Biomedical subjects

D G Onnasch

Publications and source records attributed to D G Onnasch.

32 records · Page 2Linked to original sources

PubMed1985

Hemodynamics during and immediately after the surgical creation of a supravalvular pulmonary stenosis in pigs.

The surgical creation of a supravalvular pulmonary stenosis (PS) adequate to prepare the left ventricle (LV) for anatomic correction in cases of simple transposition of the great arteries (TGA) is difficult. To gain more information on the hemodynamic changes immediately following PS of various degrees, pressures (P) in the right atrium (RA), right ventricle (RV), pulmonary artery (PA) and left ventricle (LV) as well as pulmonary flow (F) were monitored 40 minutes (30 to 50 minutes after PS (n = 15) in 10 open chested pigs (mean weight: 20.7 kg). Hemodynamic changes can be separated into an adaptation phase (AP) with an "overshoot" response of most hemodynamic parameters and a stable phase (SP) without further changes, reached after 6.5 minutes (1 to 18 minutes). This pattern was independent of the degree of PS (increase of RV Pmax: 13 to 39 mmHg). Maximal changes (p less than 0.01) during AP included: RV Pmax: +25 +/- 9 mmHg, RV EDP: +6 +/- 3 mmHg, RV dp/dt max: +315 +/- 208 mmHg/sec, LV Pmax: -43 +/- 24 mmHg, PA max. syst. flow: -0.3 +/- 0.15 ml/sec, CO: -0.45 +/- 0.3 l/min. During SP, LV Pmax and PA Pmean were normal. RV EDP and RA Pmean had decreased (p less than 0.01) but remained elevated as compared to the control values (p less than 0.01). The right ventricular maximal pressure had decreased 30% but remained elevated compared to control values (p less than 0.01). A change of RV Pmax during SP correlated (r = 0.93) with the maximal change of RV Pmax during AP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Valvular pulmonary stenosis. Natural history and right ventricular function in infants and children.

The purpose of this study was the analysis of natural history and right ventricular function of infants and children with valvular pulmonary stenosis. Available for assessment were the pressures in the right ventricle and pulmonary artery in 5 infants and 13 children obtained at two cardiac catheterizations, performed at intervals of 2 to 12 years (mean: 6.5 years) apart, as well as quantitative angiocardiographic data in another group of 38 children. There was no change in the pressure gradient between the right ventricle and pulmonary artery (PG) between the two catheterizations for those with an initial PG of less than 50 mmHg; but a mean increase of 8.6 mmHg year-1 occurred in those with an initial PG of more than 50 mmHg. There were good correlations between increase of PG and the first (r = 0.704) and the second (r = 0.904) catheterizations. End diastolic and stroke volume were normal while end-systolic volume was smaller (P less than 0.01) and ejection fraction greater (P less than 0.01) than normal. The natural history of children with a PG of more than 50 mmHg seems to be different from that with a PG of less than 50 mmHg. In the former group the increase of PG is rapid while PG in the latter does not change over many years. Right ventricular function is usually not impaired in patients with moderate and severe valvular pulmonary stenosis in the pediatric age group.

Angiocardiography↗

PubMed1985

Computerized geometric evaluation of angio- and echocardiographic images.

Since the first comprehensive computerized videometric systems for quantitative assessment of the dynamic morphology and function of the heart have been developed, angiocardiographic image generation and computer aided evaluation have improved considerably. As a second method for morphological imaging echocardiography is also established in cardiology, so that videometry branched off into angio- and echocardiometry. In this paper, the common aspects of both methods are discussed concerning manual outlining and computerized contour representation, additional storage of anatomical landmarks labelled by digits and letters, and list-directed automated evaluation of data. It allows standard graphical documentations including comparisons of global volumetric and functional results for individual patients as well as versatile research orientated evaluations of oblique semi-axes, sectorial areas, wall thicknesses, shape parameters, spatial orientation and derived global and regional functional parameters for patient groups. As an example wall thickness measured from echographic long and short axis views and from angiographic projections are compared.

Angiocardiography↗

PubMed1984

Effects of angiocardiographic contrast media on the pulmonary circulation in pigs.

In 12 open-chest pigs, mean weight 18 kg, simultaneous beat-to-beat measurements of pressure in the right and left atria and right and left ventricles, and of pressure and flow in the pulmonary artery, were performed before, during and after the injection of 0.8 ml/kg with 10 to 15 ml/s of diatrizoate, ioxaglate and iopamidol as well as mannitol, normal saline solution and own blood into the right atrium, right ventricle and pulmonary artery. Within 5 beats after injection, all determined hemodynamic values reached their maxima of change independent of site of injection and kind of injectate. After 10 to 20 beats, pulmonary resistance diminished, and the reduction was more pronounced and longer lasting the higher the osmolality of the injectate. Hemodynamic changes during the first beats were a result of the rapidly injected volume; longer lasting hemodynamic changes were associated with an osmolality-dependent decrease in pulmonary resistance.

Angiocardiography↗

PubMed1984

Right ventricular imaging with digital subtraction angiocardiography using intraventricular contrast injection.

Angiocardiography is of considerable value in the dimensional analysis of the right ventricular (RV) cavity, but conventional angiocardiography requires large amounts of contrast medium. In this study digital subtraction angiocardiography was applied to biplane RV projections of 25 children with congenital heart disease after direct injection of a small dose of contrast medium. Volume measurements were compared with those obtained by conventional angiocardiography. The amount of contrast medium required was reduced to 30%, flow rate to 57% and ventricular ectopic activity to 60% of that used in conventional angiocardiography, and the degree of radiation exposure was reduced considerably. There was a good correlation for end-diastolic (r = 0.996) and end-systolic volume (r = 0.990) determined with both techniques. Digital subtraction angiography after selective RV injection allows accurate volume measurements of the right ventricle in children with congenital heart disease. The main benefits of this method are reduction of the amount of contrast medium, flow rate during injection, radiation and ventricular ectopic activity.

Adolescent↗

PubMed1983

Short-term hemodynamic results after right ventricular outflow tract reconstruction using a cusp-bearing transannular patch.

Correction of right ventricular outflow tract obstruction remains a challenge to cardiovascular surgeons. In order to relieve this obstruction and at the same time prevent or minimize pulmonary insufficiency, we inserted a cusp-bearing transannular patch (monocusp) in 14 patients. To test this objective, we restudied 13 of these patients 0.5 to 4 months postoperatively, including quantifying pulmonary insufficiency using an accurate videodensitometric method. In all patients a degree of pulmonary insufficiency ranging from 8% to 46% of total stroke volume (mean 22.7 +/- 10.6%) was measured, and in all but one a residual right ventricular outflow pressure gradient of 2 to 22 mm Hg (mean 10 +/- 7 mm Hg) was measured. There was an inverse relation between the degree of pulmonary insufficiency and both the pressure gradient (r = -0.89) and the ratio of the pulmonary valve ring diameter to monocusp depth (r = -0.67). An ideal reconstruction of the right ventricular outflow tract obstruction, without any postoperative pulmonary insufficiency and stenosis, was not achieved by the implantation of a monocusp in the described fashion. The postoperative results were acceptable in only a few patients. A reduction of pulmonary insufficiency seems to be associated with a small residual pressure gradient as well as a relatively small cusp size. Additional studies are necessary to further improve surgical correction of right ventricular outflow tract obstruction with reproducible and predictable results.

Adolescent↗

PubMed1982

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

Volume 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 greater than 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 less than 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 degrees) 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 degrees. These data may contribute to our understanding of the physiology of normal circulation and heart function during the period of growth.

Adolescent↗

PubMed1982

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.

Adolescent↗

PubMed1981

Two-stage anatomic correction of complete transposition of the great arteries: ventricular volumes and muscle mass.

Between 1976 and 1981, 27 patients with complete transposition of the great arteries, ranging from one month to 2 1/2 years, underwent two-stage anatomic correction and 7 patients first-stage operation only. There were three early deaths after the first-stage and five after the second-stage operation and no late deaths. In seven patients the results of repeat cardiac catheterization including quantitative analysis of ventricular angiocardiograms at the different stages of the procedure were available. In these patients peak systolic pressure in the left ventricle rose to systemic levels after banding of the pulmonary artery. Left ventricular end-diastolic and stroke volumes decreased to normal levels without significant reduction of arterial oxygen saturation. One to 2 1/2 years after anatomic correction left and right ventricular function was normal, as judged by normal end-diastolic pressure, ejection fraction and ratio left ventricular muscle volume/end-diastolic volume. Minimal aortic regurgitation in five patients, mild mitral insufficiency in two and a small VSD in two contributed to elevated end-diastolic volumes of the left ventricle, observed in six patients, and of the right ventricle, found in two patients. The aortic and coronary anastomoses appeared to grow normally.

Angiocardiography↗

PubMedDate not supplied

The accuracy of experimentally determined angiographic right ventricular volume.

The purpose of this investigation was to validate in vivo the accuracy of videoangiocardiographic right ventricular volume determination. Thus the stroke volume of the right ventricle as difference of enddiastolic and endsystolic volume was determined simultaneously (n = 70) by videoangiocardiography and with an electromagnetic flowmeter in 7 open-chested pigs with an average weight of 18.5 kg. Model volumes, calculated with the multiple slices and the area-length methods on the basis of mono- and biplane angiographic right ventricular projections, were corrected conventionally and with factors appropriate for cardiac phase and spatial orientation. The correlation between electromagnetic and angiographic stroke volume was the lowest (r = 0.802) when monoplane and highest (r = 0.949) when biplane methods were used. A systematic error could be prevented (y = -0.3 + 1.0 x; Syx = +/- 1.96 ml) by applying correction factors appropriate for cardiac phase and spatial orientation. The statistical error was independent of the correction used. The correlation coefficient for the optimal corrected monoplane method based on the lateral projection was r = 0.861 and for the ap plane r = 0.930. Right ventricular stroke volume can be determined videoangiocardiographically without systemic error and with an acceptable statistical error, if spatial orientation and cardiac phase are considered. If only monoplane equipment is available, the approjection is preferable.

Angiocardiography↗

PubMedDate not supplied

A new device for slow progressive narrowing of vessels.

The 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 warrants experimental and possibly clinical application of the developed small constrictor.

Constriction↗

PubMedDate not supplied

Response of the right ventricle to progressive pressure loading in pigs.

The purpose of this study was to determine the speed and duration of progressive pressure loading of the right ventricle to systemic pressure levels, which allows right ventricular adaptation without myocardial impairment at rest. In 8 pigs with an average weight of 22 kg progressive right ventricular pressure loading of different speeds and durations was induced with a newly developed constrictor. Pressures in the right atrium, right ventricle, and pulmonary artery as well as angiocardiographic volume parameters of the right ventricle were determined weekly over a period of 4 to 7 weeks. A fast progressive right ventricular pressure increase of 3.4 mm Hg/day during 3 weeks was associated with a 20-30% reduction of ejection fraction and a 100% increase of the end-systolic volume. Increase of end-diastolic pressure was 3 to 5 fold. A slow progressive pressure increase of 1.5 to 2.2 mm Hg/day to 100 mm Hg within 4 to 5 weeks was associated with an increase of the end-diastolic pressure to a level observed in systemic ventricles, while change of ejection fraction and end-systolic volume was minimal. The faster the increase of right ventricular pressure the flatter was the peak systolic pressure/end-systolic volume relationship. It is concluded that in contrast to sudden and fast progressive increase of afterload slow progressive increase of afterload to systemic levels does not impair right ventricular myocardial function.

Animals↗

PubMedDate not supplied

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

Systolic 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.

Adolescent↗

PubMedDate not supplied

Left ventricular muscle volume in children and young adults.

A 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 less than 0.001) and in valvar aortic stenosis (1.34 +/- 0.31, n = 21, P less than 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 less than 0.001) and to the mean in TGA shortly after birth (P less than 0.05). However, it increased (P less than 0.001) to normal after banding of the pulmonary artery in TGA.

Adolescent↗