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Biomedical subjects

I D Parson

Publications and source records attributed to I D Parson.

10 recordsLinked to original sources
PubMed2001

Information technology and home glucose clamping.

Persons with diabetes are responsible for the day-to-day control of their glycemia. To assist patients in discharging this responsibility and help them achieve and sustain improvements in self-blood glucose control, we developed information technology capable of executing algorithms for "clamping glucose" at home. Algorithms for laboratory glucose clamping were translated and adapted for use by patients. The procedures were supported by a central computer and registry. Interaction with the algorithms from home required the patient to handle only a touch-tone telephone, which accessed voice response hardware in the central computer. Patients reported self-measured blood glucose levels or hypoglycemia symptoms together with dietary changes, planned exercise, stress, illness or other lifestyle events. In response, they received self-management instructions and dosing decision support. Metabolic end points were measured. System beta testing in active patients was for 1 year. Patients (n = 142) used the algorithms for their daily self-management, accumulating 1,651 patient-months of follow-up. Almost 100,000 telephone calls were received. Patients benefited. Prevalence of diabetes related crises (hyperglycemia > 400 mg/dL, hypoglycemia < 50 mg/dL or symptoms without measurement) fell approximately twofold (p < 0.05) and glycated hemoglobin levels fell 1.3% (p < 0.001), while body weight was stable. Providers benefited from the timely receipt of standardized reports to monitor the progress of their patients. Earlier intervention was possible. Information technology facilitated home glucose clamping whereby patients with diabetes received timely assistance, advice and decision support for crucial self-control of blood glucose levels. This empowered patients to achieve independence and improve diabetes self-management.

Algorithms↗
PubMed1992

Simultaneous unipolar and bipolar recording of cardiac electrical activity.

An analog mapping system using a true bipolar left ventricular balloon electrode array is described, which enables simultaneous unipolar and bipolar recordings. It is an adaptation of a previous clinical analog mapping system used in the investigation of ventricular arrhythmias. The bipolar balloon array consists of 112 electrode pairs, each having a 2-mm separation. The signals from the electrodes are sensed in parallel by separate unipolar and bipolar amplifier units, which then drive a common multiplexer bus. The bipolar recording unit consists of high quality instrumentation amplifiers with adjustable gain and exhibits a full bandwidth minimum common mode rejection of 78 dB. Using this combination, it is possible to record local cardiac micropotentials while still retaining the advantages of unipolar electrograms to track overall cardiac activation.

Catheterization↗
PubMed1991

A three-dimensional display for cardiac activation mapping.

A three-dimensional display is described that allows activation sequences from the epicardium and endocardium to be shown simultaneously on the same image. Three electrode arrays (epicardial sock, left ventricular balloon, right ventricular balloon) are represented in a three-dimensional perspective by an array of dots that are intensified when activated. This arrangement requires fewer calculations and is easier to interpret than sliced-isochronal maps but cannot represent a complete heart cycle in one image. The three-dimensional display eliminates the distortion caused by two-dimensional diagrams and facilitates activation correlation between electrode arrays. A standard, low cost microcomputer has been used to implement the activation display.

Arrhythmias, Cardiac↗
PubMed1991

The construction of endocardial balloon arrays for cardiac mapping.

The advent of multichannel recording systems has enabled clinical mapping to be performed on a beat-by-beat basis using multi-electrode arrays. Surgical ablation of ventricular arrhythmias generally requires endocardial mapping. Clinical usage has indicated that an inflatable balloon array is the most practical design and can obviate the need for ventriculotomy by a transatrial introduction in the deflated state. Successful experience with the left ventricular balloon led to the development of a right ventricular balloon array suitably configured to extend into the outflow tract. Custom moulds are used to create an appropriate balloon from liquid latex. Nylon cloth is cut from a cardboard pattern to fashion a stretchable sock to envelope the balloon. Electrodes are formed by stitching 2-mm silver beads to the balloon sock in a preconfigured pattern. Teflon-coated 31 G multi-strand stainless-steel wires 130 mm in length connect the electrode beads by solder to the multipin connectors for easy hookup to the amplifier inputs. Tygon tubing 0.53 cm in diameter fitted to the balloon allows inflation and pressure monitoring. This basic design has been successfully implemented for the last 6 years.

Arrhythmias, Cardiac↗
PubMed1988

Endocardial mapping of ventricular tachycardia in the intact human ventricle: evidence for reentrant mechanisms.

A balloon array of 112 electrodes was used to obtain simultaneous recordings of endocardial electrograms during intraoperative mapping studies of ventricular tachycardia. Introduction of the balloon through a left atriotomy and across the mitral valve allowed endocardial activation maps to be obtained in the intact left ventricle. Of 20 patients with coronary artery disease studied in this way, suggestive evidence of endocardial reentry was found in 6. Three separate reentrant mechanisms were observed. In two patients, a single broad wave front of continuous recirculating activation reminiscent of a vortex was initiated by the formation of a functional arc of block in response to premature stimuli. In five patients, premature stimuli again produced a functional arc of block, which was circumvented by two opposing wave fronts that united on the distal side. Retrograde penetration by a narrow isthmus of slow conduction through the block initiated the tachycardia, whose activation sequence was consistent with figure eight reentry. In one patient, premature stimuli produced a region of delayed potentials. Critical timing of these resulted in microreentry in an adjacent circumscribed site, which formed the site of origin of the ensuing tachycardia. The microreentrant signals were not detected by standard unipolar recordings, but were seen on simultaneously recorded high gain electrograms. In 14 patients, although mapping identified a site of origin, the activation patterns showed either radial spread or incomplete circles. Detection of reentrant mechanisms during intraoperative mapping required high density electrode arrays and refined high gain recordings. An intact ventricle may facilitate intraoperative initiation of tachycardia.

Electrocardiography↗
PubMed1984

On-line epicardial mapping of intraoperative ventricular arrhythmias: initial clinical experience.

An on-line automatic mapping system was developed for beat by beat display of epicardial activation during ventricular tachycardia induced at the time of cardiac surgery. A sock array of 110 button electrodes was used to record and display local activation on a video monitor at 8.3 ms intervals. On instant replay in slow motion, epicardial pacing sites were accurately localized to the nearest electrode. Local unipolar electrograms were also recorded, first from the sock array, then from an array of 16 transmural needle electrodes. The epicardial display was verified by retrospective manually derived maps using the recorded epicardial electrograms. In four patients with coronary artery disease and recurrent inducible ventricular tachycardia, earliest epicardial activation was located on slow motion replay within 1 minute. Subendocardial sites of early activation were located within 10 minutes by replay of electrograms from the needle array before ventriculotomy. Transmural and endocardial resection of these sites prevented inducibility of the tachycardia on postoperative electrophysiologic study in three of the four patients. There has been no clinical recurrence of ventricular tachycardia after 3 to 14 months of follow-up despite cessation of antiarrhythmic therapy in three of the patients. This technique has unique advantages over existing mapping methods. It provides beat by beat display of activation sequences so that clinical tachycardias that are short in duration or pleomorphic in configuration now become amenable to mapping. In addition, it markedly shortens total time on cardiopulmonary bypass.

Adult↗
PubMedDate not supplied

Diabetes intervention in the information age.

Sustained improvement in blood glucose control is the only treatment outcome which will reduce or eliminate the long term complications of diabetes mellitus. We have designed and evaluated an electronic information system which facilitates this task. The system is voice-interactive, physician directed and affords, to remote patients, 24 h access via touch-tone telephone. Accordingly, patients access the system each day to report self-measured blood glucose levels or hypoglycaemic symptoms together with dietary changes, planned exercise, stress, illness or other lifestyle events. In turn they receive immediate advice with respect to medication dosing changes, and other pertinent feedback. Preliminary system beta-testing for safety and efficacy was performed for one year in an open study of 204 patients derived from two independent, health-care environments. Among the two testing centres, over 60,000 telephone cells were received by the computer systems during the start-up year. Safety and efficacy expectations were met. In addition, prevalence of diabetes related crises (hyperglycaemia or hypoglycaemia) fell approximately 3-fold. Glycated haemoglobin fell significantly (1.0-1.3%) in patients actively using the system. In control groups of patients not actively using the system, there were no improvements in metabolic control while body weights were stable in all groups. The new system was safe and effective in our hands and empowered our health professionals to provide improved diabetes care.

Algorithms↗