Definition
  • Effective orifice area <1.0 cm2
  • LV ejection fraction <40%; and
  • Mean pressure gradient <30-40 mmHg
Dobutamine stress echo protocol
  1. Use a low dose starting at 2.5 or 5 mg/kg/min with an incremental increase in the infusion every 3-5 min to a maximum dose of 10-20 mg/kg/min.
  2. Stop the infusion as soon as a positive result is obtained or when the heart rate begins to rise more than 10-20 bpm over baseline or exceeds 100 bpm.
  3. Dobutamine administration should also terminated when symptoms, blood pressure fall, or significant arrhythmia occur.
  4. The report should include AS velocity, mean gradient, valve area, and ejection fraction preferably at each stage.
Findings
  1. An increase in valve area to a final valve area >1.0 cm2 suggests that stenosis is not severe.
  2. Severe stenosis is suggested by an AS jet >4.0 or a mean gradient >40 mmHg provided that valve area does not exceed 1.0 cm2 at any flow rate.
  3. Absence of contractile reserve (failure to increase SV or ejection fraction by >20%) is a predictor of a high surgical mortality and poor long-term outcome although valve replacement may improve LV function and outcome even in the subgroup.