Totally endoscopic subxiphoid pericardioscopy: early steps with a new surgical tool.

BACKGROUND: Pericardial pathology still has challenging diagnostic and treating issues. To reduce surgical trauma and pain for the patient, the authors developed a totally endoscopic echo-guided approach for both diagnostic and operative pericardioscopy. METHODS: Three steps moved from animal model (8 pigs) through concomitant open-chest interventions (7 patients) to closed-chest interventions for 10 patients with a diagnosis of severe pericardial effusion. RESULTS: A lesion of the right ventricle in one patient (10%) due to imperfect preoperative pericardial visualization needed sternotomy for repair. All the patients, except the aforementioned one, underwent surgery with local anesthesia or mild sedation. No method-related mortality was reported. CONCLUSION: The closed-chest nonintrapleural approach to the pericardium may represent an evolution, with a positive impact on the treatment of this pathology. Therapeutic maneuvers with rigid instruments in nonintubated patients are possible. Accurate patient selection and technical refinement should increase the safety and effectiveness of the method.

Relaxin induces mast cell inhibition and reduces ventricular arrhythmias in a swine model of acute myocardial infarction.

Resident cardiac mast cells, located mainly around coronary vessels and in the right atrium close to the sinoatrial node, are the main repository of cardiac histamine. Inflammatory activation of cardiac mast cells, as occurs upon acute myocardial infarction, causes the release of histamine and prostanoids. These substances lead to severe tachyarrhythmias, cardiodepressive effects and coronary spasm, thus contributing to myocardial damage and early, lethal outcome. Relaxin, known to inhibit mast cell activation, has been recently validated as a cardiotropic hormone, being produced by the heart and acting on specific heart receptors. In this study, we report on a swine model of heart ischemia/reperfusion, currently used to test cardiotropic drugs, in which human recombinant relaxin (2.5 and 5 microg/kg b.w.), given at reperfusion upon a 30-min ischemia, markedly reduced cardiac injury as compared with the vehicle-treated animals. Evidence is provided that relaxin, at both the assayed doses, causes a clear-cut, significant reduction of plasma histamine, increase in cardiac histamine content and decrease in cardiac mast cell degranulation. This is accompanied by a reduction of oxidative cardiac tissue injury (assessed as tissue malondialdehyde) and of the occurrence of severe ventricular arrhythmias. In conclusion, this study provides further insight into the cardioprotective effects of relaxin, which also involve mast cell inhibition, and confirms the relevance of histamine in the pathophysiology of ischemia-reperfusion-induced cardiac injury and dysfunction. It also offers additional evidence for the potential therapeutic effects of relaxin in animal models of disease involving mast cell activation.

Paracrine effects of transplanted myoblasts and relaxin on post-infarction heart remodelling.

In the post-infarcted heart, grafting of precursor cells may partially restore heart function but the improvement is modest and the mechanisms involved remain to be elucidated. Here, we explored this issue by transplanting C2C12 myoblasts, genetically engineered to express enhanced green fluorescent protein (eGFP) or eGFP and the cardiotropic hormone relaxin (RLX) through coronary venous route to swine with experimental chronic myocardial infarction. The rationale was to deliver constant, biologically effective levels of RLX at the site of cell engraftment. One month after engraftment, histological analysis showed that C2C12 myoblasts selectively settled in the ischaemic scar and were located around blood vessels showing an activated endothelium (ICAM-1-,VCAM-positive). C2C12 myoblasts did not trans-differentiate towards a cardiac phenotype, but did induce extracellular matrix remodelling by the secretion of matrix metalloproteases (MMP) and increase microvessel density through the expression of vascular endothelial growth factor (VEGF). Relaxin-producing C2C12 myoblasts displayed greater efficacy to engraft the post-ischaemic scar and to induce extracellular matrix re-modelling and angiogenesis as compared with the control cells. By echocardiography, C2C12-engrafted swine showed improved heart contractility compared with the ungrafted controls, especially those producing RLX. We suggest that the beneficial effects of myoblast grafting on cardiac function are primarily dependent on the paracrine effects of transplanted cells on extracellular matrix remodelling and vascularization. The combined treatment with myoblast transplantation and local RLX production may be helpful in preventing deleterious cardiac remodelling and may hold therapeutic possibility for post-infarcted patients.

Novel drug development opportunity for relaxin in acute myocardial infarction: evidences from a swine model.

The hormone relaxin has been shown to cause coronary vasodilation and to prevent ischemia/reperfusion-induced cardiac injury in rodents. This study provides evidence that relaxin, used as an adjunctive drug to coronary reperfusion, reduces the functional, biochemical, and histopathological signs of myocardial injury in an in vivo swine model of heart ischemia/reperfusion, currently used to test cardiotropic drugs for myocardial infarction. Human recombinant relaxin, given at reperfusion at doses of 1.25, 2.5, and 5 microg/kg b.wt. after a 30-min ischemia, caused a dose-related reduction of key markers of myocardial damage (serum myoglobin, CK-MB, troponin T) and cardiomyocyte apoptosis (caspase 3, TUNEL assay), as well as of cardiomyocyte contractile dysfunction (myofibril hypercontraction). Compared with the controls, relaxin also increased the uptake of the viability tracer 201Thallium and improved ventricular performance (cardiac index). Relaxin likely acts by reducing oxygen free radical-induced myocardial injury (malondialdehyde, tissue calcium overload) and inflammatory leukocyte recruitment (myeloperoxidase). The present findings show that human relaxin, given as a drug to counteract reperfusion-induced cardiac injury, affords a clear-cut protection to the heart of swine with induced myocardial infarction. The findings also provide background to future clinical trials with relaxin as adjunctive therapy to catheter-based coronary angioplasty in patients with acute myocardial infarction.

Human recombinant relaxin reduces heart injury and improves ventricular performance in a swine model of acute myocardial infarction.

This study shows that relaxin can be effective in the treatment of acute myocardial infarction. In a swine model of heart ischemia-reperfusion currently used to test cardiotropic drugs because of its similarities with human myocardial infarction, human recombinant relaxin (2.5 and 5 microg/kg body weight), given at reperfusion after a 30-min ischemia, markedly reduced the main serum markers of myocardial damage (myoglobin, CK-MB, and troponin T) and the metabolic and histopathologic parameters of myocardial inflammation and cardiomyocyte injury, resulting in overall improvement of ventricular performance (increased cardiac index) compared to the controls. These results provide a background for future clinical trials with human relaxin as adjunctive therapy to catheter-based coronary angioplasty in patients with acute myocardial infarction.

Different growth factor activation in the right and left ventricles in experimental volume overload.

Mechanical factors play a key role in activation of cardiac growth factor response in hemodynamic overload, and both cooperate in myocardial remodeling. The present study was performed to investigate whether a different growth factor response is activated in the right and left ventricles in aortocaval fistula and its effects on regional myocardial adaptation. Relations between regional growth factor expression (angiotensin II, insulin-like growth factor-I, and endothelin-1), myocyte shape changes, and collagen deposition were investigated at mRNA and peptide levels in adult pigs after the creation of an aortocaval fistula distal to the renal arteries (n=15) and in sham-operated animals (n=15). The role of angiotensin II was investigated by the administration of angiotensin-converting enzyme inhibitor or angiotensin II receptor antagonist. In the left ventricle, pure volume overload was accompanied by persistent increase of insulin-like growth factor-I mRNA expression, peptide concentration (2.2-fold versus sham at 3 months, P<0.05), and significant increase of myocyte length (+29% at 3 months, P<0.05). Conversely, the mixed pressure-volume overload faced by the right ventricle resulted in significant regional overexpression of all growth factors investigated (angiotensin II, insulin-like growth factor-I, and endothelin-1), with corresponding increase of myocyte diameter and length and collagen deposition (+117% at 3 months). Collagen accumulation in the right ventricle as well as the increase in right ventricular end-diastolic pressure at the 3-month observation were inhibited by angiotensin II antagonism. The left and right ventricles respond differently to aortocaval fistula, and local growth factor expression is closely related to the regional myocardial adaptation.

Beneficial effects of poly (ADP-ribose) polymerase inhibition against the reperfusion injury in heart transplantation.

We investigated the effect of 3-aminobenzamide (3-AB), an inhibitor of the nuclear enzyme poly(ADP-ribose) polymerase (PARP), against early ischemia/reperfusion (IR) injury in heart transplantation. In our experimental model, rat heart subjected to heterotopic transplantation, low temperature global ischemia (2 h) was followed by an in vivo reperfusion (60 min). In these conditions, and in the absence of 3-AB treatment, clear signs of oxidative stress, such as lipid peroxidation, increase in protein carbonyls and DNA strand breaks, were evident; PARP was markedly activated in concomitance with a significant NAD+ and ATP depletion. The results of microscopic observations (nuclear clearings, plasma membrane discontinuity), and the observed rise in the serum levels of heart damage markers, suggested the development of necrotic processes while, conversely, no typical sign of apoptosis was evident. Compared to the effects observed in untreated IR heart, the administration of 3-AB (10 mg/kg to the donor and to the recipient animal), but not that of its inactive analogue 3-aminobenzoic acid, significantly modified the above parameters: the levels of oxidative stress markers were significantly reduced; PARP activation was markedly inhibited and this matched a significant rise in NAD+ and ATP levels. PARP inhibition also caused a reduced release of the cardiospecific damage markers and attenuated morphological cardiomyocyte alterations, save that, in this condition, we noted the appearance of typical apoptotic markers: activation of caspase-3, oligonucleosomal DNA fragmentation, ISEL positive nuclei. Possible mechanisms for these effects are discussed, in any case the present results indicate that PARP inhibition has an overall beneficial effect against myocardial reperfusion injury, mainly due to prevention of energy depletion. In this context, the signs of apoptosis observed under 3-AB treatment might be ascribed to the maintenance of sufficient intracellular energy levels. These latter allow irreversible damages triggered during the ischemic phase to proceed towards apoptosis instead of towards necrosis, as it appears to happen when the energetic pools are depleted by high PARP activity.

Release of preformed Ang II from myocytes mediates angiotensinogen and ET-1 gene overexpression in vivo via AT1 receptor.

UNLABELLED: The role of angiotensin II in pressure overload is still debated because notwithstanding its effects on myocyte contractility angiotensin II is not an obligatory factor for the development of hypertrophy. To define the role of angiotensin II in acute pressure overload we studied the effects of AT1 blockade (valsartan 80mg per day) on myocardial contractility, cardiac growth factor gene expression, and myocardial hypertrophy in aortic banded (60mmHg) pigs. Acute pressure overload caused an abrupt reduction of myocardial contractility, measured by the end-systolic stiffness constant, and a sharp increase in end-systolic stress which rapidly normalized (within 12h) in the placebo group. In AT1-blocked animals end-systolic stiffness constant remained significantly depressed up to 24h and end-systolic stress was still elevated up to 48h (both P<0.05 vs placebo). In both groups confocal microscopy revealed that granular staining of angiotensin II in cardiomyocyte cytoplasm disappeared after 30min of pressure overload. AT1 blockade abolished following cardiac overexpression of angiotensinogen and endothelin-1 genes as shown in RT-PCR studies and the consequent angiotensin II and endothelin-1 release in the coronary circulation. Conversely, insulin-like growth factor-I and ACE mRNA overexpression, as well as the onset of left ventricular mass increase, were not significantly affected by AT1 blockade. IN CONCLUSION: (1) mechanical stress releases preformed angiotensin II from myocyte in vivo; (2) the AT1 blockade abolishes cardiac angiotensin II and endothelin-1 production with delayed recovery of myocardial contractility; whereas (3) the overexpression of insulin-like growth factor-I gene and the development of myocardial hypertrophy are not angiotensin II-mediated effects.

Poly(ADP-ribose) polymerase activation and cell injury in the course of rat heart heterotopic transplantation.

Free radicals and other reactive species generated during reperfusion of ischemic tissues may cause DNA damage and, consequently, the activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP). An excessive PARP activation may result in a depletion of intracellular NAD+ and ATP, hence cell suffering and, ultimately, cell death. The present study is aimed at clarifying the role of PARP in a heart transplantation procedure and the contribution of myocyte necrosis and/or apoptosis to this process. In our experimental model, rat heart subjected to heterotopic transplantation, low temperature global ischemia (2 h) was followed by an in vivo reperfusion (30 or 60 min). Under these conditions clear signs of oxidative stress, such as lipoperoxidation and DNA strand breaks, were evident. In addition to a marked activation, accompanied by a significant NAD+ and ATP depletion, PARP protein levels significantly increased after 60 min of reperfusion. Ultrastructural analysis showed nuclear clearings, intracellular oedema and plasma membrane discontinuity. Other relevant observations were the absence of typical signs of apoptosis like caspase-3 activation and PARP cleavage, random DNA fragmentation, rise in serum levels of heart damage markers. Our results suggest that during heart transplantation, the activation of PARP, causing energy depletion, results in myocardial cell injury whose dominant feature, at least in our experimental model, is necrosis rather than apoptosis.