Comparison of exercise and dobutamine echocardiography in the haemodynamic assessment of small size mechanical aortic valve prostheses.

OBJECTIVE: Doppler echocardiographic evaluation of prosthetic heart valve function is usually performed at rest although this situation is not representative of patients' daily activities. Following aortic valve replacement, patients most likely to remain symptomatic are those with a small aortic root and dobutamine or exercise echocardiography has been proposed to elicit the presence of abnormal haemodynamics or persistently elevated transvalvular gradients in these patients. This study was carried out to compare dobutamine echocardiography with a symptom limited treadmill exercise echocardiography in patients following aortic valve replacement with a small size (19 mm) St. Jude Mechanical valve prosthesis.

METHODS: The study population consisted of ten unselected patients following aortic valve replacement. Dobutamine was infused intravenously starting at 5 microg/kg/min and increasing by 5 microg/kg/min at 15 min interval up to 20 microg/kg/min. Heart rate, blood pressure, cardiac output (CO), peak and mean gradients as well as effective orifice area (EOA) were measured. These parameters were also measured following a symptom limited treadmill exercise.

RESULTS: Dobutamine stress increased heart rate (HR) and CO by 50 and 74%, respectively (both P<0.0002), and mean transvalvular gradient from 22+/-4.1 mmHg at rest to 40.0+/-10 mmHg at maximum stress (P<0.001). With exercise, HR and CO increased by 48 and 70%, respectively while mean transvalvular gradient increased from 22+/-3.1 mmHg at rest to 38.0+/-6.4 mmHg (P<0.0001). The maximum increase in HR, CO and mean transvalvular gradient with dobutamine and exercise were similar however. There was no significant change in the EOA with either dobutamine or exercise.

CONCLUSION: The result suggests that both treadmill exercise and dobutamine stress echocardiography are equally effective for the hemodynamic evaluation of small aortic valve prosthesis.