Biomedical subjects

Richard Sutton

Publications and source records attributed to Richard Sutton.

24 records · Page 2Linked to original sources

PubMed2002

How to test mode switching in pacemakers implanted in patients: the MOST study.

Optimal management of atrial arrhythmias with dual chamber pacemakers requires proper performance of automatic mode switching (AMS). The aim of this study was to develop a reliable technique to test the AMS function by using an external electronic device capable of mimicking the occurrence of supraventricular arrhythmias (Supraventricular Arrhythmia Simulator [SAS]). The SAS delivers low voltage pulse trains (200 mV, 20 ms) through two skin electrodes. Each pulse train lasts 15 seconds and starts synchronously with a pacing pulse of the implanted pacemaker to avoid interference from the operator. The pulse train rate is set at 350, 250, and 160 beats/min to simulate AF, atrial flutter, and atrial tachycardia (AT), respectively. Thirty-five patients implanted with Vitatron pacemakers, whose AMS system has been previously validated, were enrolled. Atrial and ventricular sensing were programmed in unipolar mode at 0.5 mV and in bipolar mode at > 2 mV, respectively. All pulses from the SAS were detected by the atrial channel at an amplitude ranging from 1 to 3 mV. The test proved to be safe and reliable at rest and during exercise. AMS occurred immediately at onset or at offset of atrial arrhythmias, and no adverse interference on pacemaker function was seen from the SAS. In conclusion, the described technique and the SAS are safe and reliable for patient and pacemaker function and can be proposed as a useful method to verify proper performance of AMS function irrespective of the type of implanted devices.

Aged↗

PubMed2002

The revised NASPE/BPEG generic code for antibradycardia, adaptive-rate, and multisite pacing. North American Society of Pacing and Electrophysiology/British Pacing and Electrophysiology Group.

In light of evolving pacemaker technology and increasing interest in multisite pacing, the Committee on the Development of Position Statements (CDPS) of the North American Society of Pacing and Electrophysiology (NASPE) created an ad hoc Pacemaker Mode Code Task Force in April 2001 under the chairmanship of David L. Hayes, MD, for the purpose of bringing the NASPE/British Pacing and Electrophysiology Group (BPEG) Generic Pacemaker Code (NBG Code) up to date. The task force, whose members are the authors of this article, designed a revised NBG Code in which three major issues were taken into account. First, it was recognized that all modern pacemakerpulse generators are capable of extensive bidirectional communication with an external programming device, making them "communicating" pulse generators as defined by the current (1987) NBG Code. Second, it was decided that a means of providing basic information regarding the location of multisite pacing would be a useful ingredient of the NBG Code. Third, in view of the extensive antibradycardia pacing capabilities common in modern implantable cardioverter defibrillators and the availability of the NASPE/BPEG Defibrillator Code (NBD Code), it was considered unnecessary for the NBG Code to address the presence or absence of antitachycardia features. The resulting updated version of the NBG Code as described herein was endorsed by the BPEG on September 20, 2001 and adopted by the NASPE Board of Trustees on October 18, 2001. The structure of the revised NBG Code differs from that of the previous version in two respects alone: Position IV specifies only the presence or absence of rate modulation, and Position V specifies only the location or absence of multisite pacing (i.e., biatrial or biventricular pacing with at least two stimulation sites in each case) more than one stimulation site in any single cardiac chamber, or any combination of these. The revised NBG Code is deliberately configured to avoid confusion with earlier mode codes, and it is the authors' hope that it will serve as an enhanced resource for communication among those engaged in every phase of the multidisciplinary practice of cardiac rhythm management.

Bradycardia↗

PubMed2002

Sentinel node biopsy and lymphoscintigraphy with a technetium 99m labeled blue dye in a rabbit model.

BACKGROUND: Lymphatic mapping for sentinel node biopsy in breast cancer and melanoma usually involves initial peritumoral injection of a radioisotope, gamma camera detection of the sentinel lymph node several hours prior to the operation, and separate perioperative injection of a blue dye. We have developed a combined approach using technetium 99m labeled blue dye (Evans Blue) for use in lymphoscintigraphy that may be injected as a single dose just prior to the operation. METHODS: In an anesthetized rabbit model we dissected a hind limb to display the popliteal node and afferent lymphatic. Technetium 99m Evans Blue ((99m)Tc-EB) (22 MBq; 0.5 mL) was injected subdermally in the dorsum of the paw. Simultaneous digital and gamma camera images were obtained at 14 time intervals to 30 minutes post injection. For each of these time intervals the percentage of radioactivity and percentage blueness of the popliteal node were determined. Urine and afferent lymphatic fluid were analyzed by chromatography. The popliteal node was excised post mortem, placed into solvent solutions and analyzed for blueness and radioactivity. RESULTS: Time-activity curves for radioactivity and time-blueness curves for Evans Blue uptake showed strong correlation (r = 0.958). Lymph analysis suggested (99m)Tc-EB is mainly bound to endogenous proteins. Urine was radioactive but not colored, (99m)Tc-EB being metabolized and excreted in the urine as 1,7-diamino-8-naphthol-2,4-disulfonic acid. Prolonged exposure of node to solvents did not dissociate any blue coloration or radioactivity. CONCLUSIONS: (99m)Tc-EB and Evans Blue are simultaneously retained and concentrated in the sentinel lymph node. This process is rapid and reproducible. (99m)Tc-EB migrates at the same rate as Evans Blue in lymph, where it is transported as bound to endogenous proteins. These dye molecules are metabolized by reductive cleavage in the liver and then excreted renally as colorless, radioactive metabolites. This novel agent has the potential to facilitate lymphatic mapping and subsequent sentinel node biopsy for a range of solid malignancies including breast cancer and melanoma.

Animals↗

PubMed2002

How and when to pace in vasovagal syncope.

This article discusses the indications for pacing in vasovagal syncope. It also reviews the literature on pacing results; notably, there are two small randomized controlled trials of pacing versus no therapy (or continued nondevice therapy) that show a clear benefit for pacing. The mode of benefit is, as yet, unclear. Pacing has to be dual chamber with some form of rate hysteresis. Ways of improving pacemaker therapy delivery in vasovagal syncope are anticipated.

Blood Pressure↗

PubMed2002

Why certain dyes are useful for localizing the sentinel lymph node.

UNLABELLED: Location of the sentinel lymph node in malignant melanoma and early breast cancer patients requires separate injections of radiocolloid and blue dye. These agents are administered at alternative times because of their different rates of transit. This study has elucidated why particular dyes are absorbed by the lymphatic system from an investigation of dye molecular structure as a function of protein binding ability. METHODS: A dye-protein binding assay was developed using size-exclusion chromatography and ultraviolet spectrophotometry and applied to a series of 20 sulfonic acid group-containing dyes. Radiochemical analyses were also used with 3 99mTc-labeled dyes to rationalize which functional groups are involved in the protein binding reaction. RESULTS: Methylene blue resulted in no protein affinity at 37 degrees C, whereas disulfonate dyes separated by 1 atom such as Patent blue or Indigo carmine gave <30% binding. Optimum protein binding (84%-100%) was achieved with those dyes containing at least 2 sulfonic acid groups separated by 2-6 atoms in their chemical structure. Seven symmetric tetrasulfonic acid azo dyes were examined, including Evans blue, to result in 59%-71% binding. CONCLUSION: Ionizable groups (sulfonic acids) that are present in the structure of dyes are directly involved in dye-protein binding. At the molecular level, there is a sulfonation reaction between sulfonic acid dyes and amino groups on the protein surface to form sulfonamide complexes. This reaction shows how the soluble dyes Evans blue and Patent blue are trapped in lymph after subdermal injection during the sentinel node biopsy procedure.

Animals↗

PubMedDate not supplied

Use of bDNA testing in the immunologically nonresponding patient who has a low or undetectable viral load by RT-PCR testing.

BACKGROUND: Studies have shown that reverse transcription-polymerase chain reaction (RT-PCR) technology underquantifies viral loads in patients with non-B clades of HIV-1. Testing with bDNA technology gave higher viral loads in these subtypes. A study was conducted to determine whether virologically responding patients on HAART who were not immunologically responding would have higher viral loads using bDNA technology and whether these differences were due to non-B clades. METHOD: Forty-eight patients receiving HAART for more than 6 months who were having inappropriate immunologic responses in spite of undetectable or very low viral loads determined by RT-PCR (<3000 copies by Roche Amplicor 1.0) were studied. These patients had bDNA viral loads performed. All patients who had bDNA viral loads equivalent to >3000 by RT-PCR had clade and genotypic studies performed. RESULTS: Fifteen patients had viral loads by bDNA that were equivalent to >3000 copies by RT-PCR. Four of these were found to have non-B clades (one D clade and three AG clade). The D clade patient had multidrug resistance; none of the AG clade patients had resistance. Of the remaining 11 patients, virus could not be recovered from 2 and 9 had a B clade. Six of these nine had genotypic resistance to HAART drugs. CONCLUSION: bDNA testing may be useful in the immunologically nonresponding patient.

Adult↗