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R C Arzbaecher

Publications and source records attributed to R C Arzbaecher.

At least 19 recordsLinked to original sources
PubMed1991

Computer analysis of the electrocardiogram during esophageal pacing cardiac stress.

It has been estimated that 15 to 30% of patients with suspected or known coronary artery disease are unable to perform an adequate exercise stress test due to a variety of reasons such as obesity, poor physical condition, claudication, etc. Transesophageal atrial pacing has been proposed as a noninvasive alternative for inducing cardiac stress in patients who cannot exercise. Although computer analysis is commonly employed to analyze the electrocardiogram (ECG) during the conventional exercise stress test, the surface ECG recorded during transesophageal atrial pacing is contaminated with large pacing artifacts which confound beat identification by standard computer software. We report the development of a robust signal processing algorithm for interpretation of the surface ECG during transesophageal atrial pacing stress. The algorithm employs novel schemes using both linear and nonlinear transformations to detect and differentiate between the pacing artifact and QRS complex even in difficult situations where the pacing artifact is in proximity to or superimposed on the QRS complex. The algorithm uses sophisticated logic for automatic recognition of sustained capture. It subsequently calculates beat-by-beat and average (over five beats) ST segment amplitude and slope. The algorithm also reports the instantaneous heart rate, RR interval, pace-to-R interval, R-wave amplitude, and estimated sinus node recovery time upon loss of sustained capture. The limitations of present exercise ECG computer methods in processing the ECG during transesophageal atrial pacing stress are evaluated and significantly improved performance by our algorithm is demonstrated.

Adult↗
PubMed1989

A system for simultaneous esophageal atrial pacing and ventricular recording in computer analysis of posterior ischemia.

Abnormalities of the posterior cardiac wall are often small and obscured by electrical activity of the anterior wall of the left ventricle or by right ventricular hypertrophy. The posterior wall is hidden from the precordial leads by the anterior wall, and electrodes placed on the back are of little use because of their distance from the heart and of the intervening high-resistivity lungs. In contrast to the body surface, the esophagus provides a unique perspective of the posterior aspects of the heart at close range. The authors employed a noninvasive approach to produce cardiac stress and simultaneously record posterior cardiac electrical activity via the esophagus. A new esophageal electrode and instrumentation were developed for acquiring a high-quality esophageal electrocardiogram (ECG) during transesophageal atrial pacing stress. They present their technique for combining stress testing and computer analysis of ST-segment changes in the esophageal ECG as well as preliminary results from one normal subject and one patient with known posteroinferior ischemia.

Cardiac Pacing, Artificial↗
PubMed1989

Evaluation of techniques for recognition of ventricular arrhythmias by implanted devices.

Implantable devices that provide antitachycardia and defibrillation capability currently have limited ability to distinguish among different cardiac rhythms. We have investigated three methods of electrogram analysis: rate, irregularity, and amplitude distribution. In 35 episodes in 19 patients, we applied these three algorithms to 15 s recorded passages of ventricular electrograms during supraventricular tachycardia (N = 11), ventricular tachycardia (N = 11), and ventricular fibrillation (N = 13). Each was individually paired with a recording of sinus rhythm from the same patient. All recordings were obtained during standard electrophysiologic testing. Each algorithm was successful at distinguishing the tachyarrhythmias from sinus rhythm at one or more levels of algorithm parameterization. Rate alone discriminated supraventricular tachycardia from ventricular fibrillation but did not distinguish between supraventricular and ventricular tachycardia. Rate combined with irregularity distinguished between ventricular tachycardia and ventricular fibrillation, but did not discriminate between ventricular and supraventricular tachycardia. Although the amplitude distribution algorithm was unable to separate perfectly any of the three tachyarrhythmias, it provided the best performance in separating supraventricular and ventricular tachycardia (82 percent sensitivity and specificity). We conclude that algorithms based on rate, irregularity, and amplitude distribution analysis of ventricular electrograms may distinguish sinus rhythm from tachyarrhythmias, but may not distinguish among tachyarrhythmias.

Algorithms↗
PubMed1986

Differentiation of sinus tachycardia from paroxysmal 1:1 tachycardias using single late diastolic atrial extrastimuli.

Existing antitachycardia devices do not discriminate perfectly between sinus tachycardia and paroxysmal tachycardias with 1:1 atrioventricular relationship (paroxysmal 1:1 tachycardias). The present study tested the hypothesis that the nature of the ventricular response to atrial extrastimulation might distinguish between sinus tachycardia and selected paroxysmal 1:1 tachycardias. In 15 patients, atrial extrastimuli were delivered during sinus tachycardia and in 13 patients during various types of paroxysmal 1:1 tachycardia, and the timing of the next ventricular beat was measured. During sinus tachycardia, in 14 of 15 patients, atrial extrastimuli which were, in turn, early by 80 and 100 ms made the next ventricular beat premature by at least 30 and 50 ms, respectively. In all 13 patients, during paroxysmal 1:1 tachycardia, atrial extrastimuli that were early by 80 and 100 ms failed to make the next ventricular beat premature by more than 10 ms. Single atrial extrastimuli that were premature by less than or equal to 100 ms did not provoke faster tachycardias in any of the patients. In this study, a technique that used single late extrastimuli during tachycardia safely distinguished sinus tachycardia from paroxysmal tachycardias. This technique might be suitable for incorporation into an antitachycardia device. Further investigation of this technique is warranted in a larger number of patients with a wider variety of tachycardias. Patients with Gemini 415As having dual anodal rings, which can be identified radiographically, are at risk for this design-dep design-dependent cross-talk and merit close observation.

Adolescent↗
PubMed1984

Reduced spinal reflexes following intrathecal baclofen in the rabbit.

Intrathecal baclofen is effective in reducing polysynaptic spinal reflexes in awake rabbits. A single lumbar infusion of 2.5-5.0 ng drug caused a significant reduction in the crossed extensor response to electrical stimulation of the plantar surface of the hindlimb. This inhibition lasted 5 h or more. At doses of 3 micrograms or less, the forelimbs were unaffected.

Animals↗
PubMed1979

Computer diagnosis of supraventricular and ventricular arrhythmias. A new esophageal technique.

Computerized arrhythmia monitors recognize only a few of the significant arrhythmias and generally fail to detect arrhythmias of supraventricular origin. This is because conventional surface leads, which are sufficient for QRS recognition, are highly inadequate for automated P-wave detection. A new two-lead system, which includes a swallowable capsule-electrode for esophageal monitoring of atrial activity, is used in an on-line arrhythmia monitor. Three interval measurements (AA, AR and RR) and a QRS shape measurement provide the foundation for a detailed interpretation of each beat. Building on the single-beat analysis, a contextual diagnostic algorithm then recognizes and reports on-line the following arrhythmias: couplets, bigeminy, trigeminy, ventricular tachycardia, supraventricular tachycardia, atrial flutter, atrial fibrillation, ventricular tachycardia with retrograde conduction to the atria, first-degree block, second-degree block, Wenckebach periodicity, advanced block, third-degree block and sinus bradycardia.

Arrhythmias, Cardiac↗
PubMed1979

Feedback control in the management of cardiac arrhythmias.

We have devised a computer technique for the control of drug therapy in the management of cardiac arrhythmias. In our system the computer monitors the electrocardiogram in real time, determines the percent of premature ventricular beats (PVBs) using a correlation coefficient technique, and compares it to a desired rhythm. If the measured rhythm departs from the setpoint, an antiarrhythmic drug is infused by the computer. Based upon the pharmacokinetics of the drug, the infusion is delivered so as to attain an immediate change in the blood drug concentration utilizing an exponential infusion technique. The control algorithm is a modified proportional controller. Closed-loop control experiments have been performed in canines with an induced myocardial infarction. The antiarrhythmic agent disopyramide phosphate was used to correct the resulting arrhythmias. Our results suggest that computer control of drug therapy can profitably be applied to the management of cardiac arrhythmias in the coronary care unit.

Animals↗