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Biomedical subjects

B K Kantharia

Publications and source records attributed to B K Kantharia.

11 recordsLinked to original sources
PubMed2001

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.

Aged↗
PubMed2000

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.

Defibrillators, Implantable↗
PubMed2000

Case report: anterograde 2:1 and retrograde 3:2 Wenckebach block during atrioventricular nodal tachycardia: controversies of the upper and lower common pathways.

The exact nature of the reentry circuit for the atrioventricular nodal reentrant tachycardia (AVNRT) and particularly the concept and role of the upper and lower common pathways is not well defined. Although it is well accepted that the His-Purkinje system and the ventricles are not an essential part of the tachycardia circuit, controversy still exists as to whether the atria are essential components of the circuit. We describe a patient in whom the AVNRT perpetuated despite the spontaneous development of 2:1 anterograde and 3:2 retrograde block. To our knowledge, such a combination of electrophysiological phenomenon has not been previously reported. The electrophysiological basis of these observations and their clinical implications are discussed.

Cardiac Catheterization↗
PubMed1999

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.

Aged↗
PubMed1999

Extraction of pacemaker and implantable cardioverter defibrillator leads.

The common reasons for removal of pacing and defibrillator leads are infection, malfunction, or design defects such as fracture of J wires in Teletronics Accufix leads (Telectronics Pacing, Englewood, CO), which impose considerable risk for cardiac morbidity and mortality. Chronically implanted leads are fixed to the myocardium by fibrous tissue. Fibrous scar tissue may also encase the lead along its course. Furthermore, fragility of the lead and its tendency to break when extraction force is applied to overcome resistance imparted by the scar tissue add to the challenge of lead extraction. Thus, the extraction of chronically implanted leads is an important issue. Until a few years ago, the only methods available for the removal of chronically implanted leads were traction on the proximal segment of the lead and cardiac surgery. New techniques were developed to extract the leads by a transvenous approach using locking stylets, sheaths, snares, and retrieval baskets. Lead extraction using intravascular countertraction methods has since evolved as a specialty of its own. Progress has also been made in developing other system, such as Excimer laser energy for lead extraction. In this article, we discuss principles, techniques, and experience with these methods of extraction of chronic pacemaker and defibrillator leads.

Cardiac Surgical Procedures↗
PubMed1999

Concomitant reentrant tachycardias from concealed accessory atrioventricular bypass tract and atrioventricular nodal reentry in a patient with Williams syndrome.

Williams syndrome is characterized by a constellation of features including mental retardation and supravalvular aortic stenosis. Other cardiovascular abnormalities including arrhythmias contributing to sudden death have been described in these patients. In this report we describe a case of a 49-year-old female with Williams syndrome who presented with severe symptomatic supraventricular tachycardia. Cardiac electrophysiology study identified a left posteroseptal concealed accessory bypass tract responsible for atrioventricular reentrant tachycardia and a concomitant typical atrioventricular nodal tachycardia. Such unusual association of combination of two different types of supraventricular tachycardia and Williams syndrome has not been previously reported. Radiofrequency ablation was successfully performed to cure these arrhythmias.

Atrioventricular Node↗
PubMed1995

Clinical utility and the predictors of outcome of overdrive transesophageal atrial pacing in the treatment of atrial flutter.

Transesophageal atria pacing (TEAP) using a pill electrode was performed in 49 patients with atrial flutter. The responses observed were (1) immediate sinus rhythm in 17 (35%), (2) delayed sinus rhythm in 13 (27%), (3) atrial fibrillation in 11 (22%), and (4) no success in 8 (16%) patients. Sinus rhythm was thus restored in 30 patients (61%). In group A, 12 of 17 patients (p < 0.05) had coronary artery disease. The patients in group D had echocardiographic evidence of right atrial enlargement (2.56 +/- 0.29 cm, p = 0.007), left atrial enlargement (4.6 +/- 0.12 cm, p < 0.0001), right ventricular dilatation (3.41 +/- 0.45 cm, p < 0.05), left ventricular dilatation (6.39 +/- 0.66 cm, p < 0.05), and depressed left ventricular ejection fraction (32 +/- 7%, p < 0.05). Optimal pacing rate (375 +/- 54 beats/min) was 41% higher than the mean atrial flutter rate (266 +/- 37 beats/min) for cardioversion to immediate sinus rhythm. Pacing current strength and the pulse width had no influence on the final outcome. On the basis of the result of the initial attempt, patients undergoing TEAP repetitively had an almost predictably similar outcome on the subsequent attempts. Thus, normal sinus rhythm could be resumed in most patients with atrial flutter by TEAP. It does not require general anesthesia and can be performed even in patients who have undergone digitalization, when a direct-current countershock may be of some concern.

Aged↗
PubMed1989

Thymopentin (TP-5) in the treatment of rheumatoid arthritis.

A randomized control trial of TP-5 in rheumatoid arthritis is reported. In a multicentre study, 76 patients were treated with TP-5 50 mg or placebo three times a week for 3 weeks as a slow intravenous injection, and followed for 7 weeks. Clinical parameters such as the Ritchie index and sum score of swollen joints improved significantly on TP-5 compared to placebo. Laboratory parameters did not change but an increased skin test score to common recall antigens was observed. Toxicity was minimal. TP-5 is a potentially useful agent in the treatment of rheumatoid arthritis, although further studies are required to determine the optimal treatment regimen.

Arthritis, Rheumatoid↗