Intraoperative Mapping and Radiofrequency Ablation of the His Bundle in a Patient with Complex Congenital Heart Disease and Intractable Atrial Arrhythmias Following the Fontan Operation

Intraoperative mapping and radiofrequency ablation of the His bundie (with epicardial ventriculor pacing) were performed in an 18-year-old woman with complex congenital heart disease and inlractable chronic atrial arrhythmias following the Fontan operation. The presence of complex intracardiac anafomy as well as the exclusion of tbe atrioventricular conduction tissue from the systemic venous circulation strongly influenced the technical approach.     

Gastric Function in Crohn's Disease

Gastric acid secretion before and after stimulation with pentagastrin was assessed in 11 patients with Crohn's disease. Age and sex-matched patients with ulcerative colitis and healthy controls were used for comparison. Basal acid output was found to be significantly elevated in patients with Crohn's disease who had had surgery (P < 0,01). This elevation was related to ileal resection rather than ileal disease. There was no difference in the maximal or peak acid outputs between any of the groups.     

The influence of methysergide on 5-hydroxytryptamine-induced changes in regional distribution of blood flow

Systemic and regional haemodynamic variables were measured at the baseline and after saline or 5-HT infusions (5 μg kg^?1 min^?1, i.v.) or methysergide injections (0–5 mg kg^?1, i.V.). Cardiac output and its complete distribution were measured by the radioactive microsphere (15 μm diam.) technique. Although 5-HT did not change the systemic variables, methysergide caused a moderate increase in systolic and mean blood pressure and heart rate. 5-HT caused a substantial increase in gastric and a moderate increase in cerebral and myocardial blood flow at the expense of that to the lungs (arteriovenous shunt + bronchial flows), kidneys and skin. While methysergide was able to reduce the vascular responses to 5-HT in stomach, skin, kidneys, heart, lungs and brain, the drug itself, like 5-HT, decreased the number of microspheres reaching the lungs. Since a large number of 15 μm microspheres can escape through the arteriovenous anastomoses to lodge in the lungs it seems likely that both 5-HT and methysergide can reduce the ‘non-nutrient’ flow through these anastomoses.     

LASER TRABECULOPLASTY: EARLY EXPERIENCE WITH A NEW PROCEDURE

Twenty-live laser trabeculoplasty procedures were performed on 20 patients. All patients were treated as inpatients so that early changes in intraocular pressure could be monitored. The range of fall was recorded: in four cases there was a significant rise in intraocular pressure in the first four hours which, if sustained, could have lead to a further visual field loss in patients with advanced chronic simple open-angle glaucoma. Patients with a high initial intraocular pressure had the greatest fall in intraocular pressure. Those patients with a more pigmented trabecular meshwork with wide open angles were the easiest to treat and gave the best signs of effective laser endpoint reaction. Gonioplasty was performed in many patients with narrow angles, which gave much better access to the posterior trabecular meshwork.     

CONDITIONING DEFICITS OF CaM-KINASE TRANSGENIC DROSOPHILA MELANOGASTER IN A NEW EXCITATORY COURTSHIP ASSAY

Courtship suppression is an associative conditioning procedure in Drosophila melanogaster that is ethologically based and capable of being tested on individual flies. We have expanded the range of the courtship conditioning by developing an excitatory procedure in which male flies learn to associate a novel odor with the courtship stimulating cues of virgin females. Wild-type males normally court other mature males very little, but following training, the odor alone is able to elicit increased levels of courtship towards an object male. Flies expressing an inhibitor of calcium/calmodulin-dependent protein kinase II (CaMKII) were previously shown to have no retention one hour after training in the courtship suppression task, as manifested in their persistent courting of a virgin female. A possible trivial explanation for this response is that the CaMKII-inhibited fly strains ( ala1 and ala2 ) were merely hyperactive courters. The poor performance of these mutants in the new excitatory conditioning procedure confirms that their conditioning deficit results from a disruption of an associative mechanism per se.     

Role of Na+:Ca2+ Exchange Current in Cs+-Induced Early Afterdepolarizations in Purkinje Fibers

Na⁺:Ca²⁺ Exchanger and EADs. Introduction: The ionic mechanisms for early afterdepolarizations (EADs) have not been fully clarified. It has been suggested that L-type Ca²⁺ current (I_caL) is the primary current generating EADs that occur near the plateau level (E-EADs) of the membrane potential (Vm) when I_caL is enhanced. The purpose of these studies was to determine accurately the range of Vm at which EADs occur in Purkinje fibers with K⁺ currents blocked by Cs⁺ and to investigate the importance of Na⁺:Ca²⁺ exchange current (I_Na:ca) as opposed to l_CaL and other currents in the generation of EADs occurring later during repolarization (L-EADs). Methods and Results: Shortened Purkinje strands from dogs and guinea pigs were superfused with physiologic solution containing Cs⁺ (3.6 mM) and a low [K⁺]_o (3.0 or 2.0 mM) to induce EADs. The Vm of origin of EADs and their evolution were measured with the aid of phase plane plots of the rate of repolarization against Vm. L-EADs occurred over a wide range of Vm (?35 to ?90 mV), generally more negative in guinea pig than in dog. Elevation of [Ca²⁺]_o, from 1.8 to 3.6 mM suppressed L-EADs within a few cycles, and they returned with continued exposure. After repeated exposures to high [Ca^:2+]₀, L-EADs migrated toward less negative Vm when |Ca²⁺]₀, was reestablished to 1.8 mM in the presence of Cs⁺. Reduction of [Na⁺]₀ from 147.5 to 112.5 mM by substitution with Li⁺ or sucrose also rapidly depressed L-EADs. Conclusions: The observation of Cs⁺-induced L-EADs over a wide range of Vm indicates that there is not a single inward gated current as a common ionic mechanism for L-EADs but does not exclude an important role for I_Na:Ca, which can operate over a wide range of Vm. The rapid suppression of L-EADs with elevated [Ca²⁺]_o, and reduced [Na⁺]_o, and the migration of EADs to more positive Vm after exposures to high |Ca²⁺]_o, are compatible with I_Nc:Ca as the major charge carrier for L-EADs.     

Development and Validation of an ECG Algorithm for Identifying Accessory Pathway Ablation Site in Wolff-Parkinson-White Syndrome

ECG Localization of Accessory AV Pathways. Introduction : Delta wave morphology correlates with the site of ventricular insertion of accessory AV pathways. Because lesions due to radiofrequency (RF) current are small and well defined, it may allow precise localization of accessory pathways. The purpose of this study was to use RF catheter ablation to develop an ECG algorithm to predict accessory pathway location.
Methods and Results : An algorithm was developed by correlating a resting 12-lead ECG with the successful RF ablation site in 135 consecutive patients with a single, anterogradely conducting accessory pathway (Retrospective phase). This algorithm was subsequently tested prospectively in 121 consecutive patients (Prospective phase). The ECG findings included the initial 20 msec of the delta wave in leads I, II, aVF, and V₁ [classified as positive (+), negative (-), or isoelectric (±)] and the ratio of R and S wave amplitudes in leads III and V₁ (classified as R ≥ S or R < S). When tested prospectively, the ECG algorithm accurately localized the accessory pathway to 1 of 10 sites around the tricuspid and mitral annuli or at subepicardial locations within the venous system of the heart. Overall sensitivity was 90% and specificity was 99%. The algorithm was particularly useful in correctly localizing anteroseptal (sensitivity 75%, specificity 99%), and mid-septal (sensitivity 100%, specificity 98%) accessory pathways as well as pathways requiring ablation from within ventricular venous branches or anomalies of the coronary sinus (sensitivity 100%, specificity 100%).
Conclusion : A simple ECG algorithm identifies accessory pathway ablation site in Wolff-Parkinson-White syndrome. A truly negative delta wave in lead II predicts ablation within the coronary venous system.