Pharmacological Modulation of Right Ventricular Endocardial-Epicardial Gradients in Brugada Syndrome.

Background We explored the hypothesis that increased cholinergic tone exerts its proarrhythmic effects in Brugada syndrome (BrS) through increasing dispersion of transmural repolarization in patients with spontaneous and drug-induced BrS. Methods BrS and supraventricular tachycardia patients were studied after deploying an Ensite Array in the right ventricular outflow tract and a Cardima catheter in the great cardiac vein to record endo and epicardial signals, respectively. S1-S2 restitution curves from the right ventricular apex were conducted at baseline and after edrophonium challenge to promote increased cholinergic tone. The local unipolar electrograms were then analyzed to study transmural conduction and repolarization dynamics. Results The study included 8 BrS patients (5 men:3 women; mean age, 56 years) and 8 controls patients with supraventricular tachycardia (5 men:3 women; mean age, 48 years). Electrophysiological studies in controls demonstrated shorter endocardial than epicardial right ventricular activation times (mean difference: 26 ms; P<0.001). In contrast, patients with BrS showed longer endocardial than epicardial activation time (mean difference: -15 ms; P=0.001). BrS hearts, compared with controls, showed significantly larger transmural gradients in their activation recovery intervals (mean intervals, 20.5 versus 3.5 ms; P<0.01), with longer endocardial than epicardial activation recovery intervals. Edrophonium challenge increased such gradients in both controls (to a mean of 16 ms [ P<0.001]) and BrS (to 29.7 ms; P<0.001). However, these were attributable to epicardial and endocardial activation recovery interval prolongations in control and BrS hearts, respectively. Dynamic changes in repolarization gradients were also observed across the BrS right ventricular wall in BrS. Conclusions Differential contributions of conduction and repolarization were identified in BrS which critically modulated transmural dispersion of repolarization with significant cholinergic effects only identified in the patients with BrS. This has important implications for explaining the proarrhythmic effects of increased vagal tone in BrS, as well as evaluating autonomic modulation and epicardial ablation as therapeutic strategies.

Mouse Proepicardium Exhibits a Sprouting Response to Exogenous Proangiogenic Growth Factors in vitro.

Angiogenesis contributes to the generation of the vascular bed but also affects the progression of many diseases, such as tumor growth. Many details of the molecular pathways controlling angiogenesis are still undefined due to the lack of appropriate models. We propose the proepicardial explant as a suitable model for studying certain aspects of angiogenesis. The proepicardium (PE) is a transient embryonic structure that contains a population of undifferentiated endothelial cells (ECs) forming a vascular net continuous with the sinus venosus. In this paper, we show that PE explants give rise to CD31-positive vascular sprouts in the presence of basic fibroblast growth factor (bFGF) and 2 isoforms of vascular endothelial growth factor A (VEGF-A), i.e. VEGF-A120 and VEGF-A164. Vascular sprouts exhibit differences in number, length, thickness and the number of branches, depending on the combination of growth factors used. Moreover, the ECs of the sprouts express various levels of mRNA for Notch1 and its ligand Dll4. Additionally, stimulation with bFGF/VEGF-A164 upregulates the expression of Lyve-1 antigen in the ECs in the sprouts. In summary, we present a new model for angiogenesis studies involving mouse PE as a source of ECs. We believe that our model may act as a supplementary assay for angiogenesis studies along with the existing models.

A double-blind, placebo-controlled randomized trial to evaluate the efficacy of docosahexaenoic acid supplementation on hepatic fat and associated cardiovascular risk factors in overweight children with nonalcoholic fatty liver disease.

BACKGROUND AND AIMS: Very little information is available on whether docosahexaenoic acid (DHA) supplementation has a beneficial effect on liver fat and cardiovascular disease (CVD) risk factors in children with nonalcoholic fatty liver disease (NAFLD). In a double-blind, placebo-controlled randomized trial we investigated whether 6-month treatment with DHA improves hepatic fat and other fat depots, and their associated CVD risk factors in children with biopsy-proven NAFLD. METHODS AND RESULTS: Of 58 randomized children, 51 (25 DHA, 26 placebo) completed the study. The main outcome was the change in hepatic fat fraction as estimated by magnetic resonance imaging. Secondary outcomes were changes in visceral adipose tissue (VAT), epicardial adipose tissue (EAT), and left ventricular (LV) function, as well as alanine aminotransferase (ALT), triglycerides, body mass index-standard deviation score (BMI-SDS), and insulin sensitivity. At 6 months, the liver fat was reduced by 53.4% (95% CI, 33.4-73.4) in the DHA group, as compared with 22.6% (6.2-39.0) in the placebo group (P = 0.040 for the comparison between the two groups). Likewise, in the DHA group VAT and EAT were reduced by 7.8% (0-18.3) and 14.2% (0-28.2%), as compared with 2.2% (0-8.1) and 1.7% (0-6.8%) in the placebo group, respectively (P = 0.01 for both comparisons). There were no significant between-group changes for LV function as well as BMI-SDS and ALT, while fasting insulin and triglycerides significantly decreased in the DHA-treated children (P = 0.028 and P = 0.041, respectively). CONCLUSIONS: DHA supplementation decreases liver and visceral fat, and ameliorates metabolic abnormalities in children with NAFLD.

Effect of vitamin D deficiency and supplementation on myocardial deformation parameters and epicardial fat thickness in patients free of cardiovascular risk.

Vitamin D deficiency is associated with impaired myocardial deformation parameters and cardiovascular disease (CVD). Increased epicardial fat thickness (EFT) is also associated with increased risk of CVD. The aim of the study is to evaluate the effect of vitamin D deficiency and supplementation on myocardial deformation parameters and EFT. The study population consisted of 50 patients with vitamin D deficiency who were free of cardiovascular risk (mean age: 42.6 ± 8.9 years, 37 female). Patients were treated with oral administration of vitamin D3. Myocardial deformation parameters and EFT were evaluated before and after treatment of those patients. Vitamin D levels significantly increased after treatment (30.5 ± 10.5 vs. 9.9 ± 5.3 nmol/l, p < 0.001). There was no significant difference between conventional echocardiographic parameters before and after treatment. Baseline EFT was significantly higher than post-treatment measurements (35.2 ± 8.0 vs. 27.5 ± 5.6 mm, p < 0.001). Post-treatment myocardial deformation parameters were also significantly higher than baseline measurements. Baseline vitamin D levels correlated with baseline EFT and left ventricular global longitudinal strain (LV-GLS). Post-treatment vitamin D levels also correlated with post-treatment EFT, body mass index, and LV-GLS. Baseline vitamin D level was an independent predictor of baseline LV-GLS (p = 0.002). Patients with impaired LV-GLS had significantly lower vitamin D levels than patients with normal LV-GLS (6.6 ± 3.8 vs. 11.0 ± 5.3 nmol/l, p = 0.005). Baseline vitamin D level was also an independent predictor of baseline impaired LV-GLS (p = 0.010). Vitamin D supplementation has beneficial effects on myocardial deformation parameters and EFT. Moreover, baseline vitamin D levels are a predictor of impaired LV-GLS.

A case of advanced lung cancer with malignant pericardial effusion treated by intrapericardial Cinobufacini injection instillation.

Malignant pericardial effusion is one of the severe complications in advanced lung cancer patients, seriously affecting the patient's cardiopulmonary function and even life. Pericardial drainage and instillation of anti-neoplastic drugs in the pericardial cavity seems to offer the best chance of controlling pericardial effusion. We reported a case concerning treatment of a 63-year-old man in advanced lung cancer with a large amount of pericardial effusion. We utilized pericardium puncture and drainage combined with instillation of Cinobufacini injection in the pericardial cavity to treat pericardial effusion. After treatment with Cinobufacini injection for two weeks, the patient was followed up in one month to assess effectiveness, quality of life, and safety. We found that the cardiac tamponade symptoms such as difficult breathing, chest distress, and palpitations were significantly relieved. The patient's quality of life was effectively improved with KPS scores increased. We also found that the levels of tumor marker CA-125 in the pericardial effusion decreased (from 340.80 U/mL to 34.85 U/mL) and pericardium B ultrasound showed that the quantity of pericardial effusion reduced significantly (from 2.5 cm to 0.6 cm). Furthermore, there were little gastrointestinal adverse reactions and myelosuppression in the patient after instillation of the Cinobufacini injection. Taken together, this provides a new way for treating cancerous pericardial effusion, especially for patients who cannot tolerate instillation of chemotherapy drugs, and is worthwhile to carry out more standardized studies in the future.

Combined anticalcification treatment of bovine pericardium with decellularization and hyaluronic acid derivative.

The objective of this work was to evaluate the effect of decellularization and hyaluronic acid derivative on the improvement of anticalcification of glutaraldehyde fixed bovine pericardium (GFBP) using a rat subcutaneous implantation model A cell extraction process was employed to remove the cells and cellular components from bovine pericardium (BP), leaving a framework of largely insoluble collagen. Then acellular BP was cross-linked by glutaraldehyde solution and treated with hyaluronic acid derivative (HA-ADH) which was obtained by coupling adipic dihydrazide (ADH) on-COOH of hyaluronic acid (HA). The results of in vivo calcification tests showed that the calcium content was decreased dramatically by decellularization alone (from 28.07 ± 18.87 to 2.44 ± 0.55 µg Ca/mg dry tissue after 8 weeks' implantation), and even less concentration was shown by the combination of HA derivative treatment and decellularization (GFaBP-HA group) (0.25 ± 0.08 µg Ca/mg dry tissue after 8 weeks' implantation). In addition, GFaBP-HA group not only presented a lower degree of calcification, but also showed lower ratios of Ca/P molar, which corresponded to amorphous calcium phosphates. The obtained results indicated that GFaBP-HA was a potential candidate for the manufacture of anticalcification bioprostheses.

KN-93, A CaMKII inhibitor, suppresses ventricular arrhythmia induced by LQT2 without decreasing TDR.

Abnormal enhanced transmural dispersion of repolarization (TDR) plays an important role in the maintaining of the severe ventricular arrhythmias such as torsades de pointes (TDP) which can be induced in long-QT (LQT) syndrome. Taking advantage of an in vitro rabbit model of LQT2, we detected the effects of KN-93, a CaM-dependent kinase (CaMK) II inhibitor on repolarization heterogeneity of ventricular myocardium. Using the monophasic action potential recording technique, the action potentials of epicardium and endocardium were recorded in rabbit cardiac wedge infused with hypokalemic, hypomagnesaemic Tyrode's solution. At a basic length (BCL) of 2000 ms, LQT2 model was successfully mimicked with the perfusion of 0.5 µmol/L E-4031, QT intervals and the interval from the peak of T wave to the end of T wave (Tp-e) were prolonged, and Tp-e/QT increased. Besides, TDR was increased and the occurrence rate of arrhythmias like EAD, R-on-T extrasystole, and TDP increased under the above condition. Pretreatment with KN-93 (0.5 µmol/L) could inhibit EAD, R-on-T extrasystole, and TDP induced by E-4031 without affecting QT interval, Tp-e, and Tp-e/QT. This study demonstrated KN-93, a CaMKII inhibitor, can inhibit EADs which are the triggers of TDP, resulting in the suppression of TDP induced by LQT2 without affecting TDR.

Stability and mechanical evaluation of bovine pericardium cross-linked with polyurethane prepolymer in aqueous medium.

The present study investigates the potential use of non-catalyzed water-soluble blocked polyurethane prepolymer (PUP) as a bifunctional cross-linker for collagenous scaffolds. The effect of concentration (5, 10, 15 and 20%), time (4, 6, 12 and 24 h), medium volume (50, 100, 200 and 300%) and pH (7.4, 8.2, 9 and 10) over stability, microstructure and tensile mechanical behavior of acellular pericardial matrix was studied. The cross-linking index increased up to 81% while the denaturation temperature increased up to 12 °C after PUP crosslinking. PUP-treated scaffold resisted the collagenase degradation (0.167±0.14 mmol/g of liberated amine groups vs. 598±60 mmol/g for non-cross-linked matrix). The collagen fiber network was coated with PUP while viscoelastic properties were altered after cross-linking. The treatment of the pericardial scaffold with PUP allows (i) different densities of cross-linking depending of the process parameters and (ii) tensile properties similar to glutaraldehyde method.

Observation on effects of aconitine via acupoint injection in rabbits.

OBJECTIVE: To investigate the ability of the pericardium meridian (PM) to mitigate or enhance the cardiotoxic effects of aconitine injected at specific acupoint and non-acupoint sites in rabbits. METHODS: This study consisted of 3 experiments that were designed to test the effects of injection of 30 µg/kg of aconitine at acupoints on the PM (Test 1), at non-acupoint sites on the PM (Test 2), and at acupoints on other meridians and non-meridian sites (Test 3). In Test 1, 24 rabbits were randomly assigned to receive injections at Quze (PC3), Tianquan (PC2), or intramuscularly. In Test 2, 24 rabbits were randomly assigned to receive injections of aconitine at non-acupoint I, non-acupoint II, or intramuscularly. In Test 3, 48 rabbits were randomly assigned to receive injections at Neiguan (PC6), Sanyinjiao (SP6), Yangjiao (GB35), a non-meridian and non-acupoint site (NMNA), intravenously, and intramuscularly. Electrocardiographs of the rabbits were performed before, during and after injection to determine the incidence of arrhythmia, latency of ventricular rhythm, and recovery rate after aconitine injection. The recovery time index and extent of arrhythmia scores were calculated. RESULTS: In all groups the incidence of arrhythmia was 100%, and the latency of ventricular rhythm was less than 30 min. In Tests 1 and 2, the recovery rates of the Quze and non-acupoint II groups were significantly higher than those of the muscular group (P < 0.05). In Test 3, the recovery time index and extent of arrhythmia scores of the Neiguan group were low. There were no significant differences between the other acupoint groups, or the NMNA group, when compared with the group receiving aconitine intramuscularly. CONCLUSIONS: Acupoints or non-acupoints along the PM could reduce the severity of the arrhythmia induced by aconitine in healthy rabbits. Meridians play an important role in protecting body functions.

Mechanism for reduced pericardial adhesion formation in hypercholesterolemic swine supplemented with alcohol.

OBJECTIVE: Previous experiments in Yorkshire swine demonstrated significantly fewer pericardial adhesions and intramyocardial collagen deposition at reoperative sternotomy in animals supplemented with vodka but not with red wine. The purpose of this experiment was to determine a mechanism for adhesion reduction. METHODS: Twenty-seven male Yorkshire swine were fed a high-cholesterol diet to simulate conditions of coronary artery disease followed by the surgical placement of an ameroid constrictor to the left circumflex coronary artery to induce chronic ischaemia. Postoperatively, control pigs continued their high-fat/cholesterol diet alone, whereas the two experimental groups had diets supplemented with either red wine or vodka for 7 weeks followed by reoperative sternotomy and cardiac harvest. RESULTS: The expression of related adhesion focal tyrosine kinase (RAFTK) and caspase 3 in the sodium dodecyl sulphate (SDS)-soluble myocardial fraction was significantly higher only in the vodka-supplemented group. In the more soluble fraction, the expression of caspase 3, cleaved caspase 3 and caspase 9 was lower in both the vodka and red wine treatment groups. CONCLUSIONS: In the SDS-soluble lysate fraction, likely representing the transmembrane/cell-extracellular matrix (ECM), a significant increase in RAFTK and caspase 3 expression was seen only in the vodka-treated animals, which may explain why this group demonstrated significantly fewer pericardial adhesions. Caspase expression/signalling was not increased in the more soluble myocardial lysate, suggesting that the increased apoptotic signalling was specific to the epicardial-ECM.

Combined anti-calcification treatment of bovine pericardium with amino compounds and solvents.

The objective of this study was to evaluate the effect of treatment with amino compounds and solvents in vivo on calcifications of glutaraldehyde (GA)-fixed pericardium. Groups of bovine pericardium samples were fixed with 0.5% GA. We used urazole and glutamate to neutralize the free aldehyde and some solvents (ethanol with octanol or octanediol) to reduce the phospholipid content in the bovine pericardial tissue. Tensile strength and thermal stability were evaluated before implantation. Twelve weeks after rat subdermal implantation, the pericardial samples were harvested from eight juvenile rats. Urazole [calcium (Ca(2+)): 11.86 ± 2.85 µg/mg; inorganic phosphorus (IP): 32.59 ± 7.73 µg/mg] or glutamate (Ca(2+): 7.95 ± 1.21 µg/mg; IP: 21.76 ± 3.48 µg/mg) alone significantly decreased the Ca(2+) and IP concentrations (without any anti-calcification treatment, Ca(2+): 277.85 ± 17.51 µg/mg; IP: 147.07 ± 8.32 µg/mg), but when used with organic solvents, the Ca(2+) and IP concentrations were the lowest (Ca(2+): 0.05 ± 0.04 µg/mg; IP: 3.36 ± 0.61 µg/mg). After anti-calcification treatment, the calcifications in microscopic images were dramatically decreased. Anti-calcification treatment with glutamate, urazole, and solvents did not worsen the physical properties of bovine pericardium, and significantly prevented in vivo calcifications compared to GA fixation only. There should be additional studies done to understand the other mechanism underlying xenograft tissue calcification.

Phytate inhibits bovine pericardium calcification in vitro.

OBJECTIVE: The present study examined the inhibitory effects of pyrophosphate, etidronate, and phytate on bovine pericardium calcification in vitro. METHODS: Bovine pericardium was glutaraldehyde fixed and then placed in a flow chamber in the presence of a synthetic physiological fluid alone (control) or the fluid plus various concentrations of pyrophosphate, etidronate, or phytate. Following a 96-h incubation, fragments were removed and assayed for calcification by measuring calcium and phosphorus levels. RESULTS: The data indicated that both pyrophosphate and etidronate at 1 mg/l (5.75 and 4.95 microM, respectively) inhibited bovine pericardium calcification, whereas neither agent had an effect at 0.5 mg/l (2.87 and 2.47 microM, respectively). Phytate was the most potent inhibitor of calcification, and the effects of this agent were apparent at levels as low as 0.25 mg/l (0.39 microM). CONCLUSIONS: While pyrophosphate, etidronate, and phytate were all able to inhibit bovine pericardium calcification in vitro, phytate was found to be the most effective.

Effect of tetrahydrobiopterin on selective endothelial dysfunction of epicardial porcine coronary arteries induced by cardiopulmonary bypass.

BACKGROUND: We hypothesized that cardiopulmonary bypass induces a selective alteration of the coronary arterial endothelial cell signal transduction which could be explained by a state of depletion and/or decreased activity of endogenous tetrahydrobiopterin (BH(4)). The aim of this study was to assess the effects of cardiopulmonary bypass and BH(4) on the endothelial function of epicardial coronary arteries in a swine model of cardiopulmonary bypass. METHODS: Swine underwent 90 min of cardiopulmonary bypass alone (N=19) or in association with a brief cardioplegic arrest with (N = 6) or without (N = 5) in vivo BH(4) administration, followed by a 60-min period following weaning from cardiopulmonary bypass and were compared to a control group (N = 7). Endothelium-dependent relaxations of epicardial coronary artery rings were studied using standard organ chamber experiments in the presence or absence of in vitro BH(4) or superoxide dismutase (SOD) and catalase. RESULTS: Cardiopulmonary bypass caused a statistically significant reduction of endothelium-dependent relaxations to serotonin (p < 0.0001), bradykinin (p < 0.001), UK14304 (p < 0.0001) and calcium ionophore (p < 0.01) in epicardial porcine coronary arteries. In vitro and in vivo BH(4) supplementation improved endothelium-dependent relaxations to serotonin and bradykinin, which were left unchanged by SOD-catalase administration. Cardiopulmonary bypass was associated with a decrease in nitric oxide availability (p = 0.002) and increased oxidative stress (p < 0.001), which were both restored by in vivo BH(4) administration (p < 0.001). CONCLUSION: Treatment with BH(4) improves the endothelial dysfunction of porcine epicardial coronary arteries, restores nitric oxide availability and reduces the oxidative stress associated with cardiopulmonary bypass.

Toxicity studies of Calycopteris floribunda Lam. in calf, rabbit and rat.

The toxicological evaluation of the plant Calycopteris floribunda Lam. was done in calf, rabbit and rat. The phytochemical screening revealed the presence of flavonoids, alkaloids, tannins and saponins. Morbidity and mortality was observed in methanol extract-treated rats and rabbits. In rabbits (25 g/kg/day) and calves (35 g/kg/day) fed fresh leaves showed morbidity and mortality with premonitory clinical signs like depression, downer status, polyuria and characteristic forelimb paresis (seen only in rabbits). The serum urea, alanine-amino transferase, glucose and total cholesterol concentrations were significantly (P<0.05) increased compared to control values. Necropsy of calves revealed the congestion of liver, lung and petechiae on epicardium. The present study indicated the toxic nature of the plant in calf, rabbit and rat.

Two stage EDTA anti-calcification method for bioprosthetic heart valve materials.

BACKGROUND: The aim of this study was to investigate the effect of two-stage EDTA treatment in diminishing calcific degeneration in bovine pericardial bioprosthetic heart valve material. MATERIAL/METHODS: Conventionally preserved pericardium specimens were divided into two groups. Group I (controls, n=18) pieces were first fixed in phosphate-buffered solution (PBS)+0.6% glutaraldehyde at +4 degrees C for 24 hours, then stored in PBS+0.2% glutaraldehyde at room temperature for 6 days. Group II (study group, n=18) pieces were treated with PBS containing 100 microg/ml ethylenediaminetetraacetic acid (EDTA) at +4 degrees C for 24 hours, then fixed in PBS+0.6% glutaraldehyde as was group I at +4 degrees C for 24 hours. After a second exposure to PBS containing 100 microg/ml EDTA at room temperature for 24 hours, they were stored in PBS+0.2% glutaraldehyde at room temperature for 4 days. Pericardial patches were inserted into the dorsal pouches of 18 juvenile male Wistar rats. After 7 weeks of implantation, all the pericardium pieces were harvested from sacrificed rats. The calcium content and biomechanical properties of the explanted tissues were evaluated and also examined histopathologically. RESULTS: The difference in the calcium content of the control and study groups was statistically significant. Biomechanical and histopathologic assessment also supported these findings. CONCLUSIONS: Application of two-stage EDTA was found to be useful in the attenuation of calcification in bioprosthetic heart valve materials with mildly increased durability. As calcification was reduced by approximately 50%, it can be considered for use with other agents as an adjuvant treatment.

Hemoglobin-based oxygen carrier provides heterogeneous microvascular oxygenation in heart and gut after hemorrhage in pigs.

BACKGROUND: In this study, the hypothesis was tested that resuscitation with hemoglobin-based oxygen carriers (HBOCs) affects the oxygenation of the microcirculation differently between and within organs. To this end, we tested the influence of the volume of an HBOC on the microcirculatory oxygenation of the heart and the gut serosa and mucosa in a porcine model of hemorrhage. METHODS: In anesthetized open-chested pigs (n = 24), a controlled hemorrhage (30 mL/kg over 1 hour) was followed by resuscitation with 10, 20, or 30 mL/kg diaspirin-crosslinked hemoglobin (DCLHb) or isovolemic resuscitation with 30 mL/kg of a 6% hydroxyethyl starch solution (HAES). Measurements included systemic and regional hemodynamic and oxygenation parameters. Microvascular oxygen pressures (microPO2) of the epicardium and the serosa and mucosa of the ileum were measured simultaneously by the palladium-porphyrin phosphorescence technique. Measurements were obtained up to 120 minutes after resuscitation. RESULTS: After hemorrhage, a low volume of DCLHb restored both cardiac and intestinal microPO2. Resuscitation of gut microPO2 with a low volume of DCLHb was as effective as isovolemic resuscitation with HAES. Higher volumes of DCLHb did not restore cardiac microPO2, as did isovolemic resuscitation with HAES, but increased gut microPO2 to hyperoxic values, dose-dependently. Effects were similar for the serosal and mucosal microPo2. In contrast to a sustained hypertensive effect after resuscitation with DCLHb, effects of DCLHb on regional oxygenation and hemodynamics were transient. CONCLUSION: This study showed that a low volume of DCLHb was effective in resuscitation of the microcirculatory oxygenation of the heart and gut back to control levels. Increasing the volume of DCLHb did not cause an additional increase in heart microPO2, but caused hyperoxic microvascular values in the gut to be attained. It is concluded that microcirculatory monitoring in this way elucidates the regional behavior of oxygen transport to the tissue by HBOCs, whereas systemic variables were ineffective in describing their response.

Cellular mechanism of pituitary adenylate cyclase-activating polypeptide-induced atrial tachyarrhythmia in canine isolated arterially perfused right atria.

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.

Effects of treatment protocols and subcutaneous implantation on bovine pericardium: a Raman spectroscopy study.

Using Raman microspectroscopy, we have studied mineral deposition on bovine pericardia, fixed according to three different protocols and either implanted subcutaneously or not implanted (controls). A lightly carbonated apatitic phosphate mineral, similar to that found in bone tissue, was deposited on the surface of a glutaraldehyde-fixed, implanted pericardium. Implanted pericardia fixed in glutaraldehyde followed by treatment in either an 80% ethanol or a 5% octanol/40% ethanol solution did not mineralize on implantation. Collagen secondary structure changes were observed on glutaraldehyde fixation by monitoring the center of gravity of the amide I envelope. It is proposed that the decrease in the amide I center of gravity frequency for the glutaraldehyde-fixed tissue compared to the nonfixed tissue is due to an increase in nonreducible collagen cross-links (1660 cm(-1)) and a decrease in reducible cross-links (1690 cm(-1)). The amide I center of gravity in the glutaraldehyde/ethanol-fixed pericardium was higher than the glutaraldehyde-fixed tissue center of gravity. This increase in center of gravity could possibly be due to a decrease in hydrogen bonding within the collagen fibrils following the ethanol pretreatment. In addition, we found a secondary structure change to the pericardial collagen after implantation: an increase in the frequency of the center of gravity of amide I is indicative of an increase in cross-links.

Identification and characterization of atrioventricular parasympathetic innervation in humans.

INTRODUCTION: We hypothesized that in humans there is an epicardial fat pad from which parasympathetic ganglia supply the AV node. We also hypothesized that the parasympathetic nerves innervating the AV node also innervate the right atrium, and the greatest density of innervation is near the AV nodal fat pad. METHODS AND RESULTS: An epicardial fat pad near the junction of the left atrium and right inferior pulmonary vein was identified during cardiac surgery in seven patients. A ring electrode was used to stimulate this fat pad intraoperatively during sinus rhythm to produce transient complete heart block. Subsequently, temporary epicardial wire electrodes were sutured in pairs on this epicardial fat pad, the high right atrium, and the right ventricle by direct visualization during coronary artery bypass surgery in seven patients. Experiments were performed in the electrophysiology laboratory 1 to 5 days after surgery. Programmed atrial stimulation was performed via an endocardial electrode catheter advanced to the right atrium. The catheter tip electrode was moved in 1-cm concentric zones around the epicardial wires by fluoroscopic guidance. Atrial refractoriness at each catheter site was determined in the presence and absence of parasympathetic nerve stimulation (via the epicardial wires). In all seven patients, an AV nodal fat pad was identified. Fat pad stimulation during and after surgery caused complete heart block but no change in sinus rate. Fat pad stimulation decreased the right atrial effective refractory period at 1 cm (280 +/- 42 msec to 242 +/- 39 msec) and 2 cm (235 +/- 21 msec to 201 +/- 11 msec) from the fat pad (P = 0.04, compared with baseline). No significant change in atrial refractoriness occurred at distances >2 cm. The response to stimulation decreased as the distance from the fat pad increased. CONCLUSION: For the first time in humans, an epicardial fat pad was identified from which parasympathetic nerve fibers selectively innervate the AV node but not the sinoatrial node. Nerves in this fat pad also innervate the surrounding right atrium.

Intrapericardial therapeutics: a pharmacodynamic and pharmacokinetic comparison between pericardial and intravenous procainamide delivery.

INTRODUCTION: Procainamide delivery into the pericardial space may produce a greater and more prolonged electrophysiologic effect, particularly in thin superficial atrial tissue, compared with intravenous delivery. METHODS AND RESULTS: Swine were randomized to sequential procainamide doses delivered intravenously (n = 6) or into the pericardial space (n = 7). The cumulative pericardial doses were 0.5, 1.5, and 3.5 mg/kg, and the intravenous doses were 2, 10, and 26 mg/kg. Pericardial procainamide prolonged right atrial effective refractory period from baseline by 22% (P < 0.01) but only at the 3.5 mg/kg cumulative dose. This dose slowed interatrial conduction time by 14% (P < 0.05) and raised atrial fibrillation threshold by 70 mA (P < 0.05). Pericardial procainamide had minimal effect on ventricular electrophysiology. Similar results occurred with a single 2 mg/kg pericardial dose in a closed chest model. Intravenous 10 and 26 mg/kg cumulative doses prolonged atrial effective refractory period from baseline by 24% and 18% (P < 0.01), respectively. The 26 mg/kg cumulative intravenous dose slowed interatrial and atrial-ventricular conduction times by 27% and 17%, respectively (P < 0.05), raised atrial fibrillation threshold, and slowed ventricular conduction time by 29% (P < 0.05). Pericardial procainamide produced pericardial fluid concentrations ranging from 250 to 1,500 microg/mL, but plasma concentrations were <1 microg/mL. Intravenous procainamide doses produced pericardial fluid concentrations similar to plasma trough concentrations 0 to 12 microg/mL. CONCLUSION: The single 2 mg/kg and 3.5 mg/kg cumulative pericardial procainamide doses prolonged atrial refractoriness and raised atrial fibrillation threshold similar to the 26 mg/kg cumulative intravenous dose, but the duration of effect was similar between delivery methods. Pericardial procainamide did not affect global or endocardial ventricular electrophysiology nor was it associated with ventricular proarrhythmia.