Is there a possibility for a glutaraldehyde-free porcine heart valve to grow?

OBJECTIVE: A challenging issue is to create a heart valve with growth and remodeling potential, which would be of great interest for congenital heart valve surgery. This study was performed to evaluate the growth and remodeling potentials of a decellularized heart valve. METHODS: In 4 juvenile sheep (age 12 +/- 1 weeks) with a weight of 24.3 +/- 4.4 kg, a 17-mm diameter decellularized porcine valve was implanted as pulmonary valve replacement. Valve growth was evaluated by transthoracic echocardiography. At explantation, valves were evaluated by gross examination, light microscopy (hematoxylin and eosin, von Kossa, Sirius red, Weigert and Gomori staining), electron microscopy and immunohistochemistry. Atomic absorption spectrometry was performed to evaluate calcium content. RESULTS: All animals showed fast recovery. The mean follow-up was 9.0 +/- 1.8 months. All sheep at least doubled their weight (54.3 +/- 9.2 kg). Echocardiography showed no regurgitation and a flow velocity of 0.7 +/- 0.1 m/s at the latest follow-up. The valve diameter increased from 17.6 +/- 0.5 to 27.5 +/- 2.1 mm (p < 0.018). Gross examination showed a similar wall thickness of the implanted valve and native pulmonary wall, with smooth and pliable leaflets. Histology showed a monolayer of endothelial cells, fibroblast ingrowth and production of new collagen. No calcification was seen at von Kossa staining, confirmed by low calcium content levels of the valve wall and leaflets at atomic absorption spectrometry. CONCLUSIONS: This glutaraldehyde-free heart valve showed not only the absence of calcification, but also remodeling and growth potential.

Influence of transmyocardial laser revascularization (TMLR) on regional cardiac function and metabolism in an isolated hemoperfused working pig heart.

The mechanism of an indirect revascularization in ischemic myocardium by transmyocardial laser revascularization (TMLR) is not yet fully understood. An improvement of clinical symptoms caused by TMLR is reported in many clinical trials with patients in which a direct revascularization is not possible. An increase of myocardial perfusion through laser channels is doubtful, because the myocardial pressure in the wall is higher than in the cavum. Therefore we measured the local cardiac function (intramyocardial pressure, wall thickness, pressure-length curves) and acute metabolic changes (tissue lactate content, tissue pO2) in ischemic and nonischemic regions before and after TMLR in isolated hemoperfused pig hearts. An isolated heart was chosen because it enabled us to separate coronary flow from flow through ventricular channels. The ischemia was induced by coronary occlusion or microembolization (eight hearts each). It should be noted that microembolization leads to conditions which are more comparable with those found in patients selected for TMLR. In the isolated working heart, the coronary perfusion can be controlled independently from perfusion through the ventricular cavum. Under the ischemic conditions mentioned above, we observed that the intramyocardial pressure in the ischemic region decreased below the left ventricular pressure, so one premise for indirect perfusion was met. TMLR after microembolization led to a significant improvement of regional cardiac work and the tissue oxygen pressure. These acute effects demonstrate the possibility of functional and metabolic amelioration by TMLR after ischemia induced by microembolization in an isolated hemoperfused pig heart.

Isolated hemoperfused heart model of slaughterhouse pigs.

A model of hemoperfused slaughterhouse pighearts is described providing a wide range of applications which leads to a reduction in animal experiments. The size of a pigheart, heart rate, coronary perfusion, metabolism, etc. are more comparable to conditions in patients than those in hearts of small laboratory animals. Global heart function can be assessed either by measuring stroke volume, ejection fraction, Emax etc. in the working model or by measuring intraventricular pressure with balloon catheters in the isovolumetric model. Regional cardiac function can be measured by sonomicrometry and ischemic and non-ischemic areas can be compared. Local metabolic changes are measurable as well with microdialysis. Cardiac function can be kept on any given functional level by infusion of norepinephrine in spite of the fact that functional parameters are lower without adrenergic drive in vitro than in vivo. Stable heart function can be maintained for several hours with only 500 to 1000 ml of blood because the blood is permanently regenerated by a special dialysis system. This model can be applied in many research projects dealing with reperfusion injuries, inotropic, antiarrhythmic or arrhythmogenic effects of certain drugs, immunological rejection, evaluation of imaging systems (NMR, echocardiography etc.) or cardiac assist devices.

Centrifugal pumps as left ventricular assist for coronary revascularization on a beating heart.

During recent years, coronary bypass surgery has progressed toward minimizing invasiveness. One important feature of this approach is performing surgery on a beating heart. During the crucial phase of such surgery, the mechanical support of the heart with a left ventricular assist device (LVAD) is a possible option. During the period from October 1, 1994 until June 30, 1997, we employed a centrifugal pump system in 118 cases of coronary artery bypass graft (CABG) procedures with LVAD support (mechanically supported CABG [SUPPCAB]). A total of 179 distal anastomoses with an average of 1.5 +/- 0.5 coronary anastomoses per patient was performed. Three types of pumps were used: 23 BioPump, 87 Isoflow, and 8 Capiox systems. The median time on mechanical support was 44 min (range, 16-116 min). The mean flow rate during support time was 3.5 +/- 0.8 L/min, which results in a calculated flow of 1.7 +/- 0.6 L/min/m2 body surface area (BSA). The average flow was 3.2 +/- 0.8 L/min with the BioPump and 3.7 +/- 0.8 L/min with the Isoflow pump, respectively (p < 0.01). The mean arterial pressure during mechanical support was 75 +/- 12 mm Hg. In 2 patients, the pump system was kept running postoperatively in the ICU. Eight of the patients received operations under resuscitation or in cardiogenic shock. Nine (7.9%) of the patients did not survive the early postoperative phase. For coronary revascularization of the anterolateral and diaphragmatic parts of the heart, the SUPPCAB procedure is feasible with excellent mechanical support of the heart by centrifugal pumps. Especially in high risk cases, this procedure can be recommended.