Not all biologics are equal!

BACKGROUND: Although the efficacy of various biologic meshes in the abdominal reconstruction of complex ventral hernia has been shown, the performance profile of various biologic mesh scaffolds in terms of hernia-specific outcomes such as recurrence, mesh explantation, and mesh infections has not been examined. AIM: To evaluate the clinical outcomes of patients who underwent complex ventral hernia repair with bioprosthetic material. METHODS: This study is a retrospective analysis of the use of bioprosthetic material in complex ventral hernia at an academic institution from January 2002 to December 2007. RESULTS: A total of 58 patients with a mean age of 57.2 years and mean body mass index (BMI) of 33.8 who underwent reconstruction of ventral abdominal defects with a bioprosthetic from January 2002 to February 2009 were included in the study. The study patients had about 4.8 previous surgeries and 43.1% of patients had reconstruction in a setting of enterocutaneous fistula, while 46.6% had a previous mesh infection. Complex ventral hernia was seen in 50 patients, while eight patients had ventral and parastomal hernia. The type of biologic used for reconstruction was human-derived (AlloDerm, 29), porcine cross-linked (CollaMend, 3; Permacol, 2), and non-cross-linked porcine (Surgisis, 16; Strattice, 8). At least one complication was seen in 72.4% of patients. Major complications noted were surgical wound infections (19.0%), seroma (8.6%), and abscess formation (5.2%). The one-year hernia recurrence rate was 27.9% and mesh explantation was needed in 17.2% of patients. AlloDerm was less likely to be explanted (13.8%) or become infected (37.9%) but more likely to recur (28.6%) compared to porcine cross-linked bioprosthesis. Porcine cross-linked biologics were more likely to become infected (60%) and explanted (40%) but less likely to recur (20%) compared to AlloDerm. Non-cross-linked porcine biologics were less likely to be explanted (16.7%) but had higher recurrence (29.4%) compared to cross-linked porcine biologics and a higher infection rate (54.2%) compared to AlloDerm. CONCLUSIONS: The results from this study underscore the difficulty of repairing complex abdominal wall defects in contaminated fields. Cross-linked porcine biologics showed relatively higher infection and explantation rates. Equivalent recurrence and explantation rates were observed for the non-cross-linked porcine biologics and AlloDerm. These data indicate that there is currently no ideal biologic for complex ventral hernia repair.

Mechanical heart valve cavitation: valve specific parameters.

Several aspects of mechanical heart valve cavitation, in particular of "severe" vapor cavitation, have been investigated in order to describe the phenomenon of cavitation itself and to classify various mechanical heart valves with respect to their tendency to cavitation. Furthermore, following the results of the measurements, a model for determination of time-dependent physical properties and dynamics of cavitation bubbles, such as size, pressure and temperature was developed. In order to classify the cavitation tendency of mechanical valves, a pulsatile hydraulic-driven circularly mock loop was used. Besides measurements of the relevant hemodynamic parameters, the leaflet velocities of the valves were also determined. In addition, numerous high-resolution pressure measurements, in particular the pressure drops necessary for the initiation of cavitation (local atrial pressure drop), were performed. For the investigation of bubble dynamics, a second pulsatile electro-magnetically-driven tester was used. The influence of density, viscosity and temperature of the fluid on the onset of cavitation was investigated. Cavitation events were recorded with a digital high-speed video camera (up to 40,500 frames/sec) for all investigated heart valves and under different conditions. A critical local upstream pressure drop (located within the model atrium after valve closure) of 450 mmHg was found for all valves as well as a valve specific correlation between left ventricular pressure gradient and local upstream pressure drop. Also, a valve dependent correlation between left ventricular pressure gradient and the local upstream pressure drop was provided. Finally, valve specific parameters were found to predict the cavitation tendency for a specific heart valve. The implementation of a suitable theoretical model allowed conclusions on bubble physics. High pressures (up to 800 bar) and temperatures (up to 1,300 degrees C) at bubble collapse have been determined. The influence of fluid parameters such as density, viscosity and temperature on the onset of cavitation is negligible within physiological range. Critical regions for cavitation for all mechanical heart valves were detected. All mechanical heart valves investigated show cavitation under different conditions (dp/dt) associated with high pressures and temperatures at bubble collapse. Cavitation bubble occurrence depends on valve design and location.