Device-based change in left ventricular shape: a new concept for the treatment of dilated cardiomyopathy.

OBJECTIVE: We tested a unique new device, the Myosplint device (Myocor, Inc, Maple Grove, Minn), which is designed to change left ventricular shape, reduce left ventricular wall stress, and improve left ventricular systolic function. METHODS: Heart failure was induced in 15 dogs over 27 days by rapid pacing (230 beats/min). Seven animals underwent sham surgery, and 8 animals received 3 transventricular Myosplint devices each. Myosplint devices were tightened to create a symmetric bilobular left ventricular shape and were adjusted to produce a calculated 20% reduction in wall stress. Hemodynamic, 2-dimensional, and 3-dimensional echocardiographic studies were recorded at baseline, immediately after Myosplint placement (acute change), and at 1 month after both groups had a reduced rate (190 beats/min) of pacing designed to maintain heart failure. RESULTS: The Myosplint group had significant sustained improvements in left ventricular ejection fraction from baseline, to the acute change, to 1 month (19% +/- 5%; 36% +/- 8%; 39% +/- 13%) and reductions of left ventricular end-systolic volumes (73 +/- 9 mL; 34 +/- 5 mL; 42 +/- 12 mL) and end-systolic wall stress by 39% (341 +/- 68 10(3) dynes x cm(- 2) to 206 +/- 28 10(3) dynes x cm(-2)) acutely and 31% (372 +/- 83 10(3) dynes x cm(-2) to 250 +/- 40 10(3) dynes x cm(-2)) at 1 month. There were no significant changes in mitral regurgitation. CONCLUSION: Application of a Myosplint device to a dilated impaired left ventricle resulted in reduced wall stress and improved left ventricular systolic function that was sustained at 1 month. Device-based shape change is a promising new opportunity to treat patients with dilated cardiomyopathy.

In vivo efficacy of silver-coated (Silzone) infection-resistant polyester fabric against a biofilm-producing bacteria, Staphylococcus epidermidis.

BACKGROUND AND AIMS OF THE STUDY: Prosthetic valve endocarditis (PVE) is an infrequent but serious complication of cardiac valve replacement. PVE is a foreign body infection predominantly based in the sewing cuff of a prosthetic heart valve leading to thromboembolism, ring abscess, paravalvular leakage, and eventual invasion of the myocardium. Mortality rates as high as 75% have been reported. A silver-coated sewing cuff is now available (St. Jude Medical mechanical heart valve SJMR Masters Series with Silzone coating) intended to inhibit the colonization and attachment to the sewing cuff of those microorganisms commonly associated with PVE. Silzone is a dense layer of metallic silver deposited on individual fiber surfaces of the valve cuff. Previously, Silzone coating was shown in vitro to decrease attachment and colonization of microorganisms with no adverse affect on biocompatibility. The present study was designed to assess the efficacy of Silzone-coated polyester fabric in vivo in a direct-contamination model. The organism chosen was a pathogenic strain of Staphylococcus epidermidis capable of producing biofilm. METHODS: Infection resistance of uncoated polyester and Silzone-coated polyester fabric was assessed by the acute inflammatory response in a guinea pig subdermal model. Fabric samples were implanted sterile or inoculated with S. epidermidis. The ability of the strain to produce biofilm was verified in vitro. Samples were explanted at one and two days postoperatively. Verification of the infecting bacteria was by colony morphology and Gram-staining properties of bacteria from the explanted samples. Inflammation was assessed histopathologically. Percent necrotic tissue within the fabric was determined by computer-assisted image analysis. RESULTS: Histopathology and image analysis of necrotic tissue showed significantly less inflammation within the Silzone-coated fabric than within uncoated polyester fabric. CONCLUSIONS: The Silzone coating reduced inflammation in this direct-contamination model using a strain of S. epidermidis that is capable of producing biofilm. This indicates a concentration of silver ions sufficient for bacteriostatic or bactericidal activity within the fabric in vivo.

Evaluation of a novel bioprosthetic heart valve incorporating anticalcification and antimicrobial technology in a sheep model.

BACKGROUND AND AIM OF THE STUDY: The St. Jude Medical (SJM) Epic valve has been designed to diminish the risk of prosthetic valve endocarditis by the use of silver-coated polyester fabric, and to inhibit dystrophic calcification by the use of ethanol pretreatment. METHODS: A 20-week juvenile sheep mitral valve implant model was used to determine safety and efficacy of the device, as well as the rate of silver release and degree of dystrophic calcification. The SJM Epic valves were compared with SJM Biocor porcine valves (not ethanol-pretreated, not silver-modified polyester fabric) and Baxter Carpentier-EdwardsR standard valves. RESULTS: Blood concentrations of silver reached a maximum of 40 p.p.b. within 10 days of SJM Epic valve implantation, and were well below toxic levels (300 p.p.b.). Blood silver concentrations returned to baseline within 30 days after surgery. Maximal silver accumulation occurred in the liver (16.75 mg/g dry weight); concentrations in the brain, spleen, kidney and lung were similar to those reported for other silver-modified prosthetic valves. No statistically significant difference was found in calcium content between SJM Epic and Biocor valves. The fibrous response to the sewing cuff was similar among the three valve types. CONCLUSIONS: At all times tested, silver release from the SJM Epic valve led to blood concentrations well below toxic levels. Although calcification in the two SJM valve groups was extremely low, the 20-week sheep model may be insufficiently sensitive to detect differences in calcium accumulation in modern bioprosthetic valves.