[Diagnostic yield of the implantable loop recorder to detect the mechanism of syncope--a single center long term experience of a tertiary care center]. / Synkopenabklärung mittels implantierbarem Loop Recorder--Langzeiterfahrung eines Zentrumspitals.

AIM: The aim of this study was to investigate the usefulness in providing diagnostic information about syncope by implantation of a loop recorder (ILR). METHODS AND RESULTS: The study population consisted of 48 consecutive patients (23 male, 25 female, mean age 42 +/- 17) with unexplained syncope who presented between 1998 and 2002 and underwent extensive cardiological screening and were followed with an implantable loop recorder (Reveal or Reveal Plus). The mean follow-up duration was 9 +/- 6 months. During this follow-up in 17 (35%) patients syncope recurred. Arrhythmia correlating with syncope was documented in 15 (88%) of these patients, in 2 (12%) patients an arrhythmia could be excluded. Of these 15 patients with arrhythmogenic cause of syncope 5 (33%) patients revealed higher degree AV-Block, 7 (47%) patients sinus bradycardia or sinus pauses, 4 (27%) due to sick sinus syndrome and 3 (20%) due to neurally mediated syncope, 3 (20%) patients had atrial tachycardias or atrial fibrillation with rapid AV-conduction. As a result of ILR findings 12 pacemakers were implanted and 2 radiofrequency ablations were performed. CONCLUSION: The ILR is a valuable and effective tool to establish an arrhythmic cause for unexplained syncope. In these cases they have an impact on subsequent clinical decision making. ILR can also be useful in ruling out arrhythmias as cause of syncope and presyncope.

[Atrila fibrillation: a review]. / Vorhofflimmern: Eine Ubersicht.

Atrial fibrillation (AF) is the most common sustained arrhythmia and increases exponentially with age. The physiologic basis are certain triggers initiating multiple micro-reentry circuits, which require a certain amount of "myocardial mass" to be sustained. There are numerous predisposing factors for AF, mostly leading to dilatation or hypertrophy of the atrial myocardium. Lone AF, however, occurs in structurally normal hearts. In the management of AF it is mandatory to decide between medical or electrical cardioversion in persistent AF and rate control in permanent AF. Medical cardioversion or prophylaxis of recurrence can be performed with Class IA, IC or Class III antiarrhythmic drugs. The choice of drugs depends on the underlying cardiac pathology of the individual patient. Patients with long duration of poor rate control during AF are at risk for tachycardia-induced cardiomyopathy. Cardioversion is safe to be performed within 48 hours after the onset of AF without prior and--if there is no risk of recurrence--without consecutive anticoagulation. When AF persists longer than 48 hours, anticoagulation for three weeks is mandatory prior to attempted cardioversion, or alternatively, transesophageal echocardiography can be performed to exclude the presence of an intraatrial thrombus. Anticoagulation has to be maintained for a minimum of four weeks after the restoration of sinus rhythm. Anticoagulation is required for paroxysmal, persistent and permanent AF. Lone atrial fibrillation in patients under the age of 60 years is an exception to these rules and does not require anticoagulation. In case of refractory AF with poor rate control, catheter ablation of the AV node with pacemaker implantation is the treatment of last choice. Early attempts to provide a cure for AF included the surgical "Maze" procedure, followed by linear catheter ablation with the goal of reducing the atrial mass. Catheter ablation of the triggers of AF, which mainly originate at the pulmonary veins and the "substrate modification" have been introduced in the last couple of years and is performed increasingly in specialized EP centers.

[ICD therapy in patients with coronary artery disease--incidence of adequate interventions]. / ICD-therapie bei Patienten mit koronarer Herzkrankheit--Inzidenz adäquater Interventionen.

BACKGROUND: The Implantable Cardioverter/Defibrillator (ICD) represents the therapy of choice for patients at risk of malignant ventricular arrhythmias. The survival benefit of the ICD vs antiarrhythmic therapy in patients with coronary artery disease and ventricular tachycardia has been proven. Recently, the ICD therapy has also been established for primary prevention in high risk patients. We report about the incidence of adequate ICD therapies in patients with coronary artery disease, who underwent ICD implantation at the University Hospital Zurich. METHODS: 104 consecutive patients (97 men, 7 women, mean age of 67 +/- 10 years) with coronary artery disease, who underwent ICD implantation in accordance with the AHA/ACC/NASPE guidelines between January 2000 and July 2003 were included in the study. Follow-up was performed every three to six months, when all ICD therapies were documented. This documentation was used for analysis of adequate or inadequate ICD therapies. RESULTS: The mean follow-up time was 383 +/- 195 days. The time to the first adequate therapy was 201 +/- 283 days. The cumulative incidence for the first adequate therapy was 21% at six months, 39% at two years and 59% at four years. In 64% of patients, who experienced adequate ICD therapies, antitachycardia pacing (ATP) and in 36% an initial shock was delivered. ATP was successful in 83% of adequately delivered episodes. In the follow-up period 12 patients died. CONCLUSION: The benefit of the ICD was apparent in patients at risk for ventricular arrhythmias and coronary artery disease after a relatively short period of time, which underlines the important role of the ICD in primary and secondary prevention.

[Stress, depression and cardiac arrhythmias]. / Stress, Depression und kardiale Arrhythmien.

A relationship between behavioural factors and cardiac arrhythmogenesis in humans has been described. Three sets of conditions contribute to the occurrence of arrhythmias: myocardial electrical instability, most often due to coronary artery disease; an acute triggering event, frequently related to mental stress; and a chronic, pervasive, and intense psychological state, often including depression and hopelessness. The autonomic nervous system plays an important role in the occurrence of cardiac arrhythmias and it is well documented that mood alterations as mental stress and depression influence cardiac autonomic balance. There is an increasing body of evidence that patients with the greatest changes in cardiac neural regulation with decreased parasympathetic tone coupled with increased sympathetic activity are at the greatest risk for developing fatal ventricular arrhythmias. These patients have a reduced heart rate variability, increased QT-dispersion and a decreased baroreceptor sensitivity. The influence of stress and depression on the autonomic nervous system and the impact on the occurrence of both atrial and ventricular arrhythmias is being discussed.

Expression of CD40 in vascular smooth muscle cells and macrophages is associated with early development of human atherosclerotic lesions.

CD40-CD154-mediated signaling has recently been described as playing a role in cellular functions involved in atherosclerotic processes. CD40 is expressed in macrophages, lymphocytes, endothelial cells, and vascular smooth muscle cells. However, cross-sectional studies investigating the expression of CD40 in atherosclerotic lesions are lacking. In the present study the expression of CD40 was studied in atherosclerotic lesions from 43 patients classified according to the World Health Organization criteria. Serial immunohistologic stainings of human iliac arteries from 43 patients were performed using monoclonal antibodies. Lesions were classified according to World Health Organization criteria, and CD40 expression was analyzed with regard to cell morphology and cellular markers by 2 independent observers. Human atherosclerotic lesions revealed a significant increase in intimal thickness, number of inflammatory infiltrates, and CD40-positive macrophages and vascular smooth muscle cells with progression of the lesions. This increase was most prominent from stage 0 to stage I. A significant correlation between intimal thickness and CD40-positive macrophages (r = 0.75, p <0.0005) and CD40-positive vascular smooth muscle cells (r = 0.81, p <0.0005) was observed. Ligation of the cellular CD40 receptor contributes to inflammatory cellular events in human vascular smooth muscle cells. These data suggest a direct association of CD40 expression in atherosclerotic lesions with early plaque development.

Efficient transcription of the human angiotensin II type 2 receptor gene requires intronic sequence elements.

To investigate mechanisms of human angiotensin II type 2 receptor (hAT2) gene regulation we functionally characterized the promoter and downstream regions of the gene. 5'-Terminal deletion mutants from -1417/+100 to -46/+100 elicited significant but low functional activity in luciferase reporter gene assays with PC12W cells. Inclusion into the promoter constructs of intron 1 and the transcribed region of the hAT2 gene up to the translation start enhanced luciferase activity 6.7+/-1.6-fold and 11.6+/-1.7-fold (means+/-S.E.M.) respectively, whereas fusion of the promoter to the spliced 5' untranslated region of hAT2 cDNA did not, which indicated an enhancement caused by intronic sequence elements. Reverse transcriptase-mediated PCR confirmed that the chimaeric hAT2-luciferase mRNA was regularly spliced in PC12W cells. A Northern blot analysis of transfected cells showed levels of luciferase mRNA expression consistent with the respective enzyme activities. Mapping of intron 1 revealed that a 12 bp sequence in the centre of the intron was required for the increase in promoter activity, whereas the 5' adjacent intronic region mediated a decrease in luciferase activity. Mutation of the 12 bp region led to altered protein binding and markedly decreased luciferase activity. Cloned into a promoterless luciferase vector, a 123 bp intron 1 fragment was able to direct reporter gene expression to the same activity as occurred in conjunction with the 5' flanking region. These results indicate that sequence elements in intron 1 are necessary for efficient transcription of hAT2. In reporter gene assays, intron 1 might by itself function as a promoter and initiate transcription from an alternative start point.

Protein kinase C-dependent regulation of the human AT1 promoter in vascular smooth muscle cells.

The expression level of angiotensin II (ANG II) type 1 receptors (AT1) determines the magnitude of ANG II signaling in vascular smooth muscle cells (VSMC). AT1 mRNA expression in cultured bovine VSMC increased twofold after 8 h of protein kinase C (PKC) activation with phorbol 12-myristate 13-acetate (PMA), whereas stimulation with forskolin did not alter the AT1 mRNA level. The expression of AT1 promoter/exon 1 [-513/+92 base pairs (bp)] luciferase constructs transfected into VSMC increased 2.4-fold with PMA stimulation. In-gel kinase assays demonstrated rapid phosphorylation of mitogen-activating protein kinases (MAPK) ERK1 and ERK2 by PMA. Electrophoretic gel mobility shift assays showed sequence-specific binding of nuclear proteins from PMA-activated VSMC, identified as activator protein 1 (AP-1) complex in competition assays, to a radiolabeled AT1-promoter fragment (-368/-399 bp). Recombinant AP-1 binds in a sequence-specific manner to the -386/-399-bp region. Site-specific mutagenesis destroying the AP-1 site, the adjacent polyoma enhancer activator 3 element, or both sites simultaneously indicated that both sites together are necessary and sufficient to control basal and PMA-induced activation of the human AT1 promoter in transfected VSMC. The capability of the phorbol ester PMA to activate the human AT1 promoter in VSMC via an AP-1 element suggests a prominent role for PKC/MAPK and Ets proteins in AT1 regulation.

Molecular biology of angiotensin receptors and their role in human cardiovascular disease.

The actions of angiotensin II in the cardiovascular system are transmitted by two known and possibly some unknown angiotensin receptor types. AT1 and AT2 both correspond to G-protein-coupled receptors with seven hydrophobic transmembrane domains, several N-glycosylation sites and a potential G-protein binding site. Cloning of coding regions and promoter sequences contributed to the understanding of receptor protein function and regulation. Angiotensin receptors with atypical binding properties for the known AT1- and AT2-specific ligands are expressed on human cardiac fibroblasts and in the human ulcrus. In several animal models, receptors with high affinity for angiotensin (1-7) have been described. AT1 stimulation is mediated by the generation of phospholipid-derived second messengers, activation of protein kinase C, the MAPkinase pathway and of immediate early genes. Recently, phosphorylation and dephosphorylation of tyrosine kinases have been associated with AT1- and AT2-mediated signal transduction. ATR are regulated by phosphorylation, internalization, modification of transcription rate and mRNA stability. Regulation is highly cell and organ specific and includes upregulation of ATR in some pathophysiological situations where the renin angiotensin system is activated. Whereas the function of AT1 in the cardiovascular system is relatively well established, there is little information regarding the role of AT2. Recent hypotheses suggest an antagonism between AT1 and AT2 at the signal transduction and the functional level. Transgenic animal models, particularly with targeted disruption of the AT1 and AT2 genes, suggest the contribution of both genes to blood pressure regulation. Genetic polymorphisms have been described in the AT1 and AT2 gene or neighbored regions and are used to analyze the association between gene defects and cardiovascular diseases. AT1 antagonists are now being introduced into the treatment of hypertension and potentially heart failure, and more interesting pharmacological developments are expected from the ongoing basic studies.

Subtype 2 and atypical angiotensin receptors in the human heart.

Angiotensin receptors have been described in the human heart and are suspected to play a central role in remodeling after myocardial infarction and in cardiac hypertrophy. Two subtypes, AT1 and AT2, have so far been described in humans, with AT2 being the dominant subtype in human atria. We have now determined subtype numbers and distribution by binding in ventricular myocardium from patients with end-stage heart failure. We found about 50-80% of subtype AT2 in the right and left ventricles from patients with end-stage heart failure due to coronary artery disease and cardiomyopathy, indicating that AT2 is the dominant angiotensin receptor subtype in the whole human heart. To determine the cellular localization of angiotensin receptors in human myocardium in addition to the known localization on myocytes, smooth muscle cells and endothelial cells, we investigated cardiac fibroblasts. They express an angiotensin receptor with yet incompletely understood binding characteristics which is coupled to proliferation and DNA synthesis. As AT2 is the dominant angiotensin receptor subtype in human heart, we cloned the complete mRNA sequence by a rapid amplification of cDNA ends (RACE) procedure and thereafter the promoter sequence from a human genomic library. Once the sequence of the mRNA and thus exon 1 was obtained by the RACE-PCR, a probe was constructed for the most 5' region of exon 1 and used for screening of a human genomic DNA bank. After cutting of the positive clones with EcoR1 and Not1, a 4000 bp fragment hybridized with the probe and was further sequenced. A functional AT2 promoter, with > 90% homology with the mouse promoter and 35% homology with the human AT1 promoter containing numerous cis-acting sequences for basal (TFIID) and inducible (AP-1, PEA-3, CBF) transcription factors in the first 1000 bp was identified.

Use of angiotensin II antagonists in human heart failure: function of the subtype 1 receptor.

THERAPEUTIC INHIBITION OF ANGIOTENSIN II: In human heart failure, specific inhibition of the cardiac effects of angiotensin II in addition to inhibition of the circulating renin-angiotensin system is an important therapeutic goal. Angiotensin II receptor subtype 1 (AT1) antagonists have been developed to specifically and selectively block the AT1 receptor and provide a more complete blockade of angiotensin II production with a marked improvement in side effects. RESULTS OF CLINICAL STUDIES: Clinical studies have shown beneficial effects from AT1 receptor antagonists. In a single dose study in patients with heart failure, the AT1 antagonist losartan decreased mean arterial pressure and pulmonary arterial pressure and increased the cardiac index, with maximal effects at 25 mg/day. The administration of losartan for 12 weeks also produced favorable hemodynamic and clinical results. The neurohormonal effects of AT1 receptor antagonists lead to decreases in plasma norepinephrine, aldosterone and atrial natriuretic peptide and an increase in plasma angiotensin II levels. EFFECT OF RECEPTOR SUBTYPE: The direct myocardial effects of angiotensin II and AT1 receptor antagonists in human hearts are determined by angiotensin receptor subtypes, their localization and regulation. We found that the receptor subtype AT2 represents the dominant receptor in normal and failing human myocardium. Angiotensin II receptors were found on isolated human cardiac fibroblasts where angiotensin II stimulated cellular proliferation via an as yet undetermined subtype. In end-stage human heart failure, angiotensin II receptors are characteristically downregulated at the protein and messenger RNA level. In a chronic rat model, the AT1 receptor antagonist losartan led to a downregulation of angiotensin II receptors in the liver, kidney, adrenal cortex and medulla. Downregulation of these receptors may represent an important mechanism by which AT1 receptor antagonists and angiotensin converting enzyme (ACE) inhibitors act to inhibit the renin-angiotensin system. CONCLUSIONS: AT1 receptor antagonists may inhibit the formation of plasma and tissue angiotensin II in heart failure to some extent. They may act synergistically with ACE inhibitors to inhibit renin-angiotensin systems completely. However, more basic data are needed to understand the effects, particularly in human myocardium.

Replication pattern of human immunodeficiency virus type 1 in mature Langerhans cells.

Langerhans cells (LC), the dendritic antigen presenting cells of the skin, mature into potent immunostimulatory cells during migration to regional lymph nodes, where they are identified as interdigitating cells (IDC). Since mature Langerhans cells (mLC) resemble IDC in phenotype and immunostimulatory capacity, we examined whether these cells were susceptible to infection with macrophagetropic and lymphotropic strains of human immunodeficiency virus type 1 (HIV-1). Highly purified cell preparations of mLC migrating from human epidermis expressed high amounts of major histocompatibility complex (MHC) class I and II antigens and of the accessory molecules CD40, CD80 and CD86, indicative of the phenotype of potent immunostimulatory cells. CD4 expression was upregulated on mLC during cultivation, independent of the presence of tumour necrosis factor alpha (TNF-alpha) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the culture medium. The macrophagetropic HIV-1 strain SF162 replicated to higher titres in mLC than the lymphotropic strain IIIB. Both strains induced syncytia, with SF162 showing a more rapid cytopathic effect. Addition of TNF-alpha enhanced virus production, due to better cell viability under TNF-alpha treatment, whereas GM-CSF did not significantly influence viability of cells and replication pattern of the virus. These findings suggest that in the infected individual IDC in lymph nodes may function as target cells for HIV-1.

[Angiotensin receptors--organ and subtype specific regulation in cardiovascular diseases by modulation of the renin-angiotensin system. Studies of the rat model and in human myocardium]. / Angiotensinrezeptoren--Organ- und subtypspezifische Regulation bei kardiovaskulären Erkrankungen und durch Modulation des Renin-Angiotensin-Systems. Untersuchungen am Rattenmodell und im menschlichen Myokard.

So far, two angiotensin receptor subtypes, called AT1 and AT2, have been described in an animal model and in human. AT1 mediates almost all known effects of angiotensin II and its gene sequence and regulation is well studied. In contrast, only few data on function and regulation of AT2 are available. The complete mRNA sequence of AT2 has only recently been cloned and sequenced. The angiotensin receptors' receptor density and subtype distribution is organ specific. In the rat, lowest densities are found in the myocardium, followed by kidney, liver, adrenal medulla and cortex. The percentage of AT1 in the different organs amounts to 80, 85, 90, 57 and 10%. Angiotensin receptor subtypes have also been quantitated in human myocardium. There, the relatively unknown subtype AT2 dominates (67%). Myocardial receptor density is low, amounting to about 11 fmol/mg protein corresponding to 1/20-1/50 of the density of beta-adrenergic receptors. Angiotensin receptors in the human heart are present on cardiac fibroblasts and induce proliferation of these cells. Blockade of the renin angiotensin system by ACEI and AT1 antagonists in the rat downregulates angiotensin receptors in liver, kidney and adrenals to about 50% in an organ- and subtype specific manner, whereas cyclosporin A upregulates receptors twice. In end-stage human heart failure, but not in early stages, angiotensin receptors are downregulated to 1/3 of control values. Regulator mechanisms at transcriptional level have been elucidated by reporter gene assays; PMA, an activator of proteinkinase C, stimulates the transcription of the AT1 gene. The organ- and subtypespecific regulation of angiotensin receptors by pharmacological agents and/or cardiovascular diseases can contribute to the understanding of these drugs and of the pathophysiology of the corresponding diseases.

Sequence specific binding of the transcription factor c-Ets1 to the human immunodeficiency virus type I long terminal repeat.

Human immunodeficiency virus type I (HIV-1) long terminal repeat (LTR) driven transcription is regulated by a variety of cellular transcription factors. Most work has focused on the two nuclear factor kappa B (NF-kB) elements indispensable for HIV-1 LTR enhancer function. We demonstrate here the specific binding of the transcription factor c-Ets1 to an U3 region of the HIV-1 LTR (nt -141 to -149) using electrophoretic mobility shift analysis with T-cell nuclear extract and in vitro translated protein. This previously not identified Ets binding site is highly conserved among different HIV-1 isolates and maps to an U3 region recently shown to be necessary for viral growth in vitro. The c-Ets proto-oncogene family of transcription factors has yet been associated with HTLV-I and HIV-2 transcription. Our present analysis suggests an important role of c-Ets proteins in HIV-1 transcription.