Ralph E. Sturm

Videodensitometric system for measurement of vessel blood flow, particularly in the coronary arteries, in man

A system that allows the objective determination of blood flow in individual blood vessels (that is, coronary arteries) in intact man is described. Roentgenographic images (produced at a rate of 60/sec) are recorded on video tape before and during a single injection of radiopaque contrast material into the circulation and replayed any number of times. The dilution and dispersal of this contrast material can then be quantitatively determined from simultaneous indicatordilution (roentgen density) curves obtained from any site within the X-ray field by multiple roentgen videodensitometric analyses of the video tape record. Cyclic nonspecific changes in roentgen density due to motion of the vessel or catheter and changes in cardiac size and position are compensated for in real time measurements by digital computer. By obtaining the difference in mean transit times from indicator-dilution curves a measured distance apart along a coronary vessel, mean blood velocity can be determined and blood flow can then be calculated as the product of velocity and the vessel cross-sectional area obtained from biplane orthogonal roentgenograms. The effects of persisting contrast medium in the myocardium and cardiac chambers superposed in the videodensitometric sampling system are minimized by computer dynamic background cancellation techniques. Simultaneous determination of flow values in a canine coronary artery by roentgen videodensitometry and electromagnetic flowmeter show a good correlation ( r = 0.95) among flow values of less than 150 ml/min. Similar coronary artery-roentgen density curves suitable for videodensitometric determination of flow have been obtained from clinical catheterization studies in man.

Biplane roentgen videometric system for dynamic (60-sec) studies of the shape and size of circulatory structures, particularly the left ventricle.

An operator interactive video system for the measurement of roentgen angiographically outlined structures is described. Left ventricular volume and three-dimensional shapes are calculated from up to 200 pairs of diameters measured from ventriculograms at the rate of 60 pairs of biplane images per second. The accuracy and reproducibility of volumes calculated by the system were established by analysis of roentgenograms of inanimate objects of known volume and by comparison of left ventricular stroke volumes calculated by the system with the stroke volumes calculated by indicator-dilution technique and aortic root electromagnetic flowmeter. Computer-generated display of the large amounts of data obtained by the videometry system is described.

Atriogenic Mitral Valve Reflux: Diastolic Mitral Incompetence Following Isolated Atrial Systoles

Cardiac and aortic pressures were recorded after stellate ganglionectomy and vagotomy. Acute heart block was produced by injecting the atrioventricular node, and atrial and ventricular systoles were controlled electronically to occur independently or in any desired relationship. Angiocardiograms recorded on video tape after injections of 4 ml 69% Renovist into the left ventricle were analyzed with a videodensitometer able to detect small refluxes of contrast medium into the left atrium and correlate them with phases of the cardiac cycle. When ventricular driving was temporarily suspended but atrial driving continued, pressure records indicated mitral valve closure after each atrial systole, but reflux of contrast medium into the atrium occurred after each systole not followed by a normally sequenced ventricular systole. Driving with a 2: 1 atrioventricular stimulation resulted in reflux, with the alternate atrial contraction dissociated from ventricular systole. Thus, the mitral valve was not effectively closed by atrial systoles that were not followed by normally sequenced ventricular systoles.

Quantitative three dimensional dynamic imaging of structure and function of the cardiopulmonary and circulatory systems in all regions of the body

The first and second generation computer assisted cross-sectional reconstruction systems, such as the EMI, ACTA and DELTA brain and whole-body scanners, because of their excellent density resolution have produced accurate cross-sectional reconstructions of the anatomical structure of stationary organs, particularly the brain, the latter of which have revolutionized clinical neuroradiology (1-4).

Electrical activity of the canine esophagus and gastroesophageal sphincter: its relation to intraluminal pressure and movement of material.

Myogenic electrical activity of the sphincter and adjacent esophagus and stomach was detected by the chronic implantation of bipolar silver/silver chloride electrodes. Action potentials occurred in the esophagus following deglutition and were synchronous with the peristaltic contractions detected from within the lumen. Continuous phasic activity was present in the gastroesophageal sphincter and the adjacent gastric fundus. Reduction of the continuous phasic electrical activity occurred in the sphincter with relaxation. Reduction of it also occurred in the fundus with distention of the esophagus or stomach and during anesthesia. With swallowing, sphincteric action potentials, related to sphincteric contraction, followed the inhibition of phasic activity in the orad segment of the sphincter, while only inhibition of phasic activity and its return occurred in the caudad segment. Esophageal distention caused inhibition of action potentials in the esophagus distal to the distention as well as inhibition of the sphincteric continuous phasic activity. The inhibition continued until the distention was terminated. After subhilar bilateral vagotomy, intraluminal pressures and myogenic action potentials were simultaneous and of lesser magnitude in the vagotomized segment of the esophagus. The motor action of the gastroesophageal sphincter was not altered by vagotomy but the incidence of response to swallowing was reduced by about 50%.

Computer graphic techniques for study of temporal and spatial relationships of multidimensional data derived from biplane roentgen videograms with particular reference to cardioangiography

Abstract Orthogonal diameters of roentgen silhouettes of a test object (balloon) were measured automatically on each of about 80 video lines comprising its biplane images recorded 60 times/sec along with intraballoon pressure, P(t), during its distention with a roentgendense liquid at a known rate and volume. The balloons surface was calculated from these data plus regional volumes, V(L,), circumferences, C(L, t), stresses, P(t) × C(L, t), and strains, ΔL L , and their derivatives. Spatial surfaces of the balloon with superposed isovalue lines and continuous surface displays of the interrelationships of these functions were generated. These multidimensional data-dense images can be photographed or recorded on a video disk for dynamic analysis during forward or reverse variable time-base and stop-action replays. Sequential 60/sec images derived from angiograms of the left ventricle with superposed isoparameter lines along with other hemodynamic variables illustrate the capability of detailed operator-computer interactive analysis of the spatial and temporal interrelationships of the various determinants of cardiac function.

Experimental studies on the mechanisms of closure of cardiac valves with use of roentgen videodensitometry

Dilution curves of roentgen contrast medium sampled just upstream to the mitral or aortic valves at a rate of 60/sec by means of a roentgen videodensitometer have been used to detect and study the phasic relations of retrograde flow across the valve orifice. Normally, vigorous ventricular systoles produce competent closure of the anatomically normal mitral valve irrespective of the presence or absence of atrial contractions. The rapid increase in ventricular pressure and the decrease in size of the annulus of the valve at the onset of ventricular systole are the major factors producing efficient closure of the atrioventricular valves. Vigorous ejection of blood by way of the aortic valve also aids in the closure of the aortic valve.

Effect of varying ventricular function by extrasystolic potentiation on closure of the mitral valve

Abstract Mitral regurgitant indexes were measured by roentgen videodensitometry in anesthetized dogs without thoracotomy before, during and after extrasystolic potentiation of ventricular contraction while the atria and ventricles were driven in normal temporal sequence simultaneously or in such a way as to induce atrial fibrillation. Small amounts of mitral reflux were observed with simultaneous atrial and ventricular driving and with atrial fibrillation in the control measurements before initiation of extrasystolic potentiation. Reflux became negligible during extrasystolic potentiation and increased beyond control levels after termination of extrasystolic potentiation. The amounts of reflux could be related to variations in ventricular function before, during and after extrasystolic potentiation. When reflux was observed with simultaneous atrial and ventricular driving or atrial fibrillation, it occurred at the onset of systole. It was probably determined by the size of the ventricle before the onset of systole, the inotropic state and the rate of pressure development in the ventricle during systole. During extrasystolic potentiation of ventricular contraction, reflux was negligible and independent of the mode of atrial driving.

Videodensitometric determination of left ventricular ejection and filling characteristics

Left ventricular ejection fraction and values proportional to mitral and aortic flow were measured throughout the cardiac cycle by videodensitometric analysis of left ventricular roentgen angiograms. The technique was used simultaneously with measurement of the dimensions of the ventricle to provide absolute values for comparison. Sensitivity of the technique was tested by the ability to detect the atrial contribution to mitral flow and left ventricular chamber volume. Roentgen videodensitometry has the advantages that much information can be extracted from videoangiograms in real-time (on-line, if need be), it requires relatively low concentration of contrast medium, and it is self-calibrating.