Retrospective analysis of mode survival, reliability of atrial sensing and incidence of atrial tachyarrhythmias in 307 single-lead VDD pacemaker patients.

Aims: The aim of this retrospective analysis was to investigate VDD mode survival, development of atrial tachyarrhythmias (AT), and long-term atrial sensing performance of VDD pacing systems.

Methods And Results: We implanted single-lead VDD pacemakers in patients with isolated atrioventricular block and performed a retrospective analysis of 307 patients who had their devices implanted between May 1994 and September 2001. In 39 patients (12.

Form analysis using digital signal processing reliably discriminates far-field R waves from P waves.

The correct detection of atrial arrhythmias by pacemakers is often limited by the presence of far-field R waves (FFRWs) in the atrial electrogram. Digital signal processing (DSP) of intracardiac signals is assumed to provide improved discrimination between P waves and FFRWs when compared to current methods. For this purpose, 100 bipolar and unipolar intracardiac atrial recordings from 31 patients were collected during pacemaker replacement and used for the off-line application of a novel DSP algorithm.

Sudden rate drop intervention rate level in patients with new 'clarity' pacemakers and carotid sinus syndrome.

Background: In patients in whom syncopal episodes are mainly caused by occasional drops in heart rate, Sudden Rate Drop intervention feature intends to provide high rate intervention pacing. New Vitatron Medical B.V.

Avoiding atrial undersensing by assessment of P wave amplitude histogram data.

Reliable sensing of the P wave is an essential requirement for the appropriate functioning of any device that uses atrial tracking to provide AV synchrony. However, a single measurement of the P wave amplitude, either at implantation or during follow-up, may not be a reliable reflection of the P wave amplitudes that occur during daily life. The P wave amplitude histogram is a new feature that automatically measures the P wave amplitude at regular intervals and provides the distribution of these measurements.

One-year follow-up of automatic adaptation of the rate response algorithm of the QT sensing, rate adaptive pacemaker.

Optimal functioning of a rate adaptive pacemaker depends upon reliable sensing of the sensor and appropriate programming of the rate of response algorithm. QT sensing pacemakers use data derived from the endocardial electrogram in the programming of the rate response algorithm. In the latest versions of these pacemakers, programming of the rate response algorithm may be performed using either a semiautomatic Fast Learn (FL) procedure or by using the newly developed, fully Automatic Slope Adaptation (ASA) mechanism.

Analysis of the morphology of the unipolar endocardial paced evoked response.

In a retrospective study we analyzed the unipolar endocardial evoked response signal (ERS) of 103 patients prior to pacemaker implantation. The objective of this study was to give a complete description of the ERS morphology and to evaluate influences on this morphology of both various electrode characteristics and pacing rate. In addition, spontaneous endocardial signals were studied.

Improved rate responsive algorithm in QT driven pacemakers--evaluation of initial response to exercise.

The QT pacemaker is a rate modulated pacemaker that uses the evoked QT interval as an indicator to determine its optimal pacing rate. Despite the generally favorable clinical results with this form of pacing, some flaws in the system have been reported, such as the frequently observed rather slow initial response of the pacing rate to physical exercise, and the phenomenon of oscillation of the heart rate. These problems can be attributed to the rate adaptive algorithm used in the current QT pacemaker.

Improved pattern of rate responsiveness with dynamic slope setting for the QT sensing pacemaker.

We have recently described the electrophysiological basis of a new algorithm for the QT (TX) sensing rate responsive pacemaker. By using the new software program running on the standard programmer it has been possible to simulate the new algorithm in ten patients with complete heart block (seven patients had implanted TX units and three were paced with an external TX pacemaker) during routine exercise testing. In this way a single-blind, intra-patient comparison of the pattern of pacing rate change using both the existing and new algorithms was possible.

Introduction of an automatic QT interval driven rate responsive pacemaker.

QT driven rate responsive pacemakers have been implanted since 1981. The more than 6 years experience and additional knowledge gained during several clinical studies have culminated in the design of an automatic rate responsive pacemaker. The adjustment of the rate responsive function to each individual patient is carried out automatically by the pacemaker, which therefore performs several measurements both at rest and during exercise.

Morphology of endocardial T-waves of fusion beats.

Recently developed stimulation techniques are capable of eliminating polarization afterpotentials caused by the emitted stimulus. A well-controlled study method was developed to initiate various degrees of fusion and to monitor changes in the morphology of the endocardial signal. The study was performed on two dogs.

Heart rate monitoring in implanted pacemakers.

Increasing pacemaker memory allows integration of heart rate monitoring into the pacemaker. Two main methods can be distinguished. 1.

Automatic refractory period.

Pacemakers have become more and more complex over the years, whereby technological advances were used to create more and new possibilities in existing pacemaker applications. As a result a demand has grown for more automatic functions to reduce the time to program the pacemakers and eleviate follow-up procedures. One of the parameters which can be adjusted automatically is the refractory period.

Nonlinear relationship between pacing and evoked QT intervals.

The paced evoked response is an established biosensor which has been used in the design of a rate responsive pacemaker. The unit is capable of sensing the interval between the delivery of a pacing stimulus and the downslope of the evoked T wave. With fixed rate pacing this interval has been shown to shorten with exercise and the main cause of this effect is thought to be mediated by the increase in the plasma catecholamines which are released on exertion.

Reliability of evoked endocardial T-wave sensing in 1,500 pacemaker patients.

Intracardiac measurements of the evoked endocardial T-wave were performed on 1,500 pacemaker patients. The sensed evoked T-wave amplitude was found to be above 0.75 mV in 94.