Irregularity of the ventricular rhythm during atrial fibrillation: effect of slow atrioventricular nodal pathway ablation.

BACKGROUND: The contribution of dual atrioventricular (AV) nodal pathway physiology to the irregularity of the ventricular rhythm during atrial fibrillation has not been clarified. HYPOTHESIS: This study was performed to assess the effects of slow AV nodal pathway ablation on the irregularity of the ventricular rhythm during atrial fibrillation. METHODS: Irregularity of the ventricular rhythm was quantified using analysis of heart rate variability. In 20 patients with AV nodal reentrant tachycardia, absolute heart rate variability during atrial fibrillation was quantified before and after slow AV nodal pathway ablation by the standard deviation of all NN intervals (SDNN). Relative heart rate variability was determined by computing the coefficient of variation, SDNN normalized for the standard deviation of the mean ventricular cycle length (MVCL-AF). RESULTS: The slope of the regression between MVCL-AF and SDNN was significantly more gradual after slow pathway ablation (slope 0.39 vs. 0.23, p < 0.001). Coefficient of variation increased in 12 patients with heart rates > 120 beats/min at baseline (18.6 +/- 3.9 vs. 22.1 +/- 2.7% MVCL-AF, p < 0.05), but decreased in 8 patients with heart rates < 120 beats/min at baseline (25.6 +/- 3.1 vs. 22.2 +/- 2.2% MVCL-AF, p = 0.05). Furthermore, coefficient of variation correlated with MVCL-AF only at baseline (slope 0.034, r = 0.66), but no relation was found after slow pathway ablation (slope 0, r = 0). CONCLUSIONS: Slow AV nodal pathway ablation alters the relation between absolute heart rate variability and mean ventricular rate during atrial fibrillation and eliminates cycle length dependency of relative heart rate variability. These data indicate that dual AV nodal pathway physiology contributes to the irregularity of the ventricular rhythm during atrial fibrillation.

Molecular characterization of Salmonella enterica subsp. enterica serovar choleraesuis field isolates and differentiation from homologous live vaccine strains suisaloral and SC-54.

Four independent molecular methods were used to characterize the Salmonella enterica subsp. enterica serovar choleraesuis live vaccine strains SC-54 and Suisaloral and to differentiate them from S. choleraesuis field isolates. Plasmid analysis revealed the presence of seven plasmid profiles. A virulence plasmid of 52-kbp was identified by hybridization with an spvB-spvC gene probe in each of the S. choleraesuis field isolates and in the Suisaloral vaccine strain, but not in the SC-54 vaccine strain. Ribotyping, performed with a gene probe that recognized 23S, 16S, and 5S rRNA genes, resulted in three closely related hybridization patterns. IS200 elements were not detected in the field isolates or in the two S. choleraesuis live vaccine strains. Macrorestriction analysis with the enzymes XbaI, SpeI, NotI, and SfiI differentiated the 29 S. choleraesuis strains included in this study into 10, 13, 8, and 13 different fragment patterns, respectively. While the Suisaloral vaccine strain showed a unique XbaI macrorestriction pattern, the fragment patterns of the SC-54 strain obtained with the different enzymes were shared by 2 to 18 S. choleraesuis field strains. A combination of plasmid analysis and macrorestriction analysis proved to be most suitable for the molecular typing of S. choleraesuis and the differentiation of both live vaccine strains from field isolates of this serovar.

[Molecular biological methods for epidemiological typing of Salmonella--a review]. / Molekularbiologische Methoden zur epidemiologischen Typisierung von Salmonellen--Ubersichtsreferat.

Various molecular typing methods for the analysis of zoonotic bacterial pathogens have been developed during the last decade. Because of their high discriminatory power, these methods have been increasingly used even in routine diagnostics. The description of several independent genotypic characteristics in addition to that of the phenotypic properties enables a complex and exact identification of bacterial strains. Molecular techniques such as plasmid analysis, ribotyping. IS200 typing as well as macrorestriction analysis represent components of a basic molecular typing system for Salmonella isolates which proved to be suitable for various epidemiological applications.

Evaluation and comparison of molecular techniques for epidemiological typing of Salmonella enterica subsp. enterica serovar dublin.

A total of 28 unrelated isolates of the Salmonella enterica subsp. enterica serovar dublin (S. dublin) collected during a 6-year period, as well as four samples of the S. dublin live vaccine strain Bovisaloral and its prototype strain S. dublin 442/039, were investigated by different molecular typing methods for the following reasons: (i) to find the most discriminatory method for the epidemiological typing of isolates belonging to this Salmonella serovar and (ii) to evaluate these methods for their capacity to discriminate among the live vaccine strain Bovisaloral, its prototype strain S. dublin 442/039, and field isolates of the serovar dublin. Five different plasmid profiles were observed; a virulence plasmid of 76 kbp as identified by hybridization with an spvB-spvC gene probe was present in all isolates. The detection of 16S rRNA genes and that of IS200 elements proved to be unsuitable for the epidemiological typing of S. dublin; only one hybridization pattern could be observed with each of these methods. The results obtained from macrorestriction analysis strongly depended on the choice of restriction enzyme. While the enzyme NotI yielded the lowest discriminatory index among all enzymes tested, it was the only enzyme that allowed discrimination between the Bovisaloral vaccine strain and its prototype strain. In contrast to the enzymes XbaI and SpeI, which only differentiated among the S. dublin field isolates, XhoI as well as AvrII also produced restriction fragment patterns of the Bovisaloral strain and of its prototype strain that were not shared by any of the S. dublin field isolates. Macrorestriction analysis proved to be the most discriminatory method not only for the epidemiological typing of S. dublin field isolates but also for the identification of the S. dublin live vaccine strain Bovisaloral.

Molecular typing of Salmonella enterica subsp. enterica serovar Enteritidis isolates.

A collection of 31 epidemiologically unrelated Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) isolates obtained during a 12-year period was characterised by different molecular typing methods. Plasmid profile analysis, the detection of plasmid-encoded virulence genes and ribotyping allowed little or no further differentiation amongst these isolates. Two different hybridisation patterns were observed by IS200-typing of the S. Enteritidis isolates. However, pulsed-field gel electrophoretic separation of restriction endonuclease-digested whole-cell DNA provided a high level of discrimination amongst the 31 S. Enteritidis isolates. This could be increased by the comparative use of the three suitable restriction endonucleases XbaI, SpeI and NotI. Thus, pulsed-field gel electrophoresis proved to be superior in its discriminatory value to other molecular methods such as plasmid analysis, ribotyping or IS200-typing and represents a most helpful tool for the epidemiological typing of S. Enteritidis isolates.

Tetracycline resistance determinants among streptococci of serological group G and L.

In the present study 56 streptococci of serological group G and L isolated from various animal species and from humans were investigated for tetracycline and minocycline resistance and for the presence of genes conferring this combined resistance. Among the 45 group G streptococci, 2 isolates from dogs, 3 from cattle and 2 from humans, respectively, as well as all 11 group L streptococci isolated from cattle, pigs or poultry were resistant to tetracycline and simultaneously to minocycline. The restriction endonuclease digested and blotted DNA-preparation of the tetracycline-and minocycline resistant group G streptococci from dogs and humans hybridized with the tet (M) gene probe, those from bovines with the tet (O) gene probe. Six group L streptococci carried the gene tet (M), whereas 5 isolates harboured the gene tet (O). The tet (M)-and tet (O) gene probes recognized complementary sequences on EcoRI-fragments of various sizes.

Insertion elements in Staphylococcus intermedius.

Staphylococcus intermedius cultures from dogs, pigeons, horses and mink were investigated for the prevalence of the insertion elements IS256 and IS257 in relation to their antibiotic resistance. Copies of IS256 could not be detected in any of the Staph. intermedius isolates tested whereas single copies of IS257 occurred in the isolates from dogs and horses. The mink strains did not harbour IS257 elements, whereas Staph. intermedius isolates from pigeons carried multiple copies of IS257 as predicted from the hybridization patterns obtained with a gene probe derived from the internal part of the IS257-encoded transposase gene. Independently of the origin of the Staph. intermedius isolates, all IS257 copies were found to be located in the chromosomal DNA. The large number of chromosomal IS257 copies in the pigeon strains might help to explain chromosomal multiresistance in many of those strains.

Pulsed-field gel electrophoretic identification of Salmonella enterica serovar Typhimurium live vaccine strain Zoosaloral H.

Salmonella enterica subsp. enterica serovar Typhimurium (Salm. Typhimurium) live vaccine strain Zoosaloral H was characterized by pulsed-field gel electrophoresis (PFGE). Each of the two suitable restriction enzymes, XbaI and SpeI, produced a unique restriction fragment pattern for this live vaccine strain which was not shared by field isolates of the same serovar. The characteristic fragment pattern proved to be stable during a 22 month observation period and was also not altered after animal passage of the vaccine strains. Thus PFGE analysis proved to be a helpful tool in the identification of Salm. Typhimurium live vaccine strain Zoosaloral H and its differentiation from wild-type isolates of the same serovar.

Use of ribotyping, IS200 typing and plasmid analysis for the identification of Salmonella enterica subsp. enterica serovar Typhimurium vaccine strain Zoosaloral H and its differentiation from wild type strains of the same serovar.

Fifty Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) isolates obtained from one vaccinated and three non-vaccinated poultry flocks as well as the commercially available vaccine strain Zoosaloral H and a S. Typhimurium reference strain were characterized genotypically to differentiate between S. Typhimurium live vaccine strain Zoosaloral H and wild type strains of the same serovar. Ribotyping revealed five different patterns one of which exclusively occurred in the vaccine strain. Seven different hybridization patterns could be observed by IS200-typing of the S. Typhimurium isolates; one of them was only detectable in the vaccine strain. Plasmid analysis showed that 51% of the S. Typhimurium isolates including the vaccine strain harboured large plasmids of approximately 60 MDa. Hybridization with a virulence gene probe identified only 48% of these large plasmids, including that of the vaccine strain, to carry this virulence-associated gene. However, restriction endonuclease analysis of the hybridizing plasmids showed that the virulence gene was located on HindIII fragments of different sizes in the plasmid of the S. Typhimurium vaccine strain Zoosaloral H and in the plasmids of the respective wild type S. Typhimurium isolates. Thus, ribotyping, IS200-typing and plasmid analysis represent at least three independent systems which allow the genotypic identification of the S. Typhimurium vaccine strain Zoosaloral H and its differentiation from wild type isolates of the same serovar.

Elimination of amino acids in renal failure.

The elimination of intravenously infused amino acids was evaluated in six patients with acute renal failure (ARF), 6 with conservatively treated chronic renal failure (CRF), 6 subjects receiving regular hemodialysis treatment (RDT), and 5 healthy control subjects. In ARF, CRF, and RDT groups, whole-body clearance (Cltot) of the 10 amino acids was elevated (113.5 +/- 1.5; 94.2 +/- 1.5 and 127.6 +/- 12.4, respectively, vs 85.2 +/- 4.8 mL.kg-1.min-1 in control subjects, P < 0.001). In ARF, Cltot of histidine, lysine, and methionine was higher and Cltot of phenylalanine and valine was lower as compared with control subjects. In CRF, Cltot of tryptophan and histidine was elevated and Cltot of phenylalanine was reduced; in RDT, Cltot of histidine, methionine, tryptophan, lysine, isoleucine, and leucine was raised. In all groups the relative clearance (% of total clearance) of phenylalanine and valine was reduced, and relative clearance of histidine and tryptophan was elevated. We conclude that in renal failure the elimination of amino acids from the intravascular space is profoundly altered and that the pattern of metabolic aberrations is similar in ARF, CRF, and RDT groups.

The effects of lisinopril on renal function in proteinuric renal transplant recipients.

Renal transplantation is frequently accompanied by systemic hypertension. In the present study we evaluated the effect of 2.5 mg lisinopril in 12 hypertensive and proteinuric renal graft recipients with stable graft function over 3 months. Only patients with absence of renal artery stenosis, at least as judged by technetium-scan imaging, were included. Lisinopril was effective in lowering systemic blood pressure. Mean arterial pressure was unchanged despite reduction of concomitant antihypertensive medication. Mean serum creatinine was unchanged during the study (1.95 +/- 0.8 mg/dl in the pretreatment period vs. 1.77 +/- 0.76 mg/dl in the intervention period, n.s.). Glomerular filtration rate remained stable (62.75 +/- 21.96 vs. 60.17 +/- 18.27 ml/min/1.73 m2, n.s.) whereas renal plasma flow increased (224.75 +/- 91.66 vs. 244.92 +/- 94.13 ml/min/1.73m2, P < 0.01), leading to a drop in filtration fraction (31.4 +/- 12.4 vs. 26.8 +/- 8.6, n.s.). Renal vascular resistance was significantly reduced following angiotensin-converting enzyme (ACE) inhibitor therapy (26,447 +/- 14,574 vs. 23,425 +/- 12,430 dyne sec cm-5/1.73 m2, P < 0.01). Mean daily proteinuric decreased significantly (2.98 +/- 2.06 vs. 2.06 +/- 2.29 g, P < 0.01) whereas in a group of patients with comparable blood pressure but without ACE inhibitor therapy and similar degree of proteinuria, 24-hr proteinuria remained stable. No severe side effects were observed--in particular, mean serum potassium showed only a slight increase and no clinically significant hyperkalemic condition was observed. When lisinopril therapy was withdrawn after 3 months, blood pressure increased in all patients, requiring reinstitution of additional antihypertensive medication. Renal hemodynamic parameters and daily proteinuria returned to baseline values. We conclude that 2.5 mg lisinopril daily was safe and effective in this group of renal transplant recipients and showed a good antihypertensive as well as antiproteinuric effect.

Lactic acidosis in thiamine deficiency.

Two chronically ill patients with limited nutritional intake during several weeks developed prolonged lactic acidosis. As no other causes of hyperlactaemia could be identified, thiamine deficiency was suspected. Supplementation of 600 mg thiamine resulted in a rapid normalisation of serum lactate levels (in patient 1 from 10.9-2.4 mmol/l; in patient 2 from 11.8-2.0 mmol/l) and acid base status (patient 1: pH from 7.11-7.30, bicarbonate from 8.6-21.2 mmol/l; patient 2: pH from 7.24-7.46, bicarbonate from 16-28 mmol/l; before and after treatment, respectively). Thiamine deficiency was confirmed by the degree of stimulation of erythrocyte transketolase activation by adding thiamine pyrophosphate, evaluated before and after thiamine replacement therapy. Stimulation decreased in patient 1 from 170% to 17% and in patient 2 from 20% to 0%, respectively. In addition to the metabolic derangement right ventricular heart failure was confirmed by echocardiography in both patients and again this was rapidly reversible by thiamine supplementation. We conclude that in malnourished patients unexplained prolonged lactic acidosis may result from thiamine deficiency, which is rapidly reversible by thiamine replacement therapy.

[Arterial hypertension in elderly patients]. / Arterielle Hypertonie bei alten Menschen.

The cardiovascular system changes in the elderly: reduced blood volume and cardiac output, diminished elastic properties of the arterial wall and increased peripheral resistance are to be expected. Arterial hypertension can be developed when these changing factors are not balanced, especially with the longer lasting of cardiovascular risk factors. Arterial hypertension can be found in nearly every second person older than 60 years living in industrial countries--it is common but nevertheless not normal in the elderly. Epidemiologic studies show the effectiveness of the antihypertensive drug therapy in the aged in diminishing cerebrovascular and coronary events and improving the quality of live. When elderly persons are treated with antihypertensive drugs, this therapy should be chosen in respect of target organ damage and accompanying health problems and with close monitoring of the antihypertensive response and tolerability.

Plasma levels of endothelin in chronic renal failure and after renal transplantation: impact on hypertension and cyclosporin A-associated nephrotoxicity.

1. Plasma levels of endothelin were measured in 30 patients with chronic renal failure, 32 patients on chronic haemodialysis treatment and 25 renal graft recipients with stable renal graft function. 2. In patients with chronic renal failure as well as in patients on regular haemodialysis treatment, mean plasma levels of endothelin were significantly increased (4.59 +/- 2.09 pg/ml, 10.08 +/- 3.12 pg/ml, respectively) when compared with normal subjects (1.88 +/- 0.6 pg/ml, P less than 0.01, P less than 0.001, respectively). 3. In the group with chronic renal failure a positive correlation between the plasma level of endothelin and the plasma concentration of creatinine was observed (P less than 0.003). 4. Renal graft recipients on cyclosporin A with stable renal graft function had a normal plasma level of endothelin suggesting that cyclosporin A nephrotoxicity is not mediated by endothelin. 5. Hypertensive patients with chronic renal failure or on regular haemodialysis and hypertensive renal graft recipients did not differ from the corresponding normotensive population with regard to the plasma level of endothelin, demonstrating that an increased plasma level of endothelin does not play a major role in the pathogenesis of renal hypertension.

Arterial baroreflex sensitivity and blood pressure variabilities before and after carotid surgery.

Carotid surgery is frequently associated with postoperative blood pressure alterations. The role of baroreceptors with regard to these alterations was assessed in 50 patients by determining the pre- and postoperative mechanoreceptor sensitivity after Valsalva maneuver and intravenous injections of angiotensin and nitroglycerine as described by Smyth, Sleight and Pickering. In addition, blood pressure was monitored perioperatively and renin and aldosterone levels were measured. In patients with arterial hypertension a postoperative increase of receptor reactivity can be seen necessitating a reduction of antihypertensive therapy in more than 50% of cases. In normotensive patients no uniform response can be observed. A possible explanation for this effect might be the local increase of pressure in the operated vascular segment. The postoperative reintegration of receptor areas which had been adjusted to a reduced pressure level might induce a more sensitive response than can be seen for the remaining receptors, which usually are less responsive in hypertensive patients.