Effect of hydration on cavity obliteration during dobutamine stress echocardiography

The purpose of this study was to determine whether it is possible to prevent or delay the onset of midventricular cavity obliteration during a dobutamine stress test with standard hydration. Left ventricular (LV) intracavitary obstruction has been reported as the mechanism for hypotension seen in approximately 20% of patients undergoing dobutamine stress echocardiography. In addition, it has been proposed that administration of a normal saline bolus prior to dobutamine infusion may avert the dynamic ventricular obstruction. We performed a standard graded dobutamine stress echocardiogram before and after fluid loading with 10 ml/kg of normal saline in 10 mongrel dogs. Measurements were made of left atrial pressure, aortic pressure, and the area of the LV cavity at the papillary muscle level throughout each infusion. Although hydration produced an increase in baseline left atrial pressure (5.7 +/- 3.2 to 8.1 +/- 2.7 mmHg, p < 0.01) and systolic blood pressure (128 +/- 18 to 139 +/- 22 mmHg, p = 0.03), there was no significant change in pre-dobutamine heart rate or systolic area. With dobutamine infusion, there was a similar change in heart rate, systolic blood pressure, diastolic area, and systolic area (SA) at each dose of dobutamine regardless of hydration status. In addition, the dose at which cavity obliteration occurred was not altered by hydration (p = NS). Although all dogs developed cavity obliteration (SA < 1.0 cm2) with dobutamine infusion, none experienced hypotension. In this canine model, cavity obliteration does not lead to systemic hypotension and cannot be prevented or delayed by volume loading.