Use of Intracardiac Echocardiography during Atrial Fibrillation Ablation

As the volume and complexity of catheter ablation of atrial fibrillation (AF) continue to rise, there is increasing attention directed at reducing exposure to ionizing radiation. This has led to the emergence of intracardiac echocardiography (ICE) as a stand‐alone imaging modality guiding AF ablation. In addition to directing transseptal puncture, ICE may be used to identify left atrial structures and to guide the manipulation of catheters. ICE may also be used to visualize the esophagus in real‐time and to assist with early identification of procedural complications. This review provides detailed step‐by‐step directions for identification of relevant structures and summarizes the use of ICE during AF ablation.     

THE EFECT OF NABUMETONE AND ITS PRINCIPAL ACTIVE METABOLITE ON IN VITRO HUMAN GASTRIC MUCOSAL PROSTANOID SYNTHESIS AND PLATELET FUNCTION

Nabumetone is a novel non-steroidal anti-inflammatory drug (NSAID) which although a weak cyclooxygenase inhibitor is convertedby the liver to metabolites which are more potent inhibitorsof cyclooxygenae. Nabumetone may thus avoid the occurrence ofgastric erosion while maintaining its efficacy as an anti-inflammatorydrug. We compared the effects of nabumetone and 6-methoxy-2-naphthylaceticacid (6MNA; the principal metabolite of nabumetone) with naproxenand indomethacin on in vitro synthesis of the gastroprotectiveprostaglandins I₂ and E₂ by human gastric mucosa. To study theeffects of 6MN A on peripheral target tissues the effects ofthe above NSAIDs on uman platelet aggregation and thromboxaneA₂ synthesis were also studied. Prostanoid synthesis by thehuman gastric mucosa was inhibited by indomethacin, naproxenand 6MNA (in this order of potency) whereas nabumetone was completelywithout effect. Platelet aggregation and thromboxane A2 synthesiswere similarly inhibited by the NSAIDS (viz. indomethacin >naproxen > 6MNA > nabumetone).These results support theview that nabumetone does not inhibit gastroprotective prostanoidsynthesis,whereas its active metabolite 6MNA is an effectiveinhibitor of prostanoid synthesis in target tissues. KEY WORDS: Prodrug, Gastropath, Prostacyclin, Prostaglandin E₂, Thromboxane A₂     

Intestinal metaplasia subtypes and Helicobacter pylori infection: A comparison of ethnic groups in New Zealand

Gastric cancer is two to four-fold more common in Maori and Pacific Island ethnic groups compared with Europeans. This study aimed to determine if intestinal metaplasia was more common in these ethnic groups. Patients attending for endoscopy for dyspepsia had six biopsies to determine the presence of Helicobacter pylori by at least two of the following tests: rapid urease test, ¹³C urea breath test, culture or histology and the presence, extent and subtypes of intestinal metaplasia. Biopsies were taken from 158 patients: Europeans (42%), Maori (23%), Pacific Islanders (35%). Helicobacter pylori and intestinal metaplasia were detected in 88 and 60% of Maori/Pacific Island patients, respectively, and 47 and 29% of Europeans, respectively. Type I intestinal metaplasia was detected in 43% of all patients, type II (26%) and type III (7.0%). The mean age of Maori/Pacific Island patients with intestinal metaplasia and type III intestinal metaplasia was 53 and 51 years respectively, compared with Europeans aged 65 and 72 years. Univariate analysis showed that intestinal metaplasia was associated with ethnicity and H. pylori ( P < 0.001) but not age, smoking, endoscopic diagnosis or gender. Intestinal metaplasia is more common and occurs at an earlier age in Maori and Pacific Island patients.     

Ventricular Pacing Induced Ventricular Tachycardia in Patients with Implantable Cardioverter Defibrillators

Appropriately timed noncompetitive ventricular pacing potentially may initiate ventricular tachycardia in patients prone to these arrhythmias. The combination of bradycardia pacing and stored electrograms in a currently available cardioverter defibrillator provides an opportunity to evaluate the occurrence of such pacing induced ventricular tachycardia. During a surveillance period of 18.7 ± 11.4 months, stored electrograms documented 302 episodes of ventricular tachycardia in 77 patients. Five patients (6.5%) demonstrated 25 episodes (1–16 per patient) of ventricular tachycardia that were immediately preceded by an appropriately paced ventricular beat (8.3% of all episodes of ventricular tachycardia). All five patients had prior myocardial infarctions and a history of monomorphic ventricular tachycardia occurring both spontaneously and in response to programmed electrical stimulation. Antitachycardia pacing terminated pacing induced ventricular tachycardia in 22 episodes; in one episode antitachycardia pacing accelerated ventricular tachycardia. In two cases shock therapy was aborted for nonsustained ventricular tachycardia. We conclude that, in selected postinfarction patients with recurrent sustained monomorphic ventricular tachycardia treated with implantable cardioverter defibrillators, appropriately timed ventricular pacing may induce ventricular tachycardia.     

DISTRIBUTION OF α1(IV) AND α3(IV) CHAINS OF TYPE IV COLLAGEN IN LUNG TUMOURS

Tumour invasion is associated with strong remodelling of the extracellular matrix, including the basement membrane (BM). The major structural component of BMs is type IV collagen, which is composed of an association of three α chains. In this study, the distribution of the α1 and α3 chains in both normal and neoplastic lung tissues has been examined by immunohistochemistry, using specific monoclonal antibodies. In normal tissues, the α1(IV) chain was found in all BMs, whereas the α3(IV) chain was only found in alveolar BMs. In 36 lung tumours, the α1(IV) chain was detected in all cases, with irregular positivity around tumour clusters and in the stroma. It was noteworthy that this stromal distribution was particularly associated with the presence of cancer cells, whatever their invasive properties. In contrast, in 22 tumours out of 36, the α3(IV) chain was only found at the interface between invasive tumour clusters and stroma, with a linear and disrupted pattern. These data show a distinctive distribution of type IV collagen chains in lung tumours, with expression of α1(IV) chain and likely neosynthesis of the α3(IV) chain around some invasive tumour clusters. The results suggest the involvement of these BM components in the process of tumour invasion. © 1997 John Wiley & Sons, Ltd.