Respiration rate (RR) and minute ventilation (MV) provide important clinical information on the state of the patient. This study evaluated the accuracy of determining these using a pacemaker impedance sensor. In 20 patients who were previously implanted with a Guidant PULSAR MAX group of pacemakers, the telemetered impedance sensor waveform was recorded simultaneously with direct volume respiration waveforms as measured by a pneumatometer. Patients underwent 30 minutes of breathing tests while supine and standing, and a 10-minute ergonometer bicycle exercise test at a workload of 50 W. Breathing tests included regular and rapid-shallow breathing sequences. RR was determined by a computerized algorithm, from impedance and respiration signals. The mean RR by impedance was 21.3 +/- 7.7 breaths/min, by direct volume was 21.1 +/- 7.6 breaths/min, range 7-66, the mean difference of RR measured by the impedance sensor, as compared with the true measurement, being 0.2 +/- 2.1 breaths/min. During the entire exercise, the mean correlation coefficient between impedance (iMV) and direct measured MV was 0.96 +/- 0.03, slope 0.13 +/- 0.05 L/Omega and range 0.07-0.26 L/Omega. Bland-Altman limits of agreement were +/- 4.6 L/min for MV versus iMV with each patient calibrated separately. The correlation coefficient for iMV versus MV over the entire 10 minutes of exercise, including the initial 4 minutes of exercise, was 0.99. The transthoracic impedance sensor of an implanted pacemaker can accurately detect respiration parameters. There was a large variation between subjects in the iMV versus MV slope during a bicycle exercise test, whereas for each subject, the slope was stable during submaximal bicycle exercise.

The SAPW provides a noninvasive marker of atrial electrophysiology.

No abstract

The purpose of this study was to assess the efficacy of overdrive, single-site right atrial appendage pacing to reduce the burden of atrial fibrillation (AF) when compared with a standard lower rate limit of 60 bpm. This was verified by using the pacemaker's Holter. Eighteen subjects with a pre-implant history of paroxysmal AF and implanted DDDR mode-switching pacemakers were recruited. The pacemaker lower rate limit was programmed in random order to 60, 75 or 90 bpm for three 2-month periods and the amount of AF quantified. In addition, the exercise tolerance (ET), general well being (GWB), functional capacity (FC) and specific symptom prevalence (SSP) were assessed. The main finding of the study was that when ranked according to the amount of AF, there was no significant difference in the amount of AF according to the pacing rate. Six patients failed to tolerate pacing at 90 bpm. There were no differences in the ET, GWB, FC and SSP scores. It is concluded that those clinicians that manage patients with paroxysmal

Dofetilide (Pfizer, Sandwich, Kent, UK) is a novel, highly specific class III methanesulfonanilide anti-arrhythmic drug. At nanomolar concentrations this agent prolongs both the atrial and ventricular effective refractory periods and action potential duration. Dofetilide's mechanism of action relies on potent blockade of the rapidly activating, inwardly rectifying component of the delayed rectifier potassium current (Ikr), the main current responsible for cardiac repolarisation. Dofetilide does not appear to interact with other cardiac ionic channels, and this explains its minimal effects upon conduction velocity, myocardial contractility and systemic haemodynamics. Dofetilide's mechanism of action makes it suitable for the termination of supraventricular and ventricular tachyarrhythmias. Small scale clinical trials have provided encouraging results, with preliminary data confirming its efficacy in the termination of atrial fibrillation and atrial flutter, and in increasing the electrical threshold for inducible ventricular tachycardia/fibrillation. The results of large scale, randomised, placebo-controlled trials are awaited in order to establish dofetilide's role in clinical practice. Due to its very specific mode of action, dofetilide has very few systemic side-effects. Dofetilide represents a novel and promising new class III agent.