Background and aim of the study: The study aim was to compare the hemodynamic profiles of the aortic standard porcine Carpentier-Edwards (C-E) and Ultracor (tilting-disc) valve using exercise and dobutamine stress.
Methods: A total of 36 patients was examined, 18 for each valve type. When analyzing the data, valve types were matched for valve size, which ranged from 21 to 25 mm. All patients were analyzed within an 18-month period after implantation. Hemodynamic variables, two-dimensional echocardiography and Doppler flows were recorded at rest. These were repeated during bicycle ergometry, performed for a maximum of four, 3-min stages, with each stage increasing in workload by 20 W. After resting, patients were subjected to dobutamine stress, administered up to a maximum 40 microg/kg/min, dependent upon heart rate.
Results: Mean (+/- SD) resting pressure drops across the C-E and Ultracor valves were comparable (maximum drop 19.4 +/- 8.6 versus 22.9 +/- 12.2 mmHg; mean drop 9.96 +/- 3.8 versus 11.83 +/- 6.6 mmHg, respectively). During exercise, the maximum cardiac flow rate attained was approximately 400 ml/s for both valve types. At this flow rate, the maximum and mean pressure differences between valve types were 6.2 mmHg and 4.4 mmHg, respectively (p = NS). During dobutamine stress, the maximum cardiac flow attained was approximately 500 ml/s, which resulted in significant differences between valve types of 11.6 and 7.3 mmHg, for maximum and mean pressure drops, respectively. When slopes of the mean pressure drop/cardiac flow were calculated for individual valves, a difference was observed between the two valve types (p = 0.02 and p = 0.039 for dobutamine and exercise, respectively).
Conclusion: Both prostheses demonstrated significant increases in pressure drop under stress conditions. The standard porcine C-E valve had a statistically better hemodynamic profile than the Ultracor prosthesis at higher flow rates. When a study cohort of patients is small, these differences will only be evident at optimal flow rates. The higher flow rates seem most easily obtained when using pharmacological stress.