Biomedical subjects

J Rysavy

Publications and source records attributed to J Rysavy.

At least 19 recordsLinked to original sources

PubMed1995

Peak systolic velocity and flow volume increase with blood pressure in low resistance systems.

This study demonstrates that when vascular resistance is low, peak systolic velocity and peak flow volume increase with increasing blood pressure. We used ischemia with reactive hyperemia to create reproducible low resistance conditions in 32 volunteers. Ischemia resulted in sharp increases in systolic and diastolic velocities, while the difference between these velocities increased minimally. Spontaneous variations in subject's systolic blood pressure were positively correlated with peak systolic volume and peak flow volume (r = 0.40 and 0.59, respectively), but resistive index was not. We conclude that low resistance flow is blood pressure dependent. Because blood pressure increases with age, tumor velocity and frequency shift thresholds may need blood pressure correction if applied over wide age ranges. The resistive index was independent of blood pressure and thus may be preferable.

Adult↗

PubMed1992

Effects of verapamil on postextrasystolic potentiation.

To assess the effects of verapamil on postextrasystolic potentiation (PESP), contrast left ventriculography was performed in ten healthy anesthetized dogs before and after the intravenous administration of verapamil, 0.1 mg/kg. During the contrast ventriculography, a single atrial premature stimulus was introduced. Ejection fractions of a control beat and postpremature beat were measured before and after verapamil. Before verapamil, the mean ejection fractions of the control beat and the postpremature beat were 60 +/- 10 percent and 67 +/- 10 percent, respectively (p less than 0.05). Following the administration of verapamil, the mean ejection fraction of the control beat decreased from 60 +/- 10 percent to 55 +/- 11 percent (p less than 0.05). However, the mean ejection fraction of the postpremature beats increased when compared with the control beats following intravenous verapamil (65 +/- 8 percent and 55 +/- 11 percent, respectively; p less than 0.05). These results suggest that PESP is not inhibited by the administration of intravenous verapamil.

Animals↗

PubMed1992

Restoration of femoral offset during hip replacement. A radiographic cadaver study.

Restoration of femoral offset is an important part of total hip arthroplasty. Since radiographs showing the femur at a sufficient degree of internal rotation to allow direct measurement of femoral offset are not usually available, templates of the prosthesis at 25 and 45 degrees of rotation were created. Radiographs of 20 cadaver femurs with a mean offset of 44 +/- 5 mm (r 36-56) were then obtained at different degrees of rotation. Simple guidelines to indicate the correct template for each projection of the femur were found. The system could be used to select a prosthesis with correct offset using radiographs obtained at angles of rotation between 20 degrees internally and 40 degrees externally.

Cadaver↗

PubMed1987

Exercise reduces persistent ductus arteriosus shunting in piglets.

To determine the effects of dynamic exercise on ductal left to right shunting and skeletal and myocardial blood flow distribution, a persistent ductus arteriosus was created by balloon catheters in neonatal piglets. At 8-10 weeks of age, aortic, pulmonary artery, and left atrial catheters were placed and radiolabelled microspheres injected for measuring left ventricular output, organ blood flows, and ductus left to right shunting at rest and during treadmill exercise (1.6 mph). At rest, effective left ventricular output and myocardial and skeletal muscle blood flows were similar in the study group and controls. Exercise increased skeletal muscle and left ventricular blood flows similarly in the control and study group and did not accentuate the exercise induced small reduction in the left ventricular subendocardial to subepicardial blood flow ratio. This was due to a significant reduction in the ductus left to right shunt during exercise (mean(SD) 34(15) vs 18(7)%, p less than 0.02) and maintenance of effective left ventricular output in the study group (447(144) vs 446(98) ml.min-1.kg-1 in controls). The reduction in ductus shunting during exercise was due to a significant decrease in systemic vascular resistance and a small increase in pulmonary vascular and ductus resistance. Thus, reduced persistent ductus arteriosus shunting and maintenance of effective left ventricular output prevents myocardial perfusion abnormalities during dynamic exercise in swine with a persistent ductus and small to moderate left to right shunts.

Animals↗

PubMed1986

Canine model for long-term evaluation of prosthetic mitral valves.

The evaluation of mechanical prosthetic heart valves would be aided by a more satisfactory animal model. For acute assessment, a variety of animals have been used, but for chronic studies, only larger animals (pigs, calves, baboons) have been employed, creating an expensive model with laboratory management difficulties. Previously, the use of dogs for chronic evaluation has been unsatisfactory because of the frequent occurrence of early sepsis and valve-related thrombotic deaths. We have modified our existing acute dog protocol to produce a successful chronic model. Our model employs perioperative systemic antibiotics, short cardiopulmonary bypass period (range 35-60 min), a minimum of perioperative intravenous lines, postoperative anticoagulation therapy, and strict postoperative antiseptic technique for blood sampling. To evaluate this model, 11 consecutive mongrel dogs underwent mitral valve replacement with either a standard Dacron sewing skirt or a newly devised carbon-coated Teflon sewing skirt No. 23 mm Bjork-Shiley Convexo Concave (CC) prosthetic valve. Nine animals (82%) survived and were evaluated after a predetermined observation interval of either 3 or 6 months for valve function, pannus formation, and possible carbon particle migration. At sacrifice, all animals had good hemodynamics and valve function, minimal pannus formation and no carbon washout. Consequently, this model provides a relatively inexpensive, reproducible method of chronic in vivo evaluation of prosthetic valve modifications.

Animals↗

PubMed1985

M-mode and two-dimensional echocardiographic analysis of the septum in experimental right ventricular infarction: correlation with hemodynamic alterations.

We investigated the changes that occur in the shape and the motion of the ventricular septum in experimental right ventricular (RV) infarction with M-mode and two-dimensional echocardiography. The echocardiographic findings were correlated with the hemodynamic alterations. Right ventricular infarction was produced by mercury embolization of the right coronary artery in five anesthetized closed-chest dogs. After embolization, the transseptal end-diastolic left-right ventricular pressure gradient reversed (3 +/- 1) to -1 +/- 1 mm Hg, p less than 0.001). The septal shape was altered by the flattening of the septum at end-diastole and a return to the normal septal shape during systole. Systolic septal motion was reversed after embolization (1 mm toward the left ventricle before embolization to 3 mm toward the RV after embolization, p less than 0.01). Septal thickening was not altered. We concluded that isolated RV free wall infarction results in the reversal of the transseptal end-diastolic pressure gradient and is associated with the flattening of the septum at end-diastole. During systole, the septum returns to its normal shape and moves toward the RV. In addition, systolic septal thickening is preserved. The motion of the septum toward the RV, together with normal septal thickening, may provide mechanical assistance to RV ejection with RV free wall infarction.

Animals↗

PubMed1985

Detachable steel spring coils for vessel occlusion.

Spring coils for vessel occlusion were modified to include a screw-on attachment for delivery wire, which permitted safe and accurate placement of the coils. We successfully implanted coils in a dog and a lamb. They were easily retrieved from within the delivery catheters and the vessels, which is not possible with conventional coils. Coil design is described.

Blood Vessels↗

PubMed1985

Percutaneous catheter balloons: failure to deflate.

Three examples of permanently inflated transluminal catheter balloons are presented. Two of these occurred during attempted percutaneous transluminal angioplasty. Nonsurgical solutions, which were successful in each case, are described. Percutaneous puncture with a needle or a larger diameter coaxial catheter under fluoroscopic guidance may be useful when this complication occurs during attempted balloon angioplasty or embolization with proximal balloon occlusion in large vessels.

Aged↗

PubMed1985

Retrievable vena caval filter percutaneously introduced.

A vena caval filter than can be introduced percutaneously via the femoral vein is described. We placed these filters in five patients without complications. Experimental work in filter removal one to two weeks after insertion in dogs has been performed.

Animals↗

PubMed1984

Nephrotoxicity of contrast media assessed by occlusion arteriography.

The authors describe an experimental model for the study of nephrotoxicity induced by contrast media, based on a standardized injection combined with occlusion of the renal artery so as to expose the kidney to a high concentration of contrast medium for ten minutes. Iopamidol, ioxaglate, and both isosmolar and hyperosmolar saline were well tolerated, but diatrizoate caused marked radiological and pathological changes. This model may be helpful in studies of the mechanisms underlying contrast medium nephrotoxicity and evaluating differences in toxicity between contrast agents.

Animals↗

PubMed1984

Long-term patency of the ductus arteriosus after balloon dilatation: an experimental study.

Balloon dilatation of the ductus arteriosus was carried out in vivo in eight piglets that were 12 to 16 days old. The ductus was functionally closed in all animals before dilatation. Long-term patency for periods of up to 6 months after the procedure was demonstrated in six animals by angiography, Doppler ultrasound examination, and at autopsy. The presence of hemodynamically significant shunts was indicated by clinical development of heart failure, pulmonary infections, and left ventricular hypertrophy. These results confirm the value of this laboratory preparation to create left-to-right shunts at the ductus level.

Angioplasty, Balloon↗

PubMed1984

Role of ischemia in contrast-induced renal damage: an experimental study.

Total and regional cortical blood flow was measured in dogs by the radioactive microsphere technique after renal damage of varying severity had been induced by combining selective injection of diatrizoate, iopamidol, or normal saline with a 10 min occlusion of the renal artery. There was extensive tubular and glomerular damage in the kidneys exposed to diatrizoate, but not in the kidneys exposed to saline. Iopamidol caused intermediate changes. Average cortical blood flow was reduced from baseline levels in all groups 5 min after perfusion was restored. After 1 hr the flow had returned to the baseline level. Analysis of variance did not show a statistically significant difference among the groups. A tendency for redistribution of flow from outer to inner cortical layers was seen, but this was present in all groups. The flow changes detected in this study cannot explain the varying severity of renal damage.

Animals↗

PubMed1984

Effect of prostaglandin inhibition on the renal vascular response to ionic and non-ionic contrast media in the dog.

In an attempt to study the role of prostaglandins in the renal vascular response to contrast media in mongrel dogs, renal arterial injections of 6 ml of either the non-ionic contrast medium Iopamidol or the ionic medium diatrizoate meglumine/Na+ were performed, before and after intravenous injection of a buffered solution of acetylsalicylic acid (10 mg/kg) (ASA). Renal blood flow was recorded using non-occluding electromagnetic flow probes. The resting renal blood flow was significantly reduced after ASA. The usual biphasic response to contrast injection was observed both before and after ASA, and using either contrast medium. Analysis of the results failed to show any difference in degree of vasodilation or vasoconstriction after ASA. We conclude that prostaglandins may affect the resting level of renal blood flow but are not mediators of the instantaneous changes in response to contrast injection.

Animals↗

PubMed1983

Maximal postextrasystolic potentiation following multiple extrasystoles: a simple means of myocardial assessment.

To obtain consistent, reproducible postextrasystolic potentiation (PESP), a single closely coupled extrasystole (ES) must be introduced using transvenous pacing. We hypothesized that multiple ES (spontaneous or catheter induced) produce maximal PESP at all coupling intervals (CI). Differences in PESP between single and double ES were assessed in dogs at varying CI by two different methods [systolic time intervals--PEP/LVET, and endocardial markers--ejection fraction (EF)]. Single ES produced variable decreases in PEP/LVET (-8.6 +/- 2.7% (SE) to -22.9 +/- 4.0%) depending on the CI duration. Double ES produced maximal decreases (-26.0 +/- 1.2%) at all CI. A similar relationship was noted for EF following single ES (8.6 +/- 2.7% to 43.0 +/- 4.0%) and double ES (42.9 +/- 1.3%). Double ES produced maximal PESP at all CI. This finding may allow simple myocardial assessment during routine left ventricular catheterization without simultaneous right ventricular catheterization.

Animals↗

PubMed1983

Nonsurgical placement of arterial endoprostheses: a new technique using nitinol wire.

A new type of endovascular prosthesis has been developed using a unique metal alloy (nitinol) with a heat-sensitive memory. Nitinol wire coil grafts were straightened in ice water and passed into the canine aorta via catheter, where they reformed into their original shapes. Follow-up aortograms demonstrated long-term patency with minimal thrombus formation. Nitinol endovascular coil grafts may eventually be used in the nonsurgical treatment of several forms of vascular disease.

Alloys↗

PubMed1983

Patency of the ductus arteriosus after balloon dilatation: an experimental study.

Balloon dilatation of the ductus arteriosus was carried out in vivo in newborn pigs and on postmortem specimens from humans and piglets. The ductus was functionally closed in all newborn animals but patency resulted in all animals after balloon dilatation. Left-to-right shunts of 50% to 70% were found with anatomic lumen sizes of 3 to 5 mm. Patency was demonstrated up to 6 weeks after dilatation. Histologic examination showed splitting of the internal elastic layer and media, areas of hemorrhage confined to the media, and preservation of the adventitia. Mediastinal hemorrhage did not occur. This new technique is useful as an animal model of patent ductus arteriosus and could theoretically be used for palliative treatment of ductus-dependent congenital heart disease.

Angioplasty, Balloon↗

PubMed1983

Effect of aspirin on angioplasty-induced vessel wall hyperemia.

Angioplasty produces a persistent 20-fold increase in blood flow through mural vasa vasorum. To assess the role of prostaglandins in this phenomenon, vessel wall blood flow in experimentally dilated carotid arteries of aspirin treated dogs was measured. Aspirin (10 mg/kg, intravenously) significantly attenuated the increase in blood flow produced by dilation (+283 +/- 91% SE, n = 6) when compared to non-aspirin-treated controls (+2356 +/- 885% SE, n = 10). This suggests that aspirin, by interfering with arachidonate metabolism, may decrease local vasodilation after angioplasty. The effect of aspirin therapy on the long-term success of angioplasty requires further study.

Angioplasty, Balloon↗

PubMed1983

A new percutaneous vena cava filter.

A new, percutaneous vena cava filter was developed and tested in 11 dogs. Nitinol wire (0.045 cm diam) spirals were straightened and passed through an 8 French Teflon catheter into the inferior vena cava. The filter resumed its original spiral shape on warming to body temperature and was left in place up to 6 weeks. Long-term patency and capture of injected radiopaque clots were demonstrated. This new filter design may be a simple alternative to currently used implants.

Animals↗