Radiofrequency Catheter Atrioventricular Node Ablation in Patients with Permanent Cardiac Pacing Systems

Following successful BF ablation of the atrioventricular node (AVN), temporary pacing is necessary prior to insertion of a permanent pacemaker. The risks and inconvenience of temporary pacing could be avoided if a permanent pacemaker is already in place. This study reports the feasibility of RF ablation of the AVN in 27 patients (age 55 ± 17 years, 15 males) with hypertrophic cardiomyopathy and pacemakers, Indications for AVN ablation were drug refractory atrial fibrillation in 24 patients, and rapid AVN conduction preventing septal pre-excitation by DDD pacemaker, inserted for relief of left ventricular outflow obstruction, in three cases. Sixteen patients had DDD devices and 11 patients had VVI devices. During RF ablation, each pacemaker was programmed to VVI at 50 beats/min. The ablation catheter was manipulated with fluoroscopic control to avoid close contact with or disturbance of the pacing leads. In 16 patients, RF ablation was performed immediately following pacemaker implantation but in the remaining patients, the AVN was ablated 6–32 months after pacemaker implantation. The power applied was 25–50 watts for a duration of 15–60 seconds. AV block was achieved in all cases but required 34 ± 36 applications for 16.5 ± 17.8 min/case. RF ablation consistently caused reversion to magnet rate in one patient and temporarily inhibited appropriate pacemaker discharge in another. However, no other pacemaker or lead malfunction was detected so that temporary pacing was not required in any case. At 6 ± 3 months follow-up, all pacemakers were functioning normally without alteration in pacing parameters from baseline. Thus. RF ablation of the AVN can be performed safely in the presence of a recently implanted permanent pacemaker, without temporary pacing.     

In-vivo Release of a GnRH Agonist from a Slow-release Poly(lactide-glycolide) Copolymer Preparation: Comparison in Rat,Rabbit and Guinea-Pig

Abstract— Different batches of 50:50 poly((±)-lactide-glycolide) copolymer (PLG) were used as biodegradable carriers for D-Phe⁶-gonadotropin-releasing hormone (GnRHa) in the form of injectable long-acting implants loaded with 10% GnRHa and tracer amounts of [¹²⁵I]GnRHa. After their injection subcutaneously into rats, rabbits, and guinea-pigs, the release kinetics of the peptide were determined by counting the radioactivity remaining in the implants (i) after recovery from the rats after death or (ii) directly on the skin above the injection site of rabbits and guinea-pigs in-vivo. No significant differences in the release pattern of the peptide amongst the three species whether the release process was controlled by diffusion or by degradation of the polymeric matrix were found. It is concluded that the results of in-vivo release tests using laboratory animals are valid for man and that enzymes are not involved in the degradation of the polymeric matrix. The results may be of general importance for the use of long-term release PLG formulations of highly active drugs, especially peptides and proteins.     

Production of Macroglobulins in Vitro and a Study of Their Cellular Origin

Lymph nodes of three patients with macroglobulinemia of Waldenströmwere studied in tissue culture and shown to synthesize 19S -globulin in vitro.

Lymph node imprints, bone marrow, and buffy coat smears of the samepatients consisted almost entirely of lymphocytes. When these were stainedwith fluorescein-conjugated antiserum to macroglobulin, large and medium-sized lymphocytes and lymphoblasts rather than mature lymphocytes or plasmacells were shown to contain the protein.

It is suggested that 19S -globulin may also be synthesized by cells belonging to the lymphoid series under normal circumstances.

Submitted on December 12, 1961 Accepted on March 8, 1962     

Reticuloendothelial Clearance of Blood Thromboplastin by Rats

Data have been presented suggesting that blood thromboplastin givenintravenously to rats is cleared by the reticuloendothelial system. (1) Thereagent given into the jugular vein or aorta caused profound defibrination,whereas injection into the portal circulation caused a milder reaction. Thesedifferences were obtained irrespective of the source of phosphatide in thethromboplastin generation mixture. (2) Reticuloendothelial blockade reducedthe protective effect of portal administration. (3) Radioactive blood thromboplastin given intravenously was rapidly cleared from the blood, and showedan organ distribution resembling that of agents known to be removed byreticuloendothelial cells. (4) Injection of the blood thromboplastin during acarbon clearance caused depression of the carbon disappearance slope.

Submitted on August 29, 1960 Accepted on October 19, 1960     

Mechanical properties of human forearm and vulvar skin

Using a newly developed suction device, the mechanical properties of forearm and vulvar skin were studied in 22 healthy women, 12 before and 10 after the menopause. The ratio between viscous deformation (Uv) and elastic deformation (Ue) and the biological elasticity, i.e. the ratio between immediate recovery (Ur) and total deformation (Uf), were both significantly lower in vulvar than in forearm skin. Ur/Uf decreased significantly with load in vulvar, but not in forearm skin, whereas Uv/Ue was not load-dependent in either site. Uv/Ue remained constant with age in both test sites, whereas Ur/Uf was significantly lower in post-menopausal women in both forearm and vulvar skin. In vulvar, but not in forearm skin, Uv/Ue was significantly correlated with body height which may be an indicator of mechanical connective tissue properties. Viscous deformation plays a lesser role and biological elasticity is decreased in vulvar compared to forearm skin. Despite differences in mechanical parameters at both sites, age-related changes seem to be similar.     

A Family with Three betadgr-Thalassemia Homozygotes

An Arab family with three homozygotes for -thalassemia is described.The single hemoglobin present in their red cells is fetal hemoglobin. A mildhemolytic condition was seen in the propositus, while the two other siblingsare completely normal. The main differential diagnosis of this condition ishomozygosity for persistent fetal hemoglobin gene.

Submitted on June 18, 1969 Accepted on August 27, 1969     

Relief of Left Ventricular Outflow Tract Obstruction Following Inadvertent Left Ventricular Apical Pacing in a Patient with Hypertrophic Cardiomyopathy

Dual chamber (DDD) pacing improves symptoms and relieves left ventricular (LV) outflow obstruction in hypertrophic Cardiomyopathy. The ventricular lead is usually positioned at the right ventricular apex (RVA). We report a patient in whom the ventricular lead had inadvertently penetrated the septum, resulting in DDD pacing from the LV apex. However, after 3 months, obstruction was reduced and symptoms were improved. Pacing from LV apex and RVA resulted in comparable hemodynamic improvement. This case suggests that the asynchronous wave of septal contraction, originating from the apex, irrespective of ventricular site, accounts for the reduction in LV outflow obstruction.     

Plasma concentration following oral and intramuscular atropine in children and their clinical effects

In a paediatric population, we compared i.m. v oral atropine pre-medication to a control group without atropine and determined atropine plasma concentrations (APC). Forty-five children were randomly assigned to one of three groups. Group I received atropine, 20 μg·kg⁻¹ i.m., 15 min prior to induction. Group II received atropine, 30 μg·kg⁻¹ orally, group III received no atropine. APC (expressed as percent of muscarine-2 receptor subtype occupancy), heart rate, rectal temperature, and salivation were determined before atropine, and 15, 25, 45, 60, 90, 120 (no APC), and 150 min following atropine. Only 10–20% of the M2-cholinoceptors were occupied after oral atropine with a peak at 90 min compared to 60–70% occupancy with a peak 25 min after i.m. atropine. The peak in M2-cholinoceptor occupation in group I was paralleled by a peak percentage change in heart rate of 15% from baseline. The peak in receptor occupation in group II did not correspond to the peak increase in heart rate. The percentage change of heart rate over time was not significantly different from baseline values in any of the groups. Bradycardia or temperature changes did not occur in any of the groups. Antisialogogue effects were observed only in group I. We conclude that atropine, 30 μg·kg⁻¹ orally is not an equipotent dosage to atropine, 20 μg·kg⁻¹ i.m.