R. van Mechelen

AIMS: To collect information on the use of the Reveal implantable loop recorder (ILR) in the patient care pathway and to investigate its effectiveness in the diagnosis of unexplained recurrent syncope in everyday clinical practice. METHODS AND RESULTS: Prospective, multicentre, observational study conducted in 2006-2009 in 10 European countries and Israel. Eligible patients had recurrent unexplained syncope or pre-syncope. Subjects received a Reveal Plus, DX or XT. Follow up was until the first recurrence of a syncopal event leading to a diagnosis or for ≥1 year. In the course of the study, patients were evaluated by an average of three different specialists for management of their syncope and underwent a median of 13 tests (range 9-20). Significant physical trauma had been experienced in association with a syncopal episode by 36% of patients. Average follow-up time after ILR implant was 10±6 months. Follow-up visit data were available for 570 subjects. The percentages of patients with recurrence of syncope were 19, 26, and 36% after 3, 6, and 12 months, respectively. Of 218 events within the study, ILR-guided diagnosis was obtained in 170 cases (78%), of which 128 (75%) were cardiac. CONCLUSION: A large number of diagnostic tests were undertaken in patients with unexplained syncope without providing conclusive data. In contrast, the ILR revealed or contributed to establishing the mechanism of syncope in the vast majority of patients. The findings support the recommendation in current guidelines that an ILR should be implanted early rather than late in the evaluation of unexplained syncope.

AIMS: Paroxysmal atrial fibrillation (PAF) is frequently encountered in pacemaker patients, most commonly in sick sinus syndrome. The combination of site-specific pacing in conjunction with an overdrive algorithm combined with antiarrhythmic drugs on the incidence of PAF in patients with a conventional indication for pacing is unknown. METHODS AND RESULTS: Patients with pacemaker indication and PAF received a DDDR-pacemaker, which included an automatic atrial overdrive (AO) algorithm. The atrial lead was implanted in either the right atrial appendage (RAA) (n = 83) or the right low-atrial septum (LAS) (n = 94). The algorithm was switched on or off in a 3 month, single blind crossover design and antiarrhythmic drugs were kept stable. A control group of 96 patients (LAS, n = 14; RAA, n = 84) without PAF served as controls to assess any proarrhythmic effect of overdrive pacing. Atrial fibrillation (AF) burden defined as cumulative time in mode switch was not reduced during automatic AO from either the RAA or from the LAS. The reduction was not effective both for AF of short (<24 h) and long (> or =24 h) duration. There was no atrial proarrhythmia induced by the overdrive algorithm in the control group. CONCLUSIONS: We could not demonstrate a reduction of AF burden defined as cumulative time in AF by the AO algorithm, in patients who are paced for standard indications and PAF, neither from the RAA nor from the LAS.

A patient free of symptoms, with a pseudoaneurysm of the left ventricle after inferoposterolateral myocardial infarction, is reported. The diagnosis was established by nuclear cardiography and echocardiography of the left ventricle.

After single chamber atrial pacemaker implantation, serial electrophysiologic studies were performed noninvasively at intervals of 3 months over a total period of 3 years in 24 patients with symptomatic sinus node dysfunction. All patients underwent invasive electrophysiologic studies before pacemaker implantation and demonstrated intact anterograde AV conduction. Patients were divided into 2 groups: group I did not require antiarrhythmic drugs during follow-up whereas group 2 received antiarrhythmic drugs. In group I (11 patients) the atrial paced heart rate producing AV Wenckebach phenomenon (AVWHR) remained stable during a mean follow-up of 22 +/- 10 months; with a variability not exceeding 10 beats min-1 with respect to the initial AVWHR obtained during preoperative electrophysiologic study. In group 2 (13 patients) with a mean follow-up of 15 +/- 8 months a mean decrease of AVWHR of 19.2 +/- 17.5 beats min-1 was present between AVWHR before and 3 months after initiation of oral antiarrhythmic drugs (P less than 0.01). During chronic (greater than 3 months) antiarrhythmic drug therapy the variability of the AVWHR never exceeded 10 beats min-1 with respect to the AVWHR obtained 3 months after the initiation of oral drug therapy. Deterioration of anterograde AV conduction during long-term follow-up of patients with symptomatic sinus node dysfunction and intact anterograde AV conduction at the time of pacemaker implantation is a consequence of orally taken antiarrhythmic drugs, rather than a consequence of degeneration of the AV conducting system.

In the Precept pacing system, the right ventricular intracardiac impedance waveform is used to evaluate either of two indicators of metabolic demand relative right ventricular stroke volume and preejection interval (PEI). PEI is known to reliably parallel contractility changes, which is reflective of physical and emotional stress. The stability and dynamic behavior of PEI were tested in ten patients with a Precept pacing system under various forms of exercise and during postural changes. Although significant patient-to-patient variability of the sensor values was observed, reflecting individual physiological differences, the chronic stability of PEI was excellent in the total device experience of 147 months. In all patients, PEI shortened significantly during bicycle ergometry from a mean value of 137.7 +/- 17.8 (range 96-162) to a mean value of 103.0 +/- 21.6 (range 92-109) (P less than 0.05). Low level bicycle exercise of short duration resulted in a prompt decrease in PEI and increase in pacing rate in all patients. There were no uniform postural responses overall, although some posture related rate changes were observed in two patients. We conclude that the first generation of a PEI based pacing system holds promise for adaptive rate pacing.