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Biomedical subjects

C Feldstein

Publications and source records attributed to C Feldstein.

4 recordsLinked to original sources
PubMed1980

Excursion of vibrating microelectrodes in tissue.

A vibrating microelectrode holder consisting of a support rod attached to the cone of a miniature loudspeaker facilitates electrode penetration into arterial wall tissue, eliminates surface dimpling, and relieves polarographic artifacts believed to be due to tissue compression. The longitudinal vibratory excursion of free microelectrode tips, measured with strobe illumination microscopy, varies from less than 0.9 to 137 micron depending on energizing voltage and frequency. Tissue penetration is achieved most effectively at the resonance frequency, about 200 Hz for the present system. Total tip excursion is not diminished when the electrode is penetrated into excised rabbit femoral artery, but tip motion relative to surrounding tissue is considerably attenuated because the arterial wall holds the electrode shaft rather firmly and follows its movements. This relative motion in tissue is only 2.7 +/- 0.8 micron at 200 Hz and 0.05 V and can be reduced further at higher frequencies without sacrificing the penetration advantages of the system. Thus under proper vibratory conditions microelectrodes can be easily inserted into the arterial wall with minimal tissue disturbance.

Animals↗
PubMed1976

Diastolic retroperfusion of acutely ischemic myocardium.

The effectiveness of coronary venous retroperfusion treatment of an ischemic myocardial segment was assessed by measurements of regional and global myocardial function in 16 dogs. The left anterior descending coronary artery was acutely occluded for 75 minutes. After the first 30 minutes of occlusion, diastolic retroperfusion was instituted for 45 minutes by synchronized pumping of arterial blood from the brachial artery into the anterior interventricular coronary vein. Data collected in the preocclusion control period, during occlusion and the subsequent retroperfusion period included simultaneous measurement os ischemic and border zone myocardial forces, epicardial electrocardiographic S-T segments, intracoronary pressure, coronary blood flow and oxygen pressure (PO2) sampled distal to the site of occlusion. Retroperfusion resulted in significant improvement from the level of regional dysfunction observed after 30 minutes of occlusion: Ischemic zone myocardial force increased 106%, epicardial S-T elevation decreased 46%, normalized peripheral left anterior descending coronary arterial flow increased 50% and distal left anterior descending PO2 decreased 44%. These regional improvements were significant when compared with findings in an untreated series of 12 dogs with 75 minutes occlusion of the left anterior descending coronary artery. Diastolic-augmented coronary venous retroperfusion with arterial blood provided significant but not complete restoration of function in the ischemic segment. Therefore, in the earliest phase of acute myocardial infarction, retroperfusion might represent a useful temporary support to an otherwise inaccessible jeopardized zone of the heart. Regional retroperfusion may constitute an effective emergency procedure, particularly when the occlusive lesions are diffuse and other medical or surgical emergency procedures are inadvisable, unavailable or ineffective.

Animals↗
PubMedDate not supplied

Transducers for myocardial research.

Seven miniaturized transducers to measure force, displacement, and thickness--singly and in combination--in animal experiments are described. The transducers are lightweight and during an open-chest procedure can be inserted within a heartbeat, removed, and reinserted, with minimum trauma. Six or more transducers of various kinds can be used simultaneously without artifacts. For closed-chest experiments a combination force-displacement transducer can be catheter-borne. A trifunctional transducer was used successfully to measure force-displacement thickness in a small area. A single conductor can be added for ECG measurement in the area where the transducer is implanted.

Animals↗