[Biplane angiographic volumetry of the right and left heart ventricle with optical image pairing]. / Biplane angiographische Volumetrie der rechten und linken Herzkammer mit optimaler Bildpaarung.

Compared to single plane angiographic systems, biplane systems offer the possibility of a merged evaluation of the two x-ray projections. A computer program was developed that allows the assessment of enddiastolic and endsystolic volumes and frame-by-frame analysis of the left and right ventricle based on representing the biplane angiograms as optimal paired images. Optimal pairing means the magnifications are fitted, resulting in identical scales for objects located in the isocenter of the gantry; furthermore the images are rotated such that paired epipolar lines in both planes represent the same cross section of a centered object. The improved border tracing is proved by comparing the vertical extents from the lateral and frontal projection of the right ventricle. The standard deviation of the differences were significantly (p < 0.01) reduced as compared to the generally used unpaired evaluation.

[The determination of myocardial perfusion parameters from coronary angiograms by analysing the passage of contrast media through the myocardium]. / Bestimmung von Parametern der Myokard-perfusion aus Koronarangiogrammen durch Analyse der myokardialen Kontrastimittelpassage.

Digital subtraction angiography allows to record the passage of contrast material through the myocardium as a time-intensity curve, the so-called densogram. Temporal changes of contrast material in a region of interest are described by a differential equation. The free parameters of this model equation are determined by a curve-fitting procedure. Four parameters of the model equation are expected to be connected with myocardial perfusion. We intended to verify this assumption by comparing changes in coronary blood flow (CBF) with changes of the different parameters. The angiograms of 9 patients without coronary artery disease were studied before and after intravenous application of dipyridamole. Changes in CBF were assessed by a videodensitometric method. Linear regressions between changes of CBF and the parameters of the differential equation show the following results: one parameter of the model equation--the ratio of regional blood flow and regional volume--remarkably underestimated CBF changes. This can be explained by an increase of regional blood volume after increased CBF due to dipyridamole. However, a close correlation was found between CBF changes and the remaining parameters. This study suggests that digital measurements from coronary angiograms using the presented model equation provide a means of assessing myocardial perfusion.

[The reliability of angiographic volume determination of the left ventricle using digital image subtraction--significance in stress tests]. / Zuverlässigkeit angiographischer Volumenbestimmung des linken Ventrikels mittels digitaler Bildsubtraktion--Bedeutung bei Belastungsuntersuchungen.

Using the technique of digital subtraction angiography (DSA), left ventricular volumes can be determined after intravenous injection of contrast medium at rest and during exercise. The significance of the well known errors of angiographic determination of left ventricular volumes was investigated in 22 patients before and during a bicycle exercise test. Before and after exercise 40 ml of contrast medium were injected (18 ml/s) intravenously to calculate left ventricular volumes. Enddiastolic and endsystolic contours of the left ventricle were traced by two investigators (A and B) on five different days. Using these contours, volumes were calculated by a computer system. The first calculation of both investigators (single measurement) and the mean value of all five calculations (repetitive measurements) were compared. In the same procedure left ventricular contours of six patients were calculated after conventional contrast ventriculography (40 ml of contrast medium). No systematic deviations were found in comparing the results of both investigators using the single or repetitive method by means of DSA: (VolB = 0.86 VolA + 12.2, r = 0.97 versus VolB = 0.96 VolA + 9.1, r = 0.99). Compared to single method the residuals (Syx) of the repetitive method were significantly smaller: Syx = +/- 16.3 ml vs +/- 8.9 ml (p less than 0.01). Similar results were found in conventional ventriculography: single method Syx = +/- 18.7 ml and repetitive method Syx = +/- 8.8 ml (p less than 0.01). Comparing the volumes determined by DSA and by conventional ventriculography, respectively, no significant differences were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Bidirectional transvenous/subcutaneous defibrillation of ventricular fibrillation in dogs: success rates, energy requirements, currents, voltages and impedance.

Four hundred and thirteen defibrillations of alternating current-induced ventricular fibrillation were performed in 10 halothane-anaesthetized dogs (body weight: 24.5-30.5 kg). Success rates, energy demands, currents, peak voltages and impedance were determined. A transvenous catheter electrode system (Medtronic 6880, right ventricular apex and superior vena cava, distance 100 or 150 mm) and subcutaneous patch electrodes (Intec 67 L, 2nd/3rd and/or 3rd/4th left intercostal space) were used for bidirectional defibrillation. Loading voltages ranged from 600 to 850 V. With an electrode distance of 100 mm and a pulse duration of 2 ms separated by 1 ms, success rates were 100%, 40% and 0% for 850.650 and 600 V, respectively. With a 3-ms pulse duration, the corresponding rates were 100%, 60% and 50%. With a 2-ms pulse duration, successful defibrillation was achieved with energies lower than 15 J in 27%, with energies between 15 and 20 J in 77%, and 100% with energies higher than 20 J. Defibrillation currents were 4.4-9.3 A for pulse 1 (superior vena cava/ventricular apex) and 6.3-13.4 A for pulse 2 (patch/ventricular apex), respectively. Effective peak voltages ranged from 510 to 787 V and from 514 to 777V and averaged 89.6% of the loading voltages. Impedance values (peak voltage/current) were 75.5-117.7 (pulse 1) and 51.7-94.9 Ohms (pulse 2). Fifty consecutive defibrillations in one animal resulted in a decrease of impedance (114.6 to 84.9 Ohms, pulse 1:75.4 to 53.0 Ohms, pulse 2). Defibrillation of ventricular fibrillation can be achieved with acceptably low energies using a bidirectional transvenous/subcutaneous system, avoiding thoracotomy and general anaesthesia for implantation of the defibrillation system.

[Systolic and diastolic blood flow velocities in the left coronary artery before and following i.v. dipyridamole. Comparative measurements using a digital image processing in 2 unstenosed vessel branches]. / Systolische und diastolische Flussgeschwindigkeiten in der linken Koronararterie vor und nach Dipyridamol i.v. Vergleichende Messungen mittels digitaler Bildverarbeitung in zwei nichtstenosierten Gefässästen.

The hemodynamic significance of coronary artery stenoses cannot be assessed by presently-used methods. Especially stenoses of small and moderate degree only reveal hemodynamic relevance during augmentation of coronary flow. It can be expected that the increase in flow is limited in a stenotic branch, compared with an unstenosed branch of the same vessel. The increase in coronary blood flow in two unstenosed branches of the same vessel, however, should be nearly identical. To prove this hypothesis, the relative increase in coronary flow was measured in two unstenosed branches of the left coronary artery by means of digital subtraction angiocardiography. Ten patients were examined before and after intravenous administration of 20 mg (on average 0.29 mg/kg body weight) dipyridamole. Dipyridamole resulted in an increase in the diameter of the left anterior descending branch (LAD) of 11% (p less than 0.005) and of the circumflex artery (RCx) of 13% (p less than 0.005). The increase in flow velocity during systole amounted to 49% in the LAD (p less than 0.001) and to 58% in the RCx (p less than 0.005); during diastole to 60% in the LAD (p less than 0.005) and 83% in the RCx (p less than 0.005). The increase in volume flow during systole amounted to 78% in the LAD (p less than 0.005) and to 89% in the RCx (p less than 0.005), during diastole to 84% in the LAD (p less than 0.005) and to 113% in the RCx (p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

[Clinical value of digital subtraction angiography in cardiology--current status and future prospects]. / Zum klinischen Stellenwert der digitalen Subtraktionsangiographie in der Kardiologie--Gegenwärtiger Stand und Zukunftsaussichten.

Advances in digital technology have made the digital processing of X-ray images possible. The principles of processing, which can be traced back to the early origin of radiology, are characterized by the aims "image enhancement" and "functional imaging". These principles have been routinely applied in digital subtraction angiography (DSA) for visualization of non-moving vessels. DSA is used with caution in cardiology mainly because methodical problems caused by the motion of the background structures. In order to assess the clinical relevance of DSA to cardiology the following questions will be answered: Which structures can be visualized? How large is the error of the parameters determined by DSA? What is the clinical relevance of these parameters? What are the advantages of DSA with regard to the examination procedure? Using DSA the left ventricle can be visualized at rest and during exercise by intravenous injection of contrast medium. The examination procedure can easily be combined with measurements of pulmonary arterial pressure. The errors of left ventricular parameters amount to: ventricular volumes: +/- 12- +/- 18 ml; ejection fraction: +/- 8%; ventricular diameters: +/- 7- +/- 13%; wall volume: +/- 48 ml; wall thickness: +/- 1.6 mm. The image quality of aorto-coronary bypass grafts visualized by intravenously injected contrast medium is sufficient to decide whether the grafts are patent or occluded. The visualization of the proximal segments of coronary arteries by intravenous injection of contrast medium is reported in rare cases.(ABSTRACT TRUNCATED AT 250 WORDS)

[Qualitative evaluation of myocardial perfusion using digital subtraction angiocardiography]. / Qualitative Beurteilung der Myokardperfusion mittels digitaler Subtraktionsangiokardiographie.

The purpose of this study was to discover whether the passage of contrast medium through the myocardium can be visualized by digital subtraction angiocardiography and whether myocardial perfusion can be determined qualitatively from the difference images. Cineangiograms (duration 20 s) were obtained during routine coronary angiography and analyzed by means of a computerized image processing system. The results show that the passage of contrast medium through the coronary artery system, myocardium and coronary veins can be visualized. In 10 patients myocardial perfusion at rest was classified qualitatively into four categories (well perfused, slightly reduced perfusion, markedly reduced perfusion and perfusion defect) from local contrast intensity and the time dependent wash-in phase of the contrast medium. Intra- and interobserver comparison of the qualitative estimation of myocardial perfusion showed a close correlation (p less than 0.001 to p less than 0.0001). In the same 10 patients myocardial perfusion at rest was evaluated from Tl-201 scintiscans by two independent observers. A comparison between the qualitative classification of local myocardial perfusion assessed by both methods revealed a close correlation (p +/- 0.049). These results indicate that myocardial perfusion at rest can be visualized by digital image processing and evaluated qualitatively from cineangiograms.

[Evaluation of myocardial perfusion based on digital subtraction angiocardiography measured contrast medium flow times]. / Beurteilung der Myokardperfusion anhand der mittels digitaler Subtraktionsangiokardiographie gemessenen Kontrastmitteleinstromzeiten.

The purpose of this study was to discover whether myocardial perfusion can be determined quantitatively by digital subtraction angiocardiography from the passage of contrast medium through the myocardium. Cineangiograms (duration 20 s) were obtained during routine coronary angiography and analyzed by means of a computerized image processing system. Regional myocardial contrast intensity was plotted versus time as a densogram for quantitative assessment. The parameter "medium rise time" showed a good reproducibility (r = 0.92). The average of medium rise time was 2.9 s in well-perfused areas, 3.7 s in less perfused areas, 5.2 s in areas with markedly reduced perfusion and 5.8 s for perfusion defects or scars using Tl-201 scintigrams as reference. The differences between the four groups were significant except between areas of markedly reduced perfusion and perfusion defects or scars (p less than 0.05). The correlation of medium rise time to the extent of the stenosis of the coronary vessel supplying the corresponding myocardial region revealed that the medium rise time on an average was 3.2 s distal to unstenosed vessels, 3.2 s distal to slightly stenosed vessels, 5.4 s distal to highly stenosed vessels and 4.7 s distal to vessel occlusion. The differences between the groups were not significant except between the groups of patients with low and high-grade coronary stenoses. These results indicate that the parameter "medium rise time" of the intensity-time curves determined by digital image processing provides a quantitative assessment of myocardial perfusion from cineangiograms.

[Left ventricular function at rest and by stress in patients with aortic valve diseases. Study using digital subtraction angiocardiography]. / Linksventrikuläre Funktion in Ruhe und unter Belastung bei Patienten mit Aortenvitien. Untersuchung mit Hilfe der digitalen Subtraktionsangiokardiographie.

Using digital subtraction angiocardiography left ventricular (LV) function and mean pulmonary artery pressure (PPA) at rest and during exercise were examined in 49 patients with aortic valve disease, 23 patients with aortic stenosis (AS), 12 patients with combined aortic valve lesions (kAV) and 14 patients with aortic regurgitation (AI). Muscular hypertrophy was present in all patients. LV-mass-to-volume ratio was significantly higher in patients with AS and kAV than in patients with AI. There was no significant difference in heart rate at rest or during exercise among the three groups. During exercise PPA increased significantly in all groups. The increase was significantly higher in patients with AS than in those with AI. End-diastolic and end-systolic volumes increased significantly in patients with AS and kAV on the average, showing no change in patients with AI. Ejection fraction decreased significantly in patients with AS and kAV and remained unchanged in patients with AI. Due to the increase in heart rate cardiac index increased significantly during exercise in all groups. In patients with pressure overloaded left ventricles (AS and kAV) the increase in filling pressure partly results in a decrease of compliance caused by hypertrophy. Thus in these ventricles LV function cannot be judged by LV filling pressures alone. In those patients in whom the indication for valve replacement was given without knowing the results of the exercise test, the changes of LV volumes and ejection fraction were abnormal during exercise on the average.(ABSTRACT TRUNCATED AT 250 WORDS)

[Digital subtraction angiocardiography--an alternative to traditional angiocardiography?]. / Digitale Subtraktionsangiokardiographie--eine Alternative zur herkömmlichen Angiokardiographie?

Intravenous (i.v.) digital angiography has been extensively and successfully used for studying peripheral arterial vessels. Its application in the heart now results in high resolution images of the cardiac chambers. Accuracy and reproducibility of left ventricular volume determination equal that of conventional cineangiocardiography. Thus, left ventricular regional and global function can be analyzed quantitatively at rest and during exercise with higher simplicity and lower risk even on an outpatient basis by i.v. digital subtraction angiocardiography. To date, however, the coronary artery system cannot be visualized by digital image processing using i.v. injection of contrast medium, i.e., in patients win whom the coronary arteries have to be examined, selective arteriography for the future, too, will be combined with direct left ventricular angiocardiography. Regarding clinical experience till now, digital subtraction angiocardiography must be characterized as a complementary rater than an alternative method to conventional cineangiocardiography.

Assessment of left ventricular function by a power index: an intraoperative study.

To investigate whether left ventricular performance can be described independent of loading conditions, twelve patients underwent intraoperatively two cineangiographies of the left ventricle with simultaneous pressure recordings. The first ventriculography was performed with ejecting left ventricle without assistance by the extracorporeal circulation. The second one was performed with ejecting left ventricle partially unloaded by the extracorporeal circulation. Myocardial perfusion pressure (mean aortic pressure) was held constant. Due to this procedure marked decreases in preload (end-diastolic wall stress: -54%) and modest changes in afterload (mean systolic wall stress: -23%) were achieved. End-diastolic volume index was reduced from 84 ml/m2 to 57 ml/m2, whereas end-systolic volume index decreased slightly from 33 ml/m2 to 29 ml/m2. Left ventricular end-diastolic pressure decreased from 12 mm Hg to 7 mm Hg, while peak pressure remained nearly unchanged. Usual parameters of ejection phase (EF, Vmw) as well as power per wall volume (PW) were markedly affected by unloading. In contrast to these parameters, the power index (PI), i.e., the ratio of power per wall volume and end-diastolic wall stress, remained unchanged when left ventricular preload was reduced: PI under control: 5.2 +/- 1.8 sec-1; PI under unloading: 5.2 +/- 1.5 sec-1. This power index can easily be determined from routine angiographies. It may provide a new approach to the assessment of left ventricular function in man.

[Digital subtraction angiocardiography: accuracy of measuring left ventricular wall thickness and wall volume during intravenous contrast media injection]. / Digitale Subtraktionsangiokardiographie: Genauigkeit der Messung von linksventrikulären Wanddicken und Wandvolumina bei intravenöser Kontrastmittelinjektion.

A comparison of left ventricular wall thickness and wall volume determined by intravenous digital subtraction angiocardiography and by conventional left ventricular angiocardiography was performed by linear regression analysis: wall thickness: WDDSA = 0.90 X WDLV , Syx = +/- 0.16 cm, r = 0.74; wall volume: WVOLDSA = 0.87 X WVOLLV , Syx = +/- 48 ml, r = 0.85. Compared to the deviation and scatter of corresponding data measured from two consecutive beats in conventional left ventricular angiocardiographies , the error of determination of wall thickness and wall volume, determined by intravenous digital subtraction angiocardiography, is more pronounced. The regression analysis of wall volumes under rest and bicycle exercise evaluated by digital subtraction angiocardiography revealed a similar inaccuracy ( Syx = +/- 46 ml). This is due to faults in recognition of the inner and outer contours of left ventricular wall. Our results show that measurements of left ventricular wall thickness and wall volumes by means of intravenous digital subtraction angiocardiography can only be performed with greater deviations compared to conventional left ventricular angiocardiograms.

[Reliability of digital subtraction angiocardiography for the evaluation of left ventricular function and physical stress]. / Zuverlässigkeit der digitalen Subtraktionsangiokardiographie zur Beurteilung der linksventrikulären Funktion unter körperlicher Belastung.

The reliability of determinations of left ventricular dimensions from digital subtraction angiocardiographies during exercise using intravenous injection of contrast material was proved in 20 patients. All angiocardiograms could be analyzed qualitatively and quantitatively only by means of the time-interval-difference (TID-) mode. Compared with other mask modes the superiority of the TID-mode results from the close temporal relationship between mask and contrasted frame. Thus, changes in position and brightness of the background structures are small, and left ventricular contours can be determined accurately despite intense respiratory movements. The intra-observer variability of determinations of end-diastolic and end-systolic volumes was +/- 12 ml (i.e. 7.5% of the mean value), corresponding inter-observer variability was +/- 24 ml (i.e. 17% of the mean value), respectively. Intra-observer deviation in determining ejection fraction was 2.8% (i.e. 4.5% of the mean value). The intra-observer variability in determining left ventricular axes was basal +/- 0.40 cm (i.e. 7% of the mean value), equatorial +/- 0.73 cm (i.e. 13% of the mean value) and apical +/- 0.34 cm (i.e. 8% of the mean value). Deviations of corresponding circumferential fiber shortening rates were basal +/- 0.22 s-1 (i.e. 14% of the mean value), equatorial +/- 0.32 s-1 (i.e. 22% of the mean value), and apical +/- 0.18 s-1 (i.e. 13% of the mean value). The results show that left ventricular dimensions can be determined accurately from intravenous angiocardiograms during exercise using digital subtraction angiocardiography.

[Relations between ventricle function, myocardial oxygen consumption and coronary circulation following sublingual administration of nitroglycerin]. / Beziehungen zwischen Ventrikelfunktion, myokardialem Sauerstoffverbrauch und Koronarfluss nach sublingualer Gabe von Nitroglycerin.

The relationships between ventricular function, coronary blood flow, and myocardial oxygen consumption after sublingual administration of 1.6 mg nitroglycerin (TNG) were investigated in 12 patients. Left ventricular volumes, determined from cineventriculograms (enddiastolic volume index and endsystolic volume index), decreased (p less than 0.005) after TNG, as did left ventricular peak pressure (p less than 0.01), left ventricular enddiastolic pressure (p less than 0.005), mean aortic pressure (p less than 0.005), and mean pulmonary artery pressure (p less than 0.001). Due to the decrease in enddiastolic volume and the insignificant change in stroke volume, ejection fraction increased (p less than 0.05). Heart rate did not change significantly. In spite of an increase in the vessel diameter (13%, p less than 0.005), systolic and diastolic coronary blood flow, measured by means of a photodensitometric technique, decreased insignificantly by an average of approx. 15%. Similarly the change in myocardial oxygen consumption, calculated according to Bretschneider, decreased insignificantly by an average of approx. 10%. The correlation of changes in coronary blood flow and myocardial oxygen consumption was evaluated statistically by the use of the 2 X 2 contingency table in conjunction with the chi 2 McNamar test: patients with a decrease in myocardial oxygen consumption also showed a decrease in coronary blood flow (p less than 0.05). This implies that coronary blood flow is determined by myocardial oxygen consumption, which is altered by the systemic effects of TNG.

Measurement of systolic and diastolic flow rates in the coronary artery system by x-ray densitometry.

The reliability of a modified videodensitometric and photodensitometric sampling technique for measuring phasic flow rates in the coronary artery system was examined. Electromagnetic flow measurements were performed in a circulatory model with continuous and pulsatile flow and intraoperatively in aortocoronary bypass grafts; cineangiograms were made simultaneously. Based on the front velocities of injected boluses of contrast medium, the densitometric measurement overestimated the electromagnetically measured flow systematically by about 20%. Systolic and diastolic flow rates in aortocoronary bypass grafts and coronary arteries determined from biplane cineangiograms in 34 patients generally revealed the typical pulsatile flow pattern familiar from electromagnetic and ultrasonic flow measurements. Flow velocities in unstenosed coronary arteries were nearly identical before and after branchings of the vessels, whereas the corresponding flow rates were higher in proximal than in distal segments. The identical flow velocities in different branches of the same vessel and the low variability of this parameter in different patients may be a suitable index of the effect of stenoses on coronary arterial blood flow.

[Digital subtraction angiocardiography: accuracy of left ventricular volume determination using intravenous injection of contrast medium]. / Digitale Subtraktionsangiokardiographie: Genauigkeit der linksventrikulären Volumenbestimmung bei intravenöser Kontrastmittelinjektion.

The usefulness and accuracy of intravenous digital subtraction angiography of the left ventricle was proved by comparison with conventional left ventricular angiocardiography. During heart catheterization two cineangiograms were performed in 20 patients at rest: one with direct injection of contrast medium into the left ventricle and the other with intravenous injection. The intravenous angiocardiograms were processed by a hardwired digital image-processing system designed by our own group. Image enhancement was obtained by subtracting a mask image from the contrasted image of the left ventricle. The utility of four different mask modes was examined by correlating end-diastolic and end-systolic volumes determined from conventional and intravenous digital subtraction angiocardiograms of the left ventricle respectively. Reliable quantitative results could only be achieved by obtaining mask and contrasted images from the same phase of the cardiac cycle. Using these special mask modes, the standard deviations of the residuals amounted to +/- 33 and +/- 36 ml respectively. The results show that intravenous digital subtraction angiocardiography allows a quantitative determination of left ventricular volumes at rest.

[Determination of phasic flow speeds in the coronary vessels by means of a simple photodensitometric technique (author's transl)]. / Bestimmung der phasischen Flussgeschwindigkeiten im Koronargefässsystem mit einem einfachen fotodensitometrischen Verfahren.

Systolic and diastolic flow rates in coronary arteries were determined from cineangiograms using a photodensitometric measurements system. The front velocity of a bolus of contrast medium was evaluated by two different methods. Measurements in aortocoronary bypass grafts showed that the photodensitometric determination of flow rates overestimated the electromagnetically measured flow by about 20%. Measurements in coronary arteries proved a good reproducibility (r=0.98) and the typical pattern of phasic flow. The velocity of flow in coronary arteries was nearly identical before and after branchings of the vessels (r=0.96).