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Biomedical subjects

D M Behrendt

Publications and source records attributed to D M Behrendt.

At least 19 recordsLinked to original sources
PubMed2001

Long-term survival after mitral valve replacement in children aged <5 years: a multi-institutional study.

BACKGROUND: Short- and long-term outcomes after prosthetic mitral valve replacement (MVR) in children aged <5 years are ill-defined and generally perceived as poor. The experience of the Pediatric Cardiac Care Consortium (45 centers, 1982 to 1999) was reviewed. METHODS AND RESULTS: MVR was performed 176 times on 139 patients. Median follow-up was 6.2 years (range 0 to 20 years, 96% complete). Age at initial MVR was 1.9+/-1.4 years. Complications after initial MVR included heart block requiring pacemaker (16%), endocarditis (6%), thrombosis (3%), and stroke (2%). Patient survival was as follows: 1 year, 79%; 5 years, 75%; and 10 years, 74%. The majority of deaths occurred early after initial MVR, with little late attrition despite repeat MVR and chronic anticoagulation. Among survivors, the 5-year freedom from reoperation was 81%. Age-adjusted multivariable predictors of death include the presence of complete atrioventricular canal (hazard ratio 4.76, 95% CI 1.59 to 14.30), Shone's syndrome (hazard ratio 3.68, 95% CI 1.14 to 11.89), and increased ratio of prosthetic valve size to patient weight (relative risk 1.77 per mm/kg increment, 95% CI 1.06 to 2.97). Age- and diagnosis-adjusted prosthetic size/weight ratios predicted a 1-year survival of 91% for size/weight ratio 2, 79% for size/weight ratio 3, 61% for size/weight ratio 4, and 37% for size/weight ratio 5. CONCLUSIONS: Early mortality after MVR can be predicted on the basis of diagnosis and the size/weight ratio. Late mortality is low. These data can assist in choosing between MVR and alternative palliative strategies.

Adolescent↗
PubMed1998

Supravalvular aortic stenosis: a modification of extended aortoplasty.

A modification of the Doty extended aortoplasty for supravalvular aortic stenosis has been recently adopted. This modification, which entails placement of an additional patch in the left coronary sinus, results in a more symmetric aortic root. This technique has been applied with success to 3 patients.

Adolescent↗
PubMed1998

Should a bicuspid aortic valve be replaced in the presence of subvalvar or supravalvar aortic stenosis?

BACKGROUND: A bicuspid aortic valve is commonly associated with other levels of left ventricular outflow tract obstruction. Providing the bicuspid aortic valve is competent and nonobstructive, repair of subvalvar or supravalvar stenosis usually focuses on the obstructive lesions, leaving the valve in situ. The aim of this report was to examine the impact of a bicuspid aortic valve on the risk of reoperation for patients undergoing operation for subvalvar or supravalvar aortic stenosis. METHODS: Since 1976, 47 patients with supravalvar or subvalvar aortic stenosis have undergone repair. The median follow-up is 5.1 years (range, 2 months to 20.1 years). Sixteen patients (34%) had a bicuspid aortic valve that was competent and nonobstructive, and 31 (66%) had a tricuspid aortic valve. RESULTS: Reoperation was required in 9 patients (56%) with a bicuspid aortic valve, in each involving aortic valve replacement with an autograft (3), homograft (2), or prosthesis (4). Six patients (19%) with a tricuspid aortic valve required reoperation, yet only 1 required aortic valve replacement. The freedom from valve replacement was 43% (70% confidence interval, 31% to 55%) in the bicuspid aortic valve group versus 100% (70% confidence interval, 94% to 99.5%) in the tricuspid group at 5 years (p = 0.0001). The freedom from any reoperation at 5 years was 43% (70% confidence interval, 31% to 55%) in patients with a bicuspid aortic valve versus 86% (70% confidence interval, 80% to 93%) in the tricuspid group (p = 0.02). CONCLUSIONS: The data suggest that patients with subvalvar or supravalvar aortic stenosis and a bicuspid valve may be better palliated with a more definitive operation such as the Ross or Ross-Konno procedure.

Aortic Stenosis, Subvalvular↗
PubMed1996

Incidence of vocal fold paralysis in infants undergoing ligation of patent ductus arteriosus.

BACKGROUND: Left-sided, iatrogenic vocal fold paralysis (IVFP) secondary to recurrent laryngeal nerve injury is a potential complication of ligation of patent ductus arteriosus (PDA). This study investigates specific risk factors associated with IVFP. METHODS: A retrospective chart review was performed for all infants 12 months of age or younger who underwent operative PDA closure at the University of Iowa from January 1, 1991, to January 1, 1994. RESULTS: Six cases of IVFP were diagnosed in 68 infants who underwent PDA ligation using clips (52.9%), suture ligatures (41.2%) or both (5.9%). Compared with infants without postoperative IVFP, infants with IVFP were smaller at birth (0.9 versus 2.3 kg; p < 0.001) and more premature (gestational age, 26.3 versus 33.8 weeks; p < 0.001), and were smaller (1.1 versus 3.4 kg; p < 0.001) and younger (31.9 versus 88.4 days; p < 0.001) at operation. Weight gain from birth to operation was significant only in infants without postoperative IVFP (p < 0.05). Although the overall incidence of IVFP in all infants undergoing PDA closure was 8.8%, five of the six cases (83.3%) of IVFP occurred in extremely low birth weight infants, ie, those weighing 1 kg or less at birth. Among the cohort of extremely low birth weight babies undergoing operation, the incidence of IVFP was 22.7%. Iatrogenic vocal fold paralysis was associated only with the use of surgical clips; however, because clips were used in 90.9% of the premature infants requiring PDA ligation, it was not possible to establish whether suture ligature is a safer technique. CONCLUSIONS: This study demonstrates that the single major risk factor for IVFP after ligation of PDA is birth weight less than 1 kg.

Birth Weight↗
PubMed1995

Long-term follow-up of extended aortoplasty for supravalvular aortic stenosis.

Extended aortoplasty is an operation that was designed to provide a symmetric reconstruction of the aortic root in patients with supravalvular aortic stenosis. The aim of this report is to provide long-term follow-up of the original cohort of 15 patients who underwent extended aortoplasty between 1975 and 1983. Follow-up was obtained in 14 patients. One patient was lost to follow-up 3 years after operation; he was included in this report. An echocardiogram, chest radiograph, and electrocardiogram were obtained for each surviving patient. The median length of follow-up was 141 months (range 36 to 238). The median preoperative gradient was 90 mm Hg (range 55 to 150). The median immediate postoperative gradient was 20 mm Hg (range 0 to 50, p < 0.05 compared with preoperative gradient) and the median long-term gradient was 32 mm Hg (range 6 to 96, p < 0.05 compared with preoperative gradient; p = not significant compared with immediate postoperative gradient). Two patients died: one of left ventricular failure after a subsequent aortic valve replacement and one of chronic left ventricular failure. The Kaplan-Meier estimate of survival at 218 months for all patients was 77.4% (70% confidence limits 62% to 93%). The estimated freedom from reoperation for all patients was 69% at 218 months (70% confidence limits 56% to 82%). Univariate analysis revealed that the presence of a bicuspid valve is a significant risk factor for reoperation (p = 0.038), but not for death (p = 0.51). The Kaplan-Meier estimate of freedom from reoperation for patients with a bicuspid aortic valve was 42.9% at 141 months (70% confidence limits 21% to 65%). Extended aortoplasty provides effective long-term relief of the pressure gradient across the supravalvular ridge. However, a significant number of patients require subsequent operations, particularly those with a bicuspid aortic valve.

Adolescent↗
PubMed1994

Contrast MR of the brain after high-perfusion cardiopulmonary bypass.

PURPOSE: To study the efficacy of contrast MR imaging in the evaluation of central nervous system complications in the cardiopulmonary bypass patient and attempt to explain their pathophysiology based on the MR appearance and the cardiopulmonary bypass protocol. METHOD: Nineteen patients were prospectively studied with contrast MR examinations the day before and 3 to 7 days after cardiopulmonary bypass, to determine the nature, extent, and number of new postoperative MR abnormalities. Cardiopulmonary bypass parameters used in our institution included: membrane oxygenation, arterial filtration with a pore size of 25 microns, and a relatively high perfusion rate to produce a cardiac index of 2.0 to 2.5 L/min per m2. RESULTS: The preoperative noncontrast MR examination showed age-related changes and/or signs of ischemia in 60% of patients on the day before surgery. However, there was no abnormal enhancement or new T2 abnormalities on any postoperative MR examination to suggest hypoperfusion or emboli. None of the 19 patients developed overt neurologic deficits postoperatively. Review of the cardiopulmonary bypass protocol used indicated significant variations in technique at different institutions. CONCLUSION: Contrast MR imaging demonstrated no new abnormalities in patients after cardiopulmonary bypass performed with strict in-line arterial filtration and relatively high perfusion. MR imaging is feasible in the early postoperative period after cardiopulmonary bypass and may offer a convenient method for evaluation of the neurologic impact of technical factors associated with cardiopulmonary bypass.

Adult↗
PubMed1993

Prophylactic myocardial revascularization based on dipyridamole-thallium scanning before peripheral vascular surgery.

Cardiac events continue to be the leading cause of perioperative mortality following peripheral vascular reconstruction. The role of preoperative cardiac screening and prophylactic myocardial revascularization in patients without clinical evidence of coronary artery disease is undefined. Fifteen patients with no clinical evidence of coronary artery disease who were found to have reversible defects on dipyridamole-thallium scans and severe correctable coronary artery disease underwent aortocoronary artery bypass grafting. There was one (6.7%) operative death. Three patients (20%) developed postoperative complications: two atrial fibrillation and one breakdown of the saphenous vein harvest site. Thirteen patients underwent subsequent peripheral vascular surgery: seven had abdominal aortic procedures, three infrainguinal reconstruction, two carotid endarterectomy and one carotid-subclavian artery bypass. There were no perioperative or late deaths, cardiac complication, electrocardiographic changes, or episodes of angina associated with the peripheral vascular procedures. Thus, dipyridamole-thallium imaging appears to help select a group of symptom-free, but high cardiac risk, vascular patients in whom preparatory myocardial revascularization and subsequent peripheral vascular surgery can be performed with acceptable mortality and morbidity. The life expectancy of these patients may be improved and, specifically, the risk of their subsequent vascular surgery may be reduced by this approach.

Adult↗
PubMed1992

Use of extracorporeal life support in patients with congenital heart disease.

OBJECTIVES: To review a large experience with extracorporeal life support in patients with congenital heart disease. To determine the major causes of mortality and morbidity in order to improve the results of using this technology in this patient population. DESIGN: Retrospective chart review. PATIENTS: Twenty-five patients between the ages of 1 day and 8 yrs. These patients had congenital heart disease and were clinically felt to be at high risk for death caused by cardiac failure or by respiratory failure complicated by congenital heart disease. INTERVENTIONS: All patients in this report were placed on extracorporeal life support to allow recovery of myocardial or pulmonary function. MEASUREMENTS AND MAIN RESULTS: Of these 25 patients, 52% were weaned from bypass support and 40% survived to discharge. Patients who were not weaned from extracorporeal life support characteristically suffered from irreversible neurologic injury, multiple organ failure, or bleeding complications. Only one patient died of irreversible cardiac failure. CONCLUSIONS: Extracorporeal life support can be useful in supporting patients with congenital heart disease with life-threatening cardiac or pulmonary failure. Improvements in limiting neurologic and bleeding complications may lead to improvements in the use of extracorporeal life support for this indication. However, prospective, randomized studies are needed to appreciate the role of extracorporeal life support in these patients.

Child↗
PubMed1992

Effects of calcium channel blockers on calcium uptake in rat aortic valve allografts.

BACKGROUND: The life span of human aortic valve allografts is finite, and many fail because of cusp rupture or calcification. Subcellular changes occurring in aortic valves in response to transplantation include the uptake of calcium. This study uses a heterotropic rat aortic valve transplant model to determine whether the calcium channel blockers diltiazem and verapamil might attenuate leaflet calcification. METHODS AND RESULTS: The 60 rats studied were divided into the following groups: 1) control: valves from normal, unoperated F1 generation of Lewis and Brown Norway cross (LBNF1) rats; 2) control: valves from syngeneic transplant combinations (Lewis/Lewis); 3) control: valves from allogeneic transplant combinations (LBNF1/Lewis, donor/recipient); 4) experimental: valves from allogeneic strain combinations treated with 30 mg/kg per day diltiazem; 5) experimental: valves from allogeneic strain combinations treated with 30 mg/kg per day verapamil. Drugs or saline (controls) were administered with osmotic pumps placed subcutaneously 2 days before transplantation. Animals were killed 3 weeks later, and the valves were harvested and prepared for calcium analysis. Energy-dispersive x-ray microanalysis was used to measure the calcium in a section of one leaflet from each valve studied. Paired t tests showed that allograft valves treated with diltiazem or verapamil contained significantly less calcium than allograft controls treated with saline (p < 0.001). When all five groups were subjected to one-way ANOVA, the valves in the allograft control group contained significantly more calcium than all other groups. All other groups were not different from each other. CONCLUSIONS: The calcium channel blockers verapamil and diltiazem were effective in preventing early calcification that occurs in aortic valves after transplantation. Thus, these agents might play a role in prolonging the life of human aortic valve allografts.

Analysis of Variance↗
PubMed1992

Pulmonary resection for fungal infection in children undergoing bone marrow transplantation.

Recipients of bone marrow transplants for hematologic malignancies are at risk for a variety of infectious complications. We have reviewed our experience with six patients 2 to 15 years of age who developed significant fungal infections of the lungs before or after bone marrow transplant. No patient was known to have active fungal or bacterial infection at the time bone marrow transplant was performed. In two patients fungal infections were diagnosed before bone marrow transplant, and operations were performed to permit bone marrow transplant under optimal conditions. Four patients had pulmonary mycoses discovered after bone marrow transplant, and underwent operation 12 to 24 days following transplant. Operations consisted of lobectomy (three), multiple unilateral wedge resections (one), staged segmentectomy and contralateral wedge resection (one), and staged bilateral wedge resection (one). Survival following bone marrow transplant was achieved for 6 months and 11 months in patients undergoing lung resection before transplant, and for 24, 30, 39, and 60 days in patients undergoing lung resections after transplant. Bone marrow transplant recipients are at high risk of pulmonary mycoses, and a vigorous search for occult fungal infections should be carried out before transplant. Aggressive operative treatment of fungal infections of the lungs combined with antifungal chemotherapy before transplant may offer the best hope of extended survival.

Adolescent↗
PubMed1991

Production of endothelium-dependent relaxation responses by saphenous vein grafts in the canine arterial circulation.

To determine if venous endothelium can acquire the ability to elicit endothelium-dependent relaxation responses, five dogs underwent femoral artery bypass with autogenous saphenous vein. The veins were harvested 15 to 17 months later. Endothelium-dependent relaxation was determined by measuring tension of deendothelialized coronary arteries mounted on a tensiometer and superfused with the effluent of the vein grafts. These grafts were perfused with acetylcholine and calcium ionophore A23187, which cause case vascular smooth muscle relaxation by means of endothelium-dependent relaxing factor production. Control arteries and veins were obtained from other dogs for comparison. In response to acetylcholine from 10(-9) to 10(-4) mol/L, the final cumulative relaxation produced in the detector coronary artery (mean +/- SD) was 64.2% +/- 25.7% by the control arteries, 14.2% +/- 5.5% by the vein bypass graft, and 5.3% +/- 5.6% by the control veins. In response to A23187 from 10(-8) to 10(-4) mol/L, the final cumulative relaxation was 66.2% +/- 19.0% by the control arteries, 30.6% +/- 8.9% by the vein bypass grafts, and 5.3% +/- 5.6% by the control veins. The differences were significant between the vein bypass grafts and the control arteries (p less than 0.04 for acetylcholine; p less than 0.04 for A23187) and the control veins (p less than 0.03 for acetylcholine; p less than 0.02 for A23187). Perfusion of saphenous veins used as chronic arterial bypass grafts with either acetylcholine or A23187 produced detector vessel relaxation, consistent with endothelium-dependent relaxing factor production. The magnitude of the relaxation response did not approach that from perfusion of control arteries.

Animals↗
PubMed1991

Aortic valve replacement with pulmonary or aortic allografts.

Limited availability of aortic valve allografts suggests consideration of pulmonary valve allografts for aortic valve replacement (AVR). From 1987 through 1990, 20 patients underwent AVR with cryopreserved aortic allografts (group 1). Five patients underwent AVR with pulmonary allografts (group 2) because no aortic allografts of the appropriate size were available. Indications for AVR in group 1 were endocarditis in five patients, aortic insufficiency in six, and aortic stenosis in nine. Indications for AVR in group 2 were endocarditis in two patients and aortic insufficiency in three. In group 1 there was one operative death and two late deaths resulting from noncardiac causes. There were no operative or late deaths in group 2. Follow-up was complete (group 1: 1-32 months [mean, 14 months]; group 2: 1-24 months [mean, 13 months]). All surviving patients remain in New York Heart Association (NYHA) class I or II. Postoperative catheterization was performed in 21 of 24 surviving patients. All patients have been followed since hospitalization with serial studies that included computerized cine tomography of the chest and echocardiograms. No false aneurysms, stenoses, or clinically significant regurgitation have occurred, although one patient in group 2 showed 2+ insufficiency at catheterization. One group 1 patient required repeat AVR for recurrent endocarditis. There were no reoperations in group 2. Although longer-term follow-up with larger numbers of patients is necessary, it seems that operative and early postoperative results for AVR have been similar with aortic and pulmonary valve allografts. In selected patients AVR with pulmonary allografts may be appropriate to consider when properly sized aortic allografts are unavailable.

Adult↗
PubMed1991

Pericardial influence on internal defibrillation energy requirements.

There is no consensus regarding optimal positioning of patch leads for implantation of automatic implantable cardioverter defibrillators. We compared the energy (in joules) required for 50% and 80% successful termination of ventricular fibrillation with titanium-mesh patch leads outside intact normal pericardium and directly on the epicardium in 13 open-chest dogs. Talc was then instilled into the pericardial space to stimulate adhesion formation and pericardial thickening. After 3 weeks of recovery, thoracotomy and defibrillation testing were repeated in nine dogs with the patch leads outside the thickened, adherent pericardium. There were no significant differences in defibrillation energy requirements between locations (p greater than 0.10). In addition, a comparison of electrical impedance measurements at 10 joules showed no significant differences (p greater than 0.30). In this animal model, defibrillation energy requirements were not altered by positioning the patch leads outside normal intact pericardium rather than placing them directly on the epicardium. Furthermore, thickened, adherent pericardium interposed between the patch leads and the heart does not increase defibrillation energy requirements. These data suggest that placement of automatic implantable cardioverter defibrillator patch leads outside the pericardium in patients (including those with pericardial adhesions from previous cardiac operations) will not adversely affect defibrillation efficacy and thus can simplify the implantation procedure.

Animals↗
PubMed1990

Prolonged extracorporeal life support of pediatric and adolescent cardiac transplant patients.

Options for mechanical support of pediatric patients with severe heart failure who are awaiting transplantation or have undergone transplantation are limited. This report examines 3 patients placed on extracorporeal life support (ECLS) while awaiting transplantation and 3 patients who underwent transplantation and suffered subsequent heart failure due to rejection or postoperative myocardial dysfunction. The overall survival rate was 2 of 6. The 2 surviving patients had a failing transplanted heart. There were no survivors among the patients placed on ECLS as a bridge to transplantation. In each case a contraindication to transplantation developed before a donor heart could be obtained. The mean time of ECLS support was 147.5 hours (range, 70 to 370 hours). The ECLS circuit did not affect cyclosporin levels or antirejection therapy. Extracorporeal life support can be used to support pediatric cardiac transplant patients with biventricular failure due to acute rejection or postoperative dysfunction. Although the results have been discouraging, ECLS may still have a role as a bridge to transplantation. However, complications can develop during ECLS that may preclude transplantation.

Adolescent↗