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Biomedical subjects

R J Schilling

Publications and source records attributed to R J Schilling.

At least 19 recordsLinked to original sources
PubMed2005

Catheter ablation of permanent atrial fibrillation: medium term results.

OBJECTIVE: To investigate the feasibility of catheter ablation as a treatment for symptomatic patients with longstanding permanent atrial fibrillation (AF). METHODS: Radiofrequency ablation was applied to encircle all pulmonary veins (PVs) and create lines from the left inferior PV to the mitral valve, along the roof of the left atrium between the PVs, and along the tricuspid valve-inferior vena cava isthmus. A seven day Holter was recorded at discharge and at follow up to assess arrhythmia burden. If patients developed a symptomatic, sustained atrial arrhythmia a repeat ablation procedure was advised. RESULTS: 42 patients underwent the procedure that took a mean of five hours with 50 minutes of fluoroscopy. After a median follow up of 8.4 months, 31 of 41 surviving patients (76%) were in sinus rhythm. Of these, 29 patients were no longer taking any antiarrhythmic drugs but 22 (52%) required more than one procedure. During follow up 49% experienced a sustained atrial tachycardia. Twenty six repeat procedures were performed. Maintenance of sinus rhythm after the first, second, or third procedure was 36% (15 of 42), 58% (11 of 19), and 71% (5 of 7), respectively. From a total of 68 procedures there were two serious complications (2.9%): a stroke from which a full recovery was made, and a PV stenosis. CONCLUSION: Catheter ablation can be used to cure longstanding permanent AF; however, there is a significant complication rate. Whether this is offset by a mortality benefit associated with sinus rhythm is unknown. Many patients will need more than one procedure to achieve success.

Atrial Fibrillation↗
PubMed2005

Ventricular arrhythmia, Cheyne-Stokes respiration, and death: observations from patients with defibrillators.

OBJECTIVE: To determine whether ventricular arrhythmia related to nocturnal hypoxaemia during Cheyne-Stokes respiration (CSR) explains the observation that CSR is an independent marker of death in heart failure. DESIGN: Prospective, observational study. PATIENTS: 101 patients at high risk of clinical serious ventricular arrhythmia fitted with an implantable cardioverter-defibrillator (ICD). MEASUREMENTS: Patients were studied at baseline for CSR during sleep. Arrhythmia requiring device discharge was used as a surrogate marker for possible sudden cardiac death. RESULTS: 101 patients (42 with CSR) were followed up for a total of 620 months. Twenty six patients experienced 432 ICD discharge episodes. Twenty four (6%), 210 (49%), 125 (29%), and 73 (17%) episodes occurred across the time quartiles 0000-0559, 0600-1159, 1200-1759, and 1800-2359, respectively. Kaplan-Meier analysis showed a relative risk of 1 (95% confidence interval 0.5 to 2.2, p = 1) for device discharge in the CSR group. The average (SED) numbers of nocturnal ICD discharges per patient per month of follow up were 0.01 (0.01) and 0.04 (0.02) for patients with and without CSR, respectively (p = 0.6). CONCLUSION: These findings refute the proposition that CSR is related to heart failure death through nocturnal serious ventricular arrhythmia.

Aged↗
PubMed2004

Atrial pacing for the prevention of atrial fibrillation after coronary artery bypass graft surgery: a review of the literature.

Atrial fibrillation (AF) occurs in 20-40% of patients after coronary artery bypass graft surgery (CABG) and contributes to increased morbidity and expenditure after CABG. The limited efficacy of pharmacological treatment to prevent post-CABG AF has stimulated research into alternative prophylactic strategies for the arrhythmia. This article critically reviews the trial evidence in the literature regarding the efficacy of epicardial atrial pacing to prevent post-CABG AF. Thirteen randomised controlled trials of either right, left, or biatrial pacing to prevent post-CABG AF were identified. Overall, prophylactic biatrial epicardial pacing appears to be effective prophylaxis against post-CABG AF and to reduce postoperative hospital stay. The efficacy of single site right or left atrial pacing is less clear. Further data are required to determine both the efficacy of single site atrial pacing and the cost effectiveness of pacing strategies to prevent AF after CABG.

Atrial Fibrillation↗
PubMed2001

Modulation of the binding affinity of myelopoietins for the interleukin-3 receptor by the granulocyte colony-stimulating factor receptor agonist.

Myelopoietins (MPOs) are a family of recombinant chimeric proteins that are both interleukin-3 (IL-3) receptor and granulocyte colony-stimulating factor (G-CSF) receptor agonists. In this study, MPO molecules containing one of three different IL-3 receptor agonists linked with a common G-CSF receptor agonist have been examined for their IL-3 receptor binding characteristics. Binding to the alpha-subunit of the IL-3 receptor revealed that the affinity of the MPO molecules was 1.7-3.4-fold less potent than those of their individual cognate IL-3 receptor agonists. The affinity decrease was reflected in the MPO chimeras having approximately 2-fold slower dissociation rates and 2.7-5.5-fold slower association rates than the corresponding specific IL-3 receptor agonists alone. The affinity of binding of the MPO molecules to the heteromultimeric alphabeta IL-3 receptor expressed on TF-1 cells was either 3-, 10-, or 42-fold less potent than that of the individual cognate IL-3 receptor agonist. Biophysical data from nuclear magnetic resonance, near-UV circular dichroism, dynamic light scattering, analytical ultracentrifugation, and size exclusion chromatography experiments determined that there were significant tertiary structural differences between the MPO molecules. These structural differences suggested that the IL-3 and G-CSF receptor agonist domains within the MPO chimera may perturb one another to varying degrees. Thus, the differential modulation of affinity observed in IL-3 receptor binding may be a direct result of the magnitude of these interdomain interactions.

Binding, Competitive↗
PubMed2001

Characterization of the anatomy and conduction velocities of the human right atrial flutter circuit determined by noncontact mapping.

OBJECTIVES: This study was done to characterize human right atrial (RA) flutter (AFL) using noncontact mapping. BACKGROUND: Atrial flutter has been mapped using sequential techniques, but complex anatomy makes simultaneous global RA mapping difficult. METHODS: Noncontact mapping was used to map the RA of 13 patients with AFL (5 with previous attempts), 11 with counterclockwise and 2 with clockwise AFL. "Reconstructed" electrograms were validated against contact electrograms using cross-correlation. The Cartesian coordinates of points on a virtual endocardium were used to calculate the length and thus the conduction velocity (CV) of the AFL wave front within the tricuspid annulus-inferior vena cave isthmus (IS) and either side of the crista terminalis (CT). RESULTS: When clearly seen, the AFL wave front split (n = 3) or turned in the region of the coronary sinus os (n = 6). Activation progressed toward the tricuspid annulus (TA) from the surrounding RA in 10 patients, suggesting that the leading edge of the reentry wave front is not always at the TA. The IS length and CV was 47.73 +/- 24.40 mm (mean +/- SD) and 0.74 +/- 0.36 m/s. The CV was similar for the smooth and trabeculated RA (1.16 +/- 0.48 m/s and 1.22 +/- 0.65 m/s, respectively [p = 0.67]) and faster than the IS (p = 0.03 and p = 0.05 for smooth and trabeculated, respectively). CONCLUSIONS: Noncontact mapping of AFL has been validated and has demonstrated that IS CV is significantly slower than either side of the CT.

Adult↗
PubMed2000

Catheter ablation of ventricular tachycardia related to coronary artery disease: the role of noncontact mapping.

There are a number of limitations associated with conventional mapping for ablation of ventricular tachycardia (VT) in ischemic heart disease, such as the high recurrence rates after initially successful ablation. The development of a noncontact mapping system capable of producing high-resolution isopotential maps of the entire left ventricle has enabled rapid identification of diastolic activity that maintains VT for ablation. With this system it is possible to map nonsustained and fast unstable as well as stable VTs. In this article we review the historic background and concepts of noncontact mapping, its clinical application, and the results of ablations for human VT guided by this mapping system.

Body Surface Potential Mapping↗
PubMed2000

Endocardial mapping of atrial fibrillation in the human right atrium using a non-contact catheter.

BACKGROUND: Endocardial mapping of atrial fibrillation in humans is limited by its low resolution and by complexities in the arrhythmia and atrial anatomy. METHODS AND RESULTS: A catheter mounted non-contact multielectrode was deployed in the right atrium of 11 patients with atrial fibrillation and used to reconstruct 3360 electrograms, superimposed onto a computer-simulated model of the endocardium, using inverse solution mathematics. This allows construction of isopotential maps of the right atrium. Patients had either sustained atrial fibrillation (n=3) for >6 months or developed atrial fibrillation during the study (n=8). Spontaneous initiation of atrial fibrillation was recorded in one patient and was demonstrated by the non-contact system to arise from two successive atrial ectopic beats from the site of a roving contact catheter. Reconstruction of electrograms recorded during atrial fibrillation was validated by comparison with contact electrograms with cross-correlation. During established atrial fibrillation, four patients predominantly had a single right atrial wave front, two had two wave fronts and five patients had three to five wave fronts for most of the time. Periods of electrical silence were seen in the right atrium in eight patients, after which, activity emerged from consistent septal sites alone, suggesting a left atrial origin. During intravenous administration of flecainide, atrial fibrillation in two patients terminated spontaneously or following pacing manoeuvres, while in the remaining patient sinus rhythm was restored via atrial tachycardia. CONCLUSION: Non-contact mapping of the right atrium has demonstrated modes of initiation and termination of atrial fibrillation, characterized different patterns of right atrial activation in atrial fibrillation and suggests that the left atrium may sustain atrial fibrillation in some patients. Simultaneous mapping of the right and left atrium is required to further elucidate the mechanisms of human atrial fibrillation.

Adult↗
PubMed1999

Feasibility of a noncontact catheter for endocardial mapping of human ventricular tachycardia.

BACKGROUND: Catheter ablation of ventricular tachycardia (VT) is limited by difficulty in identifying suitable sites for ablation. This study assesses use of a system capable of simultaneous endocardial mapping of the human left ventricle to map and guide radiofrequency (RF) catheter ablation of VT. METHODS AND RESULTS: A catheter-mounted noncontact multielectrode array was used to reconstruct 3360 electrograms, superimposed onto a computer-simulated endocardial model. Of 24 patients studied, 20 had ischemic heart disease. Exit sites were demonstrated by the noncontact system in 80 (99%) of 81 VTs, with complete VT circuits traced in 17 (21%). In another 37 VTs, 36+/-30% (mean+/-SD) of the diastolic interval was identified. Thirty-eight VT morphologies were ablated with 154 RF energy applications. Successful ablation was achieved by 77% of RF applications to relevant diastolic activity identified by the system and was significantly more likely (P<0.0001) than by RF at the VT exit or remote from diastolic activation. Over a mean follow-up of 1.5 years, 14 patients (64%) have had no recurrence of VT, and only 2 target VTs (5.3%) have recurred. Five patients have had recurrence of other VTs. CONCLUSIONS: This noncontact mapping system identified diastolic portions of the circuit in most VTs studied and can safely map and guide ablation of human VT.

Adult↗
PubMed1999

Noncontact mapping of cardiac arrhythmias.

The development of new mapping systems is beginning to overcome some of the limitations of conventional techniques by offering percutaneous deployment, simultaneous acquisitions of data, high-resolution maps, and correlation of anatomy and electrophysiology, in addition to a catheter location system. The noncontact mapping system continues to undergo development and does not completely address all requirements for an ideal mapping system. The limitations of the system include deterioration in the quality of electrogram reconstruction with increasing distance between the MEA and the endocardium, the inability of the noncontact system to identify subendocardial activation, and problems with distinguishing noise from low-amplitude diastolic electrograms.

Arrhythmias, Cardiac↗
PubMed1999

Mapping and ablation of ventricular tachycardia with the aid of a non-contact mapping system.

OBJECTIVE: Treatment of ventricular tachycardia (VT) in coronary heart disease has to date been limited to palliative treatment with drugs or implantable defibrillators. The results of curative treatment with catheter ablation have proved disappointing because the complexity of the VT mechanism makes identification of the substrate using conventional mapping techniques difficult. The use of a mapping technology that may address some of these issues, and thus make possible a cure for VT with catheter ablation, is reported. PATIENTS AND INTERVENTION: The non-contact system, consisting of a multielectrode array catheter (MEA) and a computer mapping system, was used to map VT in 24 patients. Twenty two patients had structural heart disease, the remainder having "normal" left ventricles with either fasicular tachycardia or left ventricular ectopic tachycardia. RESULTS: Exit sites were demonstrated in 80 of 81 VT morphologies by the non-contact system, and complete VT circuits were traced in 17. In another 37 morphologies of VT 36 (30)% (mean (SD)) of the diastolic interval was identified. Thirty eight VT morphologies were ablated using 154 radiofrequency energy applications. Successful ablation was achieved by 77% of radiofrequency within diastolic activation identified by the non-contact system and was significantly more likely to ablate VT than radiofrequency at the VT exit, or remote from diastolic activation. Over a mean follow up of 1.5 years, 14 patients have had no recurrence of VT and only two target VTs have recurred. Five patients have had recurrence of either slower non-sustained, undocumented or fast non-target VT. Five patients have died, one from tamponade from a pre-existing temporary pacing wire, and four from causes unrelated to the procedure. CONCLUSION: The non-contact system can safely be used to map and ablate haemodynamically stable VT with low VT recurrence rates. It is yet to be established whether this system may be applied with equal success to patients with haemodynamically unstable VT.

Adult↗