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Biomedical subjects

W S Ring

Publications and source records attributed to W S Ring.

At least 55 records · Page 3Linked to original sources
PubMed1987

Long-term evaluation of aortic valvotomy for congenital aortic stenosis.

Aortic valvotomy (AV) for relief of congenital aortic stenosis (AS) is a palliative operation, and the purpose of this study was to determine the long-term benefit. After analyzing the symptoms at time of operation, 177 patients were separated by age at AV: newborns (1-14 days) 26, infants (2 weeks-1 year) 19, and children (greater than or equal to 1 year) 132. The newborn with critical AS typically presents with severe cardiac failure and the infant with moderate failure, whereas children may be asymptomatic. In the newborn group, final diagnosis has been made exclusively by noninvasive cardiac echogram since 1984. The presence of a hypoplastic left ventricle (HLV) and/or endocardial fibroelastosis (EFE) are the most important determinants of mortality. Operative survival was 11 of 13 (85%) in the newborn group if HLV/EFE were not present. No operative deaths for AV occurred after 1965 in children. When present, a preoperative electrocardiographic strain pattern resolved in 80% of patients. Of 33 reoperations (21%), four were required 1.0 (0.5-2) years later for newborns, five were required for infants 7.2 (1.5-20) years later, and 24 were required in children 11.0 (1.5-25) years later. These included 10 repeat valvotomies and 23 aortic valve replacements (AVRs) with a 91% survival rate. In summary, although valves of patients with congenital AS are morphologically abnormal, valvotomy is beneficial. It was found that (1) the operative survival rate has been 100% over the past 20 years for children and currently is greater than 80% in newborns in the absence of HLV/EFE; (2) reoperation rate is higher in newborns and infants; (3) benefit was shown by a sharp decrease in obstruction initially and improved ECG later; (4) long-term follow-up revealed a subset of patients who are asymptomatic and have only mild residual obstruction over 20 years after AV.

Actuarial Analysis↗
PubMed1987

Left ventricular function in malnutrition.

Twenty-one dogs were chronically instrumented with ultrasonic left ventricular dimension transducers and micromanometers to elucidate the effects of acute protein-calorie malnutrition on cardiac function. Ten dogs received a regular diet for 3 wk, whereas 11 dogs received a protein-calorie-deficient diet designed to achieve a mean weight loss of 20-25% over a 3-wk period. Studies of cardiac function were performed in awake intact animals at base line (1 wk postoperatively) and after 3 wk. In the malnourished dogs, cardiac mass was lost in proportion to total body mass loss. Mean cardiac mass fell from 115 to 91 g. This was largely due to wall thinning in this group. Heart rate dropped from 125 to 79 beats/min with malnutrition and ejection fraction increased from 29.8 to 34.6%. Cardiac output fell from 2.98 to 2.38 l/min, but cardiac index normalized to body surface area was unchanged. No significant changes in hemodynamics were observed in the control group. In the malnutrition group, global ventricular contractility, as measured by the load-independent index of systolic function or the slope of linear relationship between end-systolic pressure and end-systolic volume (EmaxPV), decreased slightly from 3.56 to 2.81 mmHg/ml (P = 0.07). However, Emax calculated from circumferential stress and strain data was unchanged. This indicates that depressed contractility was due to loss of cardiac muscle mass rather than any change in the myocardium per se. Response to beta-adrenergic stimulation was unchanged with starvation. Acute protein-calorie malnutrition causes significant cardiac atrophy that is reflected in decreased cardiac output and slightly reduced contractility but not in intrinsic properties of the myocardium.

Animals↗
PubMed1987

Effects of transplantation on atrioventricular nodal accommodation and hysteresis.

In the present study, atrioventricular nodal accommodation and hysteresis characteristics were evaluated in awake, unsedated dogs, before (n = 10) and after cardiac transplantation (n = 10). Chronically instrumented animals were atrially paced at a cycle length (CL) of 400 ms, followed by an abrupt decrease in pacing CL to 300 ms, followed by an abrupt return in pacing CL to 400 ms (with pacing sustained for 60 s at each CL). Atrioventricular nodal conduction characteristics (assessed by AH intervals) were simultaneously monitored. Under control conditions, AH intervals lengthened rapidly after an abrupt decrease in pacing CL [mean time for AH interval lengthening to stabilize (Tonset) = 2 +/- 1 s], whereas AH intervals lengthened more slowly (P less than 0.05) after transplantation (Tonset = 41 +/- 4 s). Similarly, after an abrupt increase in pacing CL, control AH intervals shortened rapidly [mean time for AH interval to return to base line (Tonset) = 5 +/- 1 s], whereas AH intervals shortened more slowly (P less than 0.05) after transplantation (Tonset = 42 +/- 5 s). Thus accommodation appears to be an intrinsic atrioventricular nodal response (present after cardiac denervation by transplantation) to abrupt, sustained atrial CL changes. Furthermore equivalence (P = NS) in atrioventricular nodal accommodation responses to symmetric CL decreases and increases after transplantation suggests that hysteresis [i.e., nonequivalence (P less than 0.05) in atrioventricular nodal accommodation responses], as seen under control conditions, results primarily from extrinsic (neural) modification of intrinsic atrioventricular nodal responses to symmetric CL changes.

Adaptation, Physiological↗
PubMed1987

Potentiation of cardiac electrophysiologic effects of verapamil after autonomic blockade or cardiac transplantation.

Cardiac electrophysiologic effects of verapamil in vivo are the result of both direct and indirect actions on the heart (the latter due to augmentation of sympathetic neural tone, diminution of parasympathetic neural tone, and increased circulating catecholamines). In this study we assessed the interaction of verapamil's direct and indirect actions on electrophysiologic properties of the heart in awake, previously instrumented, unsedated dogs. After administration of intravenous verapamil (0.2 mg/kg), electrophysiologic effects were assessed serially over a 1 hr period in 10 awake dogs before (group 1 studies) and during pharmacologic autonomic blockade (group 2 studies), and in a subset of these dogs (n = 5) after orthotopic cardiac transplantation (group 3 studies). In group 1 dogs, sinus cycle length (SCL) initially shortened after verapamil (postverapamil 379 +/- 50 msec vs baseline of 494 +/- 72 msec, p less than .001) and subsequently gradually prolonged. In groups 2 and 3, transient SCL shortening was absent. SCL prolonged promptly after verapamil, and sinus arrest developed in two of 10 group 2 and two of five group 3 animals. Verapamil exerted a negative dromotropic effect on atrioventricular node conduction in all three experimental groups, as assessed by drug-induced changes in minimum cycle length with sustained 1:1 atrioventricular conduction and measurements of atrioventricular node effective and functional refractory period. However, compared with findings in group 1, this negative dromotropic effect occurred more rapidly and was markedly potentiated in groups 2 and 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Normalization of sympathetic nervous system function after orthotopic cardiac transplant in man.

Plasma norepinephrine (PNE) levels are significantly elevated in patients with endstage congestive heart failure. To assess whether this abnormality is reversible, 32 patients were studied before and 3 to 9 months after orthotopic cardiac transplantation. PNE decreased after the transplant procedure form 739 +/- 363 to 301 +/- 161 pg/ml (p less than .05). In 13 patients, PNE was measured sequentially during the first 3 months after the transplant procedure. PNE decreased from 590 +/- 293 to 321 +/- 208 pg/ml at 2 weeks and remained stable at 1 month (308 +/- 239 pg/ml), 2 months (307 +/- 196 pg/ml), and 3 months (331 +/- 131 pg/ml), even while arterial hypertension developed. No correlation was found between PNE, systolic, diastolic, or mean arterial pressure and cyclosporine A blood levels. These data demonstrate that normalization of plasma levels of norepinephrine occurs shortly after cardiac transplantation in man. This decrease in PNE is probably independent of immunosuppression therapy. Finally, the development of arterial hypertension in cyclosporine A-treated cardiac transplant patients is not due to activation or persistent activation of the sympathetic nervous system.

Adult↗
PubMed1987

Clinical considerations of cardiac transplantation in organ transplantation: preoperative and postoperative evaluation.

Cardiac transplantation is being performed with increasing frequency worldwide; over 840 transplants were performed in 1985. All facets of cardiac transplantation are reviewed, including preoperative evaluation of both recipients and donors, technical aspects of the surgical procedure, and postoperative care of the recipient. Immunosuppression, complications, and long-term statistics are also reviewed. Particular care is taken to discuss pertinent radiographic studies as they apply to cardiac transplantation.

Adult↗
PubMed1987

Central aorta-pulmonary artery shunts in neonates with complex cyanotic congenital heart disease.

Methods of palliating critical pulmonary oligemia in neonates with complex cyanotic congenital heart disease continue to evolve. Pulmonary artery distortion and other complications of the use of native vessels to increase pulmonary blood flow has led to the more frequent use of polytetrafluoroethylene shunts either in a central position or as a modified Blalock-Taussig shunt. Central aorta-pulmonary artery shunts have largely fallen into disfavor because of previously reported unacceptably high incidences of complications such as shunt thrombosis, congestive heart failure, and pulmonary artery distortion. This report details our experience palliating 23 neonates with pulmonary atresia or severe pulmonary stenosis by placing central aorta-pulmonary artery shunts utilizing a short segment (less than 1 cm) of polytetrafluoroethylene. Although three of the 23 died postoperatively, none of the 23 patients had evidence of shunt thrombosis. Congestive heart failure, a potential complication of any pulmonary artery shunt, was present in eight of the 20 survivors but did not require shunt takedown and was readily controlled by digoxin. Repeat catheterization was performed in 12 patients; pulmonary angiography showed good growth of both pulmonary arteries and there was no evidence of pulmonary artery hypertension. Although minor pulmonary artery distortion was present in two patients, this distortion was centrally located and easily remedied at the time of total correction. Thus we have found the central aorta-pulmonary artery shunt to be an extremely effective and reliable means of palliating pulmonary artery hypoplasia as a result of pulmonary atresia or severe pulmonary stenosis in neonates.

Angiocardiography↗
PubMed1987

Left ventricular dysfunction in a canine model of chronic cyanosis.

States of low cardiac output frequently complicate the postoperative course of patients undergoing repair of cyanotic congenital heart lesions. The relative contribution of chronic cyanosis alone to the postoperative deterioration in left ventricular function remains unknown. To study the effects of chronic cyanosis on left ventricular function, nine dogs underwent inferior vena cava-to-left atrial anastomosis, a model that minimizes abnormal left ventricular hemodynamic loads. After at least 6 months of chronic cyanosis (mean arterial pO2 of 44 mm Hg and mean hematocrit of 61%), the dogs were instrumented with ultrasonic dimension transducers and micromanometers for collection of left ventricular pressure-dimension data. Studies were performed 7 to 10 days after recovery from instrumentation while the dogs were awake and alert. Nine normal dogs were also instrumented and served as controls. Pressure and dimension data were collected during transient vena cava occlusions before and after the combined administration of propranolol and atropine to produce autonomic blockade. Contractile function as measured by dP/dt, ejection fraction, and the stroke work-end diastolic length relationship was decreased by autonomic blockade to a similar extent in both normal and cyanotic dogs. After autonomic blockade, normal dogs were able to maintain stroke volume and cardiac index by utilization of Frank-Starling reserves (increased left ventricular end diastolic volume). In contrast, dogs with cyanosis were unable to maintain stroke volume and cardiac index or to increase left ventricular end diastolic volume after autonomic blockade. Dogs with cyanosis had reduced ventricular diastolic compliance, and they more fully used Frank-Starling reserves to maintain normal stroke volume and cardiac index in the control state when compared with normal dogs. The diminished preload reserves of the cyanotic dogs limited systolic performance (stroke volume and cardiac index) only at reduced levels of contractility produced by autonomic blockade.

Animals↗
PubMed1986

Endomyocardial biopsy in the cardiac allograft recipient. A review of 570 biopsies.

The morphologic abnormalities present in 570 endomyocardial biopsies from 39 cardiac allograft recipients and 16 autopsy hearts are described, and criteria pertinent to the diagnosis of rejection discussed. Entirely normal myocardium was apparent in 16% of the biopsies. Abnormalities related to biopsy of previous biopsy site occurred in 69%, and mononuclear infiltrates of varying intensity were present in 64% of the biopsies. Acute rejection was diagnosed in 17 (43.6%) patients in 32 (5.6%) of the biopsies and five hearts at autopsy. Seven of the biopsies with acute rejection were follow-up biopsies after a previous diagnosis of acute rejection and represented ongoing acute rejection. Similarly, three patients with rejection at autopsy died with ongoing rejection. The overall frequency of acute rejection was thus 0.70 episodes per patient. The most reliable histologic feature in the diagnosis of acute rejection in cyclosporine immunosuppressed recipients was a diffuse mononuclear infiltrate, apparent at low magnification. Myocyte necrosis, said to be critical in the diagnosis of rejection in cyclosporine-treated patients, was not a reliable indicator in the authors' experience.

Adolescent↗
PubMed1986

Management of pulmonary atresia with intact ventricular septum.

Infants with pulmonary atresia and intact ventricular septum pose a difficult clinical problem. Pulmonary valvotomy has been widely recommended for relief of the right ventricular obstruction, and most infants also have had an aortopulmonary shunt placed to ensure pulmonary blood flow. We have evolved a different approach that includes placement of a right ventricular outflow tract patch initially and continuation of prostaglandin E1 infusion postoperatively until the need for a shunt can be determined. We report here our management of 15 neonates with this diagnosis and suprasystemic right ventricular pressures. All of the infants were placed on a regimen of prostaglandin E1 before the operation to improve pulmonary blood flow, and all had an outflow patch placed early in life. Satisfactory postoperative right ventricular function, which would allow both outflow patching and ductus ligation, could be confidently predicted in only two of the 15 patients. For nine of the 15 an outflow patch was placed and prostaglandin was infused postoperatively to provide pulmonary blood flow until right ventricular function became adequate. Early in the series, three other infants were judged to need an aortopulmonary shunt in addition to decompression by an outflow patch, and one infant had only a shunt placed. Postoperatively, adequate pulmonary blood flow was present in all, and 11 of the 15 (73%) survived. Three of the deaths (average 2.8 days) after the outflow patch operation probably resulted from premature cessation of the prostaglandin infusion. One neonate with an outflow patch and a shunt died of myocardial ischemia because of coronary artery steal through right ventricular sinusoids. One late death occurred suddenly in the child with only a shunt, presumably because of an arrhythmia. The remaining survivors (10/15, 67%) are alive and have had complete repair. Study of these patients has also revealed that the definition of adequate right ventricular size needs to be more liberal. Five of the 10 surviving patients had a residual atrial septal defect with a right-to-left shunt at the ages of 1 to 3 years, but balloon occlusion of the atrial septal defect during cardiac catheterization revealed that the right ventricle in these patients was functionally adequate. These five children subsequently underwent closure of the atrial septal defect, and in two the aortopulmonary shunt was also taken down. In summary, correction was achieved in all survivors, in contrast to reported studies in which many patients are living with shunts.(ABSTRACT TRUNCATED AT 400 WORDS)

Angiography↗
PubMed1985

Myocardial perfusion in compensated and failing hypertrophied left ventricle.

This study examined blood flow in the hypertrophied left ventricle with and without failure. Left ventricular hypertrophy was produced in 20 dogs by banding the ascending aorta at 6-7 wk of age; studies were performed after animals reached adulthood. Sixteen dogs had compensated hypertrophy, while four dogs had cardiac failure manifested by left ventricular dilatation and end-diastolic pressures greater than 18 mmHg. The degree of hypertrophy, assessed by left ventricular-to-body weight ratio, was similar in animals with compensated hypertrophy (7.29 +/- 0.26 g/kg) and failure (8.45 +/- 0.15); both were greater than control (4.50 +/- 0.15, P less than 0.01). Left ventricular systolic pressure was similar in compensated hypertrophy (184 +/- 9 mmHg) and failure (226 +/- 29), as compared with control (130 +/- 4; P less than 0.01). Left ventricular blood flow measured with microspheres was 0.89 +/- 0.07 ml X min-1 X g-1 in control animals, was increased to 1.34 +/- 0.05 with compensated hypertrophy (P less than 0.001), and was further increased with failure to 1.86 +/- 0.40 (P less than 0.05). The left ventricular wall thickness-to-cavity diameter ratio was increased to 0.63 +/- 0.04 with compensated hypertrophy but was only 0.40 +/- 0.05 in dogs with failure (P less than 0.01), suggesting that wall stress was greater in hearts with failure. These data suggest that increased blood flow rates in dogs with failure resulted from increased myocardial O2 requirements due to increased systolic wall stress. Need for increased blood flow during resting conditions in dogs with failure would impair the ability for further coronary vasodilation during periods of cardiac stress.

Animals↗
PubMed1985

Improved immunosuppression for heart transplantation.

Since 1981, at the University of Minnesota, and more recently at Washington University in St. Louis, cyclosporine has been used as the main immunosuppressive agent for heart transplantation. It was initially combined with prednisone and given in a manner similar to that described at Stanford. In late 1983, concern regarding the nephrotoxic side effects of cyclosporine were heightened due to the fact that a potential recipient had chronic renal insufficiency secondary to renal damage suffered during previous heart surgery. In this patient it was decided to use lower doses of cyclosporine and to add azathioprine to maintain adequate immunosuppression. Initially, the same prednisone therapy was employed. This patient had an uncomplicated course following heart transplantation and was discharged with a normal renal function. This experience was the origin of a trial consisting of using cyclosporine, azathioprine, and prednisone as immunotherapy for heart transplantation. This report describes the results of this therapy in 17 patients.

Azathioprine↗
PubMed1984

Global left ventricular contractility in three models of hypertrophy evaluated with Emax.

Using the load independent contractility index, end-systolic pressure-volume ratio (Emax), contractility of the hypertrophied left ventricle (LV) from three different models was evaluated in conscious, resting dogs. The experimental animals included 12 dogs with perinephritic hypertension (HYP) (aortic diastolic pressure 130 +/- 5 mm Hg), 12 dogs who underwent aortic banding (AOB) at 6 to 8 weeks of age (resting aortic gradient 110 +/- 15 mm Hg), and 12 dogs with chronic fluid overload from aortocaval fistula (ACF). These were compared with 12 normal dogs (CTL). LV dimension and pressure were measured with ultrasonic tranducers and micromanometers. All three models resulted in hypertrophy with significant (P less than 0.01) increase in LV weight-to-body weight ratio (6.3 +/- 0.4, 8.4 +/- 0.5, 6.3 +/- 0.4, respectively, vs 4.4 +/- 0.1 g/kg). Cardiac output (6908 +/- 740 vs 2424 +/- 276 ml/min) and end-diastolic volume (118 +/- 11 vs 50 +/- 4 ml) were significantly (P less than 0.01) increased in AOB (18 +/- 1 vs 9 +/- 2 mm Hg). dp/dtmax was not significantly different among all groups. Emax (CTL = 5.3 +/- 0.4 mm Hg/ml) was not significantly changed in HYP (9.5 +/- 2.1) but was significantly (P less than 0.01) increased in AOB (14.1 +/- 2.6), and significantly (P less than 0.01) depressed in ACF (2.4 +/- .03). Thus, LV hypertrophy from systemic hypertension (HYP) or proximal aortic hypertension (AOB) is, at least initially, associated with preservation of contractility and normal hemodynamic performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Left ventricular adaptation to volume overload from large aortocaval fistula.

The manner in which the left ventricle responds to an acute volume overload has not been well defined. Left ventricular performance was studied in six chronically instrumented resting awake dogs in the control state and serially after creation of a large abdominal aortocaval shunt. Ultrasonic transducers measured minor and major axis diameters and equatorial wall thickness. Left ventricular pressure was obtained with micromanometers. Cardiac contractility was evaluated by the load-independent contractility index, EMAXsc (slope of the normalized end-systolic equatorial midwall circumferential stress-equatorial midwall circumference relationship). By 1 week postshunt, the dog had clinical signs of congestive heart failure (ascites, dyspnea, limb edema); although systolic aortic pressure remained stable, heart rate, end-diastolic volume, pulse pressure (systolic minus diastolic pressure), cardiac output, minute work and dp/dtmax were significantly increased. At 1 week the calculated left ventricular mass was increased by 10.1% +/- 4.0% above control. EMAXsc was significantly increased immediately after shunting but returned to control at 1 day and was less than control at 1 week. Thus adaptation of the left ventricle to acute volume overload is characterized by use of inotropic, chronotropic, and Starling reserves. However, chronic volume overload is characterized by decreased inotropic state and an apparent increase in hemodynamic performance (dp/dtmax, cardiac output, minute work), which appears to be maintained by an increase in cardiac mass and by chronotropic and Starling reserves.

Adaptation, Physiological↗
PubMed1983

Characteristics of ventricular function in severe hemorrhagic shock.

Although left ventricular (LV) function appears altered by severe hemorrhagic shock (HS), the mechanisms of this dysfunction have been difficult to characterize. Depression in the LV function curve could be caused by altered diastolic or systolic function. It has been difficult to assess the systolic function, but the use of the rate and load independent index of contractility, Emax (the slope of the end-systolic pressure-dimension relationship), offers a new approach to the quantification of systolic mechanical performance. Emax and the LV diastolic pressure-strain relationship were measured in 15 chronically instrumented dogs by sonomicrometric and micromanometric techniques. Gradual LV unloading was obtained from transient vena caval occlusion. After control study, each dog underwent 2 hours of HS (mean aortic pressure 40 mm Hg), followed by reinfusion of all shed blood. Upon reinfusion, Emax was not decreased; however, all dogs had a significant decrease in LV compliance. During the next 4 days, the LV compliance of the eight survivors progressively returned toward control, while Emax remained stable. All seven nonsurvivors demonstrated progressive loss of LV compliance, and Emax was significant decreased prior to death. Cardiac contractility appeared improved immediately after shock, but a consistent decrease in compliance was observed. Reversal of abnormal diastolic function was demonstrated in all survivors and progressive depression in all nonsurvivors. Depression in systolic function was observed only in nonsurvivors immediately prior to death.

Animals↗
PubMed1982

Esophageal replacement with jejunum in children: an 18 to 33 year follow-up.

Since 1947 a total of 32 staged jejunal interpositions have been performed in children for total esophageal replacement. There have been no failures of the jejunum to reach the neck, no loss of graft, and no deaths. The first 16 of these 32 children have now reached adulthood and form the basis for this report on the late functional results of staged jejunal interposition. Among these 16 patients there occurred four cervical fistulas which healed without sequelae (25%), one cervical stricture which necessitated dilatation but not revision (6%), one early cervical revision for necrosis of the distal tip of the graft (6%), and no complications related to the distal anastomosis. Long-term follow-up (range 18 to 33 years; mean 27 years) was obtained in 100% (16/16) of patients. A barium swallow was obtained in 81% (13/16) at a mean of 25 years following initial reconstruction (range 14 to 33 years). The fact that all patients could eat a regular diet at normal speeds indicates satisfactory long-term function. Two patients (13%) reported mild cervical dysphagia. A barium swallow in one of these patients revealed no abnormalities. The other was found to have an apparent esophageal diverticulum which resulted because the jejunum was end-to-side to the esophagus. This was recently corrected 27 years after the initial reconstruction and represented the only late complication of the procedure. There were no late strictures or peptic ulcerations. Motility of the jejunal limb was normal in 12 of the 13 patients studied. These results demonstrate that staged jejunal interposition can be accomplished reliably and safely in children with excellent long-term functional results and a minimum of late complications. The jejunum should be considered as an alternative to colon and gastric tubes for total esophageal replacement in children.

Adolescent↗