Electrophysiologic effects of ethmozin in patients with ventricular tachycardia

Ten patients with recurrent episodes of ventricular tachycardia (VT) had electrophysiologic studies in the basal state and on chronic oral ethmozin (12.1 ± 0.6 SE mg/kg/day). Ethmozin significantly prolonged the AH interval (basal: 75 ± 8 SE msec; ethmozin: 91 ± 10 msec, p < 0.05), the HV interval (51 ± 3; 66 ± 5 msec, p < 0.01), and the QRS duration (101 ± 4; 118 ± 4 msec, p < 0.001). Atrial and ventricular refractory periods and the corrected QT interval were not significantly affected by ethmozin. VT was induced in 7 of 10 patients in the basal state by means of programmed right ventricular extrastimulation or rapid burst ventricular pacing. On oral ethmozin nine patients had inducible VT. VT cycle length was consistently prolonged on ethmozin (250 ± 13; 326 ± 14 msec, p < 0.001). Four of the seven patients with VT on basal ambulatory monitoring had total abolition of spontaneous VT on ethmozin. Ethmozin failed to prevent induction of VT in most patients despite significant reductions in ventricular arrhythmia on ambulatory monitoring. Further studies comparing VT induction with ambulatory monitoring in patients on ethmozin are needed to confirm these findings and to define the clinical significance of this dissociation.     

Ventricular tachycardia with congenital ventricular diverticulum

A 24-year-old man presented with symptomatic, recurrent, sustained ventricular tachycardia (VT). He was found to have a basal inferior left ventricular diverticulum. His sustained VT was reproduced by programmed electrical stimulation and was unresponsive to procainamide, tocainide, propafenone, and flecainide. Endocardial mapping followed by resection and cryoablative surgery was performed. The patient had only one recurrence after 18 months, with subsequent control with procainamide for over 14 months.     

A novel echocardiographic predictor of in-hospital mortality and mid-term haemodynamic improvement after pulmonary endarterectomy for chronic thrombo-embolic pulmonary hypertension.

AIMS: To study whether pre-operative assessment, using echocardiography, of the timing of a particular feature in the pulmonary flow (pulmonary flow systolic notch) may predict in-hospital mortality and mid-term haemodynamic improvement after pulmonary endarterectomy (PEA) for chronic thrombo-embolic pulmonary hypertension (CTEPH). METHODS AND RESULTS: Fifty-eight of 61 consecutive CTEPH patients (aged 53 +/- 14 years; 36 women) who underwent PEA between June 2002 and June 2005 were studied. Clinical, haemodynamic, and echocardiographic variables were assessed pre-operatively and at 3 months post-PEA. Timing of the notch was expressed as notch ratio (NR). Pre-operatively, seven patients had no notch, 33 had NR < 1.0, and 18 had NR > 1.0. NR was associated with in-hospital mortality (P < 0.01). Moreover, multivariable analysis revealed that among pre-operative variables, NR was an independent predictor of residual-increased pulmonary artery systolic pressure (>40 mmHg) at 3 months post-PEA (P = 0.01). Receiver operator characteristic analysis established NR = 1.0 as optimal cutoff to distinguish patients at risk of such unfavourable outcomes, with NR > 1.0 conferring higher risk. CONCLUSION: NR is related with in-hospital mortality and residual pulmonary hypertension after PEA. NR > 1.0 is associated with a higher risk of such unfavourable outcomes. NR may be considered a determinant of eligibility for PEA.     

Usefulness of sotalol for drug-refractory malignant ventricular arrhythmias

Fifty patients with recurrent sustained symptomatic ventricular tachycardia (43 patients) or ventricular fibrillation (7 patients) resistant to a mean of 2.8 + 1.4 antiarrhythmic drugs were treated with sotalol, a beta-adrenergic receptor antagonist, and 45 underwent invasive electrophysiologic testing before and after sotalol therapy. The arrhythmia became noninducible in 10, was slower and hemodynamically well tolerated in 12 and was poorly tolerated in 23. Four patients were empirically treated with long-term administration of oral sotalol as were 21 patients who either had noninducible arrhythmia (10 patients) or had hemodynamically stable ventricular tachycardia (11 patients). In these 25 patients treated with long-term administration of sotalol, there was no recurrence of ventricular tachycardia in the group with noninducible arrhythmia, whereas 37% of patients with inducible ventricular tachycardia had new ventricular tachycardia or sudden death. Programmed ventricular stimulation with up to three extrastimuli proved to be an excellent predictor of drug efficacy and a good predictor of inefficacy. A positive prior response to amiodarone was not a reliable indicator of a positive response to sotalol. Side effects included those attributed to both beta-adrenergic blockade as well as proarrhythmic effects. The latter were observed in two of four patients with a QT interval greater than 600 ms. Sotalol was found to be effective therapy for a subset of patients with ventricular tachycardia unresponsive to type IA drugs.     

Diagnostic Value of Detecting Feline Coronavirus RNA and Spike Gene Mutations in Cerebrospinal Fluid to Confirm Feline Infectious Peritonitis

Background: Cats with neurologic feline infectious peritonitis (FIP) are difficult to diagnose. Aim of this study was to evaluate the diagnostic value of detecting feline coronavirus (FCoV) RNA and spike (S) gene mutations in cerebrospinal fluid (CSF). Methods: The study included 30 cats with confirmed FIP (six with neurological signs) and 29 control cats (eleven with neurological signs) with other diseases resulting in similar clinical signs. CSF was tested for FCoV RNA by 7b-RT-qPCR in all cats. In RT-qPCR-positive cases, S-RT-qPCR was additionally performed to identify spike gene mutations. Results: Nine cats with FIP (9/30, 30%), but none of the control cats were positive for FCoV RNA in CSF. Sensitivity of 7b-RT-qPCR in CSF was higher for cats with neurological FIP (83.3%; 95% confidence interval (95% CI) 41.8–98.9) than for cats with non-neurological FIP (16.7%; 95% CI 6.1–36.5). Spike gene mutations were rarely detected. Conclusions: FCoV RNA was frequently present in CSF of cats with neurological FIP, but only rarely in cats with non-neurological FIP. Screening for spike gene mutations did not enhance specificity in this patient group. Larger populations of cats with neurological FIP should be explored in future studies.     

Expansion of the fusion stalk and its implication for biological membrane fusion

Over the past 20 years, it has been widely accepted that membrane fusion proceeds via a hemifusion step before opening of the productive fusion pore. An initial hourglass-shaped lipid structure, the fusion stalk, is formed between the adjacent membrane leaflets (cis leaflets). It remains controversial if and how fusion proteins drive the subsequent transition (expansion) of the stalk into a fusion pore. Here, we propose a comprehensive and consistent thermodynamic understanding in terms of the underlying free-energy landscape of stalk expansion. We illustrate how the underlying free energy landscape of stalk expansion and the concomitant pathway is altered by subtle differences in membrane environment, such as leaflet composition, asymmetry, and flexibility. Nonleaky stalk expansion (stalk widening) requires the formation of a critical trans-leaflet contact. The fusion machinery can mechanically enforce trans-leaflet contact formation either by directly enforcing the trans-leaflets in close proximity, or by (electrostatically) condensing the area of the cis leaflets. The rate of these fast fusion reactions may not be primarily limited by the energetics but by the forces that the fusion proteins are able to exert.Membrane fusion is a fundamental process in cell biophysics, being involved in viral infection, endo- and exocytosis, and fertilization. The textbook example of membrane fusion comprises three experimentally observed metastable lipidic structures—namely, the rhombohedral stalk (1, 2), the hemifusion diaphragm (HD) (3–5), and the toroidal fusion pore (6). These structures represent (local) free energy minima that are connected via transient states (free energy barriers) within the fusion pathway. How the stalk transitions (expands) into the fusion pore remains controversial (7–9). Different pathways have been proposed based on experimental observations (3, 5, 10–13), molecular simulations (8, 9, 14–20), continuum elastic models (15, 21, 22), and self-consistent field theory (23, 24).Arguably, the best-studied fusion reactions are the ones mediated by influenza hemagglutinin and soluble N-ethylmaleimide-sensitive-factor attachment receptor (SNARE) molecules. Hemagglutinin-mediated fusion displays an unusual sensitivity toward point mutations in its amphiphilic fusion peptide. Here, even single point mutations can selectively trap the fusion reaction in a hemifused state (25). Hemagglutinin therefore very likely plays an active, essential role in the subsequent evolution of hemifusion intermediates (20). In contrast, it remains unclear if SNARE molecules play a role therein. SNARE molecules subject force on the membrane via the ends of the transmembrane domains (TMDs) (26). The X-ray–resolved structure of the postfusion neuronal SNARE complex suggests that TMDs come together during the fusion reaction, and may actively drive fusion up to the expansion of the fusion pore (27). However, in vitro and in vivo experiments, where the TMD was either replaced by a lipid anchor or partly truncated, provided mixed results concerning the essence of subsequent driving forces after initial membrane merger (28, 29).To discern whether the fusion machinery plays an active role after stalk formation, we estimated the lower bound of the free energy barrier against expansion of the stalk. If stalk expansion faces a substantial free-energy barrier even under extremely fusogenic conditions (i.e., the lower bound of the free energy barrier), then fast, in vivo fusion reactions, such as synaptic fusion, likely involve an active mechanism.We performed coarse grained molecular dynamics simulations, where computational efficiency is enhanced by representing several atoms by a single interaction site, to study the progression of a stalk formed between two highly curved “dimples” with a curvature of –1/10 nm⁻¹. We modeled such a scenario by studying the fusion process of a 20-nm–sized vesicle with its own periodic image (Fig. 1). Such an extreme curvature approaches the upper bound of membrane curvature that fusion proteins, such as synaptotagmin, can generate when being overexpressed on the membrane (30). The exaggerated curvature stress of the here-modeled fusion site should approach the lower bound of the in vivo expansion barrier (31, 32). In addition, we explored the effect of phosphatidylethanolamine (PE) lipids and cholesterol, the two abundant “fusogens” in the plasma membrane, on the expansion of the metastable stalk.Open in a separate windowFig. 1.(A) A 20-nm–sized vesicle, mimicking the protein-free cap of a (protein) induced dimple or nipple, fuses with its own periodic image. To ensure free flow of lipid material (tensionless conditions), two artificial pores with a radius 1.6 nm are present at the vesicle’s foot. The simulation box can freely adjust its length in the Z dimension, as well as in the XY dimension. The green circles depict the hydrophilic probes which mimic the squeezing action of one or multiple SNARE complexes. (B) Example of a scenario where widening of the stalk is driven by the presence of multiple neuronal SNARE complexes (26, 51). The C termini of the transmembrane domains (green circles) exert a squeezing force on both the trans-leaflets and thereby drive thinning and widening of the stalk. Lipids: tails are shown in gray, head groups (spheres) in tan, cholesterol in brown. SNAREs: syntaxin-1A in red, synaptobrevin-2 in green, and SNAP-25 in green. Transmembrane domains are shown in yellow.In total we performed more than 500 simulations of 1.6 μs each to study four relevant scenarios: (i) The leaflets of the surrounding bulk membrane are in equilibrium and material freely flows between the bulk membrane and the dimple; (ii) the flow of material between the dimple’s cap and the surrounding bulk membrane is restricted/inhibited due to the crowding of nearby fusion proteins; (iii) a tension difference between the leaflets is induced by, e.g., an asymmetric ion concentration; and (iv) the presence of shape-stabilizing matrix proteins on the trans-leaflets of viral envelopes (11) or a membrane adhered to a solid support (supported bilayers).To estimate the free energy required for (protein-mediated) expansion of the stalk, we placed a hydrophilic probe consisting of eight bundled solvent beads in each vesicle. We alter the equilibrium distance between the probes within the simulations (Fig. 2 and SI Appendix, Methods). Such a scenario mimics, e.g., the hydration shell(s) of the charged TMD ends (C termini) of SNARE molecules (Fig. 1B) that come together during the fusion reaction (27), and thereby exert a squeezing force on the stalk (26).Open in a separate windowFig. 2.The expansion barrier of the stalk—standard hemifusion mechanism. The figures show the fusion reaction between the membranes (at 310 K) in response to pulling two hydrophilic probes (green) toward each other through the center of the stalk. This process mimics the action of SNARE zipping where the hydrophilic transmembrane domain C termini are pulled together. (Upper) The required free energy for facilitating such a process. (Lower) Corresponding formation of the hemifusion diaphragm. The initial stalk (I) expands linearly (II) before expanding radially (III and IV). Once the barrier (III) of 17–24 k_BT is overcome, the subsequent formation/expansion of the hemifusion diaphragm (IV) becomes spontaneous (plateau region). The addition of 40% POPE does not significantly affect the barrier of stalk widening. The addition of 30% cholesterol marginally increases the barrier against stalk widening (from 17 to 24 k_BT). Trans-leaflets are shown in yellow, cis leaflets in gray. The example shows the situation for the pure POPC membrane (PC head groups are shown in tan).First, we considered a scenario where the leaflets of the dimple are in equilibrium and the chemical potential of the cis and trans-leaflets remains constant during the fusion process. Free lipid exchange is facilitated between all four leaflets by placing two artificial 1.6-nm–sized pores at the foot of the dimple, which facilitate a lipid flip-flop rate of 0.4 ns⁻¹ (33, 34) (Fig. 1A and SI Appendix, Fig. S1). Because the pores allow a free exchange of lipids and solvent, and because the x-, y-, and z-dimensions of the simulation box are semi-isotropically coupled to the same external pressure bath (1 bar), we can assume no lateral tension is present in the leaflets.     

Ablation of cardiac tissues by an electrode catheter technique for treatment of ectopic supraventricular tachycardia in adults

Five patients with chronic or recurrent ectopic supraventricular tachycardias unresponsive to drugs underwent programmed stimulation, endocardial mapping, and attempted catheter ablation of the arrhythmia focus. For attempted ablation, an intracardiac electrode catheter was positioned near the exit point of the tachycardia and served as the cathode while a chest wall patch served as the anode. In two patients with tachycardia originating near the coronary sinus, discharges of 200 or 400 J each were delivered to two electrodes at the earliest area of endocardial activation. These two patients with incessant tachycardia remain free of tachycardia for 17 and 11 months, respectively. In one patient with tachycardia originating from the right atrial appendage, both catheter and surgical ablation proved unsuccessful in that a new focus of atrial tachycardia supervened. This patient subsequently underwent successful catheter ablation of the atrioventricular junction. Two patients with junctional tachycardia underwent catheter ablation of the atrioventricular junction. Complete atrioventricular block followed atrioventricular junctional ablation and these patients required permanent cardiac pacing. The junctional tachycardia was replaced by sinus rhythm with episodes of unsustained atrial tachycardia. However, after 13 +/- 5 months follow-up, neither of the patients require antiarrhythmic drugs. Catheter ablation can be effective for atrial foci near the coronary sinus os, and can be performed with preservation of atrioventricular conduction. Arrhythmia ablation is possible in those with atrioventricular junctional tachycardia but requires the sacrifice of atrioventricular conduction. After ablation, other automatic atrial foci may become operative and complicate use of dual-chamber pacemakers.     

Adverse drug reaction-related hospitalisations: a nationwide study in The Netherlands.

BACKGROUND: The incidence of adverse drug reaction (ADR)-related hospitalisations has usually been assessed within hospitals. Because of the variability in results and methodology, it is difficult to extrapolate these results to a national level. OBJECTIVES: To evaluate the incidence and characteristics of ADR-related hospitalisations in The Netherlands in 2001. METHODS: We conducted a nationwide study of all hospital admissions in 2001. Data were retrieved from a nationwide computer database for hospital discharge records. All acute, non-planned admissions to all Dutch academic and general hospitals in 2001 were included in the study (n = 668 714). From these admissions we selected all hospitalisations that were coded as drug-related, but intended forms of overdose, errors in administration and therapeutic failures were excluded. Hence, we extracted all ADR-related hospitalisations. We compared age, sex and the risk of a fatal outcome between patients admitted with ADRs and patients admitted for other reasons, as well as the most frequent main diagnoses in ADR-related hospitalisations and which drugs most frequently caused the ADRs. In addition, we evaluated to what extent these ADRs were reported to the Netherlands Pharmacovigilance Centre Lareb for spontaneous ADR reporting. RESULTS: In 2001, 12 249 hospitalisations were coded as ADR related. This was 1.83% of all acute hospital admissions in The Netherlands (95% CI 1.80, 1.86). The proportion increased with age from 0.8% (95% CI 0.75, 0.85) in the <18 years group to 3.2% in the >/=80 years group (95% CI 3.08, 3.32). The most frequent ADR-related diagnoses of hospitalisations were bleeding (n = 1048), non-specified 'unintended effect of drug' (n = 438), hypoglycaemia (n = 375) and fever (n = 347). The drugs most commonly associated with ADR-related hospitalisations were anticoagulants (n = 2185), cytostatics and immunosuppressives (n = 1809) and diuretics (n = 979). Six percent of the ADR-related hospitalisations had a fatal outcome (n = 734). Older age and female gender were associated with ADR-related hospitalisations. Only approximately 1% of the coded ADRs causing hospitalisation were reported to our national centre for spontaneous ADR reporting. CONCLUSION: The proportion of ADR-related hospitalisations is substantial, especially considering the fact that not all ADRs may be recognised or mentioned in discharge letters. Under-reporting of ADRs that result in hospital admission to our national centre for spontaneous ADR reporting was considerable.