Opening and closure characteristics of different types of stented biological valves.

BACKGROUND: In an increasingly senescent population stented biological valves have regained renewed popularity because of the absence of anticoagulation, while the stented design allows for safe and easier implantation. Constructed bovine pericardial valves as well as valves with porcine cusps are used, both of which exhibit good clinical results although degeneration still appears. While clinical hemodynamic studies did not show particular differences between both valves types, the opening and closure behavior of native cusps and artificially constructed pericardial leaflets is different. It is unclear whether these phenomena account for differences in load and stress which may influence onset and course of degeneration. MATERIAL AND METHODS: Edwards Perimount (EP) and Medtronic Mosaic (MM) heart valves with diameters of 21 mm, 23 mm, and 25 mm were investigated in a pulse duplicator. Movements of the valves were visualized with a high-speed camera (1000 frames/sec). Mean transvalvular gradient (mm Hg), dissipated power (mW), and power transfer by stretching (mW), mean orifice area (mm2), opening time (ms), and closure time (ms) were analyzed in a range of cardiac outputs from 1.4 l/min to 6.3 l/min and 70 beats per minute. RESULTS: Closure times were generally longer than opening times for both valve types. Opening time of EP valves was longer than opening time of the MM valves of the same size (EP23: 31.2 +/- 2.5 ms; MM23: 12.7 +/- 0.1 ms). With respect to closure times, however, there were no marked differences between all valves (EP23: 69.3 +/- 2.0 ms; MM23: 63.2 +/- 6.3 ms). Smaller sized Perimount valves exhibited lower mean transvalvular gradients than Mosaic valves of the same size (EP23: 7.21 +/- 0.07 mm Hg; MM23: 10.5 +/- 0.15 mm Hg). In larger sizes these differences diminished. Power transfer to the valve's structures was significantly enhanced in EP valves (EP23: 134 +/- 1.3 mW; MM23: 64 +/- 0.9 mW). CONCLUSIONS: While valves with constructed pericardium showed lower mean transvalvular gradients, particularly in the smaller sizes, this valve type exhibited alterations of movement performance in contrast to porcine valves. It can be speculated that constant power transfer to the valve's structures may result in an earlier degeneration because of the impact of the increased load and stress on the suspension apparatus of the constructed pericardial leaflets.

Different tilting disc valves show similar rotation-dependent impairment in hemodynamic performance under a tilted implantation position.

BACKGROUND: Aortic annulus calcification can promote tilted implantation of mechanical valves. This study evaluates the hemodynamics of tilting disc valves under this condition. METHODS: 23 mm and 25 mm Ultracor (UC) and Medtronic-Hall-Easy-Fit (MH) valves were investigated in a pulse-duplicator under physiological conditions. Mean pressure gradient (dP(mean)), systolic energy loss (dW(sys)), effective orifice area (EOA), closure (V(Cl)), leakage (V(L)), and total regurgitation volume (V(R)) were assessed. Valves were independently positioned at five axial rotations (0 - 180 degrees , zero defined as major orifice facing the top of the "tilt-ramp") and three tilt angles (0 degrees, 10 degrees, 20 degrees) by lifting the prosthesis in the noncoronary sinus. RESULTS: Diameter-enhanced MH valves exhibited a better systolic performance but a higher regurgitation than corresponding UC valves. Moderate tilting showed a rotation-independent increase in dP(mean) and dW(sys) and a decrease in V (R) and EOA with no fundamental differences between valve types. Further tilting caused small additional changes at 90 - 180 degrees rotation. At 0 degrees rotation, however, dramatic regurgitation occurred throughout. CONCLUSION: Tilting worsened systolic performance regardless of valve type. It should therefore be avoided. Due to extensive regurgitation at 0 degrees rotation, this position should be corrected whenever tilting is inevitable.

Behavioral treatment of obese binge eaters: do they need different care?

This study investigated the relationship between binge eating and the outcome of weight loss treatment. Participants in a 48-week trial of a structured diet combined with exercise and behavior therapy were classified into one of four groups: no overeating; episodic overeating; subthreshold binge-eating disorder(BED); and BED. Binge eating status was not associated with either dropout or adherence to the diet, but did affect weight loss and mood. The BED group lost significantly more weight at the end of treatment than all other groups, even when adjusting for initial weight. At 1-year follow-up, there were no differences among groups in weight loss or weight regain. The BED group began treatment with significantly higher BDI scores, but improvement in mood occurred by week 5. On the basis of these findings, and a review of the recent literature, we conclude that obese binge eaters respond as favorably to standard dietary and behavioral treatments as do obese nonbingers.

Exercise in the treatment of obesity: effects of four interventions on body composition, resting energy expenditure, appetite, and mood.

This study investigated changes in body composition, resting energy expenditure (REE), appetite, and mood in 128 obese women who were randomly assigned to 1 of 4 treatment conditions: diet alone, diet plus aerobic training, diet plus strength training, or diet combined with aerobic and strength training (i.e., combined training). All women received the same 48-week group behavioral program and were prescribed the same diet. Exercising participants were provided 3 supervised exercise sessions per week for the first 28 weeks and 2 sessions weekly thereafter. Participants across the 4 conditions achieved a mean weight loss of 16.5 +/- 6.8 kg at Week 24, which decreased to 15.1 +/- 8.4 kg at Week 48. There were no significant differences among conditions at any time in changes in weight or body composition. Women who received aerobic training displayed significantly smaller reductions in REE at Week 24 than did those who received strength training. There were no other significant differences among conditions at any time on this variable or in changes in appetite and mood.

Rupture characteristics of the deep bolivian earthquake of 9 june 1994 and the mechanism of deep-focus earthquakes.

The M(w) = 8.3 deep (636 kilometers) Bolivian earthquake of 9 June 1994 was the largest deep-focus earthquake ever recorded. Seismic data from permanent stations plus portable instruments in South America show that rupture occurred on a horizontal plane and extended at least 30 by 50 kilometers. Rupture proceeded at 1 to 3 kilometers per second along the down-dip azimuth of the slab and penetrated through more than a third of the slab thickness. This extent is more than three times that expected for a metastable wedge of olivine at the core of the slab, and thus appears to be incompatible with an origin by transformational faulting. These large events may instead represent slip on preserved zones of weakness established in oceanic lithosphere at the Earth's surface.

Binge eating disorder, weight cycling, and psychopathology.

This study examined differences among a total of 70 obese binge eaters, nonbingers, and problem eaters in depression, cognitive function, weight- and eating-related disturbances, and weight cycling. Subjects diagnosed with binge eating disorder (BED) scored significantly higher on depression and on several measures of cognitive dysfunction than did subjects in the other two groups. In addition, they reported significantly greater preoccupation with thinness and feelings of ineffectiveness, as well as a greater likelihood of eating in response to negative emotions. No relationship, however, was found between binge eating and weight cycling. Comparison of subjects identified as low- and high-weight cyclers revealed no significant differences between these two groups on depression, cognitive dysfunction, or the majority of the other measures of weight- and eating-related disturbance. The findings are discussed in terms of the implications for treating persons with BED and/or a history of weight cycling.

1.06-microm laser damage of thin film optical coatings: a round-robin experiment involving various pulse lengths and beam diameters.

A number of commercially available optical coatings, both antireflective and high reflective, have been tested for their laser-induced damage threshold, involving a total of eight different laboratories. The results obtained and the experimental methods used at these laboratories were discussed among the participants in this round robin at a minisymposium held at Balzers, Liechtenstein, 9-10 Dec. 1982. A final report of the round robin and a summary of the conclusions drawn at that symposium are presented.