic stenosis (AS) and contractile reserve (CR), but its prognostic utility has become controversial in recent studies. We evaluated the impact of DSE on aortic valve physiological, structural, and left ventricular parameters in low-gradient AS. Consecutive patients undergoing DSE for low-gradient AS evaluation from September 2010 to July 2016 were retrospectively studied, and DSE findings were divided into four groups: with and without severe AS and/or CR. Relationships between left ventricular chamber quantification, CR, aortic valve Doppler during DSE, and calcium score [by computerized tomography (CT)] were analyzed. There were 258 DSE studies performed on 243 patients, mean age 77.6 ± 10.8 yr and 183 (70.1%) were males. With increasing dobutamine dose, apart from systolic blood pressure, left ventricular ejection fraction, flow, cardiac power output, and longitudinal strain magnitude, along with aortic valve area and mean aortic gradient were all significantly increased ( < 0.05). Flow and mean gradient increased in both the presence and absence of CR, whereas stroke volume and aortic valve area increased mainly in those with CR only. The aortic valve area increased in both patients with low and high calcium scores; however, the baseline area was lower in those with a higher calcium score. During DSE, aortic valve area increases with increase in aortic valve gradient. Higher calcium score is associated with lower baseline aortic valve area, but the aortic valve area still increases with dobutamine even in presence of a high calcium score. We show that even in most severe aortic stenosis, there is some residual valve pliability. This suggests that a complete loss of pliability is not compatible with survival.