Matthias Karck

Pharmacological Activation of Soluble Guanylate Cyclase Protects the Heart Against Ischemic Injury

Background— The role of the nitric oxide/cGMP/cGMP–dependent protein kinase G pathway in myocardial protection and preconditioning has been the object of intensive investigations. The novel soluble guanylate cyclase activator cinaciguat has been reported to elevate intracellular [cGMP] and activate the nitric oxide/cGMP/cGMP–dependent protein kinase G pathway in vivo. We investigated the effects of cinaciguat on myocardial infarction induced by isoproterenol in rats. Methods and Results— Rats were treated orally twice a day for 4 days with vehicle or cinaciguat (10 mg/kg). Isoproterenol (85 mg/kg) was injected subcutaneously 2 days after the first treatment at an interval of 24 hours for 2 days to produce myocardial infarction. After 17 hours, histopathological observations and left ventricular pressure-volume analysis to assess cardiac function with a Millar microtip pressure-volume conductance catheter were performed, and levels of biochemicals of the heart tissues were measured. Gene expression analysis was performed by quantitative real-time polymerase chain reaction. Isolated canine coronary arterial rings exposed to peroxynitrite were investigated for vasomotor function, and immunohistochemistry was performed for cGMP and nitrotyrosine. The present results show that cinaciguat treatment improves histopathological lesions, improves cardiac performance, improves impaired cardiac relaxation, reduces oxidative stress, ameliorates intracellular enzyme release, and decreases cyclooxygenase 2, transforming growth factor-β, and β-actin mRNA expression in experimentally induced myocardial infarction in rats. In vitro exposure of coronary arteries to peroxynitrite resulted in an impairment of endothelium-dependent vasorelaxation, increased nitro-oxidative stress, and reduced intracellular cGMP levels, which were all improved by cinaciguat. A cardioprotective effect of postischemic cinaciguat treatment was shown in a canine model of global ischemia/reperfusion. Conclusion— Pharmacological soluble guanylate cyclase activation could be a novel approach for the prevention and treatment of ischemic heart disease.

Comparative investigation of the left ventricular pressure-volume relationship in rat models of type 1 and type 2 diabetes mellitus

Diabetes mellitus (DM) is associated with characteristic structural and functional changes of the myocardium, termed diabetic cardiomyopathy. As a distinct entity independent of coronary atherosclerosis, diabetic cardiomyopathy is an increasingly recognized cause of heart failure. A detailed understanding of diabetic cardiac dysfunction, using relevant animal models, is required for the effective prevention and treatment of cardiovascular complications in diabetic patients. We investigated and compared cardiac performance in rat models of type 1 DM (streptozotocin induced) and type 2 DM (Zucker diabetic fatty rats) using a pressure-volume (P-V) conductance catheter system. Left ventricular (LV) systolic and diastolic function was evaluated in vivo at different preloads, including the slope of the end-systolic P-V relation (ESPVR) and end-diastolic P-V relationship (EDPVR), preload recruitable stroke work (PRSW), maximal slope of the systolic pressure increment (dP/dt(max)), and its relation to end-diastolic volume (dP/dt(max)-EDV) as well as the time constant of LV relaxation and maximal slope of the diastolic pressure decrement. Type 1 DM was associated with decreased LV systolic pressure, dP/dt(max), slope of ESPVR and dP/dt(max)-EDV, PRSW, ejection fraction, and cardiac and stroke work indexes, indicating marked systolic dysfunction. In type 2 DM rats, systolic indexes were altered only to a lower extent and the increase of LV stiffness was more pronounced, as indicated by the higher slopes of EDPVR. Our data suggest that DM is characterized by decreased systolic performance and delayed relaxation (mainly in type 1 DM), accompanied by increased diastolic stiffness of the heart (more remarkably in type 2 DM). Based on the sophisticated method of P-V analysis, different characteristics of type 1 and type 2 diabetic cardiac dysfunction can be demonstrated.

Transplanted human cord blood-derived unrestricted somatic stem cells improve left-ventricular function and prevent left-ventricular dilation and scar formation after acute myocardial infarction

Objective: Functional improvement after acute myocardial ischaemia (MI) has been achieved by transplantation of different adult stem and progenitor cell types. It is controversial whether these cell types are able to form novel functional myocardium. Alternatively, graft-related or immune-related paracrine mechanisms may preserve existing myocardium, improve neovascularisation, affect tissue remodelling or induce endogenous de novo formation of functional myocardium. We have applied an alternative somatic cell type, human cord-blood-derived unrestricted somatic stem cells (USSCs) in a porcine model of acute MI. Methods: USSCs were transplanted into the acutely ischaemic lateral wall of the left ventricle (LV). LV dimension and function were assessed by transoesophageal echocardiography (TEE) pre-MI, immediately post-MI, 48 hours and 8 weeks after USSC injection. Additionally, apoptosis, mitosis and recruitment of macrophages were examined 48 hours post-engraftment. Results: Gender-specific and species-specific FISH/immunostaining failed to detect engrafted donor cells 8 weeks post-MI. Nevertheless, cell treatment effectively preserved natural myocardial architecture. Global left ventricular ejection fraction (LVEF) before MI was 60% (7%). Post-MI, LVEF decreased to 34% (8%). After 8 weeks, LVEF had further decreased to 27% (6%) in the control group and recovered to 52% (2%) in the USSC group (p<0.01). Left-ventricular end-diastolic volume (LVEDV) before MI was 28 (2) ml. 8 weeks post-MI, LVEDV had increased to 77 (4) ml in the control group. No LV dilation was detected in the USSC group (LVEDV: 26 (2) ml, p<0.01). Neither apoptosis nor recruitment of macrophages and mitosis were different in either groups. Conclusions: Transplantation of USSCs significantly improved LV function and prevented scar formation as well as LV dilation. Since differentiation, apoptosis and macrophage mobilisation at infarct site were excluded as underlying mechanisms, paracrine effects are most likely to account for the observed effects of USSC treatment.

Comparison of Ascending Aorta Versus Femoral Artery Cannulation for Acute Aortic Dissection Type A

Background— The site of cannulation for repair of ascending aortic dissection remains controversial. We present our experience with ascending aortic cannulation for acute aortic dissection type A. Methods and Results— From January 1988 to September 2007, we operated on 242 patients for acute aortic dissection type A. Medical records of 235 patients who received ascending aortic cannulation or femoral cannulation were retrospectively reviewed. Long-term follow-up was complete in 97% of patients. Cannulation was accomplished in 82 patients through the ascending aorta and in 153 patients through the femoral artery. Preoperative patient characteristics were almost comparable between groups. Similarly, there were no differences in preoperative patient characteristics and intraoperative parameters including operation time, bypass time, cross-clamp time, hypothermic circulatory arrest time, and percentage of total arch replacement. The 30-day mortality rate was 14% in the aortic group and 23% in the femoral group (P=0.07), and incidence of stroke was 4.9% in the aortic group and 4.5% in the femoral group (P=0.86). During follow-up (mean, 5.5 years), survival at 5 years and 10 years was 65% and 41% in the aortic group and 64% and 46% in the femoral group, respectively (P=0.97). Conclusions— The cannulation site should be chosen according to the patient’s pathology and status, and the present study suggests that ascending cannulation in patients with acute aortic dissection type A can be a safe alternative, offering acceptable early and long-term outcomes.

Staged heart transplantation and chemotherapy as a treatment option in patients with severe cardiac light-chain amyloidosis

The prognosis of advanced cardiac light‐chain amyloidosis is poor. Heart transplantation might enable causative therapy and ultimately improve prognosis.

The phosphodiesterase-5 inhibitor vardenafil improves cardiovascular dysfunction in experimental diabetes mellitus

Background and purpose:u2002 Patients with diabetes mellitus exhibit generalized endothelial and cardiac dysfunction with decreased nitric oxide production. Elevated intracellular cyclic guanosine monophosphate (cGMP) levels contribute to an effective cardioprotection in different pathophysiological conditions. In this study, we investigated whether chronic treatment with the phosphodiesterase‐5 inhibitor vardenafil could improve diabetic cardiovascular dysfunction by up‐regulating the nitric oxide–cGMP pathway in the vessel wall and myocardium.

Vardenafil protects against myocardial and endothelial injuries after cardiopulmonary bypass

OBJECTIVESnPhosphodiesterase-5 inhibitors and elevated myocardial cyclic guanosine monophosphate levels can induce potent cardioprotection-like effects against ischaemia-reperfusion injury. We investigated the effects of vardenafil, a selective phosphodiesterase-5 inhibitor on myocardial and endothelial functions during reperfusion in a canine model of cardioplegic arrest and extracorporal circulation.nnnMETHODSnVehicle-treated (control, n=8) and vardenafil-treated (30 microgkg(-1) intravenous (IV); n=8) anaesthetised dogs underwent hypothermic cardiopulmonary bypass with 60 min of hypothermic cardiac arrest. Left and right ventricular end-systolic pressure volume relationship (E(es)) was measured by a combined pressure-volume conductance catheter at baseline and after 60 min of reperfusion. Left anterior descending coronary blood flow and endothelium-dependent vasodilatation to acetylcholine were determined. Isolated coronary arterial rings were investigated for vasomotor function using an in vitro organ bath system.nnnRESULTSnPharmacological preconditioning with vardenafil led to significantly higher plasma cyclic guanosine monophosphate levels and myocardial adenosine triphosphate content to a better recovery of left and right ventricular E(es) (Delta left ventricular E(es) given as percent of baseline: 74.2+/-4.5% vs 50.4+/-5.0%, p<0.05) and to a higher coronary blood flow (58+/-12 vs 24+/-7 mlmin(-1), p<0.05). Endothelium-dependent vasodilatory responses to acetylcholine - measured both in vivo and in vitro - were improved in the vardenafil group.nnnCONCLUSIONSnApplication of vardenafil improves myocardial and endothelial functions after cardiopulmonary bypass with hypothermic cardiac arrest. The observed protective effects imply that phosphodiesterase-5 inhibition could be a novel therapeutic option in the protection against ischaemia-reperfusion injury in cardiac surgery.

Dose-dependent effects of a selective phosphodiesterase-5-inhibitor on endothelial dysfunction induced by peroxynitrite in rat aorta

Reactive oxygen species, such as peroxynitrite, induce oxidative stress and DNA injury leading to endothelial dysfunction. It has been proposed, that elevated intracellular cyclic GMP (cGMP)-levels may contribute to an effective cytoprotection against nitro-oxidative stress. We investigated the dose-dependent effects of vardenafil, an inhibitor of phosphodiesterase-5, on endothelial dysfunction induced by peroxynitrite. In organ bath experiments, we investigated the endothelium-dependent (acetylcholine) and -independent (sodium nitroprusside, SNP) vasorelaxation of isolated aortic rings of rats. Endothelial dysfunction was induced by peroxynitrite. In the treatment groups, rats received low doses (0.01-5 microg/kg) or high doses (5-300 microg/kg) of vardenafil. DNA strand breaks were assessed by the TUNEL method. Immunohistochemical analysis was performed for cGMP and nitrotyrosine. Exposure to peroxynitrite resulted in an impairment of endothelium-dependent vasorelaxation of aortic rings. Pre-treatment with lower doses of vardenafil led to an improvement of endothelial function as reflected by the higher maximal vasorelaxation (R(max)) to acetylcholine. Interestingly, at higher doses, R(max) to acetylcholine was attenuated leading to U-shaped dose-response curves. The endothelium-independent vasorelaxation to SNP under peroxynitrite stress showed a significant left-shift of the SNP concentration-response curves in the vardenafil groups without any alterations of the R(max). Vardenafil-pre-treatment significantly reduced DNA-breakage, reduced nitrosative stress, and increased cGMP score in the aortic wall. Our working hypothesis is that improvement of endothelial function could be mainly due to the cytoprotection of endothelium by vardenafil. This work supports the view that acute PDE5-inhibition might be advantageous in the treatment of endothelial dysfunction induced by disturbed NO-cGMP pathway due to nitro-oxidative stress.

High defibrillation threshold in patients with implantable defibrillator: how effective is the subcutaneous finger lead?

OBJECTIVEnEven in the era of high output implantable cardioverter defibrillator (ICD) devices, a certain proportion of patients cannot be successfully defibrillated with 10 J safety margin. In practice, either the use of a single- or double-coil lead does not guarantee successful termination of induced ventricular fibrillation. Therefore, we investigated the effectiveness of the subcutaneous finger lead placed at the subcutaneous tissue dorsal to the left ventricle in terms of defibrillation threshold (DFT) lowering.nnnMETHODSnTwo thousand, eight hundred and three consecutive, unselected patients underwent first-time ICD implantation or ICD device exchange from 6/1999 through 3/2007. The mean age of the patients was 65.4 years. A total of 79.3% of the patients were male. The only implanted subcutaneous lead was the 6996 model by Medtronic Inc.nnnRESULTSnOne hundred and seventy-seven patients (6.3%) received a subcutaneous finger lead implantation. According to the current institutional DFT testing protocol, any failure of the two standard DFT tests in first-time ICD implantation or a failure at the single test in ICD exchange operations was the trigger for subcutaneous finger lead implantation. The proportion of subcutaneous finger lead implantations increased parallel to a markedly larger amount of implantations. Since high output devices became standard, the implantation number of subcutaneous finger leads decreases. The mean of unsuccessful DFTs prior to subcutaneous finger lead implantation was 27.2+/-5.3 J. After subcutaneous finger lead implantation, the mean successful DFT was 17.9+/-3.3 J. No complication due to subcutaneous finger lead implantation occurred.nnnCONCLUSIONnThe subcutaneous finger lead is a quick, safe and effective method for DFT lowering.

INHIBITION OF SMOOTH MUSCLE CELL MIGRATION AND NEOINTIMA FORMATION IN VEIN GRAFTS BY OVEREXPRESSION OF MATRIX METALLOPROTEINASE-3

OBJECTIVEnSaphenous vein grafts suffer from neointima formation following bypass surgery. Matrix metalloproteinases (MMPs) play important roles in this process. We examined MMP-3 for its therapeutic potential to prevent smooth muscle cell migration and neointima formation in venous bypass grafts using adenovirus-mediated gene transfer.nnnMETHODSnHuman aortic smooth muscle cells (HASMC) were transduced with adenoviral vectors encoding ss-galactosidase (Ad.ssgal) [corrected] or human MMP-3 (Ad.hMMP-(3)), [corrected] and characterized for migration in the amniotic membrane stroma as an in vitro model of the vascular wall. Cholesterol-fed New Zealand white rabbits underwent jugular vein bypass grafting into carotid arteries. Before insertion, grafts were incubated ex vivo with either Ad.ssgal [corrected] or hMMP-3. Transgene expression was characterized by immunohistochemistry and in situ zymography. Grafts (n = 6) were explanted after 28 days and intimal hyperplasia was quantified.nnnRESULTSnMigration of HASMC was significantly reduced when transduced with Ad.hMMP-(3) [corrected] compared to controls (P < .001). Immunocytochemistry of Ad.hMMP-(3) [corrected] transduced venous grafts localized this protein to the intima. In situ-zymography showed increased MMP activity in the intima of Ad.hMMP-(3) [corrected] transfected grafts. Stenosis degree (P = .001), intima/media-ratio (P = .023) and lesion thickness (P = .003) were significantly reduced in grafts transduced with Ad.MMP-3 in comparison to controls. There was no difference inside control groups.nnnCONCLUSIONnMMP-3 overexpression inhibits formation of intimal hyperplasia in arterialized vein grafts. Adenovirus mediated gene transfer of MMP-3 may be of clinical use to prevent vein graft stenosis following bypass surgery.