Haemodynamic performance of aortic pericardial bioprostheses and bileaflet prostheses at rest and during exercise: implications for the surgical management of patients with small aortic roots.

OBJECTIVE: To determine the haemodynamic behaviour, at rest and during exercise, of aortic valve pericardial bioprostheses and different 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 effective 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.

Clinical experience with the Ionescu-Shiley xenograft valve: four to five-year follow-up.

Between January 1977 and July 1981, 132 Ionescu-Shiley xenografts were implanted in 124 patients. Early and late mortality was 13.7% (17/124) and 9.2% (10/107), respectively. Cumulative survival rates at 4 to 5 years were 76% (aortic) and 84% (mitral). Thromboembolic analysis showed 0.72 episodes per 100 patients per year, without chronic anticoagulation. The thromboembolism free rates were 96.8% (mitral) and 100% (aortic); 75% of the mitral patients were in atrial fibrillation. No primary valve dysfunction was detected. In the aortic position (8 patients with valve stent diameter from 19 to 25 mm), the mean peak systolic gradient pressure was 10 +/- 5.5 mm Hg, and calculated valve surface areas were 1.6 +/- 0.5 cm2 at rest and 2 +/- 0.1 cm2 after exercise. A satisfactory correlation between catheterization-derived valve area (from hemodynamic data) and valve stent diameter was obtained (r = 0.94). In the mitral position, the mean diastolic gradient pressure was 4.7 +/- 3.1 mm Hg at rest and 13.8 +/- 0.9 after exercise with the 27 mm xenograft. The corresponding calculated surface areas were 2.8 +/- 6 cm2 and 3 +/- 0.8 cm2. The present data show minimal thrombogenicity without chronic anticoagulation, even in patients with atrial fibrillation or enlarged left atrium and advantageous hemodynamic characteristics, particularly in those with small aortic annuli.

Umbrales agudos y cronicos en la estimulacion epicardica de la cara diafragmatica del ventriculo derecho. / Acute and chronic thresholds in epicardial stimulation of diaphragmatic wall of right ventricle

Desde marzo de 1974 a noviembre de 1979, hemos implantado un total de 244 electrodos epicardicos, 29 en la cara anterior y 215 en la cara diafragmatica del ventriculo derecho usando en 212 ocasiones un abordaje subcostal extrapleural. En 174 casos consecutivos hemos practicado un estudio electrofisiologico preoperatorio con medicion de voltaje corriente, resistencia y amplitud de la onda R, en diferentes zonas del ventriculo derecho realizando un estudio comparativo entre dos tipos de electrodos epicardicos. En 21 casos se realizo medicion de los umbrales cronicos a 32 meses de media de la primoimplantacion. Hubo una muerte quirurgica (0.4%) con una morbilidad del 7.4%. La media de seguimiento es de 20 meses. En el grupo de pacientes con mapeo, los umbrales fueron significativamente menores que en el grupo no mapeado (p 0.001). En cuanto a los umbrales cronicos, estos se incrementan en ambos grupos de pacientes, siendo mucho menor en el mapeado, hecho que esta en relacion con los hallazgos agudos