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Biomedical subjects

H G Ringertz

Publications and source records attributed to H G Ringertz.

33 records · Page 2Linked to original sources
PubMed1982

Calculation of left ventricular volume using implanted tantalum markers: a method reproducible despite rotation of the heart.

Endocardial markers implanted by catheter have been used to estimate the left ventricular volume by outlining the ventricle in orthogonal planes. However, if the position of the ventricle with respect to the biplane radiographic system changes, the projected outlines formed by the markers will narrow and the calculated volume will decrease. Therefore, a mathematical technique to correct this error was developed. It was tested by extensively rotating silicone casts of the left ventricle to which markers were glued. Except for one position at which the volume deviated by 4.5 ml, all the calculated volumes of the casts were reproducible to within 2 ml.

Animals↗
PubMed1981

Effect of the normal pericardium on the left ventricular diastolic pressure-volume relationship.

Closed chest placement of tantalum screws in the endocardium was performed an biplane cineradiography of these markers was used to measure LV dimensions while changing total blood volume. Measurements were then repeated following thoracotomy, pericardiotomy and reclosure of the thorax. The LV pressure-volume curves obtained after pericardiotomy always were shifted down and to the right from curves obtained before thoractomy and pericardiotomy. The divergence between the curves increased as LV volume increased, the curves being identical at small LV volumes and at low diastolic pressures. In each experiment the curves diverged before LV diastolic pressure exceeded 10 mm Hg, however.

Animals↗
PubMed1981

Validation of geometric methods for estimating segmental myocardial motion of the left ventricle at cineangiography.

Functional myocardial changes which result from ischemia are typically local rather than total. For assessing such regional changes quantitatively, left ventricular angiography has been used. The ventricular image has been divided into several components which can be measured individually. In order to test the validity of such methods, left ventricles of 5 dogs were labeled with endocardial tantalum markers and the segmental myocardial motion was estimated using cineangiography. Variance analysis of beat to beat measurements of total ejection fractions was performed. Total ejection fraction demonstrated the least variation with an average 3.5 per cent, segmental myocardial shortening 15 and regional stroke volumes 13 to 18 per cent. Intermethodologic variation with different regional volume measurements was 11 to 13 per cent. Regional stroke volume calculations showed large methodologic variations in beat to beat analysis. Conclusions and clinical decisions based on such measurements should be drawn with caution.

Animals↗
PubMed1979

Pulmonary systemic flow ratios in atrial septal defect assessed by ventricular volume measurements.

Twenty-eight patients with isolated secundum atrial septal defects were examined with right and left heart catheterization and cardioangiography. The radiographically assessed pulmonary-systemic stroke volume ratios and the physiologically determined pulmonary-systemic flow ratios correlated well. However, some striking discrepancies were observed the possible causes of which are discussed.

Adolescent↗
PubMed1979

Tantalum labelling in vivo of cardiac ventricular chambers in dogs.

Demarcating fixed points in cardiac ventricles in the dog by catheter placement of tantalum coils has been shown to provide an excellent physiologic model. A new method emplying direct ventricular puncture has been developed for implanting these markers. The method has several advantages over an earlier peripheral catheter technique. Apical approach allows easier screw placement near the aortic and pulmonary valves. Peripheral vessels are left intact and pressure monitoring as well as contrast medium injection can be performed through the same catheter.

Animals↗
PubMed1976

Arthrography of the knee. II. Isolated and combined lesions.

The findings in 1 349 abnormal cases out of 2 836 arhtrographies of the knee have been evaluated statistically. Isolated and combined lesions of menisci, medial collateral and cruciate ligaments have been compared. Type and degree of the individual lesion change with increased complexity of combined injuries. A sequential grading for some lesions has been established. A dominant direction of rupture was found differing in themedial and lateral meniscus. Vertical ruptures anf ruptures of the posterior part of the medial meniscus were positively correlated to more complex injuries.

Humans↗
PubMedDate not supplied

A method for the study of regional ischemic dysfunction in the intact dog. Permanent endocardial markers and the pressure-length loop.

A radiographic method for use in the closed-chest dog is described which allows the quantitation of segmental mechanical performance. Previous work has shown that the area of the pressure-length loop (an approximation of a stress-strain integral) is a useful measure of the mechanical work performed by a segment of myocardium. The position of radiopaque markers previously placed to define segments of myocardium is recorded by biplane cineradiography. From simultaneous measurements of left ventricular pressure the integral of pressure with respect to segment length during one cardiac cycle is calculated. An example illustrating the utility of this model for the study of regional myocardial ischemia is presented.

Animals↗
PubMedDate not supplied

Assessment of human right ventricular cast volume by CT and angiocardiography.

Angiocardiographic methods available for cardiac chamber volume measurements have been shown to be less accurate although more practical than CT for the evaluation of the LV. To explore the capability of CT for RV volume measurements, silastic casts of seven normal RV were measured by a displacement method, conventional angiocardiographic biplane methods, and CT. The displacement method used degassing beneath vacuum to remove air trapped in the casts, and the actual volumes, which varied between 62 and 188 cc, were measured by Archimedes' principle. Cast volumes measured by biplane angiogram methods displayed a varying degree of spread around the regression line, caused by the chamber's irregular shape and its variation in orientation relative to the x-ray beams. CT measurements were in all aspects significantly more accurate.

Angiocardiography↗
PubMedDate not supplied

The effect of linear contrast flow acceleration on catheter tip recoil in selective arteriography.

We investigated the effect of the device known as the linear accelerator flow control (linear-rise) available on some angiographic power injectors used for delivering contrast medium. Its influence on catheter tip recoil during selective arteriography was evaluated in two glass models, which simulated assessment of catheter position in visceral and cerebral arterial branches. Contrast medium was injected over a clinical range with and without the linear flow accelerator in operation. Biplane high speed video recordings simultaneously referenced time in thousandths of seconds and the catheter position. The linear flow accelerator failed to prevent, but did delay, catheter tip recoil in proportion to the prolongation of contrast medium injection time. These laboratory results conformed with the findings of catheter behavior during similar experiments in animals undergoing arteriography.

Angiography↗