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Biomedical subjects

A D Bernstein

Publications and source records attributed to A D Bernstein.

67 records · Page 4Linked to original sources
PubMed1983

Pseudomalfunctions of dual-chamber pacemakers.

The proliferation of dual-chamber pacemakers has created a host of electrocardiographic problems relating to interpretation. The term "pseudomalfunction" identifies an electrocardiographic finding that looks like pacemaker malfunction but is not. Several different models of dual-chamber pacemakers, which are either presently available or in clinical evaluation, produce different types of pseudomalfunctions. These are classified and described. Intimate knowledge of individual pacemaker characteristics is required for proper evaluation of these units.

Action Potentials↗
PubMed1983

Implications of constant-energy pacing.

Some cardiac pacemakers maintain constant energy per stimulus by automatically increasing the stimulus duration as battery depletion causes the stimulus amplitude to decline. This feature does not guarantee an invariant capture safety margin, however, because the stimulus energy at threshold increases for stimulus durations exceeding the geometric mean of the voltage and current chronaxie times. A method is described for identifying the impulse duration at which the initial capture safety margin begins to be lost with constant-energy pacing.

Cardiac Pacing, Artificial↗
PubMed1983

R-wave triggering of external instrumentation during cardiac pacing.

Monitoring and diagnostic instruments often utilize electrocardiographic R-wave detection for measuring heart rate or for timing of measurement processes. During cardiac pacing stimulus artifacts commonly interfere with the operation of such instruments because they are misinterpreted as R-waves. This phenomenon creates problems in assessing the hemodynamics during gated blood-pool scans, coronary care monitoring, and intra-aortic balloon pumping. A straightforward solution is found in the nature of the electrical signals involved in which the stimulus artifacts are detected independently and are removed from the signal fed to the R-wave detector.

Cardiac Pacing, Artificial↗
PubMed1983

Notation system and overlay diagrams for the analysis of paced electrocardiograms.

With the advent of adaptive dual-chamber pacing, the interaction between the pacemaker and the heart is becoming increasingly complex and the interpretation of paced electrocardiograms more difficult. We have developed a set of notation conventions for use in teaching and rhythm-strip analysis. Easily-drawn symbols delineate successful, unsuccessful, and inhibited pacing and sensing events as well as refractory and blanking periods. Another application is to generate movable transparent overlays after programming a pacemaker, to be used in interpreting subsequent rhythm strips.

Cardiac Pacing, Artificial↗
PubMed1981

Corrosion of pacemaker electrodes.

As improvements in pacemaker components and design increase pacemaker life, problems with other components may emerge such as corrosion of the electrodes. Explanted electrodes were examined under a scanning electron microscope and the degree of corrosion was graded and correlated with the reasons for explantation, the status of the explanted pacemaker, and the duration of the implant. Fifty-six explanted electrodes were removed for loss of capture or sensing, pacemaker extrusion, broken wires, or after death. A numerical grading system was used to qualitate the degree of corrosion. The pacemaker itself was retrieved in 50 cases, permitting evaluation of the entire pacing system. The dc component of the pacemaker output was measured. Without the aid of magnification most electrodes appeared shiny and smooth. With one exception all corrosion was microscopic. Significant corrosion was seen on all pacemaker electrodes that had been connected to pacemakers with dc offset currents greater than 5 microamperes. All except the "youngest" explanted electrode showed some degree of corrosion. The data suggest that corrosion was directly related to the duration of implantation. With the possible exception of one case, no consistent adverse clinical effects were observed, even when electrodes were heavily corroded. Whether or not corrosion eventually will progress to the point that clinical problems become manifest cannot be predicted at this time.

Arrhythmias, Cardiac↗
PubMed1976

Adult intussusception; case report of recurrent intussusception and review of the literature.

An unusual case of lymphoma is presented in which small bowel intussusception due to a lymphomatous nodule caused an acute abdomen, requiring small bowel resection. Four weeks later a second intussusception caused intestinal obstruction, necessitating a second laparotomy and bowel resection. The high incidence of malignant tumor in adult cases leads us to recommend primary resection without manual reduction in all but rectosigmoid and selected small bowel cases.

Adult↗
PubMed1975

Staging laparotomy in the treatment of metastatic melanoma of the lower extremities.

Twenty-six consecutive patients with melanoma of the lower extremities metastatic to the superficial inguinal lymph nodes were subjected to laparotomy. No patient had preoperative evidence of tumor dissemination past the superficial inguinal nodes. However three patients (12%) had metastases to the liver or para-aortic lymph nodes documented at laparotomy and were not subjected to iliac and obturator lymph node dissection. One of these patients had concomitant local recurrence of melanoma at the ankle. The other two patients had superficial inguinal lymph nodes at least 5 cm in diameter, although two other such patients with similar 5 cm lymph nodes did not have positive intra-abdominal findings. The remaining 23 of the 26 patients underwent ipsilateral iliac and obturator lymph node dissection, which proved positive in 3/23 patients (13%). Of these 23 patients undergoing iliac and obturator node dissection, 18 had clinically positive (and microscopically positive) superficial inguinal nodes prior to their dissection, while the remaining 5 patients had clinically negative (but microscopically positive) superficial inguinal nodes. The three cases of positive dissected iliac and obturator nodes occurred among the 18 patients with clinically positive superficial inguinal nodes (17%). Among the 5 patients with clinically negative, microscopically positive superficial groin nodes, there was no detectable deep inguinal nodal spread (or hepatic or para-aortic involvement).

Adolescent↗
PubMedDate not supplied

Intravenous digital subtraction angiography with iohexol.

Iohexol is a nonionic water-soluble iodinated contrast medium with chemical and physical properties similar to those of metrizamide. A randomized double-blind study was performed in 40 patients undergoing intravenous digital subtraction angiography for suspected carotid and vertebral disease to compare the radiographic imaging quality and side effects of iohexol with those of Renografin-76 (diatrizoate meglumine and diatrizoate sodium). The use of iohexol yielded a higher percentage of "excellent" images with a lesser incidence of image degradation due to swallowing and motion. Iohexol was also associated with milder and less frequent patient discomfort. No clinically significant changes in laboratory data parameters were observed with either contrast medium.

Adult↗
PubMedDate not supplied

Microcomputer and microprocessor applications in cardiac pacing.

Modern adaptive dual-chamber cardiac pacemakers offer millions of combinations of noninvasively programmable operating parameters. Some pacemakers and most pacemaker programmers are microprocessor based; these "software-organized" pacemakers can undergo substantial functional redesign by noninvasive programming even after implantation. Ancillary instrumentation used in making measurements during implant and follow-up is often microcomputer based, as is experimental instrumentation used in pacing research. As electrical control of cardiac dysrhythmias becomes more sophisticated, microcomputer applications in many aspects of pacing are proliferating in research, manufacturing, and clinical practice.

Computers↗