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Biomedical subjects

J McC Anderson

Publications and source records attributed to J McC Anderson.

4 recordsLinked to original sources
PubMed2004

Wearable and implantable monitoring systems: 10 years experience at University of Ulster.

Over the past 10 years or more, NIBEC and, more recently, Sensor Technology and Devices Ltd have been at the forefront of developments in sensor-related technologies which underpin a wide range of monitoring systems presently commercialised by leading multinationals. Systems developed/ commercialised include astronaut-monitoring arrays, cardiac mapping harnesses, ECG electrodes, Telemedicine systems and implant sensor arrays. This paper presents the main developments in this area and discusses outstanding issues for future research.

Astronauts↗
PubMed2003

Transvenous cardioversion--a novel asymmetric rectangular biphasic waveform from a radiofrequency defibrillator compared with conventional waveforms in atrial fibrillation.

BACKGROUND: We investigated a novel device that delivered biphasic and monophasic shocks without tilt, in transvenous cardioversion of atrial fibrillation (AF). The device contains a radiofrequency (RF) transmitting primary, a 15mm air gap and a passive secondary unit that produces the required direct current waveform. METHODS: The device was assessed in 10 anaesthetised and ventilated sheep (65 +/- SD 12kg). Defibrillation leads were positioned in the distal coronary sinus and the lateral right atrium. The novel RF defibrillator was assessed using rectangular monophasic or biphasic pulses and compared to conventional (C) tilted waveforms (Ventritex HVS-02). During AF placebo shocks were delivered to a 50 Omega dummy load. Sustained AF was induced by rapid atrial pacing and 5 attempts at cardioversion were made for each waveform. Success was defined as reversion to sinus rhythm within 5 beats of shock delivery. RESULTS: No arrhythmic complications were observed for the 400 shocks delivered. CONCLUSION: A reduction in phase 2 voltage does not affect the efficacy of rectangular waveforms but does facilitate energy reduction. Asymmetric rectangular biphasic waveforms with phase 2 voltage at 50% of phase 1 are more efficacious than equivalent voltage conventional waveforms for transvenous cardioversion of AF. The novel defibrillator is safe and effective. Design modifications will enable this device to be used as an implantable defibrillator with an external RF power source.

Animals↗
PubMed2003

Body surface mapping improves early diagnosis of acute myocardial infarction in patients with chest pain and left bundle branch block.

OBJECTIVE: To test prospectively depolarisation and repolarisation body surface maps (BSMs) for mirror image reversal, which is less susceptible to artefact, in patients with acute ischaemic-type chest pain, and to compare these BSM criteria with previously published 12 lead ECG criteria. METHODS: An 80 lead portable BSM system was used to map patients presenting with acute ischaemic-type chest pain and a 12 lead ECG with left bundle branch block (LBBB). Acute myocardial infarction (AMI) was defined by serial cardiac enzymes. Each 12 lead ECG was assessed by the criteria of Sgarbossa et al and Hands et al for diagnosis of AMI. Depolarisation and repolarisation BSMs were assessed for loss of mirror image reversal of QRS with ST-T isointegral map patterns and a change in vector angle from QRS to ST-T outside 180+/-15 degrees -findings typically seen in LBBB with AMI. RESULTS: Of 56 patients with chest pain and LBBB, 18 had enzymatically confirmed AMI. Patients with loss of BSM image reversal were significantly more likely to have AMI (odds ratio 4.9, 95% confidence interval 1.5 to 16.4, p = 0.007). Loss of BSM image reversal was significantly more sensitive (67%) for AMI than either 12 lead ECG method (17%, 33%) albeit with some loss in specificity (BSM 71%, 12 lead ECG 87%, 97%). Patients with AMI compared with those without AMI had a greater mean change in vector angle outside the normal range (180+/-15 degrees ), particularly between QRS isointegral and ST60 isopotential (the potential 60 ms after the J point at each electrode site) BSMs (19 degrees v 9 degrees, p = 0.038). Loss of image reversal and QRS-ST60 vector change outside 180+/-15 degrees had 61% sensitivity and 82% specificity for AMI (odds ratio 7.0, 95% confidence interval 2.0 to 24.4, p = 0.001). CONCLUSIONS: BSM compared with the 12 lead ECG improved the early diagnosis of AMI in the presence of LBBB.

Adult↗