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A R J Mitchell

Publications and source records attributed to A R J Mitchell.

13 recordsLinked to original sources
PubMed2005

Semi-automatic boundary detection to improve reporting of regional left ventricular function.

AIMS: The reporting of regional left ventricular function is based on subjective assessment of endocardial motion and thickening and has a significant learning curve. We hypothesized that the use of an semi-automatic boundary detection system generating images with superimposed moving endocardial borders and a fixed end-diastolic reference border could improve the reporting of regional function. METHODS: We obtained 58 resting contrast images of 15 patients and using a new boundary detection system (Quamus), generated images with superimposed endocardial borders. The contrast images, images with additional Quamus borders and Quamus borders alone were assessed by two level 1 and two level 2 echocardiographers. They scored regional function and results were compared to two level 3 experienced stress echocardiography readers. RESULTS: The addition of borders improved the agreement of level 1 echocardiographers (weighted Kappa increased from 0.55 to 0.64) but did not change for level 2 echocardiographers (0.63 to 0.64) and has the potential to be a useful training tool.

Contrast Media↗
PubMed2004

The role of pacemaker and defibrillator therapy for the treatment of atrial fibrillation.

The development of pacemaker and defibrillator technology has provided a new direction for the treatment of recurrent symptomatic atrial fibrillation (AF). Sophisticated atrial preventative pacing algorithms are now available and newer implantable devices have additional atrial termination pacing therapies. Results from studies examining the effectiveness of atrial anti-tachycardia pacing algorithms have suggested that 50% of atrial arrhythmias (including AF) can be pace terminated using these devices. The atrial defibrillator has recently been shown to be a safe and effective method of restoring and maintaining sinus rhythm in selected patients. Symptoms and quality of life can be improved and some patients demonstrate increased sinus rhythm duration (sinus rhythm begets sinus rhythm) with repeated use of the device. This review article discusses the current application of device therapy for the management of AF and explores some of the merits and limitations of these devices.

Aged↗
PubMed2004

The clinical and electrophysiological implications of asymptomatic atrial fibrillation.

Atrial fibrillation (AF) is the commonest arrhythmia encountered in clinical practice and is frequently associated with significant symptoms. Asymptomatic AF may also increase the risks of heart failure, thromboembolism and cardiomyopathy but its prevalence is significantly underestimated by routine surveillance methods. The development of long-term external monitors and implantable devices has offered a new insight into the true prevalence of asymptomatic AF. Similar management strategies should be applied to both symptomatic and asymptomatic patient groups and anticoagulation should be continued indefinitely in those with a history of AF and risk factors for thromboembolism. Enhanced detection of clinically silent AF could improve outcomes but the resource implications will be significant.

Atrial Fibrillation↗
PubMed2003

Diazepam or midazolam for external DC cardioversion (the DORM Study).

AIMS: To compare the clinical efficacy and tolerability of two intravenous sedatives for physician-led DC cardioversion of atrial arrhythmias. METHODS AND RESULTS: One hundred and forty-one patients attending for elective DC cardioversion of atrial arrhythmias were randomized to intravenous midazolam or diazepam. Sedation was administered using titration protocols. Procedure times, operator satisfaction scores and adverse events were documented. The patients immediate, 24- and 48-h recall and awareness of after-effects were obtained from questionnaires. Seventy-one patients received midazolam (mean 12.5 mg) and 70 patients received diazepam (mean 28.1 mg). There were 16 minor adverse events with midazolam (20% hypotension, 3% oxygen desaturation) and nine with diazepam (7% hypotension, 6% required additional analgesia), P = 0.14. There were no major adverse events. Sedation time was 5.0 +/- 3.4 min for midazolam and 6.5 +/- 3.4 min for diazepam (P = 0.0016). Patients awoke 77 +/- 46 min post-sedation with midazolam and 39 +/- 24 min with diazepam (P < 0.0001). There was no recall of the procedure at 48 h and no difference in awareness of after-effects between the two groups at 24 or 48 h, P = ns. CONCLUSION: Physician-led cardioversion of atrial arrhythmias using intravenous sedation is effective and well tolerated. Sedation with diazepam was associated with fewer minor adverse events and a quicker recovery time than midazolam.

Atrial Fibrillation↗
PubMed2003

Primary cardiac lymphoma.

We present a case of primary cardiac lymphoma, which is a rare condition compared with secondary metastatic involvement and is associated with poor prognosis. This case demonstrates the use of transthoracic echocardiography for the assessment of tumour regression in response to chemotherapy.

Aged↗
PubMed2002

What is the optimal electrode configuration for atrial defibrillators in man?

AIMS: To compare the atrial defibrillation threshold (DFT) for two electrode configurations in patients with drug refractory persistent atrial fibrillation (AF). METHODS AND RESULTS: 11 patients, 73% male, mean age 60.9 (range 38 to 83), underwent implantation of a Medtronic Jewel AF dual chamber defibrillator (model 7250). A step-up atrial DFT was performed in a randomized sequence for two electrode configurations: (1) Right atrial to distal coronary sinus electrode (RA > CS) and (2) defibrillator can to right ventricular and right atrial electrodes (CAN > RV + RA). The RA > CS configuration restored SR in 10 patients (91%). The CAN > RA + RV configuration restored SR in four patients (36%). The mean atrial DFT was significantly lower for the RA > CS than CAN > RA + RV configuration (10 +/- 7 Joules vs 25 +/- 6 Joules), P < 0.01. At 3 months post implantation, AF was reinduced and the protocol was repeated for the optimal electrode configuration. There was no significant difference in the atrial DFT compared with that at implant. CONCLUSION: The right atrium to coronary sinus electrode configuration significantly reduces the atrial DFT. The atrial DFT also remains stable at 3 months post-implantation. Patients with persistent AF undergoing insertion of an atrial defibrillator should have a coronary sinus electrode implanted.

Adult↗
PubMed2002

Effect of atrial antitachycardia pacing treatments in patients with an atrial defibrillator: randomised study comparing subthreshold and nominal pacing outputs.

OBJECTIVE: To assess the true efficacy of antitachycardia pacing on spontaneous persistent atrial fibrillation in patients with an implanted atrial defibrillator, by comparing the effects of nominal pacing treatment with subthreshold pacing treatment. DESIGN: The effects of antitachycardia pacing and burst 50 Hz atrial pacing on spontaneous atrial arrhythmias were evaluated six months after implantation of a Medtronic Jewel AF((R)) atrial defibrillator. SETTING: Cardiology department in a district general hospital. PATIENTS: 15 patients with persistent atrial fibrillation. INTERVENTIONS: Patients were randomised to either "nominal" output pacing treatment or surface ECG and endocardial electrogram proven subthreshold "sham" pacing treatment for three months, and then crossed over to the alternative treatment for a further three months. RESULTS: During the nominal output phase, 31 episodes of atrial fibrillation were treated with 53 bursts of 50 Hz pacing, 98 sequences of ramp atrial pacing, and 61 sequences of burst atrial pacing. Atrial fibrillation was not pace terminated during any episode. Thirty one episodes of atrial tachycardia were treated with 19 bursts of 50 Hz atrial pacing, 103 sequences of ramp atrial pacing, and 38 sequences of burst atrial pacing. Termination of atrial tachycardia was observed in 17 episodes. During the "sham" pacing period, no episodes were terminated by any pacing treatment. CONCLUSION: Atrial antitachycardia pacing treatments are ineffective at terminating persistent atrial fibrillation but may be useful in terminating episodes of atrial tachycardia or flutter, thus reducing the burden of arrhythmia.

Adult↗