Joseph Rysavy

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.

Transcatheter closure of patent ductus arteriosus in piglets

To better determine the risks of transcatheter closure of a patent ductus arteriosus (PDA), a model of PDA was made in newborn piglets by using 5- to 7-mm angioplasty catheters to dilate the probe PDA. This maneuver resulted in a permanent PDA in most piglets. Four to 6 weeks later PDA closure was attempted using the Rashkind PDA occluder. Twelve such procedures were attempted, using clean but nonsterile technique. Nine of 12 PDAs were successfully closed. Two failures were the result of inability to successfully traverse the PDA. This problem was solved by using a long sheath to position the device properly. Four complications occurred, all related to device release: left pulmonary artery embolization in 1 case, femoral artery embolization in 1, torn pulmonic valve cusp in 1 and lodgment of a prosthesis on a pulmonic valve cusp. Two successfully implanted devices were infected at necropsy. This study demonstrates the value of a piglet model in testing transcatheter PDA occlusion devices, the importance of sterile technique in such procedures, the hazards of device retrieval through the right heart and the feasibility of transcatheter PDA closure.

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.

Retrieving the Amplatz retrievable vena cava filter.

The new Amplatz retrievable filter was placed 15 times into the inferior vena cava (IVC) of 7 dogs. Retrieval of the filter was attempted in 11 cases after 1 week and in 3 cases after 2 weeks. The retrieval was successful and without complication in all 14 cases. The 15th placement resulted in thrombotic occlusion of the IVC, and no retrieval was attempted.

Complications of Wedge Hepatic Venography

During wedge hepatic venography, mechanical injection should be accomplished at the lowest possible rate in order to avoid hemorrhagic infarction. Small amounts of contrast material should be administered. Hepatic angiography may result in an area of tumor blush at the site of a previous wedge injection.

The use of the bristle brush for transcatheter embolization.

Small nylon brushes with a stainless steel core have been found safe and effective for transcatheter arterial occlusion. Studies performed in 14 dogs demonstrate the brushes result in rapid occlusion of the renal artery. Follow-up studies for periods up to ten months document the safety and permanence of the occlusion. The animal studies reported herein suggest that these devices can be safely used in humans in cases where large artery occlusion is desired.

The effect of hypoxia and posterior hypothalamic stimulation on colonic blood flow in the weanling puppy

Abstract (1) Posterior hypothalamic stimulation causes a 36% reduction in colonic perfusion in the puppy with a simultaneous rise in vascular resistance. Neither effect is seen in the presence of hypoxia. (2) Hypoxia alone produces a 17% increase in colonic perfusion with a 33% decrease in resistance. In the presence of PHS, hypoxia is associated with an 83% increase in perfusion and a 43% reduction in resistance. (3) The data suggest that sympathetic overactivity may play a role in the genesis of the ischemic lesion of neonatal necrotizing enterocolitis, while hypoxia may be operative in the development of the hemorrhagic lesions. This concept is discussed in relation to other hypotheses regarding the genesis of this disease.

Experimental myocardial infarction in the closed-chest dog: A new technique

The reliable and safe production of myocardial infarction in closed-chest animals is of paramount research interest. To date, the injection of particulate matter and the introduction of occlusive solid plugs have been described. Because of the limited size of the catheter, only small branches could be occluded, which resulted in a high incidence of mortality. A new simple technique is described that allows occlusion of a major coronary artery at a preselected site. An Ivalon (polyvinyl alcohol) plug compressed around the tip of an introducing wire is advanced through a selectively placed catheter into the coronary artery. It is felt in place for 5 minutes and assumes its original size upon contact with blood. Once the plug is re-expanded, the wire is withdrawn. The new technique was carried out successfully on nine dogs with no immediate fatality and myocardial infarction as demonstrated by cine ventriculography and histopathologic examination.

Single barbed stainless steel coils for venous occlusion. A simple but useful modification

Embolization of coils into the lungs has been reported following their use for the obliteration of large arteriovenous fistulas. So far, except for a recent report, they have not been used on the venous side of the circulation. Experimental studies at our institution demonstrated that the placement of coils on the venous side can result in embolization to the lungs, even when oversized coils are introduced. A simple, easy to perform modification of the standard stainless steel coils (Gianturco-Wallace-Chuang spring embolus and coilons) makes these devices safe embolic agents for used on the venous side of the circulation, as for example in the obliteration of spermatic veins.

Selective transcatheter embolization of the upper gastrointestinal tract: an experimental study.

Transcatheter gastric embolization using Ivalon shavings was performed on three groups of dogs. The left gastric artery and splenic branches (the short gastric and left gastroepiploic arteries) were embolized in Group I, the left gastric artery in Group II, and the splenic branches in Group III. Infarctions of the gastric mucosa occurred only in Group I. Ischemic ulcers developed in three of the five dogs in Group I and in one of the three dogs in Group II. The study suggest that embolization can only be performed safety if particles of 0.3 mm or larger are used.