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Biomedical subjects

R W Anderson

Publications and source records attributed to R W Anderson.

At least 199 records · Page 11Linked to original sources
PubMed1977

Surgical treatment of supraventricular tachyarrhythmias.

In this report, we have outlined our experiences with the direct surgical treatment of 16 patients with supraventricular tachyarrhythmias (SVTA). Re-entry supraventricular tachycardia (SVT) was demonstrated by the 4 patients who had retrograde-conducting Kent pathways. The SVT was corrected by the successful division of the Kent bundle in 3 and a partially successful His bundle division in one patient. The remaining 9 patients with re-entry, which included 6 with Kent pathways and WPW, all had His bundle section. The remaining 3 with His interruption had focal tachycardias associated with dysfunction of the atrioventricular (AV) node. Of the 13 His bundle interruptions, nine were successful, three resulted in questionable AV conduction, and one failed. Problems with suture ligation and cautery explained the failures. Cryothermia was the most successful procedure used. However, excision of that portion of the atrium containing the AV node shows promise of being satisfactory. The possibility is discussed of using measures much more precise and less destructive than His bundle interruption for SVTA.

Adolescent↗
PubMed1976

The three-dimensional dynamic geometry of the left ventricle in the conscious dog.

The dynamic geometry of the left ventricle was assessed with the use of chronically implanted pulse-transit ultrasonic dimension transducers. The orientation of the transducers allowed the measurement of left ventricular minor and major axis diameters and equatorial wall thickness in the conscious dog. The left ventricle was modeled as a three-dimensional, prolate ellipsoidal shell. Left ventricular and pleural pressures were measured with high fidelity micromanometers. Aortic blood flow was obtained with electromagnetic flow probes. To test the assumptions inherent in this technique, left ventricular mass, internal volume, stroke volume, and peak aortic flow were computed from the dimension data and compared to directly measured values. Correlation coefficients of 0.95 or greater were obtained for each of these comparisons. In addition, the calculated left ventricular mass was constant to within +/- 6% of the mean value throughout the cardiac cycle. We found that the dynamic contraction pattern of the left ventricle was dependent on the physiological state of the dog. Furthermore, in the conscious state, shortening of the minor axis diameter, lengthening of the major axis diameter, and slight thickening or thinning of the wall were noted during isovolumic contraction (isovolumic ellipticalization pattern). In the open-chested, anesthetized state, however, marked rearrangements in geometry were observed during isovolumic contraction manifested by lengthening of the minor axis diameter, and significant thickening of the wall (isovolumic sphericalization pattern). We also observed that left ventricular volume was significantly diminished in the open-chested state. The isovolumic contraction pattern in open-chested dogs could be changed from sphericalization to ellipticalization by increasing end-diastolic volume with the infusion of saline. During a vena caval occlusion in the conscious state, the contraction pattern changed from isovolumic ellipticalization to isovolumic sphericalization as the end-diastolic volume decreased. Thus, the exact pattern of left ventricular contraction was found to be a function of left ventricular volume.

Animals↗
PubMed1976

Evaluation of the force-frequency relationship as a descriptor of the inotropic state of canine left ventricular myocardium.

The short-term force-frequency characteristics of canine left ventricular myocardium were examined in both isolated and intact preparations by briefly pertubing the frequency of contraction with early extrasystoles. The maximum rate of rise of isometric tension (Fmas) of the isolated trabeculae carneae was potentiated by the introduction of extrasystoles. The ratio of Fmas of potentiated to control beats (force-frequency ratio) was not altered significantly by a change in muscle length. However, exposure of the trabeculae to isoproterenol (10(-7)M) significantly changed the force-frequency ratio obtained in response to a constant frequency perturbation. Similar experiments were performed on chronically instrumented conscious dogs. Left ventricular minor axis diameter was measured with implanted pulse-transit ultrasonic dimension transducers, and intracavitary pressure was measured with a high fidelity micromanometer. Atrial pacing was performed so that the end-diastolic diameters of the beats preceding and following the extrasystole could be made identical. Large increases in the maximum rate of rise of pressure (Pmas) were seen in the contraction after the extrasystole. The ratio of Pmax of the potentiated beat to that of the control beat was not changed by a 9% increase in the end-diastolic diameter, produced by saline infusion. Conversely, isoproterenol significantly altered this relationship in the same manner as in the isolated muscle. Thus, either in vitro or in situ, left ventricular myocardium exhibits large functional changes in response to brief perturbations in rate. The isoproterenol and length data indicate that the force-frequency ratio reflects frequency-dependent changes in the inotropic state, independent of changes in length.

Animals↗