Peter Kalmár

INCREASE IN MYOCARDIAL Gi-PROTEINS IN HEART FAILURE

The contractile response and myocardial content of Gi-proteins were examined in cardiac preparations from explanted hearts of four different patients with end-stage heart failure. Three patients had idiopathic dilated cardiomyopathy and one patient had inflammatory heart disease. Preparations from patients with idiopathic dilated cardiomyopathy showed reduced contractile response to the cAMP-increasing agent isoprenaline and an increase in myocardial Gi-proteins, compared with preparations from non-failing hearts. Therefore it is conceivable that an increase in myocardial Gi-proteins is causally related to heart failure due to idiopathic dilated cardiomyopathy. In the preparation from the patient with inflammatory heart disease the contractile response to isoprenaline was not reduced and likewise content of Gi-proteins was not changed.

Increased messenger RNA level of the inhibitory G protein alpha subunit Gi alpha-2 in human end-stage heart failure.

In human heart failure the positive inotropic and cAMP-elevating effects of both beta-adrenoceptor agonists and phosphodiesterase inhibitors are diminished. This has been explained at least in part by an increase in the inhibitory signal-transducing G protein (Gi) and unchanged stimulatory G protein (Gs). In the present study we determined the mRNA expression pattern of the alpha subunits of Gi-1, Gi-2, Gi-3, and Gs in myocardial tissue samples of patients undergoing heart transplantation. Northern blot analysis of total RNA extracted from left ventricles with 32P-labeled cDNAs demonstrated expression of Gi alpha-2, Gi alpha-3, and Gs alpha mRNA. In contrast, Gi alpha-1 mRNA was not detectable. To investigate whether the increased ratio of Gi/Gs might be due to altered gene expression, we compared mRNA levels of Gi alpha-2, Gi alpha-3, and Gs alpha in left ventricular myocardium from failing hearts with idiopathic dilated cardiomyopathy (n = 8) and ischemic cardiomyopathy (n = 6) and from nonfailing hearts from transplant donors (n = 8). Compared with nonfailing control hearts, the Gi alpha-2 mRNA was increased by 75 +/- 26% (p less than 0.05) in idiopathic dilated cardiomyopathy hearts and 90 +/- 26% (p less than 0.05) in ischemic cardiomyopathy hearts. Gi alpha-3 and Gs alpha mRNA levels were similar in the three groups. The results suggest that as in other mammalian species, Gi alpha-2 and Gi alpha-3 mRNA are the predominant Gi alpha mRNA subtypes in human ventricular myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Basal and isoprenaline-stimulated cAMP content in failing versus nonfailing human cardiac preparations

We measured force of contraction and cAMP content in human isolated electrically driven right ventricular trabeculae carneae with and without the addition of isoprenaline (0.2 microM). Basal cAMP content was approximately 200% higher in preparations from nonfailing hearts than from hearts with end-stage myocardial failure. Isoprenaline was less effective in increasing force of contraction in failing (by approximately 100%) than in nonfailing cardiac preparations (by approximately 500%). With isoprenaline, cAMP content was approximately 50% lower in failing than in nonfailing preparations. We conclude that the reduced increase in force of contraction of failing human cardiac preparations with isoprenaline added may be causally related to an inadequately increased cAMP content.

Reduced α1- and β2-adrenoceptor-mediated positive inotropic effects in human end-stage heart failure

1 α1‐Adrenoceptor (phenylephrine in the presence of propranolol) and β2‐adrenoceptor (fenoterol)‐mediated positive inotropic effects were investigated in human ventricular preparations isolated from five nonfailing (prospective organ donors) and from eight explanted failing hearts with end‐stage idiopathic dilative cardiomyopathy (NYHA IV). 2 For comparison, the nonselective β‐adrenoceptor agonist isoprenaline, the phosphodiesterase (PDE) inhibitor 3‐isobutyl‐1‐methylxanthine (IBMX), the cardiac glycoside dihydroouabain, and calcium were studied. 3 Furthermore, the influence of IBMX on adenosine 3′: 5′‐cyclic monophosphate (cyclic AMP) PDE activity as well as total β‐adrenoceptor density, β1‐ and β2‐adrenoceptor subtype distribution, and α1‐adrenoceptor density were compared in nonfailing and failing human heart preparations. The radioligands (−)‐[125I]‐iodocyanopindolol for β‐adrenoceptor binding and [3H]‐prazosin for α1‐adrenoceptor binding were used. 4 The inotropic responses to calcium and dihydroouabain in failing human hearts were unchanged, whereas the maximal α1‐ and β2‐adrenoceptor‐mediated positive inotropic effects were greatly reduced. The inotropic effects of the other cyclic AMP increasing compounds, i.e. isoprenaline and IBMX, were also reduced to about 60% of the effects observed in nonfailing controls. The potency of these compounds was decreased by factors 4–10. 5 The basal PDE activity and the PDE inhibition by IBMX were similar in nonfailing and failing preparations. 6 The total β‐adrenoceptor density in nonfailing hearts was about 70 fmol mg−1 protein. In failing hearts the total number of β‐adrenoceptors was markedly reduced by about 60%. The β1/β2‐adrenoceptor ratio was shifted from about 80/20% in nonfailing to approximately 60/40% in failing hearts which was due to a selective reduction of β1‐adrenoceptors. The β2‐adrenoceptor population remaining unchanged. α1‐Adrenoceptor density was increased from about 4 fmol mg−1 protein in nonfailing to 10 fmol mg−1 protein in failing hearts. 7 Changes in PDE activity and adrenoceptor downregulation cannot completely explain the reduced positive inotropic effects of α1‐ and β2‐adrenoceptor agonists in failing human hearts. This supports the hypothesis that impairment of other processes such as the coupling between receptor and effector system, i.e. the respective G‐proteins, are equally important in end‐stage heart failure.

Evidence for alpha 1-adrenoceptor-mediated increase of inositol trisphosphate in the human heart.

In human-isolated ventricular myocardium the alpha 1-adrenoceptor agonist phenylephrine has a positive inotropic effect but its mechanism is largely unknown. We studied the effects of phenylephrine in trabeculae isolated from three nonfailing human hearts. We found that the force of contraction rose concentration-dependently (1-300 mumol/L), maximally, to about 235% of control (at 100 mumol/L). The inositol phosphates were increased to 195-262%, whereas the phosphatidylinositol phosphate and phosphatidylinositol bisphosphate decreased to 69-73% of control. The present results suggest that the alpha 1-adrenoceptor-mediated increase in inositol trisphosphate and the positive inotropic effect may be causally related in the normal human heart.

Regional distribution of β1- and β2-adrenoceptors in the failing and nonfailing human heart

SummaryTotal β-adrenoceptor density and β1- and β2-subtype distribution in right and left atria and in different ventricular regions from 14 failing and seven nonfailing human hearts have been compared. End-stage heart failure was due to idiopathic dilated cardiomyopathy (n=8) or ischaemic cardiomyopathy (n=6).In nonfailing hearts the total β-adrenoceptor density was similar in the right and left atria and in all the ventricular regions studied (about 70 to 80 fmol/mg protein). The β1:β2-adrenoceptor ratio in both nonfailing atria was similar (about 70:30%) and was significantly smaller than in the different regions of both ventricles (about 80:20%). The β1-subtype density was similar in nonfailing atria and ventricles (about 55 fmol/mg protein). The β2-subtype density was significantly higher in the right and left atrium (about 25 fmol/mg protein) than in both ventricles (about 15 fmol/mg protein).In patients with end-stage heart failure due to idiopathic dilated cardiomyopathy or ischaemic cardiomyopathy the total β-adrenoceptor density was reduced by 50–60% in all regions. On the other hand, the β1- and β2-subtype distribution differed with the cause of heart failure. In patients with idiopathic dilated cardiomyopathy, the β1-adrenoceptor density was lower in all regions, but the β2-adrenoceptor density was not significantly reduced. In patients with ischaemic cardiomyopathy both β1- and β2-adrenoceptors were reduced in all regions.It is concluded that downregulation of β-adrenoceptors in patients with end-stage idiopathic dilated cardiomyopathy or ischaemic cardiomyopathy occurs uniformly throughout the heart. The results support the hypothesis that changes in β-adrenoceptor subtypes may be related to the cause of heart failure.

Effects of isomazole on force of contraction and phosphodiesterase isoenzymes I-IV in nonfailing and failing human hearts.

The phosphodiesterase (PDE) inhibitor isomazole increased the force of contraction to 278.3 ± 89.1% (n = 7) of the predrug value in ventricular trabeculae carneae isolated from nonfailing human hearts. This effect can be attributed mainly to a PDE III or a combined PDE III/IV inhibition since at the concentration of the maximal positive inotropic effect of isomazole, PDE III and PDE IV were completely inhibited. In explanted failing human hearts (end-stage myocardial failure, NYHA IV), isomazole increased the force of contraction only marginally to 110.1 ± 10.7% of the predrug value. The lack of a distinct positive inotropic efficacy of isomazole in failing human hearts could not be explained by an impairment of PDE inhibition since the properties of the PDE I-IV isoenzymes separated by DEAE-Sepharose chromatography and the inhibitory effects of isomazole did not differ in both preparations. The positive inotropic effect of the β-adrenoceptor agonist isoprenaline was also reduced in failing hearts. However, in the presence of isomazole, the diminished positive inotropic effect of isoprenaline was restored to values obtained with isoprenaline alone in nonfailing hearts. Thus, the decreased effect of inotropic drugs like isoprenaline or isomazole in preparations from failing human heart might be explained mainly by a diminished cAMP formation due to a defect in receptor-adenylate cyclase coupling.

Aortic valve replacement with homografts. An overview

ZusammenfassungDie Implantation (eigentlich Transplantation) frischer oder kryokonservierter menschlicher Herzklappen (Homografts) in Aortenposition gehört seit über 30 Jahren zum herzchirurgischen Repertoire. Homografts sind attraktive Alternativen zu mechanischen oder xenobiologischen Klappen, da eine Antikoagulation vermieden und eine nahezu normale Anatomie hergestellt werden kann. Behandelnde Ärzte sollten über die verfügbaren Implantate, die Operationsmethoden und die zu erwartenden Ergebnisse informiert sein, um Patienten mit Klappenvitien entsprechend beraten zu können und individuelle Komplikationsmöglichkeiten in der Nachsorge früh zu erfassen.Dargelegt wird eine Literaturübersicht zum Thema Homograftklappen. Es erfolgt eine Schilderung des Verfahrens der Graftgewinnung, der Herstellung und der Konservierung. Die Einsatzgebiete von Homografts werden erläutert und die Operationstechniken (subkoronar, Miniroot, Wurzelersatz) sowie die Ross-Operation diskutiert. Erwähnung findet auch der Einsatz von Homograftklappen bei frühkindlichen Herzfehlern. Komplikationen und wichtige Aspekte der Nachsorge werden kommentiert.Homografts eignen sich zum Aorten- und Pulmonalklappenersatz bei speziellen Indikationen (jugendlicher Patient, Kontraindikation zur Antikoagulation, Endokarditis). Angaben zu Langzeitergebnissen schwanken je nach Zentrum, eingesetzter Operationsmethode und Klappentyp. Pulmonale Homografts in Aortenposition sind im Gegensatz zu aortalen Homografts negativ zu beurteilen. Der Stellenwert von Homografts und der Ross-Operation im Vergleich zu ungestützten Xenografts sollte durch weitere möglichst multizentrische Langzeitstudien überprüft werden. Im Bereich der Kinderherzchirurgie haben sich Homografts bewährt, vor allem zur Rekonstruktion der rechtsventrikulären Ausflussbahn. Homograftimplantate in Mitralposition gehören noch nicht zur klinischen Routine und zeigen bislang enttäuschende Resultate. Die wesentliche Limitation im Einsatz von Homografts ist ihre geringe Verfügbarkeit; deshalb können Homografts nur begrenzt für die oben erwähnten speziellen Indikationen zur Verfügung gestellt werden.AbstractThe implantation of fresh or cryopreserved human heart valves (homografts) in aortic position is a tool in cardiac surgery since 30 years. Homografts are attractive alternatives to the implantation of mechanical or xenobiological prostheses, because anticoagulation can be avoided and a near normal anatomy can be restored. Physicians should know about the several kinds of grafts and operative techniques to adequately take care of the patients in follow-up.This overview on the literature covers methods of harvesting, preparation and conservation of homografts according to standard protocols of the European Homograft Bank in Brussels. Their use in the therapy of human valvular disease is discussed with special emphasis to operative techniques (subcoronary, root) and the Ross procedure and in pediatric surgery. Complications and aspects of postoperative care are discussed including immunologic phenomena.Homografts are useful tools for aortic valve replacement, especially in juveniles, in the presence of contraindications for anticoagulation and in endocarditis. Whereas aortic homografts have excellent long-term results, pulmonic homografts show a significant rate of malformation. Further studies should be performed to clarify the role of the Ross operation or stentless xenografts compared to homografts in aortic position. In pediatric cardiac surgery homografts are of value especially for the reconstruction of the right ventricular outflow tract. Homografts in mitral position show dissapointing results up to now. The major limitation in the use of homografts is the mismatch of availability and request, therefore homografts can only be used for the above mentioned special indications.The implantation of fresh or cryopreserved human heart valves (homografts) in aortic position is a tool in cardiac surgery since 30 years. Homografts are attractive alternatives to the implantation of mechanical or xenobiological prostheses, because anticoagulation can be avoided and a near normal anatomy can be restored. Physicians should know about the several kinds of grafts and operative techniques to adequately take care of the patients in follow-up. This overview on the literature covers methods of harvesting, preparation and conservation of homografts according to standard protocols of the European Homograft Bank in Brussels. Their use in the therapy of human valvular disease is discussed with special emphasis to operative techniques (subcoronary, root) and the Ross procedure and in pediatric surgery. Complications and aspects of postoperative care are discussed including immunologic phenomena. Homografts are useful tools for aortic valve replacement, especially in juveniles, in the presence of contraindications for anticoagulation and in endocarditis. Whereas aortic homografts have excellent long-term results, pulmonic homografts show a significant rate of malfunction. Further studies should be performed to clarify the role of the Ross operation or stentless xenografts compared to homografts in aortic position. In pediatric cardiac surgery homografts are of value especially for the reconstruction of the right ventricular outflow tract. Homografts in mitral position show disappointing results up to now. The major limitation in the use of homografts is the mismatch of availability and request, therefore homografts can only be used for the above mentioned special indications.

Intensified medical therapy in heart transplant candidates

Abstract Background: Because of donor shortage, heart transplantation (HTx) as therapy for end-stage heart failure is limited by a mortality rate of 25% on waiting lists, and lists are steadily increasing. Aim: To analyse whether an intensive medical therapeutic regimen for heart failure (based on the results of frequent haemodynamic studies) can delay or even prevent the need for HTx. Methods: Data analysis of 517 patients who were referred to our institution for HTx from 1984 to 1996 is presented. Characteristics and management of 359 non-emergency, New York Heart Association (NYHA) III or IV heart transplant candidates, without contraindications (and with sufficient compliance) are described. All candidates receiving conventional therapy with ACE inhibitors, digitalis and diuretics at entry were evaluated. Drug therapy was intensified as follows: a further reduction of preload; a further reduction of afterload; individualised diuresis; and amiodarone therapy. Results: Under this regimen, clinical and haemodynamic parameters improved in many patients. Only 95 patients (26%) were primary non-responders to intensified medical therapy and had to be listed for HTx early (during the first year of follow-up). Actuarial survival rates of the early listed versus the early responding HTx candidates, at 1 and 5 years, were 68.3%/87% and 41%/59%, respectively (p=0.02). An additional benefit of co-therapy with amiodarone and calcium antagonists was found. The most important mode of cardiac death was sudden (32% at 5 years), whereas mortality due to pump failure was much lower (13% at 5 years). Only 38 patients (16%):had to be listed for HTx in further follow-up. Conclusions: Intensive medical therapy in heart transplant candidates may be an alternative to immediate HTx, especially in times of donor shortage or in countries without a transplantation program. Responders to therapy showed a similar or even better prognosis than HTx patients. This conservative approach may allow available donor hearts to be saved for those patients most needing a transplant.

Pharmacokinetic behavior of ciprofloxacin both in native cardiac and porcine valves treated in glutaraldehyde

When judging a probable therapeutic success for antibiotic management of bioprosthetic endocarditis, sufficient drug levels in heterologous valve tissues play a very important role. The pharmacokinetic behavior of ciprofloxacin was investigated in native and porcine valvular tissues and compared with plasma levels during a 90- to 120-min period of surgery. Analysis was carried out by HPLC using excised valvular tissues (Hancock T 505). In all, 15-20 patients were investigated in each group. The antibiotics were administered intravenously or per os. Tissue concentrations after onset of the procedures showed ciprofloxacin plasma concentrations of 2.09-0.47 micrograms g in the native and 3.98-1.99 micrograms/g in the heterologous valvular tissues.