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New Findings: What is the central question of this study? Can the triangular appearance of ventricular action potential, indicating proarrhythmic profile of antiarrhythmic agent, be approximated by specific changes on an electrocardiogram (ECG)? What are the main finding and its importance? The triangulation of the ventricular action potential seen when antiarrhythmic drugs induce a greater lengthening of the late repolarization compared to the initial repolarization in epicardium is closely approximated by a greater prolongation of the T wave upslope relative to the interval between the J point and the start of the T wave (the JT start interval) on the ECG. These findings may improve the power of ECG assessments in predicting the drug-induced arrhythmia resulting from slowed phase 3 repolarization., Abstract: Antiarrhythmic drugs prescribed to treat atrial fibrillation can occasionally precipitate ventricular tachyarrhythmia through a prominent slowing of the phase 3 repolarization. The latter results in the triangular shape of ventricular action potential, indicating high arrhythmic risk. However, clinically, the utility of triangulation assessments for predicting arrhythmia is limited owing to the invasive nature of the ventricular action potential recordings. This study examined whether the triangulation effect can be detected indirectly from electrocardiogram (ECG) analysis. Epicardial monophasic action potentials and the ECG were simultaneously recorded in perfused guinea-pig hearts. With antiarrhythmics (dofetilide, quinidine, procainamide and flecainide), a prolongation of the initial repolarization seen in the action potential recordings was closely approximated by lengthening of the interval between the J point and the start of the T wave (the JT start interval) on the ECG, whereas a prolongation of the late repolarization was paralleled by widening of the T wave upslope. Dofetilide, quinidine and procainamide induced a prominent slowing of the phase 3 repolarization in epicardium, leading to triangulation of the action potential. These effects were accompanied by a greater prolongation of the T wave upslope compared to the JT start interval. Flecainide elicited a proportional prolongation of the initial and the late ventricular repolarization, and therefore failed to induce triangulation, based on analysis of both epicardial action potential and ECG profiles. Collectively, these findings suggest that the ratio between the durations of the T wave upslope and the JT start interval may represent the ECG metric of the ventricular action potential triangulation induced by antiarrhythmic drugs., (© 2022 The Authors. Experimental Physiology © 2022 The Physiological Society.)

The objective of this study was to evaluate the effect of chemical treatment with glutamic acid to avoid calcification of biological cardiac valves. The bovine pericardium (BP) tissues were fixed with 0.5% glutaraldehyde (BP/GA), followed by treatment with glutamic acid (BP/GA + Glu) for neutralization of the free aldehyde groups. Microscopic analysis showed that the wavy structure of collagen fibrils was preserved, but changes in elastin's integrity occurred. However, the treatment did not promote undesirable changes in the thermal and mechanical properties of the modified BPs. These samples were systematically studied in rat subcutaneous tissue: control (BP/GA) and anticalcificant (BP/GA + Glu). After 60 days, both groups induced similar inflammatory reactions. In terms of calcification, BP/GA + Glu remained more stable with a lower index (3.1 ± 0.2 μg Ca 2+ /mg dry tissue), whereas for BP/GA it was 5.7 ± 1.3 μg Ca 2+ /mg dry tissue. Bioprostheses made from BP/GA + Glu were implanted in the pulmonary position in sheep, and in vivo echocardiographic analyses revealed maintenance of valvar function after 180 days, with low gradients and minimal valve insufficiency. The explanted tissues of the BP/GA + Glu group had a lower average calcium content 3.8 ± 3.0 μg Ca 2+ /mg dry tissue. The results indicated high anticalcification efficiency of BP/GA + Glu in both subcutaneous implant in rats and in the experimental sheep model, which is an advantage that should encourage the industrial application of these materials for the manufacture of bioprostheses., (© 2020 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.)

Background High epicardial adipose tissue (EAT) attenuation (Hounsfield units [ HUs] ) on computed tomography is considered a marker of inflammation and is associated with an increased risk of cardiovascular events. Statins reduce the volume of EAT , but it is unknown whether they affect EAT HUs . Methods and Results We reviewed the chest computed tomographic scans of 420 postmenopausal women randomized to either 80 mg of atorvastatin or 40 mg of pravastatin daily and rescanned after 1 year to measure change in coronary artery calcium score. EAT HUs were measured near the proximal right coronary artery and remote from any area of coronary artery calcium. Computed tomographic images were also queried for subcutaneous adipose tissue (SubQ) attenuation ( HUs ) change over time. The mean patients' age was 65±6 years. The baseline EAT HU value was higher than the SubQ HU value (-89.4±24.0 HU versus -123.3±30.4 HU ; P<0.001). The EAT HU value decreased significantly in the entire cohort (-5.4±29.7 HU [-6% change]; P<0.001), but equally in the patients given atorvastatin and pravastatin (-6.35+31 HU and -4.55+28 HU ; P=0.55). EAT HU change was not associated with change in total cholesterol, low-density lipoprotein cholesterol, coronary artery calcium, and EAT volume (all P=not significant). Change in high-density lipoprotein cholesterol was marginally associated with EAT HU change ( P=0.07). Statin treatment did not induce a change in SubQ HUs . Conclusions Statins induced a decrease in EAT HUs over time, independent of intensity of low-density lipoprotein cholesterol lowering. The positive effect on EAT and the neutral effect on SubQ suggest that statins induced a decrease in metabolic activity in EAT by reduction in cellularity, vascularity, or inflammation. The clinical significance of the observed change in EAT HUs remains to be demonstrated.

Background Whether chronic obstructive sleep apnea ( OSA ) could promote epicardial adipose tissue ( EAT ) secretion of profibrotic adipokines, and thereby contribute to atrial fibrosis, and the potential therapeutic effects of metoprolol remain unknown. Methods and Results A chronic OSA canine model was established by repeatedly clamping the endotracheal tube for and then reopening it for 4 hours every other day for 12 weeks. In a metoprolol treatment group, metoprolol succinate was administered daily for 12 weeks. The EAT infiltration and left atrial fibrosis were examined. The expressions of adipokines secreted by EAT and hypoxic 3T3-L1 adipocytes were detected. The changes in collagen synthesis, transforming growth factor-β1 expression, and cell differentiation and proliferation in cardiac fibroblasts induced by hypoxic 3T3-L1 adipocyte-derived conditioned medium were further analyzed. Chronic OSA induced infiltration of EAT into the left atrium. OSA enhanced the profibrotic effect of EAT on the adjacent atrial myocardium. Moreover, OSA induced profibrotic cytokine secretion from EAT . We also found that hypoxia induced adipokine secretion in cultured adipocytes, and the medium conditioned by the hypoxic adipocytes increased collagen and transforming growth factor-β1 protein expression and cell proliferation of cardiac fibroblasts. More importantly, metoprolol attenuated infiltration of EAT and alleviated the profibrotic effect of EAT by inhibiting adipokine secretion. Metoprolol also inhibited hypoxia-induced adipokine secretion in adipocytes and thereby blocked the hypoxic adipocyte-derived conditioned medium-induced fibrotic response of cardiac fibroblasts. Conclusions Chronic OSA enhanced the profibrotic effect of EAT on the neighboring atrial myocardium by stimulating the secretion of profibrotic adipokines from EAT , which was significantly attenuated by metoprolol. This study gives insights into mechanisms underlying OSA -induced atrial fibrillation and also provides experimental evidence for the protective effects of metoprolol.

An experiment was designed to find the suitable acellular bovine pericardium (ABP) patch in pericardial cavity reconstruction and to evaluate the effect of sodium hyaluronic acid (NaHA) on inflammatory reaction in prevention of pericardial adhesions. The pericardial adhesion model was established in 20 rabbits, weighing from 3.2 to 3.6 kg. Groups were classified as follows: Group A (n = 5), the control group, the pericardium was directly closed; Group B (n = 5), 0.15% glutaraldehyde-treated ABP (low cross-link degree); Group C, 0.3% glutaraldehyde-treated ABP (middle cross-link degree); Group D, 0.15% glutaraldehyde-treated ABP + NaHA solution. Blood samples were collected at 6 h, 24 h, 3 days, and 5 days, to assay postoperative inflammatory reaction. The tenacity and severity of adhesions were evaluated 2 months after operation, by macroscopic and microscopic examinations, and Q-PCR (real-time quantitative polymerase chain reaction) test was used to quantitatively analyze the associated genes with adhesion. Pericardium regeneration was demonstrated by immunohistochemical technique to identify mesothelial cells. In Group D, the serum concentration of tumor necrosis factor-α (TNF-α) was significantly lower in the early postoperative period, and the mean adhesion score (adhesion between the epicardium and ABP) was significantly lower compared with the control group (Groups D vs. A: 0.20 ± 0.45 vs. 2.00 ± 0.71, P = 0.009*). The signs of degradation of the ABPs were observed 2 months postoperation in Groups D and B. Immunohistochemically, the positive cytokeratin AE1 staining results demonstrated the relatively total regeneration of the pericardium in Group D. Signs of regeneration were observed in Group D. Compared with the control group, the level of TGF-β2 in Group D was significantly lower (0.00132 ± 0.00114, P = 0.022*). The TGF-β3 level was statistically significant, being highest in Group D (0.00805 ± 0.00136, P = 0.029*). The mean quantity of Smad6 in Group D was also lower than the other groups. Low cross-link degree ABP may be an efficient physical block between the epicardium and the sternum and also an ideal scaffold for pericardial tissue regeneration, whereas combined use with NaHA may significantly reduce postoperative pericardial adhesions. The signal transduction pathway of transforming growth factor-β (TGF-β) and Smad6 may play a key role in the formation of pericardial adhesion., (© 2013 Wiley Periodicals, Inc. and International Center for Artificial Organs and Transplantation.)

Isoproterenol in high doses induces infarction-like myocardial damage and structural and functional remodelling of the ventricular myocardium. The purpose of the present study was to investigate ventricular repolarization in a rat model of isoproterenol-induced heart failure. Isoproterenol was administered twice to female Wistar rats (170 mg/kg, s.c., 24 h apart). Four weeks after the injections, cardiac output was measured and unipolar epicardial ventricular electrograms were recorded in situ. Activation-recovery intervals were calculated to assess repolarization. Histological examination of the heart ventricles was also performed. Heart failure in rats treated with isoproterenol was indicated by myocardial histopathological damage and reduced cardiac output. In rats with heart failure, the regional differences in activation-recovery interval prolongation over the ventricular epicardium resulted in increasing heterogeneity in the activation-recovery interval distribution and increasing repolarization heterogeneity of the ventricular subepicardium. Myocardial damage and haemodynamic changes in heart failure induced by isoproterenol were accompanied by significant changes in ventricular repolarization, which were not associated with myocardial hypertrophy., (© 2013 Wiley Publishing Asia Pty Ltd.)

The mechanical behavior of calf pericardium, a biomaterial utilized in the manufacture of cardiac bioprostheses, in response to a short tensile cyclic test has been evaluated. The trial involved 120 samples cut longitudinally or transversely, subjected to 10 cycles until a stress of between 1 and 3 MPa was reached. Tests of hardness and tear propagation were performed, and the results were compared with a control series. The energy loss was also computed, and it was approximately 10-fold greater in the first cycle than the loss in the subsequent nine cycles. Despite this singularity, they correlated very precisely. The effect of the direction in which the tissue is cut on energy loss was not significant nor the difference between hardness prior to and after testing. The results of the tear propagation tests gave no statistical differences prior to and after testing. From the obtained results, it seems that the test carried out does not affect significantly the mechanical properties of calf pericardium., (© 2012, Copyright the Authors. Artificial Organs © 2012, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.)

Major problems with biological heart valves post-implantation are associated with progressive structural deterioration and calcification attributed to glutaraldehyde processing, dead cells, and cell fragments present in the native tissue. In spite of these problems, glutaraldehyde still is the reagent of choice. The results with acellular matrix xenograft usually prepared by detergent treatment in association with enzymes are rather conflicting because while preserving mechanical properties, tissue morphology and collagen structure are process dependent. This work describes a chemical approach for the preparation of an acellular bovine pericardium matrix intended for the manufacture of heart valve bioprostheses. Cell removal was performed by an alkaline extraction in the presence of calcium salts for periods ranging from 6 to 48 h. The results showed that cell removal was achieved after 12 h, with swelling and negative charge increasing with processing time. Nevertheless, collagen fibril structure, ability to form fibrils, and stability to collagenase were progressive after 24-h processing. There was no denaturation of the collagen matrix. A process is described for the preparation of acellular bovine pericardium matrices with preserved fibril structure and morphology for the manufacture of cardiac valve bioprostheses and may be used in other applications for tissue reconstruction., (© 2011, Copyright the Authors. Artificial Organs © 2011, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.)

Calcification is one of the major causes of failure of heart valve bioprostheses (HVBs) derived from glutaraldehyde (GA)-processed bovine pericardium (BP) or porcine aortic valves. New crosslinking reagent procedures are still far from giving satisfactory results, and this is the main reason why GA is still the reagent of choice for the fixation of native tissue intended for HVB manufacture. Nevertheless, two new findings with respect to GA processing may significantly improve HVB performance postimplantation: the finding that increasing concentrations of GA result in a decrease in calcification; the blocking of free aldehyde usually by nucleophyles or the treatment of processed material at low pH. This work investigates the in vitro properties of BP fixed with GA followed by the treatment with glutamic acid under alkaline conditions in order to prepare BP materials with lower calcification potential postimplantation. In comparison to conventional processing, except for the tensile strength that was slightly lower, elongation and toughness were higher than the accepted values. No significant differences were observed in the performance indexes (mean pressure gradient, mean effective area, regurgitant fraction, performance and efficiency indexes) with wear resistance over 150 × 10⁶ cycles. These results indicate that the processing of BP described in this work may be of potential use in the manufacture of HVBs., (© 2011, Copyright Braile Biomedica Ltda. Artificial Organs © 2011, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.)

Grafts of biological tissues have been used since the 1960s as an alternative to the mechanical heart prostheses. Nowadays, the most consolidated treatment to bovine pericardial (BP) bioprostheses is the crosslinking with glutaraldehyde (GA), although GA may induce calcification in vivo. In previous work, our group demonstrated that electron beam irradiation applied to lyophilized BP in the absence of oxygen promoted crosslinks among collagen fibers of BP tissue. In this work, the incorporation of silk fibroin (SF) and chitosan (CHIT) in the BP not treated with GA was studied. The samples were irradiated and then analyzed for their cytotoxicity and the ability of adhesion and growth of endothelial cells. Initially, all samples showed cytotoxicity. However, after a few washing cycles, the cytotoxicity due to acetic acid and ethanol residues was removed from the biomaterial making it suitable for the biofunctional test. The samples modified with SF/CHIT and electron beam irradiated favored the adhesion and growth of endothelial cells throughout the tissue., (© 2011, Copyright the Authors. Artificial Organs © 2011, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.)

1. Flecainide and quinidine exert contrasting pro-arrhythmic and anti-arrhythmic effects in mouse hearts containing the loss-of-function, Scn5a(+/-), and the gain-of-function, Scn5a(+/DeltaKPQ), mutations in their sodium channel alpha-subunits. 2. The following properties were accordingly compared in wild-type and Scn3b(-/-) hearts modelling modifications in the beta-subunit, before and after introduction of either agent: (i) ventricular arrhythmogenecity and effective refractory periods (VERP) in response to programmed electrical stimulation (PES); (ii) monophasic action potential waveforms recorded from the left ventricular epicardium and endocardium; (iii) action potential durations (APD) obtained from the monophasic action potentials; and (iv) critical intervals derived from the APD and VERP values. 3. Ventricular tachycardia was induced by PES in 11 out of 15 Scn3b(-/-) hearts and 0 out of 17 wild-type hearts. This incidence was reduced to three out of eight Scn3b(-/-) hearts but increased to three out of eight wild-type hearts with flecainide. 4. Arrhythmogenic incidence was reduced to two out of eight Scn3b(-/-) hearts and remained at 0 out of eight wild-type hearts in the presence of quinidine. 5. Ventricular effective refractory periods were prolonged and endocardial and epicardial APD shortened, resulting in negative critical intervals in both Scn3b(-/-) and wild-type hearts treated by either flecainide or quinidine. Nevertheless, endocardial APD remained consistently longer than epicardial APD, leaving similar, positive endocardial-epicardial, differences, DeltaAPD, in treated and untreated Scn3b(-/-) and wild-type hearts. 6. It is concluded that both flecainide and quinidine exert anti-arrhythmogenic effects in Scn3b(-/-) hearts, doing so through modifying VERP rather than DeltaAPD, in contrast to their differing effects in Scn5a(+/-) and Scn5a(+/DeltaKPQ) hearts.

Objective: Chymase, a serine protease, is released from mast cells, which is closely associated with adhesion formation. Chymase activates transforming growth factor-beta1 (TGF-beta1), which promotes tissue fibrosis. Recently we have found that chymase may play an important role in adhesion formation in hamsters. Accordingly, this study was designed to confirm that a chymase inhibitor prevents postoperative cardiac adhesions in large animals., Methods: In 14 dogs, the epicardium was abraded 200 times with gauze and the mid-portion of the left anterior descending coronary artery (LAD) was exposed with No. 15 blade. Either chymase inhibitor (CI group, n = 7) or placebo (P group, n = 7) was sprayed into the pericardial cavity, then the pericardium was closed. Cardiac chymase activity, the level of TGF-beta1 in the pericardial fluid, the density of epicardial mast cells, the adhesion area between the heart and the pericardium, and the presence of adhesion between the mid-LAD and the pericardium were evaluated 1 and 2 months after surgery. Five nonsurgical dogs were used as a control for cardiac chymase activity., Results: Cardiac chymase activity and TGF-beta1 level were lower in CI group than in P group (53.7 +/- 35.0 vs. 93.4 +/- 20.4 microU/mg protein, p = 0.01, 3.2 +/- 0.9 vs. 4.3 +/- 1.1 microg/mL, p = 0.06, respectively). In CI group, the density of mast cells (19 +/- 5 vs. 32 +/- 8 cells/cm, p < 0.01), the adhesion area (2.2 +/- 0.8 vs. 7.5 +/- 1.5 cm2, p < 0.01), and adhesions between the heart and the mid-LAD (0% vs. 57%) were all reduced., Conclusion: Chymase inhibitor suppresses cardiac chymase activity and reduces the TGF-beta1 level, resulting in a reduction of cardiac adhesion in a large animal.

1. Pituitary adenylate cyclase-activating polypeptide (PACAP) induces atrial tachyarrhythmia (AT). However, the cellular mechanism responsible for this remains unclear. 2. In six canine isolated arterially perfused right atria, high-resolution optical mapping techniques were used to measure action potentials during control conditions and after PACAP injection (1 nmol). 3. During steady state pacing at a cycle length of 300 msec, the action potential duration was shorter during PACAP than during control (P < 0.001). In addition, maximum repolarization gradients during PACAP (4 +/- 1 msec/mm) were similar to those during control (5 +/- 1 msec/mm; n = 6). Transmural repolarization gradients were also similar between the two groups. 4. After PACAP, AT was easily initiated with a single premature extrastimulus and was associated with a focal pattern of activation. However, AT was not initiated by a single premature stimulus during control. 5. In conclusion, the PACAP-induced AT is associated with a focal pattern of activation that is independent of local repolarization gradients. These data suggest that increased dispersion of repolarization is not necessarily required for the induction of AT.

This work assesses the effect of lyophilization on the cytotoxicity and residual aldehyde concentration of glutaraldehyde-treated and lyophilized bovine pericardium (group A), comparing it to conventional glutaraldehyde-treated bovine pericardium (group B). Cytotoxicity was measured by incubating a pericardium sample from each group in saline and assessing the eluant's influence on cellular growth. Residual aldehydes were measured by HPLC. Although both groups' eluants exhibited some cytotoxicity, the eluant from group A was less cytotoxic, with a cytotoxicity index (IC50(%)) of 41%. Group B eluants all had marked cytotoxic effects; cell growth was 24.15% of the negative control at the most dilute eluant concentration (6.25%). The mean residual glutaraldehyde level was less in group A than in group B (2.36 +/- 0.11 and 9.90 +/- 3.70 g/l, respectively; n=3, P < 0.05), but residual formaldehyde levels did not differ. These results demonstrate that compared with conventional glutaraldehyde-treated bovine pericardium, lyophilized pericardium is less cytotoxic, with fewer glutaraldehyde residues.

Background: Halothane is known to potentiate catecholamine-induced depression of conduction velocity in Purkinje fibers but not endocardial muscle fibers. The purpose of this study was to examine the interactions of halothane with epinephrine and isoproterenol on canine epicardial conduction velocity at moderately elevated extracellular potassium concentration ([K]0)., Methods: Epicardial muscle strips (10x10x2 mm) were superfused with Tyrode's solution containing 4 or 8 mM [K]0 in the presence of 5 microM epinephrine or 1 microM isoproterenol with or without 0.8 mM halothane. Conduction velocity in the longitudinal and transverse directions relative to epicardial fiber orientation was recorded during alternate stimulation in each direction., Results: In the presence of halothane, a change from 4 to 8 mM [K]0 decreased (P< or =0.05) longitudinal and transverse conduction velocities by 26% and 21%, respectively. Isoproterenol alone at 4 and 8 mM [K]0 depressed (P<0.05) both longitudinal and transverse conduction velocities. However, the depression of longitudinal conduction velocity by isoproterenol at 4 mM [K]0 was attenuated by halothane. Epinephrine with or without halothane depressed (P<0.05) both longitudinal and transverse conduction velocities at 8 but not at 4 mM [K]0., Conclusion: The results do not support a synergistic interaction between halothane and epinephrine on myocardial conduction but do demonstrate depression of conduction by epinephrine at 8 mM [K+]0, a potassium ion concentration comparable to those reported following epinephrine infusions.

Cardiovascular calcification, the formation of calcium phosphate deposits in cardiovascular tissue, is a common endstage phenomenon affecting a wide variety of bioprostheses. The purpose of the present paper is to study the possibility that some antiplatelet drugs (aspirin and persantine) and certain vitamins (vitamin C, vitamin B6, and vitamin E) and their combinations might prevent the mineralization of glutaraldehyde treated bovine pericardium (GABP) by modifying the pericardial surface. In this experimental protocol, we used Golomb and Wagner's (1991) in vitro model for studying GABP calcification and a diffusion cell with 2 compartments for evaluating the diffusion of calcium across the GABP. The results showed that a combination of aspirin and vitamins (0.5 mg% aspirin, 1.5 mg% vitamin C, 4 mg% vitamin B6, and 2 mg% vitamin E) in a metastable calcium phosphate solution not only reduced the transport of calcium ions through GABP, but along with the combinations of 0.5 mg% aspirin and 5 mg% persantine also produced significant reductions in GABP calcification. The exact mechanism of these changes in the calcification of GABP are still unknown. From these in vitro findings, it appears that a combined vitamin therapy with low doses of aspirin may be beneficial for platelet suppression and thereby prevent thrombosis. In addition, the vitamins may modify calcium transport and interfere with the adsorption at the surface, thus reducing GABP calcification. However, an important question that remains unanswered is whether this inhibitory effect would continue if the antiplatelet drugs and vitamins were discontinued. For the answer, more in vivo studies are needed to develop applications.

Atrial connections in a single-unit total artificial heart (TAH) may be difficult to make because of the rigidity of the device and the fixed position of the atrial inlets. We developed a technique to separate the natural atrial borders in an experimental implantation of a unitary TAH. In this technique, the interatrial groove was dissected to separate the posterior wall of the right atrium from the roof of the left atrium before cardiopulmonary bypass (CPB) was initiated. After initiation of CPB and cardiectomy, the atrial septum was separated completely, and the right atrial wall was reconstructed with glutaraldehyde-treated autopericardium. We believe that this simple adjunctive technique provides increased mobility of the atrial cuffs and allows for an easier connection of the unitary TAH.

Treatment of glutaraldehyde-fixed pericardium with L-glutamic acid and storage in bacteriostatic preservatives (paraben) stably antagonizes free, reactive aldehyde groups within the fixed bioprosthetic heart valve tissue. In 63-day subcutaneous implants in rats, the calcification rate of this treatment (13.3 +/- 2 mg calcium/g wt tissue) was markedly reduced as compared to conventionally treated tissue (169 +/- 24 mg/g; p less than 0.05). To test the influence of tissue-released toxic aldehydes on spontaneous endothelial cell ingrowth in vivo, vascular grafts (8-cm long, 6-mm diameter) from fixed pericardium treated with L-glutamic acid were interposed into the carotid arteries in ten sheep. They were compared to grafts from conventionally treated pericardium implanted at the contralateral side. Following 3 months of implantation, planimetry revealed 49% +/- 20% of the surface of conventionally preserved pericardium to be covered with red thrombus, but only 12% +/- 5% in L-glutamic acid treated pericardium (p less than 0.05). The ultrastructural findings of a closed endothelial cell layer on the graft surface reveals the new technique to be a promising approach towards increased biocompatibility of aldehyde-fixed bioprosthetic heart valves.