Ventricular Arrhythmias in Dilated Cardiomyopathy

Although prognosis of dilated cardiomyopathy (DCM) has improved due to advances in diagnosis and therapy, still too many sudden cardiac deaths occur in DCM. Spontaneous ventricular ectopy is a very common finding in patients with DCM, but the prognostic significance of Holter monitoring remains controversial. Other noninvasive methods, e.g., late potentials and QT dispersion, have not yet contributed to the evaluation of prognosis for arrhythmogenic events in DCM. Programmed ventricular stimulation has been repeatedly used to stratify long-term prognosis, yet satisfactory data are still missing as many deaths occur in patients without inducible arrhythmias. Several prognostic studies are still in progess, and preliminary data for the use of ICDs already appear to be promising. In patients with poor left ventricular function and ICDs in situ, prognosis is determined by progression of heart failure. Heart transplantation may be the ultimate therapeutic instrument for end-stage heart failure patients. For patients with advanced DCM and increased risk for malignant arrhythmias who are unsuitable for orthotopic heart transplantation, the combined therapy with an ICD and dynamic cardiomyoplasty may be an alternative treatment.     

Changes in AV Node Conduction Curves Following Slow Pathway Modification

GELLER, J.C., et al. : Changes in AV Node Conduction Curves Following Slow Pathway Modification. Dual AV node physiology often persists after successful slow pathway (SP) ablation, and the mechanism of tachycardia elimination is unresolved. Therefore, AV node conduction curves were analyzed following successful ablation (  4 ± 1  energy applications) in 85 consecutive patients (58 women, age  50 ± 2  years) with typical AVNRT. Twenty-seven patients (32%) had complete elimination (group 1) whereas 58 (68%) patients had persistence (group 2) of dual AV node physiology. A significant increase in the AV node Wenckebach cycle length (WB-CL) was observed in both groups (  310 ± 9 to 351 ± 15 ms  in group 1, and  325 ± 8 to 369 ± 9 ms  in group  2, P < 0.05  ). A decrease in the fast pathway (FP) ERP (  339 ± 15 to 279 ± 12 ms  ) and an increase in the maximum FP AH interval (  141 ± 5 to 171 ± 7  ) were observed only in group 1 (P < 0.05). In group 2, no change in the SP ERP (  267 ± 7 to 280 ± 10 ms  ) was observed, and the change in the maximum SP-AH following ablation showed a significant inverse relation to the maximum SP-AH at baseline in group 2. In conclusion, (1) an increase in the WB-CL is observed independent of the persistence or elimination of dual physiology after successful ablation; (2) when dual physiology is eliminated, significant changes in the FP ERP and the maximum FP-AH occur; (3) when dual physiology persists, FP physiology and the SP ERP remain unchanged, and a significant inverse relation between the change in the maximum SP-AH following ablation and the maximum baseline SP-AH is observed.     

Paroxysmal Atrial Fibrillation and High Degree AV Block: Use of Single-Lead VDDR Pacing with Mode Switching

Dual chamber rate responsive pacing incorporating a mode switching option is increasingly listed in patients with chronic paroxysmal atrial fibrillation and high degree AV block. Single-lead VDDR pacemakers have been rarely used for this indication. The purpose of this study was to determine thnir reliability of atrial sensing during atrial fibrillation, the percentage of at rial synchronous ventricular pacing, and the behavior of the sinus rate outside the phases of atrial fibrillation. We studied ten patients with a single-lead VDDR pacemaker implanted for this indication. Follow-up visits were performed at predischarge and after 1, 3, 6, 12. 18, and 24 months. During the mean follow-up period of 18.9 ± 6.9 months, the atrial sensing thresholds in sinus rhythm remained stable. Atrial synchronous ventricular stimulation was achieved in 68,7 ±31.2% (median 82.5%) of the whole follow-up time. All patients showed an adequate atrial rate response during sin us rhfthm. Atrial fibrillation was detected by the pacemakers in 24.0 ± 29.8% of time. In 3 of 10 patients the duration of atrial fibrillation showed a steady increase from visit to visit. The sensed amplitudes of atrial fibrillation ranged from 0.1–1.0 mV. A programmed atrial sensitivity of 0.1 mV was necessary to achieve complete sensing of atrial fibrillation. None of the patients experienced tachycardias with optimized pacemaker programming. Single-lead VDDR pacing incorporating a mode-switching option is useful in patients with high degree AV block and paroxysmal atrial fibrillation, since it provides atrial synchronous ventricular pacing in more than two-thirds of follow-up time. In a subgroup of patients, a progressive increase of the time during atrial fibrillation was demonstrated. A reliable detection of paroxysmal atrial fibrillation requires the programming of the atrial sensitivity to its most sensitive value.     

Importance of an Individually Programmed Atrioventricular Delay at Rest and on Work Capacity in Patients with Dual Chamber Pacemakers

Despite higher costs, expenditure, and the necessity of repeatedly reprogramming of dual chamber pacemakers, they are increasingly implanted to achieve an optimal work capacity. The influence of an individually programmed atrioventricular (AV) delay hetween 100–250 msec on physical work capacity in 12 patients (68 ± 16 years) with dual chamher pacemakers implanted for high degree AV block was studied. During radionuclide ventriculography at rest the "optimal AV delay" with the maximal achieved left ventricular ejection fraction and the "most unfavorable AV delay" with the least achieved ejection fraction were determined. The ejection fraction at rest with the "optimal AV delay" was 5t ±14% and with the "most unfavorable AV delay" 45 ± 15% (P < 0.001). In random order each patient was assigned to either AV delay and a spiroergometry was performed to determine maximum oxygen uptake (max VO₂). which correlates best with work capacity, at a respiratory quotient of 1.1. The results show neither a difference in maximum oxygen uptake (1,262 ± 446 mUmin with the optimal AV delay, 1,248 ± 400 mL/min with the most unfavorable AV delay, respectively) nor in heart rate, blood pressure, exercise duration, maximal workload, and minute ventilation. Thus, an individually programmed AV delay affects left ventricular ejection fraction at rest. In contrast, an individually programmed A V delay has no influence on physical work capacity in patients with a dual chamber pacemaker.     

Ventricular Tachycardia Surgery in 1992: Did the Automatic Defibrillator Change This Approach?

The role of ventricular tachycardia (VT) surgery has been changed since the automatic implantable cardioverter defibrillator (ICD) is available. We studied the follow-up of 131 patients who underwent mapping guided surgery due to recurrent VT refractory to antiarrhythmic drug treatment. There were 65 patients operated upon between 1980–1985 (group I) and 66 patients between 1986–1991 (group II). Ten patients (8%) died perioperatively (< 3 weeks after surgery) [7/65 patients, 11%, in group I and 3/66 patients, 5%, in group II (P = 0.15)]. During a mean follow-up of 41 ± 24 months, 38 of 121 patients died (31%), significantly more patients in group I (24/58 patients, 41%) than in group II (14/63 patients, 22%) (P < 0.05). In group I, there was a higher incidence of sudden (7/58 patients, 12%) or cardiac death (15/58 patients, 26%) than in group II (sudden death 4/63 patients, 6%, cardiac death 7/63 patients, 11%) (P < 0.05). There was a similar incidence of VT recurrences between group I(9/65 patients, 14%) and group II (9/66 patients, 14%). Our data show that the indication for VT surgery has changed since the ICD is available because of better patient selection.     

The role of reactive nitrogen intermediates in modulation of gametocyte infectivity of rodent malaria parasites

Direct feeding of Anopheles stephensi mosquitoes on mice infected with Plasmodium vinckei petteri showed that, during the periods of schizogony in the blood, the infectivity of gametocytes was markedly reduced. This could be prevented by prior injection of the L-arginine analogue, Nw-nitro-L-arginine (NwNLA) showing that the altered infectivity was due to reactive nitrogen intermediates (RNI). Similar effects on transmission of P. yoelii nigeriensis were demonstrated in vitro by membrane feeding of the mosquitoes. The in vitro reduction in infectivity could be reversed by injecting the L-arginine analogue either into the infected mouse donor of serum, or into the membrane feeding chamber. Elevated levels of TNF and IL-6 were demonstrated during the course of infection but did not correlate well with nitrogen radical activity. Similarly, direct measurements of NO₂- and NO₃- did not reflect the nitrogen radical activity revealed by addition of the specific L-arginine analogue.     

The age dependence of stereotyped behaviours in blind infants and preschoolers

As part of a research programme on early intervention and family care for blind infants and preschoolers, the Bielefeld Parents' Questionnaire for Blind and Sighted Infants and Preschoolers was given to 85 parents of congenitally blind children. All 85 children (from 5 to 72 months) in the sample were totally blind and had no further serious disabilities. A comparison of five age groups of blind infants and preschoolers indicated that the repertoire of stereotyped behaviour patterns depended on age. After expanding from the first to the second year of life, the range of different stereotyped behaviours decreased from the age of 3 years up to school enrollment. The amount of stereotyped behaviours showed a similar course. Among the individual stereotyped behaviours, only the frequency of eye poking and body rocking increased from the first to the second year of life and then maintained a relatively high level across the entire preschool age range. The situational and person-specific conditions under which stereotyped behaviours could typically be observed also appeared to change with the child's age. While in the first years of life, monotony and arousal situations dominated among the elicited stereotyped behaviours, the 4- to 6-year-old blind children increasingly exhibited stereotyped behaviours in situations in which they were confronted with cognitive and concentrative demands. Various possible explanations of the age dependence of stereotyped behaviour patterns in blind infants and preschoolers are discussed.     

Safety of Antitachycardia Pacing in Patients with Implantable Cardioverter Defibrillators and Severely Depressed Left Ventricular Function

The purpose of this study was to investigate the efficacy and safety of antitachycardia pacing (ATP) in third-generation implantable Cardioverter defibrillators (ICDs) for terminating spontaneously occurring ventricular tachycardias (VTs) in patients with severely depressed left ventricular (LV) function. Ninety-one patients with active ATP were followed for 16 ± 13 months. During this period, 775 VT episodes occurring in 36 patients were treated by ATP. The patients were divided into two groups according to their LV ejection fraction (LVEF): group A with LVEF ± 30% (n = 20), and group B with LVEF ± 30% (n = 16). There were no differences between both groups in age, gender, underlying heart disease, indication for ICD therapy, or drug therapy. The VT rates were comparable (group A: 183 ± 16 beats/min; group B: 180 ± 21 beats/min; P = NS). Eighty-three percent of all episodes (n = 332) in group A and 93% of the VTs (n = 443) in group B were ATP terminated (P ± 0.01). Ten percent of VTs in group A were accelerated by ATP into the ventricular fibrillation zone versus 2% in group B (P ± 0.01). The individual termination rate and acceleration rate per patient were comparable in both groups. All VT episodes unresponsive to ATP were converted by backup shocks. The efficacy of first-shock therapy was similar in both groups (group A: 89%; group B: 97%; P = NS). The proportion of patients who needed at least one backup shock for unsuccessful ATP was comparable in both groups (group A: 65%; group B: 56%; P= NS). We conclude that ATP is effective and safe in patients with recurrent VTs and severely depressed LV function, and it can be safely programmed in this group of patients to minimize the use of shock therapy.     

Effects of 1% chlorhexidine gel treatment on sympathetic adrenergic nerves in human buccal mucosa

The effect of treatment with a commercially available 1 % chlorhexidine gel (Hibitane Dental) in custom trays for 14 days (10 min daily) on the sympathetic adrenergic nerves in biopsies from human buccal mucosa was investigated. Chemical assay of endogenous noradrenaline concentration and immunocytochemical demonstration of tyrosine hydroxylase served as markers for structural and functional integrity of the adrenergic nerves. The mean concentration of noradrenaline in chlorhexidine treated tissues did not differ from the mean concentration in control. No morphologic or fluorescence intensity differences of the tyrosine hydroxylase immunoreactivity were found in the chlorhexidine treated tissues when compared to controls. These findings indicate that a relatively intense treatment with a commercially available 1% chlorhexidine gel does not affect the adrenergic innervation of human buccal mucosa.     

Fibrocartilage in the transverse ligament of the human acetabulum

Biomechanical experiments on isolated hip joints have suggested that the transverse ligament acts as a bridle for the lunate articular surface of the acetabulum during load bearing, but there are inherent limitations in such studies because the specimens are fixed artificially to testing devices and there are no modifying influences of muscle pull. Further evidence is thus needed to substantiate the theory. Here we argue that if the horns of the lunate surface are forced apart under load, the ligament would straighten and become compressed against the femoral head. It would thus be expected to share some of the features of tendons and ligaments that wrap around bony pulleys and yet previous work has suggested that the transverse ligament is purely fibrous. Transverse ligaments were removed from 8 cadavers (aged 17–39 y) and fixed in 90% methanol. Cryosections were immunolabelled with antibodies against collagens (types I, II, III, VI), glycosaminoglycans (chondroitins 4 and 6 sulphate, dermatan sulphate, keratan sulphate) and proteoglycans (aggrecan, link protein, versican, tenascin). A small sesamoid fibrocartilage was consistently present in the centre of each transverse ligament, near its inner surface at the site where it faced the femoral head. Additionally, a more prominent enthesis fibrocartilage was found at both bony attachments. All fibrocartilage regions, in at least some specimens, labelled for type II collagen, chondroitin 6 sulphate, aggrecan and link protein, molecules more typically associated with articular cartilage. The results suggest that the ligament should be classed as containing a ‘moderately cartilaginous’ sesamoid fibrocartilage, adapted to withstanding compression. This supports the inferences that can be drawn from previous biomechanical studies. We cannot give any quantitative estimate of the levels of compression experienced. All that can be said is that the ligament occupies an intermediate position in the spectrum of fibrocartilaginous tissues. It is more cartilaginous than some wrap‐around tendons at the wrist, but less cartilaginous than certain other wrap‐around ligaments, e.g. the transverse ligament of the atlas.