Lawrence E. Widman

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A new software architecture for automatic interpretation of the electrocardiographic rhythm is presented. Using the hypothesize-and-test paradigm, a semiquantitative physiological model and production rule-based knowledge are combined to reason about time- and space-varying characteristics of complex heart rhythms. A prototype system implementing the(More)
BACKGROUND Typical atrial flutter (AFL) results from right atrial reentry by propagation through an isthmus between the inferior vena cava (IVC) and tricuspid annulus (TA). We postulated that the eustachian valve and ridge (EVR) forms a line of conduction block between the IVC and coronary sinus (CS) ostium and forms a second isthmus (septal isthmus)(More)
BACKGROUND Differentiation between ventriculoatrial (VA) conduction over an accessory AV pathway (AP) and the AV node (AVN) may be difficult, especially in patients with a septal AP. METHODS AND RESULTS A new pacing method, para-Hisian pacing, was tested in 149 patients with AP and 53 patients without AP who had AV nodal reentrant tachycardia (AVNRT).(More)
INTRODUCTION Delta wave morphology correlates with the site of ventricular insertion of accessory AV pathways. Because lesions due to radiofrequency (RF) current are small and well defined, it may allow precise localization of accessory pathways. The purpose of this study was to use RF catheter ablation to develop an ECG algorithm to predict accessory(More)
Pulsus alternans is a condition in which the arterial pressure generated by the heart oscillates between two levels on a beat-to-beat basis. We evaluated the onset of pulsus alternans in chronically instrumented dogs subjected to tachycardia and inferior vena caval occlusion. During pulsus alternans, the left ventricular (LV) end-diastolic volume (EDV) was(More)
BACKGROUND The Internet is a novel, rapidly growing means of worldwide public communication. METHODS We reviewed all unsolicited electronic mail and other communications from nonmedical individuals requesting medical information over a 12-month period from the physician at 1 established site on the World Wide Web. This site was the only Internet site with(More)
  • L E Widman
  • 1989
Current symbolic knowledge representation techniques are inadequate for describing complex dynamic systems, which are time-varying and contain feedback loops. These systems are particularly difficult to represent when quantitative knowledge about the relationships within the system is incomplete. This paper describes a symbolic extension of the system(More)