Dietrich G. W. Onnasch

Dimensions of the great arteries, semilunar valve roots, and right ventricular outflow tract during growth: Normative angiocardiographic data

SummarySystolic and diastolic diameters of the right and left pulmonary arteries (RPAD, LPAD), descending thoracic aorta (DTAD), right ventricular infundibulum (RVID), and pulmonary and aortic valve roots at the proximal, commissural and distal levels were estimated from angiocardiograms in 24 infants, children, and adolescents without heart disease, and correlated with body surface area (BSA), stroke volume (SV), cardiac output (CO), and ventricular volumes.The relationships between cardiovascular diameters and BSA were better expressed by a power function than by the other functions tried. We obtained different exponents for pulmonary and aortic valve annuli and the more distally measured great arteries (RPAD, LPAD, and DTAD), suggesting different growth patterns. The right ventricular infundibular shortening fraction (RVISF) was weakly correlated with BSA (r=-0.328), and the values obtained indicated constancy during normal growth. There was a direct proportional relationship between the pulmonary valve annulus diameter and the cube root of the right ventricular volume (r=0.952), as well as between SV and cross-sections of the right pulmonary artery (RPAC;r=0.916), left pulmonary artery (LPAC;r=0.878) and descending thoracic aorta (r=0.962). RPAC and LPAC were strongly correlated (r=0.940), the RPAC being significantly larger than the LPAC.

Binary reconstruction of the heart chambers from biplane angiographic image sequences

The aim of this work is the three-dimensional (3-D) reconstruction of the left or right heart chamber from digital biplane angiograms. The approach used, the binary reconstruction, exploits the density information of subtracted ventriculograms from two orthogonal views in addition to the ventricular contours. The ambiguity of the problem is largely reduced by incorporating a priori knowledge of human ventricles. A model-based reconstruction program is described that is applicable to routinely acquired biplane ventriculographic studies. Prior to reconstruction, several geometric and densitometric imaging errors are corrected. The finding of corresponding density profiles and anatomical landmarks is supported by a biplane image pairing procedure that takes the movement of the gantry system into account. Absolute measurements are based on geometric isocenter calibration and a slice-wise density calibration technique. The reconstructed ventricles allow 3-D visualization and regional wall motion analysis independently of the gantry setting. The method is applied to clinical angiograms and tested in left- and right-ventricular phantoms yielding a well shape conformity even with few model information. The results indicate that volumes of binary reconstructed ventricles are less projection-dependent compared to volume data derived by purely contour-based methods. A limitation is that the heart chamber must not be superimposed by other dye-filled structures in both projections.

Left and right ventricular adaptation to right ventricular overload before and after surgical repair of tetralogy of Fallot

On the basis of angiographic projections, left (n = 43) and right (n = 56) ventricular volume data were obtained in patients with tetralogy of Fallot before and after surgical repair. The postoperative patients were divided into 3 groups according to the degree of an additional volume load secondary to a residual ventricular septal defect or pulmonary insufficiency, or both. The decreased left ventricular ejection fraction (p less than 0.01) in preoperative tetralogy of Fallot in the presence of a normal sized left ventricle suggests depressed global myocardial function, which is not improved after surgical repair, even if excellent results are achieved. A certain functional reserve, however, seems to be preserved, since the ejection fraction did not decrease further with increasing additional volume loads. Similar enlargement of the right ventricle secondary to comparable degrees of pulmonary insufficiency and residual ventricular septal defect indicates similar effects of additional diastolic and systolic filling on right ventricular function in patients with tetralogy of Fallot after surgical repair. Even in patients with excellent surgical results, such as those without significant right ventricular outflow tract obstruction and additional volume load, right ventricular pump function is depressed, the ejection fraction being significantly (p less than 0.01) lower than normal. The further decrease of global myocardial function with increasing volume load suggests a loss of functional reserve. Attempts to minimize right ventricular volume load after surgical repair seem advisable.

Automated Video-Angiocardiographic Image Analysis

This paper describes a hardware-software system for handling the two main groups of cardiological data: a) physiological variables such as voltages, pressures, etc., and b) morphological data, derived from x-ray images or angiocardiograms, such as dimensions, areas, or volumes. We will concentrate in particular on some aspects of automated image processing–i. e., the analysis of the size, shape, and contraction pattern of the ventricles from video-angiocardiograms.

Value of image enhancement and injection of contrast medium for right ventricular volume determination by two-dimensional echocardiography in congenital heart disease

To determine factors that influence the accuracy of echocardiographically estimated right ventricular volume and to improve the echocardiographic input information by applying image enhancement techniques, quantitative contrast echocardiography (4-chamber view) and biplane angiocardiography were performed in 23 children during routine diagnostic cardiac catheterization. Volumes calculated on the basis of unprocessed and processed echocardiographic cross sections (area-length method and sphere model) underestimated angiocardiographic volumes significantly (p less than 0.01), and more so in end-diastole (50.6%) than in end-systole (35.9%). Thus, ejection fraction was significantly (p less than 0.01) underestimated; mean values were 0.48 +/- 0.12 and 0.60 +/- 0.08, respectively. The best comparison between echocardiography and angiocardiography at end-diastole was achieved with the sphere model using image enhancement techniques and injection of contrast media, where y = 0.54x - 6.8, r = 0.97, sy.x = 7.3. Correlations, however, in which unprocessed echocardiograms were used showed only slightly less good correlations. With the 6 image-enhancement techniques, a more homogeneous structure of the image and a more distinct outline of the internal surface was achieved. The statistical error improved only slightly. The echocardiographic 4-chamber view allows right ventricular volume determination with an acceptable accuracy. Its underestimation is related to inadequate visualization of trabeculations and mainly to the models used. Application of image enhancement techniques allows easier outlining of the internal cavity surface. The advantage gained by the combination of contrast infection and image enhancement techniques does not warrant the routine central injection of available contrast material.

A new device for slow progressive narrowing of vessels

SummaryThe purpose of this work was to develop a device which allows slow progressive banding of a great artery in infants within 4 to 5 weeks. Employed was the hygroscopic casein ameroid. When brought in contact with fluids, an ameroid cylinder expands characteristically. An early phase of fast expansion proceeds gradually to a phase of slow growth. Size, shape, and encasement of ameroid as well as temperature and type of surrounding fluid modify but do not alter the typical pattern of expansion. The developed constrictor (weight: 5.8 kg, length: 18 mm, diameter: 12 mm) includes a stainless steel socket containing an ameroid cylinder (length: 8.5 mm, diameter: 8 mm). The expanding ameroid pushes a piston with a concave extension (makrolon) a maximum of 2 mm against the artery, which is fixed to the metal housing by a teflon band (width: 4 mm, thickness: 0.5 mm). The band runs in 2 fitting grooves on the metal housing to which it is fixed by a metal ring with a precisely manufactured internal thread allowing exact tightening and loosening of the band around the artery.Utilization of inert materials like teflon, makrolon, and stainless steel warrents experimental and possibly clinical application of the developed small constrictor.

Geometric image correction and iso-center calibration at oblique biplane angiographic views

In the X-ray image intensifier TV system there are geometric image distortions which can be subdivided into pincushion distortions, S-shaped warping, image twisting, and shifting. These errors depend partly on the direction of the geomagnetic field relative to the image intensifier axis and are to be corrected for each view specifically. For caudal or cranial views there is the additional problem that in biplane images the slices of an object are projected on oblique lines. Based on four small bronze washers marking a centered square on each image intensifier screen, a dewarping program automatically calculates a nonlinear polynomial transformation. Then, all points of the image or the study are dewarped and centered accordingly. At the same time, the geometric calibration factors are derived. From the registered viewing angles, those angles are calculated by which both images have to be rotated for biplane assignment. Both optimal biplane visualization and the basis for further analyses are achieved.<<ETX>>

Left ventricular muscle volume in children and young adults

SummaryA computer-assisted method of estimating left ventricular muscle volume and its clinical application in 193 children and young adults is described. Wall thickness was measured at the lower half of the left cardiac border in the angiographic posteroanterior projection of the left ventricle, where only three points are marked when the left ventricular contour is traced. The intra- and interobserver reproducibility of the wall thickness were both within 1 mm. The individual beat-to-beat variability was 0.6 mm, 10% of the mean thickness.In normal left ventricles, the ratio between ventricular muscle volume and end-diastolic volume, the muscle volume index (MVI), was independent of body surface area, being 1.01+0.14 (mean±SD,n=28). MVI was normal in ventricles which were volume loaded secondary to a ventricular septal defect (n=9) or ductus arteriosus (n=11). It was significantly increased in aortic coarctation (1.66±0.44,n=24,P<0.001) and in valvar aortic stenosis (1.34±0.31,n=21,P<0.01). In tetralogy of Fallot (n=34) MVI was normal. MVI was significantly reduced in the case of pressure and possibly volume-underloaded left ventricles of simple transposition of the great arteries (TGA) (0.53±0.15,n=15) at the age of one year, compared to normal (P<0.001) and to the mean in TGA shortly after birth (P<0.05). However, it increased (P<0.001) to normal after banding of the pulmonary artery in TGA.

Size and function of the human left and right ventricles during growth. Normative angiographic data.

SummaryVolume parameters of 63 left (LV) and 50 right ventricles (RV) were calculated from bi-plane angiocardiograms of infants, children and adolescents. Seventeen of the LV were from patients who were normal or had only minor abnormalities, 26 were from patients with atrial septal defect and left-to-right shunt less than 170% and 20 were from patients with pulmonary stenosis and pressure gradients less than 50 mmHg. Sixteen of the RV were from patients who were normal, 6 from patients with slight aortic regurgitation, 17 from patients with aortic stenosis or coarctation and pressure gradients less than 30 mmHg and 11 from patients with patent ductus arteriosus and left-to-right shunt less than 60%. The ejection fraction (EF) of RV [0.626±0.050 (SD)] was smaller than that of LV (0.711±0.064). There was no significant correlation (p>0.05) with body surface area (BSA) (LV: r=−0.055; RV: r=−0.063) or heart rate (HR) at rest (LV: r=0.197; RV: r=0.179). However, EF correlated significantly with the endsystolic volume (ESV) (normalized for BSA1.22) (LV: r=−0.82; RV: r=−0.72), but not with the normalized enddiastolic volume (EDV) (LV: r=−0.05; RV: r=−0.22).For LV as well as RV, EDV and ESV, stroke volume and LV mass were proportional to BSA1.22. In contrast, the cardiac output, being the same for RV and LV, increased in proportion to BSA. There was, however, a significant correlation (r=0.465; p<0.001) between cardiac index (CI) and HR at rest. At 100 beats/min CI was 4.57±0.88 litre/min/m2.The evaluation of the spatial position of LV and RV yielded a significant descent (about 18°) of both ventricular apices relative to their respective semilunar valves during the period of growth. In patients with atrial septal defect (mean shunt 86%), the apex of the normal LV was shifted posteriorly by 20°.These data may contribute to our understanding of the physiology of normal circulation and heart function during the period of growth.

Influence of the two-stage anatomic correction of simple transposition of the great arteries on left ventricular function

To evaluate the influence of the 2-stage anatomic correction of simple transposition of the great arteries on left ventricular (LV) function, pressure and angiocardiographic volume data were analyzed during resting conditions shortly before banding of the pulmonary trunk (n = 12) and before (n = 17) and after anatomic correction (n = 11), and compared with data from controls (n = 12). Age at banding and anatomic correction was between 1 and 44 months (mean 16 +/- 10) and between 13 and 47 months (mean 24 +/- 10), respectively. The interval between anatomic correction and the investigation ranged from 10 to 29 months (mean 20 +/- 7). After banding, LV ejection fraction decreased (p less than 0.01) and LV peak systolic pressure (p less than 0.01) as well as LV end-diastolic pressure (p less than 0.05) increased. After anatomic correction, these variables and LV end-systolic wall stress were not significantly different from control values. The LV end-systolic wall stress-ejection fraction relation in 7 of 11 patients after anatomic correction was within control range. The highest values were found in the youngest patients at banding and at anatomic correction. In contrast to measures of global myocardial function, such as LV ejection fraction and LV end-diastolic pressure data, the LV end-systolic stress-ejection fraction relation suggest that LV function may not be normal in some patients 20 months after anatomic correction. Young age at operation, however, appears to be advantageous in preserving LV function. Hemodynamic alterations after banding probably reflect LV adaptation to systemic pressures in a hypoxemic circulation.