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Biomedical subjects

R W Frater

Publications and source records attributed to R W Frater.

At least 91 records · Page 5Linked to original sources
PubMed1986

The preoperative bleeding time as a predictor of postoperative hemorrhage after cardiopulmonary bypass.

To determine whether the preoperative bleeding time, the most reliable indicator of in vivo platelet dysfunction, can prognosticate excessive postoperative hemorrhage and, hence, the need for infusion of platelet concentrations, we studied blood loss versus bleeding time in 43 patients undergoing coronary bypass grafting. There was no correlation between bleeding time and either fall in hemoglobin level (r = 0.04) or chest tube drainage (r = 0.004). In addition, bleeding time did not correlate with the number of units of platelet concentrate (r = 0.12) or packed red cells (r = 0.2) infused. The bleeding time, which has been recommended as an essential screening test before all cardiopulmonary bypass procedures, need not be performed as a preoperative screen in otherwise healthy patients with no history of bleeding abnormalities and a normal coagulation profile.

Bleeding Time↗
PubMed1986

Aortic valve insufficiency due to aortic dilatation: correction by sinus rim adjustment.

Idiopathic dilatation of the aortic root may commonly cause chronic insufficiency of the aortic valve. In these patients the cusp and sinuses are normal or virtually normal in area and pliability and the coronaries are not displaced. The insufficiency in these patients may be totally corrected by an adjustment of the intercommissural distance at the sinus rim level. The dilated ascending aorta is dealt with separately by whatever technique is appropriate. Five patients with aortic insufficiency due to idiopathic ascending aorta dilatation are described. All underwent successful correction of the insufficiency by adjustment of the intercommissural distance at the sinus rim level and thus far the correction has been maintained for up to 16 months after surgery in each.

Adult↗
PubMed1986

Transesophageal irrigation for the treatment of mediastinitis produced by esophageal rupture.

Esophageal rupture in the thorax, unless small and contained, is followed by the early onset of fulminant mediastinitis. When the rupture occurs in the cervical esophagus, mediastinitis will also occur if cervical drainage is delayed and the infection is allowed to spread along the periesophageal planes towards the mediastinum. The purpose of this article is to report the good results obtained in the treatment of life-threatening sepsis from esophageal rupture with the combination of continuous per oral transesophageal irrigation of the mediastinum and drainage of the irrigating fluid by accurately positioned chest tubes connected to a wall-suctioning system. When the patient cannot swallow, mediastinal irrigation is accomplished via a nasogastric tube positioned by the upper esophagus proximal to the perforation. Irrigation by mouth was also used for the treatment of cervical perforations with the drainage tubes positioned in the neck. With this method in eight patients, sepsis has invariably been controlled, and in six cases, in which no irreversible damage to the esophagus existed, the perforations have healed spontaneously. There was no death resulting from mediastinitis, which is most often the lethal factor in esophageal rupture.

Esophageal Diseases↗
PubMed1986

Immediate tricuspid valve replacement for endocarditis. Indications and results.

Tricuspid valve excision for tricuspid endocarditis in addicts is recommended to avoid early reinfection, continued sepsis, and late reinfection because of the resumption of intravenous drug abuse. Valvectomy is allegedly well tolerated hemodynamically by some, but it leads to heart failure in at least a third of patients. In our experience in 10 addicts with staphylococcal endocarditis who had failed to respond to antibiotic therapy, tricuspid valve replacement allowed all 10 to leave the hospital free of infection and free of heart failure. Resumption of drug addiction in three led to septic death, but not necessarily to tricuspid reinfection. Two returned to jobs requiring a high level of physical labor and tolerated this without difficulty. We find no need to follow the practice of tricuspid valve excision for tricuspid endocarditis in addicts. Those who refrain from drug abuse are well served by valve replacement. Those who do not are doomed with or without a tricuspid valve.

Acute Disease↗
PubMed1986

Retained intracardiac air. Transesophageal echocardiography for definition of incidence and monitoring removal by improved techniques.

Retained intracardiac air is a continuing hazard for cardiopulmonary bypass. M-mode transesophageal echocardiography of the left atrium, left ventricle, and aorta is a highly sensitive method for detecting retained intracardiac air bubbles. In 15 patients having valve operations and 18 having coronary bypass, M-mode transesophageal echocardiography was used to record air bubbles during and for 15 minutes after bypass. Routine air clearing methods were used: needle aspiration of the ascending aorta (combined coronary and valve operations) and left atrial, left ventricular, and aortic aspiration after careful passive chamber filling (valve operations). Air was detected in 12 of 15 (79%) patients having valve operations and two of 18 (11%) patients having coronary bypass. One with air in the aorta had visible right coronary air embolism. Three patients with positive echograms had transient central nervous system disturbances. In a further 11 patients having valve operations, an ascending aorta-venous shunt was created before bypass was discontinued, but air continued to be present in the left atrium. Finally, in seven patients, we added the following maneuvers to our routine: positive chamber filling with echocardiographic demonstration of left atrial stretching, vigorous chamber ballottement, specific echo-directed chamber aspiration, and maintenance of cardiopulmonary bypass until transesophageal echocardiography showed no retained air. Although small amounts of atrial air could still be detected for a minute or two in some patients, this technique appears finally to have eliminated significant retained air and its consequences. A sensitive technique for intracardiac air detection reveals retained air surprisingly often after cardiopulmonary bypass. There are both possible and probable adverse consequences of this air. After valve operations, it is most difficult to eliminate air from the left atrium. There are three essential elements of air removal: First is mobilization of the air; positive chamber filling, stretching of the atrial wall, and ballottement are critical. Second is removal of mobilized air; continuous ascending aorta-venous shunting and nonsuction venting of the left atrium are very important. Third is proof of elimination of air before cardiopulmonary bypass is terminated; transesophageal echocardiography is vital for this.

Adult↗
PubMed1985

Effects of timing of atrial systole on LV filling and mitral valve closure: computer and dog studies.

Atrioventricular (AV) delay that results in maximum ventricular filling and physiological mechanisms that govern dependence of filling on timing of atrial systole were studied by combining computer experiments with experiments in the anesthetized dog instrumented to measure phasic mitral flow. Ventricular filling volume is maximized at AV delay of 100 ms in the computer study and 80 ms in the dog study. At any time in diastole atrial contraction accelerates mitral flow, opening the mitral valve widely; atrial relaxation then decelerates mitral flow, moving the valve leaflets toward closure. The time the valve remains closed following atrial systole varies inversely with AV delay. When AV delay is optimal, the mitral valve is moving rapidly toward closure but is not yet closed at onset of ventricular systole. The decline in filling volume as AV delay decreases below its optimum value is primarily the result of premature termination of atrial ejection by ventricular systole. As AV delay increases above its optimal value, filling volume progressively decreases because of premature mitral valve closure that limits effective diastolic filling period. There is no significant retrograde mitral flow at any point in diastole for any AV delay.

Animals↗
PubMed1984

The Meadox unicusp pericardial bioprosthetic heart valve: new concept.

To obtain a valve with better hemodynamic performance and longer durability than the currently available bioprostheses, a single-cusp pericardial xenograft has been developed. This valve has been tested extensively both in vitro, in a pulse duplicator and in a fatigue-testing system, and in vivo, in a series of dogs and sheep. Hemodynamic studies showed improved hemodynamic performance compared with other biological and mechanical valves. Effective orifice areas were larger and performance indexes higher, especially in the small sizes. Accelerated fatigue testing showed durability significantly superior to that of other biological devices. Animal experiments have established that the single cusp remains pliable even after more than two years of insertion. There is a low incidence of calcification and good preservation of the collagen matrix. This preliminary experience demonstrates that the unicusp pericardial xenograft has superior hemodynamics, increased resistance to fatigue-induced lesions, and a low incidence of calcification. These results might indicate an extended in vivo durability for this device.

Actuarial Analysis↗
PubMed1984

Replacement of mitral valve chordae with autologous pericardium in dogs.

Glutaraldehyde-tanned autogenous pericardium was compared with untreated autogenous pericardium as a tissue for replacement of anterior chordae tendinae of the mitral valve. Tanned autogenous pericardial chordae have a marked fibrous reaction at their healing ends but retain central pliability. Untreated autogenous pericardial chordae become uniformly fibrosed and stiff. Both retain their length, heal well to the papillary muscle and cusp, and are considered as potentially useful chordal substitutes in the right circumstances. Some of the response of the host to implanted tanned xenograft tissue must be related to the consequences of tanning rather than a reaction to foreign tissue.

Animals↗
PubMed1984

Intramural pseudodiverticulosis of the esophagus.

Two cases of esophageal intramural pseudodiverticulosis are presented. A brief review is made of previously published reports. This entity, first described in 1960, is still rarely diagnosed. Its etiology is still debatable. However, as more cases are published, it becomes more apparent that esophageal intramural pseudodiverticula can be found as part of a distinct syndrome with diffuse intramural pseudodiverticulosis, as originally described by Mendl, or localized in a limited extension of the esophagus as a response to esophageal obstruction.

Aged↗
PubMed1984

Long-term follow-up of the Ionescu-Shiley mitral pericardial xenograft.

In a group of 40 patients discharged from the hospital after mitral valve replacement with an Ionescu-Shiley pericardial xenograft from January, 1977, to December, 1980, seven instances of valve failure occurred. This unprecedented incidence of bioprosthetic dysfunction after mitral valve replacement with the Ionescu-Shiley pericardial xenograft led us to update the follow-up of our patients receiving this valve in the mitral position. The results of our survey showed, at 6 years postoperatively, an actuarial survival rate of 72%, an actuarial probability of being free from emboli of 62%, and an actuarial freedom from prosthetic failure of 60%. The explanted valves showed complete absence of the neoendothelial lining of the Dacron-covered frame and lesions resembling those observed in Ionescu-Shiley pericardial xenografts removed from our fatigue test system after a mean of 29 +/- 17 X 10(6) cycles. This similarity prompted a classification of tears occurring in the mitral Ionescu-Shiley pericardial xenograft, which is of extreme importance, since the clinical presentation and outcome of patients with a failing valve differs according to the type of rupture. The lesions of the cusp observed in clinical specimens were possibly related to the continuous trauma of the tissue against the bare Dacron cloth during closure of the valve. It is concluded that (1) actual durability and thrombogenicity of the Ionescu-Shiley pericardial xenograft in the mitral position needs to be carefully reassessed, (2) close follow-up of such patients by clinical and two-dimensional echocardiographic evaluation is advisable after the third postoperative year, and (3) failure of the mitral Ionescu-Shiley pericardial xenograft may occur suddenly, and awareness of this complication is the clue to prompt recognition and treatment of such patients.

Adult↗
PubMed1984

Protamine-induced circulatory changes.

The effects of rapid protamine administration via the left and right atria were compared. Preliminary studies first confirmed the safety of protamine administration via these routes, although decreases of up to 20 mm Hg were seen in the systolic blood pressure following protamine injection via the right atrium. Seventeen patients undergoing coronary artery bypass graft were studied, of whom nine received protamine via the right atrium and eight via the left atrium. Measurements of arterial pressure, left and right atrial pressure, cardiac output, and calculation of systemic vascular resistance and left ventricular stroke work index were made before and after protamine administration. Plasma histamine levels were measured in left atrial blood samples in 10 patients, before and after protamine injection. No significant change occurred after injection via the left atrial route, whereas a significant decrease in the systolic blood pressure and systemic vascular resistance with a transient increase in the cardiac index occurred after protamine administration via the right atrium. Plasma histamine levels were significantly higher after right atrial injection. It is concluded that histamine is released as protamine traverses the lungs following right atrial injection and produces peripheral vasodilation. Possible mechanisms for histamine release are discussed.

Aged↗
PubMed1984

Calcification of implanted xenograft pericardium. Influence of site and function.

In a series of 23 dogs, glutaraldehyde-fixed xenograft pericardium was implanted as a left atrial wall patch (Group I, 11 dogs), as a substitute for the mitral valve chordae (Group II, 12 dogs), and as an external pericardial patch (Group III, five dogs, in which one of the two former procedures was associated). All dogs of Group I survived and were put to death after 12 months. The atrial patch appeared thickened and shrunken in all, with intense fibrous reaction, calcification, and even bone formation. The structural changes were minimal in the external aspect of the patch, not in contact with the host's endocardium and blood. Eight dogs of Group II survived from 7 months to 3 years. In all, the pericardial chordae were thickened and calcified with good healing at the suture lines; that their original length was retained, however, allowed for good valve function. In the dogs of Group III the pericardial substitute appeared well preserved after 12 months, not calcified, and without noteworthy degenerative changes. Minimal or absent epicardial adhesions were noted. We conclude that (1) the tendency for xenograft pericardial tissue to calcify is strongly influenced by the site of implantation and function and by contact with host blood and endocardium; (2) heterologous pericardium may be considered suitable for closure of pericardial defects after open cardiac operations, and (3) studies on calcification of biological tissue should be carried out by long-term evaluation of such tissues inside the heart.

Animals↗
PubMed1984

Fatigue-induced failure of the Ionescu-Shiley pericardial xenograft in the mitral position. In vivo and in vitro correlation and a proposed classification.

Four patients had signs of primary bioprosthetic dysfunction within the fourth postoperative year after mitral valve replacement with an Ionescu-Shiley pericardial xenograft; they represent approximately 9% of patients with Ionescu-Shiley pericardial xenograft mitral valves followed up for more than 3 years at our institution. Pathological investigation showed severe incompetence of all explanted valves due to cusp tears and lacerations. Histologic study of the pericardial tissue disclosed mild to moderate collagen degeneration, without infection or calcification. Neoendothelial formation on the Dacron cloth of the sewing ring was either absent or minimal. The high incidence of valvular incompetence prompted us to try to establish a correlation between the in vivo and in vitro modes of failure of the Ionescu-Shiley pericardial xenograft. For this purpose, 10 unimplanted Ionescu-Shiley pericardial xenograft valves were tested in a fatigue test system. Severe fatigue-induced lesions occurred in this group after an average of 29.09 +/- 17.26 X 10(6) cycles; initial failure could be recognized in six of them after an average of 16.94 +/- 20.12 X 10(6) cycles. Valves tested in the fatigue test system showed tears and lacerations similar to those noted in the Ionescu-Shiley pericardial xenografts obtained from the four patients (which were assumed to have functioned for more than 100 X 10(6) cycles in each case). Correlation between results of the fatigue testing and our clinical experience enabled us to recognize four types of tears which may occur in the Ionescu-Shiley pericardial xenograft. The results of this investigation showed the following: (1) Primary tissue failure of the Ionescu-Shiley pericardial xenograft may occur suddenly. (2) A classification of tears occurring in Ionescu-Shiley pericardial xenograft valves is useful since the clinical presentation of patients may differ according to type and location of the lesion. (3) In the manufacture of pericardial valves, particular care must be observed in selection of the tissue and in the frame design. (4) Improvement of the quality control is one of the clues to enhance durability of the Ionescu-Shiley pericardial xenograft.

Aged↗
PubMed1983

Effects of heart rate on experimentally produced mitral regurgitation in dogs.

The effects of increasing heart rate (HR) on the hemodynamics of acute mitral regurgitation (MR) were studied in 8 open-chest dogs. Filling volume, regurgitant volume and stroke volume were calculated from electromagnetic probe measurements of mitral and aortic flows. The left atrial-left ventricular systolic pressure gradient was measured with micromanometers. The calculated effective mitral regurgitant orifice area varied from 10 to 128 mm2, with a consequent regurgitant fraction (regurgitant volume/filling volume) of 24 to 62%. After crushing the sinus node, HR was increased stepwise from 90 to 180 beats/min by atrial pacing while maintaining aortic pressure constant. With increasing HR, filling volume, stroke volume, regurgitant volume and regurgitant time decreased; total cardiac output, forward cardiac output, regurgitant output, systolic pressure gradient, regurgitant fraction and the regurgitant orifice did not change; left ventricular end-diastolic pressure decreased; and left atrial v-wave amplitude increased. These results indicate that in acute experimental MR with a wide spectrum of incompetence, the relative distribution of forward and regurgitant flows did not change with large increases in HR. At rates greater than 150 beats/min the atrial contraction occurs early and increases the amplitude of the left atrial v wave. This may contribute to the severity of pulmonary congestion in patients with MR.

Acute Disease↗
PubMed1983

Reproducible replacement of elongated or ruptured mitral valve chordae.

Anatomical rules that make it possible to accurately replace mitral anterior cusp chordae tendineae with tanned xenograft pericardium are defined. Anterior and posterior cusp chordae were replaced with xenograft and autologous pericardium in 11 patients who had ruptured or elongated chordae. The xenograft occasionally became calcified; however, because it did not become elongated or shortened, competence was maintained for up to 3 years. Insufficiency was corrected, and the correction maintained for up to 4 months. Degenerative disease proved easier to treat than rheumatic disease. Two-dimensional echocardiography was a valuable aid in both preoperative planning and postoperative evaluation.

Adult↗
PubMed1983

Experimental atrioventricular bioprosthetic valve insertion: a simple and successful technique.

Animal testing has become mandatory for the development of new prosthetic heart valves. It is very expensive. Low mortality and morbidity are essential in controlling costs. A simple technique for atrioventricular valve replacement in dogs and sheep that includes normothermic cardiopulmonary bypass, the maintenance of a beating heart and the avoidance of excision of the natural valve is described. Results have been excellent.

Animals↗