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Biomedical subjects

R Arzbaecher

Publications and source records attributed to R Arzbaecher.

At least 19 recordsLinked to original sources
PubMed1998

Rapid drug infusion for termination of atrial fibrillation in an experimental model.

Episodes of paroxysmal atrial fibrillation (PAF) in the ambulatory patient might be terminated promptly by intravenous infusion from an implanted drug delivery system. We have explored this concept in a series of experiments using rapid intra-atrial infusions in dogs. In the acute studies, rapid intra-atrial infusions of procainamide were delivered during continual measurements of epicardial monophasic action potentials (MAP), atrial effective refractory periods (ERP), and right to left atrial conduction times (CT) in 9 dogs. In the chronic studies, 20 episodes of sustained PAF were induced in 4 dogs after six weeks of rapid or burst atrial pacing from a specially programmed implanted pacemaker. Rapid infusions of procainamide were then delivered to the right atrium through a previously implanted catheter connected to a subcutaneous access port. Procainamide significantly increased the duration of the atrial MAP, ERP and CT in the acute experiments. It also terminated induced PAF within five minutes of the end of infusion in all twenty of the chronic experiments. We conclude that rapid intra-atrial infusion of procainamide is very effective in this animal model of PAF, and that such infusion prolongs atrial MAP, ERP and CT.

Action Potentials↗
PubMed1997

Probability density function revisited: improved discrimination of VF using a cycle length corrected PDF.

The probability density function (PDF) describes the fraction of time an electrogram signal spends at the baseline. In normal rhythm the signal is at baseline during the period between electrogram complexes, while in fibrillation the signal exhibits continuous activity and spends little time at baseline. However, time spent at the baseline is dependent on the rate of the rhythm, which limits the ability of the PDF algorithm to discriminate ventricular fibrillation from fast nonfibrillatory rhythms. A cycle length corrected version of the PDF algorithm has been formulated, which only examines the electrical activity between detected beats. The algorithm was developed utilizing a training set of 77 endocardial recordings and tested utilizing a test set of 90 endocardial and 56 epicardial recordings. Ventricular fibrillation was detected with 100% sensitivity and 98% specificity.

Algorithms↗
PubMed1994

Sensitivity and specificity of a dual-chamber arrhythmia recognition algorithm for implantable devices.

Present ventricular rate-based arrhythmia detection algorithms lack specificity. Using a training set of 109 endocardial electrogram recordings, a sensitive and specific dual-chamber arrhythmia recognition algorithm has been developed. The algorithm uses atrial and ventricular rates, irregularity, degree of beat-to-beat similarity, and measure of electrogram complex distinctiveness to arrive at a diagnostic conclusion. A test set of 121 endocardial electrogram recordings obtained during provocative electrophysiology studies was then used for blinded validation of the algorithm. In normal rhythm, 1:1 tachycardia, atrial tachycardia, atrial flutter, atrial fibrillation, ventricular tachycardia, and ventricular fibrillation, the percentages of sensitivity/specificity were, respectively, 100/99, 100/99, 80/99, 89/98, 91/97, 92/100, and 100/98. Although ventricular rate alone can usually distinguish normal rhythm, ventricular tachycardia, and ventricular fibrillation, it is confounded by atrial arrhythmias and 1:1 tachycardias. When tested on a database, a ventricular rate-only algorithm resulted in sensitivity/specificity of 100/65, 90/78, and 100/99%, respectively, for these three rhythms. Therefore, the dual-chamber algorithm based on both temporal and morphologic measures provides better distinction of normal rhythm and ventricular tachycardia than existing methods, without sacrificing sensitivity.

Arrhythmias, Cardiac↗
PubMed1993

Autoregressive modeling of epicardial electrograms during ventricular fibrillation.

During ventricular fibrillation (VF), electrograms from bipolar epicardial electrodes generally appear to have little organization or structure. We sought to identify any well defined organization or structure in these signals by determining if they could be modeled as an autoregressive stochastic process with a white noise excitation during the short time period (6.5-8 s) typically used by automatic implantable defibrillators. The autoregressive model is then used to synthesize VF signals using a white noise excitation with the same probability distribution function as the estimated excitation determined from the autoregressive model for that particular true VF episode. Both the original and ten synthesized VF signals for each patient are then compared using root mean square (rms) amplitude, the number of zero crossings per second, the amplitude distribution of the signals, the rate, and percent variation of rate. The results of examining the synthesized VF waveforms indicate that the rms amplitudes are similar to the true VF waveforms. While the synthesized VF signals had higher rate, more regular RR intervals, more zero crossings per second, and spent less time at baseline than the VF signal from which they were generated, these differences are generally not significant (p > or = 0.05). The use of such synthesized VF signals may allow more thorough testing of VF detection algorithms than is possible with the present limited libraries of human VF recordings.

Defibrillators, Implantable↗
PubMed1992

Validation of an adaptive software trigger and arrhythmia diagnostic algorithm.

The authors have developed an algorithm for the identification of arrhythmias using intracardiac atrial and ventricular leads. The algorithm is based on the rate of the depolarizations and a measure of the organization of electrical activity in each of the cardiac chambers. The most important requirement of the algorithm is to identify the occurrence of each cardiac event correctly. A robust amplitude-adaptive software trigger is developed, which accurately detects depolarizations in both chambers. With this reliable trigger the authors demonstrate the veracity of the arrhythmia identification algorithm.

Algorithms↗
PubMed1992

Robust adaptive parameter estimators in arrhythmia detection.

The authors consider the statistical analysis of threshold crossing intervals, as applied to estimation of tachycardia rates from intracavitary electrograms. The authors developed a class of robust algorithms designed to produce minimum variance estimates for tachycardia rates. The authors formulated the algorithms using order statistic filters, and obtained the minimum variance unbiased order statistic estimator. The potential gain in efficiency achieved by this approach is demonstrated via a representative example. The results indicated that the order statistics operator can produce dramatic reductions for typical errors in error variance as compared to linear estimators.

Algorithms↗
PubMed1989

The effect of drugs and lead maturation on atrial electrograms during sinus rhythm and atrial fibrillation.

Antitachycardia devices need more accurate means to identify arrhythmias. Previous studies have found that sinus rhythm can be distinguished from a variety of tachyarrhythmias by algorithms that are based on time-domain and frequency-domain analysis of intracardiac electrograms. Amplitude distribution analysis (time-domain) and power density spectral analysis (frequency-domain) are two of the techniques that have seemed to hold promise. However, previous studies have not evaluated whether lead maturation or drugs such as lidocaine, propranolol, verapamil, or isoproterenol can interfere with the ability of these algorithms to distinguish among cardiac rhythms. In the present study, five dogs had permanent atrial pacing leads placed. On a series of days, recordings were made from the atrial leads during sinus rhythm and induced sustained atrial fibrillation, both before and after administration of cardioactive drugs. For up to 1 month after implantation, progressive lead maturation did not prevent differentiation of atrial fibrillation from sinus rhythm by either amplitude distribution analysis or power density spectral analysis. However, the difference between the power density spectra of sinus rhythm and atrial fibrillation became progressively less with time. Isoproterenol, lidocaine, verapamil, and propranolol had no consistent effects on amplitude distribution analysis of atrial electrograms during sinus rhythm or atrial fibrillation. However, there were marked effects of drugs on amplitude distribution characteristics in individual dogs. Propranolol and lidocaine produced consistent changes in power density spectra during sinus rhythm and atrial fibrillation, respectively; both drugs reduced the ability of power density spectral analysis to differentiate sinus rhythm from atrial fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1988

Diagnosis of atrial fibrillation using electrograms from chronic leads: evaluation of computer algorithms.

This study compares the performance of three detection algorithms for the recognition of atrial fibrillation in chronic pacing leads. Multiple serial recordings were obtained of wideband and filtered electrograms from chronic atrial and ventricular leads in dogs for a period up to 55 days following implantation. Each dog was recorded in sinus rhythm and induced atrial fibrillation. Four days were chosen for processing: The day of implantation and a day in the first, second or third, and fifth weeks. Three signal processing methods were assessed for performance in detection of atrial fibrillation: software recognition of rate with automatic threshold control, amplitude distribution, and frequency spectral analysis. A software trigger for rate determination was adjusted to thresholds of 10, 20, and 30% of maximum baseline-to-peak amplitude. At 10%, a rate boundary anywhere between 420 and 560 beats per minute (bpm) perfectly separated atrial fibrillation from sinus rhythm even though atrial electrograms were contaminated with large QRS deflections and double-sensing was present. At 20% and 30%, a rate boundary around 300 bpm could be used, but sensitivity and specificity were reduced to 90%. In amplitude distribution analysis, a percent of time within a baseline window provided perfect separation of atrial fibrillation from sinus rhythm. In all cases, the signal was within this window less than 43% of the time in atrial fibrillation, and more than 43% in sinus rhythm. In spectral analysis, frequency bands were examined for power content. In the 6 to 30 Hz band atrial fibrillation contained the greater power. Choosing 58% of total power as a discriminant, sensitivity and specificity of atrial fibrillation detection were 100% and 95% respectively.

Algorithms↗
PubMed1986

A single atrial extrastimulus can distinguish sinus tachycardia from 1:1 paroxysmal tachycardia.

We have developed a tachycardia detection scheme for use in an antitachycardia pacemaker in which the use of a properly timed atrial extrastimulus provides a means of discriminating sinus tachycardia from pace-terminable 1:1 tachycardias. An atrial extrastimulus is delivered in late diastole (80 ms premature), and the ventricular response is monitored. In sinus tachycardia, the ventricular response is expected to appear early as well, but in pace-terminable tachycardias, such as AV reentrant and ventricular with VA conduction, the ventricular rhythm will be unperturbed. Testing of the algorithm was performed in 34 patients. In 29 patients, atrial extrastimuli were delivered during sinus tachycardia, and in 22 patients during various types of 1:1 paroxysmal tachycardia. In one patient the procedure was completely automated, i.e., delivery of the atrial extrastimuli and diagnosis were microcomputer controlled. In 28/29 cases, the delivery of an atrial extrastimulus 80 to 120 ms early during sinus tachycardia elicited a ventricular response at least 28 ms early. In 22/22 patients with 1:1 paroxysmal tachycardia, atrial extrastimuli 80 to 120 ms early failed to produce a significant change in ventricular cycle length. This technique appears to be promising for prevention of inadvertent pacing of sinus tachycardia in an antitachycardia pacemaker.

Diagnosis, Computer-Assisted↗