We conclude that despite undeniable recent improvements in the design of artificial heart valves, 19 mm aortic prostheses continue to create significant obstruction of the left ventricular outflow tract and, possibly as a consequence of this, fail to bring about significant reduction in left ventricular hypertrophy.

Objective-To determine the haemodynamic behaviour, at rest and during exercise, of aortic valve pericardial bioprostheses and diVerent sizes of bileaflet prosthesis. Design-Observational study. Setting-Tertiary medical centre. Patients and interventions-74 patients (33 women, 41 men; mean age 64 years) in whom 40 pericardial bioprostheses and 34 bileaflet prostheses sized 19, 21, or 23 mm had been implanted to replace aortic valves. Main outcome measures-Doppler echocardiography at rest and at peak exercise, between 12 and 47 months after surgery. Results-All patients achieved a significant increase in heart rate, systolic blood pressure, and cardiac output with exercise. Transvalvar pressure fall, valve area, and left ventricular systolic and diastolic function indices also underwent significant changes with exercise. Reductions in peak and mean transvalvar pressure, at rest and at peak exercise, were greater in patients with small valves (p < 0.05). Valve areas and eVective area index were greater in the patients with larger valves (p < 0.001). There were no significant differences between patients with mechanical and biological prostheses with regard to transvalvar pressure fall and valve areas at rest and at peak exercise. Conclusions-19 mm and 21 mm aortic prostheses and bioprostheses continue to create significant obstruction, particularly with exercise. (Heart 1999;82:149-155)

Long-term survival was investigated in 202 patients who underwent isolated aortic valve replacement (AVR) with 19 mm valves. There were 171 women with a mean age of 69+/-9 years and 31 men with a mean age of 64+/-13 years. Patients had a mean body surface area of 1.61+/-0.13 m(2). Patient-prosthesis mismatch was moderate in 196 and severe in six patients. The mean follow-up for all patients was 78 months. There were 79 late deaths. The actuarial survival rates for all patients were 95+/-1% at 1 year, 75+/-2% at 5 years, 56+/-2% at 10 years, 41+/-2% at 15 years, 34+/-3% at 20 years and 34+/-2% at 25 years. Patients over 70 years old had a lower survival rate (P=0.0001). There were significant differences between ejection fraction (EF) >55% and EF <55% (P=0.0305). AVR with 19 mm valves appeared to provide satisfactory mid-term survival. Age and low EF were risk factors for shorter survival.

The hemodynamics of five designs of 19 mm pericardial aortic valve bioprostheses were examined in 47 resting patients by Doppler echocardiography. The salient differences among the five designs are that valve leaflets are mounted inside the support frame in one (the Carpentier-Edwards valve, evaluated in 4 patients) and outside the frame in the other four (the Ionescu-Shiley (16 patients), Mitroflow (4), Bioflo (8) and Labcor-Santiago (15)); and that two models have either total (Bioflo) or partial (Labcor-Santiago) protective pericardial sheaths on the stent, while the other three do not. The hemodynamic parameters determined included transvalvular pressure drop, valve area, left ventricular outflow tract diameter, subvalvular/valvular velocity ratio and subvalvular/valvular velocity-time integral ratio. There were no significant differences among the various valves as regards left ventricular outflow tract diameter, subvalvular/valvular velocity ratio or subvalvular/valvular velocity-time integral ratio. Negative correlation between left ventricular outflow tract diameter and subvalvular velocity (r = -0.66, P < 0.001) confirmed the need to correct for prevalvular velocities when using the Bernouilli equation to calculate the pressure drop across small pericardial aortic valve bioprostheses. The Bioflo design caused significantly greater pressure drops (peak 38.3 +/- 8.3 mmHg, mean 24.6 +/- 4.8 mmHg) and smaller areas (0.82 +/- 0.17 cm2) than the Ionescu-Shiley (20.3 +/- 5.6 and 11.7 +/- 3.8 mmHg, 1.19 +/- 5.3 and 10.1 +/- 3.1 mmHg, 1.27 +/- 0.12 cm2) valves.

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