Effect of different location of atrial lead position on nearfield and farfield electrograms in dual chamber pacemaker-defibrillators.

The normal functioning of dual chamber pacemaker-cardioverter defibrillator (AV pacer/ICD) may be affected by oversensing of the farfield R wave (FFRW) by the atrial channel. This study aimed to investigate whether placement of the AV pacer/ICD's atrial lead at a lateral (LAT) wall location compared to a medial (MED) location i.e. the appendage of the right atrium, would reduce the amplitude of FFRWs but not the nearfield atrial electrograms (AEGMs) during sinus rhythm (SR) and ventricular fibrillation (VF). In 17 patients, real time electrograms were recorded during SR and induced VF through the atrial lead initially at the MED and subsequently at the LAT location. In 10 patients the electrograms in SR were also recorded on a computerized data acquisition and recording system at different band-pass filter settings. Although FFRWs were recorded both at MED and LAT locations, they were much smaller, 3.5+/-4.1mm during SR and 1.7+/-2.2mm during VF at the LAT location. At 30-500Hz band-pass filter, lower amplitudes of FFRWs 0.14+/-0.09 mV were recorded at the LAT location. The V/A ratios of the amplitudes of FFRWs and AEGMs were smaller at the LAT location during SR and VF. The nearfield AEGMs were of similar amplitudes at the MED and LAT locations. These data indicate that lower amplitudes of FFRWs are recorded by placement of the atrial lead at the lateral wall of the right atrium. Oversensing of FFRWs may be prevented to improve functioning of the AV pacer-ICD.

Feasibility, safety, and determinants of extraction time of percutaneous extraction of endocardial implantable cardioverter defibrillator leads by intravascular countertraction method.

Previous studies of the removal of implantable cardioverter defibrillator (ICD) leads have been restricted to case reports or small series. In this report, we describe our experience in ICD lead extraction by intravascular countertraction method using Cook's extraction kit. A total of 47 high-voltage (HV) leads, 3 rate sensing (S) leads, and 2 subcutaneous arrays were removed from 42 patients (33 men, 9 women; mean age 59 years [range 14 to 81]). One HV superior vena cava (SVC) lead and 11 HV right ventricular (RV) leads were explanted by manual traction only and defined in the "lead removal" category. One S lead was removed using a femoral venous approach. The remaining 37 leads were explanted by SVC approach using extraction sheaths and defined in the "lead extraction" category. Twenty leads were extracted for "infectious" (group A) and 17 leads for "noninfectious" (group B) etiologies for which extraction times of 27.0+/-18.0 and 27.0+/-15.0 minutes (mean+/-SD), respectively, were not different. Although extraction time, 34.0+/-11.0 minutes, for leads implanted for >48 months was longer than 23.0+/-16.0, 28.0+/-18.0, and 24.0+/-14.0 minutes, for leads with implant durations of 12, 24, and 48 months, respectively, such differences were not statistically significant. The extraction time, however, was directly related to the degree of fibrosis around the lead, 39.0+/-15.0 minutes for leads with severe fibrosis compared with 13.0+/-6.0 minutes for the leads with mild fibrosis (p<0.001). Patient's age, sex, or history of coronary artery bypass graft surgery did not significantly affect extraction time. All except the initial 2 lead extractions were performed in the electrophysiology laboratory. No mortality or serious complications associated with the procedure using these methods were observed.

Efficacy and safety of catheter ablation in octogenarians.

OBJECTIVES: To determine whether catheter ablation is safe and effective in patients over the age of 80. BACKGROUND: There is a tendency to withhold invasive therapy in the elderly until it has been proven safe and effective. METHODS: Over a two-year period from February 1, 1996 to February 1, 1998, 695 consecutive patients underwent 744 catheter ablation procedures of supraventricular and ventricular arrhythmias. These patients were divided into three groups based on age: > or =80 years, 60 to 79 years and <60 years. Acute ablation success, using standard criteria and complication rates for these three groups were determined. RESULTS: There were 37 patients > or =80 years, 275 patients 60 to 79 years and 383 patients <60 years old. The overall acute ablation success rate for the entire group was 95% with no difference in rates among the three groups (97%, > or =80 years; 94%, 60-79 years; 95%, <60 years). The percentage of patients undergoing His bundle ablation was greatest in the > or =80-year-old group (43% vs. 19% vs. 2%, p < 0.01), and the percentage of patients undergoing accessory pathway ablation was greatest in the <60-year-old patients (0% vs. 4% vs. 25%, p < 0.01). The overall complication rate for the entire group was 2.6%, and there was only one major/life-threatening complication. There was no difference in complication rates among the groups (0%, > or =80 years; 2.2%, 60 to 79 years; 3.1%, <60 years). Based on the sample size, the 95% confidence interval is 0% to 7.8% for an adverse event in the octogenarian. CONCLUSIONS: Catheter ablative therapy for the arrhythmias attempted in the very elderly appears to be effective with low risk. Ablation results appear to be comparable with those noted in younger patients.

Radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia after orthotopic heart transplantation.

Patients with orthotopic heart transplantation may develop a variety of arrhythmias. Successful radiofrequency catheter ablation for tachyarrhythmias from manifest and concealed accessory bypass tracts in transplant patients has been previously reported. We present a patient with orthotopic heart transplantation who developed typical atrioventricular nodal tachycardia, which was successfully treated by radiofrequency catheter ablation.

Implantable cardioverter-defibrillator follow-up: what everyone needs to know.

Over the past few years, remarkable advances in the treatment of ventricular tachycardia, ventricular fibrillation, and sudden cardiac death have occurred. One of the most significant treatment modalities has been the addition of the implantable cardioverter-defibrillator (ICD). Because of the rapidly expanding indications for ICD therapy, it is common for internists, family practitioners, emergency room physicians, and general cardiologists to treat defibrillator patients. Basic skills related to ICD follow-up are therefore essential for many physicians. In this review, we will summarize routine device follow-up, provide instructions regarding emergency ICD deactivation, discuss common complications and how to detect them, and answer some frequently asked questions.

Adenosine as an antiarrhythmic agent.

Adenosine produces acute inhibition of sinus node and atrioventricular (AV) nodal function. This profound but short lived electrophysiologic effect makes adenosine a suitable agent for treating supraventricular tachycardias (SVT) that incorporate the sinus node or AV node as part of the arrhythmia circuit, or for unmasking atrial tachyarrhythmias or ventricular pre-excitation. Its antiadrenergic properties also make it an effective agent for use with some unique atrial and ventricular tachycardias. Appropriate dosing and rapid bolusing with intravenous administration is required. Recognition of infrequent proarrhythmic risks and potential drug interactions with xanthine derivatives and dipyridamole should maximize its safe and effective use. This review will highlight adenosine's mechanism of action, administration, clinical indications, efficacy, and risks when used in tachyarrhythmic management.

Bacterial attachment to the chorioamniotic membranes.

Intra-amniotic infections are believed to result from bacteria of cervical and vaginal origin which gain access to the amniotic sac. The logical sequence in this process would be bacterial attachment to the maternal surface, followed by migration through the chorioamniotic membranes to the fetal surface. Fresh sterile chorioamniotic membranes were interposed between two arms of specially constructed incubation vessels. Bacteria (Escherichia coli, group B streptococci, or Neisseria gonorrhoeae) were inoculated into the arm (containing a basal salt medium) contiguous with the maternal surface. The arm contiguous with the fetal surface of the membrane contained pseudoamniotic fluid. At intervals up to 24 hours after inoculation, the membranes were removed, washed, fixed in glutaraldehyde, and examined by means of scanning and transmission electron microscopes. The ability of group B streptococci and E. coli to attach to and invade the chorioamniotic membranes was demonstrated by this technique. It appeared that group B streptococci had a greater capacity to attach and invade than did E. coli, whereas N. gonorrhoeae predictably failed to attach.