To examine the risk of ventricular fibrillation in patients with the Wolff-Parkinson-White syndrome, we compared patients who had this syndrome and a history of ventricular fibrillation related to preexcitation with patients who had the syndrome without this history. Ventricular fibrillation occurred during atrial fibrillation, with rapid conduction over the accessory pathway, and these patients had a higher prevalence of both reciprocating tachycardia and atrial fibrillation (14 of 25 vs. 18 of 73, P = 0.004) and multiple accessory pathways (five of 25 vs. four of 73, P = 0.012). The shortest preexcitation R-R interval during atrial fibrillation was less in the group with ventricular fibrillation (mean shortest R-R, 180 vs. 240 milliseconds, P less than 0.0001) as was the average R-R interval (mean average R-R, 269 vs 340 milliseconds, P less than 0.0001). Patients with Wolff-Parkinson-White syndrome who are most susceptible to ventricular fibrillation have a history of atrial fibrillation and reciprocating tachycardia, demonstrate rapid conduction over an accessory pathway during atrial fibrillation and have multiple accessory pathways.

The laser sheath uses optical fibers, delivering pulsed ultraviolet excimer laser light, to vaporize fibrotic tissue binding intravenous cardiac leads to the vein or heart wall during lead extraction from the implant vein. The total investigational experience with laser sheaths is reported. During the period from October 1995 to December 1999, 2,561 pacing and defibrillator leads were treated in 1,684 patients at 89 sites in the United States with three sizes of laser sheath. Endpoints were complete removal of the lead, partial removal (leaving the tip behind), or failure (abandoning the lead, onset of complications, change to transfemoral or transatrial approach). Minimal follow-up at 30 days was recorded. Of the leads, 90% were completely removed, 3% were partially removed, and the balance were failures. Major perioperative complications (tamponade, hemothorax, pulmonary embolism, lead migration, and death) were observed in 1.9% of patients with in hospital death in 13 (0.8%). Minor complications were seen in an additional 1.4% of patients. Multivariate analysis showed that implant duration was the only preoperative independent predictor of failure; female sex was the only multivariate predictor of complications. Success and complications were not dependent on laser sheath size. At follow-up, various extraction related complications were observed in 2% of patients. The learning curve showed a trend toward fewer complications with experience. Lead extraction with the laser sheath can be safely practiced with high success rates. Success is independent of laser sheath size. Major complications can be expected in < 2% of patients, and occur more often during an investigator's early experience.

Of the 400,000-500,000 permanent pacemaker leads implanted worldwide each year, around 10% may eventually fail or become infected, becoming potential candidates for removal. Intravascular techniques for removing problematic or infected leads evolved over a 5-year period (1989-1993). This article analyzes results from January 1994 through April 1996, a period during which techniques were fairly stable. Extraction of 3,540 leads from 2,338 patients was attempted at 226 centers. Indications were: infection (27%), nonfunctional or incompatible leads (25%), Accufix or Encore leads (46%), or other causes (2%). Patients were 64+/-17 years of age (range 5-96); 59% were men, 41% women. Leads were implanted 47+/-41 months (maximum 26 years), in the atrium (53%), ventricle (46%), or SVC (1%). Extraction was attempted via the implant vein using locking stylets and dilator sheaths, and/or transfemorally using snares, retrieval baskets, and sheaths. Complete removal was achieved for 93% of leads, partial for 5%, and 2% were not removed. Risk of incomplete or failed extraction increased with implant duration (P<0.0001), less experienced physicians (P<0.0001), ventricular leads (P<0.005), noninfected patients (P<0.0005), and younger patients (P<0.0001). Major complications were reported for 1.4% of patients (<1% at centers with >300 cases), minor for 1.7%. Risk of complications increased with number of leads removed (P<0.005) and with less experienced physicians (P<0.005); risk of major complications was higher for women (P<0.01). Given physician experience, appropriate precautions, and appropriate patient selection, contemporary lead removal techniques allow success with low complication rates.

From December 1988 to April 1994, the extraction of 2,195 intravascular pacing leads from 1,299 patients was attempted at 193 centers. Indications were: infection (54%, including 10% septicemia), pacemaker reoperation with removal of nonfunctional or incompatible leads (40%), and other causes (6%). Extraction was attempted via the implant vein using locking stylets and dilator sheaths, via the femoral vein using snares, retrieval baskets, and sheaths, or via both approaches. Leads had been implanted for 0.2 months to 24 years (mean 56 months). At the conclusion of the intravascular procedure, 86.8% of the leads were completely removed, 7.5% were partially removed, and 5.7% were not removed. For physicians performing their first case, 12% of leads were not removed; for physicians who had performed more than 10 cases, only 2% of leads were not removed. Of the 189 leads where extraction attempts had previously failed, 75.1% were completely removed, 14.8% were partially removed, and 10.1% were not removed. Scar tissue increased in severity with implant duration, was a complicating factor, and was the main cause of failure to remove leads. Use of the femoral approach increased with implant duration (5% of leads implanted 12 months or less, 11% of leads 13 months to 3 years, 20% of leads 4-7 years, and 31% of leads 8-24 years), primarily because of increasingly abundant scarring and prior lead damage. Fatal and near fatal complications occurred in 2.5%, including 8 (0.6%) deaths (3 hemopericardium/tamponade, 1 hemothorax, 3 pulmonary embolus, 1 stroke).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine was administered intravenously to 17 patients undergoing intracardiac electrophysiologic studies. At a mean dose of 179 + 88 /ag/kg (±+ SD), adenosine suppressed sinus node automaticity and depressed atrioventricular (AV) nodal conduction. These effects were less than 20 sec in duration and were not influenced by muscarinic blockade with atropine (0.02 to 0.03 mg/kg). Adenosine at this dose had no Received June 20, 1983; revision accepted August 18, 1983. Dr. Belardinelli is the recipient of an NIH Research Career Development Award (1 K04 HL00969-0l).Dr. Sellers is the recipient of an American Heart Association Virginia Affiliate fellowship award 5-31757. 1254sinus rate and AV conduction in humans, but they reported no effect on atrial arrhythmias. We have recently demonstrated in isolated guinea pig and rabbit hearts and in the heart of the anesthetized dog in situ that the AV delay produced by adenosine is localized to the AV node.6 I Data from our laboratory and others have also suggested that adenosine released during ischemia or hypoxia may mediate the sinus bradycardia or AV nodal block seen in these conditions.7-9 These effects of adenosine in animals appear to be the result of an interaction with a specific extracellular receptor that is blocked by methylxanthines but not by atropine.'0The dose-response relationship of adenosine for its electrophysiologic and hemodynamic effects in man has not been previously characterized. In this study we sought to determine the nature and time course of the electrophysiologic effects of graded doses of intravenous adenosine in man and to assess the hemodynamic changes produced by the doses required to produce these effects. We also sought to test the hypothesis that the production of transient AV nodal block by an intravenous bolus of adenosine might permit the safe and CIRCULATION