Hemodynamic and physical performance during maximal exercise in patients with an aortic bioprosthetic valve: comparison of stentless versus stented bioprostheses.

OBJECTIVES: The objective of this study was to compare stentless bioprostheses with stented bioprostheses with regard to their hemodynamic behavior during exercise. BACKGROUND: Stentless aortic bioprostheses have better hemodynamic performances at rest than stented bioprostheses, but very few comparisons were performed during exercise. METHODS: Thirty-eight patients with normally functioning stentless (n = 19) or stented (n = 19) bioprostheses were submitted to a maximal ramp upright bicycle exercise test. Valve effective orifice area and mean transvalvular pressure gradient at rest and during peak exercise were successfully measured using Doppler echocardiography in 30 of the 38 patients. RESULTS: At peak exercise, the mean gradient increased significantly less in stentless than in stented bioprostheses (+5 +/- 3 vs. +12 +/- 8 mm Hg; p = 0.002) despite similar increases in mean flow rates (+137 +/- 58 vs. +125 +/- 65 ml/s; p = 0.58); valve area also increased but with no significant difference between groups. Despite this hemodynamic difference, exercise capacity was not significantly different, but left ventricular (LV) mass and function were closer to normal in stentless bioprostheses. Overall, there was a strong inverse relation between the mean gradient during peak exercise and the indexed valve area at rest (r = 0.90). CONCLUSIONS: Hemodynamics during exercise are better in stentless than stented bioprostheses due to the larger resting indexed valve area of stentless bioprostheses. This is associated with beneficial effects with regard to LV mass and function. The relation found between the resting indexed valve area and the gradient during exercise can be used to project the hemodynamic behavior of these bioprostheses at the time of operation. It should thus be useful to select the optimal prosthesis given the patient's body surface area and level of physical activity.     

Occupational asthma due to various agents. Absence of clinical and functional improvement at an interval of four or more years after cessation of exposure

We have previously shown that in some subjects with occupational asthma caused by various agents, there is no improvement approximately two years after exposure ended. These results could be explained by the short interval between diagnosis and follow-up. In the current study, we saw 28 subjects with occupational asthma at two intervals, 2.3 years (range, three months to 5.7 years) and 5.8 years (range, 4.3 to 10.9 years) after the cessation of exposure. Various causes of occupational asthma were included. The diagnosis was confirmed in 26 of the cases by specific inhalation challenges in the laboratory, and in the remaining two cases by combined monitoring of peak expiratory flow rates and bronchial responsiveness. All subjects had symptoms of asthma at both follow-up assessments. There were no changes in the need for medication, spirometry, or bronchial hyperresponsiveness. Depending on the interval of the follow-up, four to six subjects required inhaled steroid agents in addition to the usual bronchodilators, 11 had FEV1 less than 80 percent of predicted, and 26 or 27 had an abnormal PC 20 histamine. Only two subjects demonstrated sustained improvement in PC 20 at the first and second follow-ups, and one other showed changes during the second follow-up assessment which were not present at the first. We conclude that except for three subjects, the need for medication did not diminish, nor did airway obstruction and hyperresponsiveness improve in this group of subjects with occupational asthma long after exposure ended. These results differ from other studies, which demonstrated that some recovery takes place in a greater proportion of individuals.