Association of Body Mass Index With Clinical Features and Outcomes in Adults With Fontan Palliation

Background With improving survival of patients with single ventricle physiology who underwent Fontan palliation, there is also an increase in the prevalence of overweight and obesity in these patients. This tertiary care single-center study aims to determine the association of body mass index (BMI) with the clinical characteristics and outcomes in adults with Fontan. Methods and Results Adult patients (aged ≥18 years) with Fontan who were managed at a single tertiary care center between January 1, 2000, and July 1, 2019, and had BMI data available were identified via retrospective review of medical records. Univariate and multivariable (after adjusting for age, sex, functional class, and type of Fontan) linear and logistic regression, as appropriate, were utilized to evaluate associations between BMI and diagnostic testing and clinical outcomes. A total of 163 adult patients with Fontan were included (mean age, 29.9±9.08 years), with a mean BMI of 24.2±5.21 kg/m² (37.4% of patients had BMI ≥25 kg/m²). Echocardiography data were available for 95.7% of patients, exercise testing for 39.3% of patients, and catheterization for 53.7% of patients. Each SD increase in BMI was significantly associated with decreased peak oxygen consumption (P=0.010) on univariate analysis and with increased Fontan pressure (P=0.035) and pulmonary capillary wedge pressure (P=0.037) on multivariable analysis. In addition, BMI ≥25 kg/m² was independently associated with heart failure hospitalization (adjusted odds ratio [AOR], 10.2; 95% CI, 2.79-37.1 [P<0.001]) and thromboembolic complications (AOR, 2.79; 95% CI, 1.11-6.97 [P=0.029]). Conclusions Elevated BMI is associated with poor hemodynamics and worse clinical outcomes in adult patients with Fontan. Whether elevated BMI is the cause or consequence of poor clinical outcomes needs to be further established.

Journey Toward Improved Long-Term Outcomes After Norwood-Sano Procedure: Focus on the Aortic Arch Reconstruction

The disadvantage of right ventricle-to-pulmonary artery (RV-PA) shunt is the need for more unplanned interventions to address stenosis in the shunt or branch pulmonary arteries, as compared to the modified Blalock-Taussig shunt group. Ring-enforced RV-PA PTFE conduit and dunk technique minimized these complications and right ventricle (RV) damage. Aortic arch obstruction increases afterload and leads to ventricular dysfunction and tricuspid regurgitation; therefore, most surgeons prefer to use homograft, autologous pericardium, or bovine pericardium to reconstruct the neoaorta. Artificial materials decrease the elastic properties, increase wall stiffness, and decrease the distensibility of the aorta; and as a result, RV function gradually deteriorates. This inelastic reconstructed aorta may be one of the reasons why long-term outcomes after the Fontan procedure are worse in hypoplastic left heart syndrome (HLHS) patients, in comparison to non-HLHS. Reconstruction of the neoaorta without any patch materials, or at least techniques that largely minimize the use of non-autologous materials, will offer a further refinement of our ability to optimize ventriculoarterial coupling and thereby long-term RV function.

Outcomes among adult survivors of total cavopulmonary Fontan palliation for single ventricle

OBJECTIVE

This tertiary centre study aims to identify factors associated with adverse outcomes in adult survivors with total cavopulmonary connection (TCPC) Fontan palliation for single ventricle.

METHODS

This retrospective review of medical records identified adult (≥18 years) survivors of TCPC Fontan palliation who were followed at a single tertiary centre between 1 January 2000 and 1 July 2019. Adverse outcomes were defined as arrhythmia, pacemaker/implantable cardioverter defibrillator placement, liver cirrhosis, protein losing enteropathy, hospitalisation for heart failure, thromboembolic complication and/or death.

RESULTS

160 adult TCPC patients met the inclusion criteria: 117 (73.1%) extracardiac and 43 (26.9%) lateral tunnel. The median (IQR) duration of follow-up since TCPC palliation was 17.5 (11.8-21.3) years. An adverse outcome occurred in 87 (54.4%) patients. Adverse outcome-free survival rates at 10, 20 and 25 years post TCPC were 89% (95% CI 82% to 93%), 60% (95% CI 50% to 69%) and 24% (95% CI 15% to 35%), respectively. On multivariate analysis, extracardiac Fontan (HR 2.21, 95% CI 1.20 to 4.08, p=0.011) was observed to be an independent risk factor for adverse outcomes after adjusting for age, race, morphology of the systemic ventricle and history of fenestration.

CONCLUSIONS

In this single-centre retrospective study of adult survivors of TCPC palliation, extracardiac Fontan was associated with an increased hazard for adverse outcomes. This finding could guide clinicians in developing risk modification strategies and management decisions to improve long-term outcomes in these patients.

360-Degree Cone Reconstruction for Ebstein's Anomaly

Several modifications of the cone procedure as first described by da Silva have been reported. We have used a complete 360-degree leaflet detachment coupled with a 60-degree counterclockwise rotation in performing the cone procedure in children and adults. We believe that complete leaflet detachment coupled with counterclockwise rotation provides both for better alignment of the leaflets and subvalvular apparatus and for a more symmetric distribution of tension after leaflet reattachment, thus potentially resulting in better valve function and longevity of repair.

S-Nitrosohemoglobin Levels and Patient Outcome After Transfusion During Pediatric Bypass Surgery

Banked blood exhibits impairments in nitric oxide (NO)‐based oxygen delivery capability, reflected in rapid depletion of S‐nitrosohemoglobin (SNO‐Hb). We hypothesized that transfusion of even freshly‐stored blood used in pediatric heart surgery would reduce SNO‐Hb levels and worsen outcome. In a retrospective review (n = 29), the percent of estimated blood volume (% eBV) replaced by transfusion directly correlated with ventilator time and inversely correlated with kidney function; similar results were obtained in a prospective arm (n = 20). In addition, an inverse association was identified between SNO‐Hb and postoperative increase in Hb (∆Hb), reflecting the amount of blood retained by the patient. Both SNO‐Hb and ∆Hb correlated with the probability of kidney dysfunction and oxygenation‐related complications. Further, regression analysis identified SNO‐Hb as an inverse predictor of outcome. The findings suggest that SNO‐Hb and ∆Hb are prognostic biomarkers following pediatric cardiopulmonary bypass, and that maintenance of red blood cell‐derived NO bioactivity might confer therapeutic benefit.

Scimitar Syndrome-Complex Surgical Revision 3 Decades After Repair

We present a case of a 39-year-old woman with scimitar syndrome who had a 2-patch repair 3 decades previously and presented with a right-to-left shunt of the inferior vena cava (IVC) to the left atrium resulting from baffle dehiscence. We discuss details of our reoperative repair.

Venous Myocardial Infarction in an Infant with Obstructed Totally Anomalous Pulmonary Venous Drainage and Coronary Sinus Ostial Atresia

We report a rare causal association between obstructed supracardiac totally anomalous pulmonary venous drainage and coronary sinus ostial atresia. Our 12-week-old patient developed venous myocardial infarction secondary to coronary venous hypertension because her sole route of coronary venous drainage was obstructed. She recovered after the obstruction was relieved by balloon dilation. Surgical repair then included anastomosis of the pulmonary venous confluence to the left atrium, ligation of the vertical vein, and unroofing of the coronary sinus. Coronary sinus ostial atresia is rarely diagnosed before autopsy.

Pyloric exclusion for treatment of complicated duodenal atresia

Duodenal atresia (DA) is a well-described congenital anomaly that usually responds well to surgical correction. Associated defects are common, and these confounding variables often influence outcome. The authors present a case of a newborn female with an unusual constellation of problems including DA with annular pancreas, trisomy 21, and coarctation of the aorta. She developed protracted complications postoperatively and was treated with an innovative surgical strategy.

Long-term Outcome and Risk of Heart Block After Surgical Treatment of Subaortic Stenosis

Although mortality following repair of subaortic obstruction is low, aggressive resection may increase morbidity. We sought to evaluate outcomes and risk of atrioventricular heart block (AVB) after subaortic resection in the current era. Simple obstruction was defined as a discrete subaortic membrane and complex as multilevel or diffuse narrowing. Limited resection included membranectomy and limited myomectomy. Aggressive resection included Konno, modified Konno, and Ross. Specified variables were obtained from a chart review. The 185 consecutive patients (1991-2008) ranged in age from 1 day to 21.8 years (5.1 ± 5.1 years) with 2 early and 4 late deaths. Actuarial survival was 97%, 95%, and 95% at 1, 5, and 10 years, respectively. Reoperations were required in 29 of 185 patients (15.7%); 2 required a third operation (1%). Freedom from reoperation in all patients was 97%, 83%, and 73% at 1, 5, and 10 years, respectively. Accessory mitral valve tissue ( P < .001) and age <3 months ( P = .004) predicted the need for reoperation. Transient or permanent high-degree AVB was documented in 33 of 185 patients (17.8%). Complex anatomy ( P = .01) and aggressive resection ( P < .001) increased the risk of acquiring AVB. The AVB was permanent in 21 of 185 (11.4%) patients, and pacemaker implantation was undertaken in 20 of 185 (10.8%) patients. Complex anatomy ( P = .04) and modified Konno procedure ( P = .03) increased the risk of acquiring a pacemaker. Aggressive resection lowered the frequency of recurrence but increased the risk of AVB. When aggressive resection is considered for long-term relief of subaortic obstruction, the risk of reobstruction must be balanced with the risk of AVB and the need for pacemaker implantation.

Management of deep wound complications with vacuum-assisted therapy after Berlin Heart EXCOR ventricular assist device placement in the pediatric population

Wound complications after ventricular assist device (VAD) placement remain a formidable challenge to surgeons. The Berlin Heart EXCOR VAD is a versatile pulsatile system that has been successful in pediatric patients of all ages and sizes. Prevention of device-related complications such as infection, particularly in pediatric patients, remains an essential issue in minimizing patient morbidity and mortality. The introduction of vacuum-assisted wound closure (VAC) therapy and its application in VAD-related wound complications provide an efficient and effective method for wound healing. We report our experience in the management of deep wound complications in two pediatric patients after placement of the Berlin Heart EXCOR VAD. The wound VAC system proved to achieve complete wound healing without any infectious complications.

Coarctation repair in neonates and young infants: is small size or low weight still a risk factor?

OBJECTIVE

Previous reports of neonatal coarctation repair demonstrate a high rate of recurrent arch obstruction in small neonates. This study assesses the effect of patient size on reintervention and survival in neonates and infants undergoing repair of simple aortic coarctation.

METHODS

From 1996 to 2006, 167 neonates and infants younger than 90 days with simple coarctation underwent repair. Median patient age was 16 days (range, 1-85 days). Median patient weight was 3.4 kg (range, 0.8-6.0 kg), with 29 patients weighing less than 2.5 kg. All 167 patients included in the study underwent repair through a left thoracotomy.

RESULTS

There was 1 early death (1/167, 0.6%). Median follow-up of 4.8 years (range, 0-11.8 years) demonstrated 2 late deaths unrelated to recurrent coarctation. Eighteen patients underwent intervention for recurrent arch obstruction a median of 0.48 years postoperatively (range, 0.14-9.8 years). All were treated with balloon angioplasty and have required no additional intervention. Actuarial freedom from reintervention was 90% at 1 year and 89% at 5 years for infants weighing more than 2.5 kg and 89% at 1 year and 86% at 5 years (P = .31) for infants weighing less than 2.5 kg. There was no difference between survival or reintervention for neonates 30 days of age or younger compared with infants 31 to 90 days of age. Use of polypropylene sutures and female sex did correlate with increased reintervention.

CONCLUSIONS

Low weight does not affect survival or reintervention rates after coarctation repair in neonates and infants less than 3 months of age. Balloon angioplasty is an effective treatment for recurrent obstruction after coarctation repair in infancy. In the current era, timing of the operation should be based on clinical status.

Cardiovascular surgery in children with Marfan syndrome or Loeys-Dietz syndrome

OBJECTIVE

This study was undertaken to assess the frequency and outcome of cardiovascular surgery in children with Marfan or Loeys-Dietz syndrome.

METHODS

A retrospective review from 2 regional Marfan subspecialty clinics was performed. Between 1997 and 2007, 204 children with Marfan syndrome and 17 children with Loeys-Dietz syndrome were followed serially. Of these patients, 35 were identified who had undergone cardiovascular surgery at 18 years of age or less. Demographic, echocardiographic, and surgical data were collected.

RESULTS

Surgery was performed at a median of 3 years (0-15 years) after diagnosis and a mean age of 11.5 +/- 6.2 years. Aortic root replacement was the initial surgery in 30 patients, and mitral valve surgery was the initial surgery in 8 patients, with 3 patients undergoing both. Aortic root replacement was performed using a composite root replacement in 9 patients and valve-sparing techniques in 21 patients (remodeling in 8 patients and reimplantation in 13 patients). Eight patients underwent reoperation at a mean of 4.7 +/- 3.0 years after aortic surgery: 3 for aortic insufficiency, 2 for dissection, 2 for valve thrombosis, and 1 for a distal aneurysm. Adverse outcomes included reoperation in 8 patients, aneurysm in 1 patient, and death due to dissection or stroke in 3 patients. Variables associated with an adverse outcome included preoperative aortic insufficiency, valve replacement, and absence of angiotensin-converting enzyme inhibitor therapy.

CONCLUSION

Patients with Marfan or Loeys-Dietz syndrome requiring surgery during childhood have a favorable long-term outcome. Those undergoing valve-sparing root replacement or mitral valve repair have a low risk for reoperation. Postoperative angiotensin-converting enzyme inhibitor therapy confers clinical benefit.

Postoperative Pericardial Adhesion Prevention Using Carbylan-SX in a Rabbit Model

INTRODUCTION

The presence of dense adhesions within the pericardial space complicates reoperative cardiac surgery. Prior attempts to reduce adhesion formation after primary cardiac surgery using medications or biomaterials have had variable success. Carbylan-SX (Carbylan Biosurgery Inc., Palo Alto, CA) is a hyaluronan-based biomaterial, which has been shown to be effective at reducing adhesions in a nonthoracic rat model. This study evaluates whether Carbylan-SX can effectively reduce postoperative adhesions within the pericardial cavity.

METHODS

Thirty-eight New Zealand white rabbits underwent a left lateral thoracotomy. A pericardiotomy was made and epicardial adhesions were induced on the anterior surface of the heart using a Dremel device (Racine, WI). The rabbits were divided into four groups: controls with abrasions only receiving no treatment (n=10), Carbylan-SX films (n=10), Carbylan-SX aerosolized hydrogel (n=10), and Seprafilm (n=8). The pericardial sac and chest were subsequently closed. Rabbits were sacrificed at a mean of 15 days. For histological analysis, each heart was divided into 12 separate 1 mm sections. Computer imaging software was used to measure the adhesion thickness and the mean of 12 random measurements for each animal was recorded and statistical analysis performed.

RESULTS

Histological analysis revealed all treatment groups to be significantly better than the control (2159 mum thickness, P<0.0001) at preventing adhesions. The Carbylan-SX film and Carbylan-SX aerosolized hydrogel both proved to be better at preventing adhesions than Seprafilm (Genzyme Corp., Cambridge, MA) with an average adhesion thickness of 454 and 577 microm, respectively, compared with 1319 microm for Seprafilm (P<0.0001 and P<0.0005, respectively). The Carbylan-SX film and Carbylan-SX aerosolized hydrogel were equally effective at preventing adhesion formation.

CONCLUSION

Carbylan-SX film and Carbylan-SX aerosolized crosslinkable hydrogel are equally effective methods of reducing postoperative pericardial adhesions within the pericardial cavity. Both the Carbylan-SX film and aerosolized hydrogel showed a significantly greater reduction in adhesions than Seprafilm. Clinical application of Carbylan-SX could have significant therapeutic implications in the future.

Intermediate-term results of repair for aortic, neoaortic, and truncal valve insufficiency in children

OBJECTIVE

Repair of aortic valve insufficiency is difficult, and durability is relatively unknown in children. This study evaluates the intermediate-term results of repair of the systemic semilunar valve, including the native aortic valve, neoaortic valve (anatomic pulmonary), and truncal valve.

METHODS

We reviewed the records of 54 children (aged 2 days to 18 years) who underwent repair of the functional aortic valve for moderate or greater insufficiency from 1991 to 2005. Valve anatomy was tricuspid aortic in 26 patients, bicuspid aortic in 11 patients, tricuspid neoaortic in 9 patients, bicuspid neoaortic in 1 patient, and truncal valve in 7 patients. Multiple surgical techniques were used in most of the 54 patients, including leaflet plication in 17, leaflet repair in 15, commissuroplasty in 32, pericardial cusp augmentation in 8, and sinus of Valsalva reduction in 3.

RESULTS

There was 1 early death and no late deaths. Actuarial freedom from reoperation was 68% at 5 years and 58% at 10 years. Freedom from aortic valve replacement was 82% at 5 years and 73% at 10 years. Duration of cardiopulmonary bypass was the most significant risk factor for reoperation with multivariate analysis. Of the 40 patients who have not undergone reoperation, 37 have had follow-up echocardiograms with the latest study (4.5 +/- 4.2 years) demonstrating trace to 1+ insufficiency in 23 patients, 1 to 2+ in 12 patients, 2 to 3+ in 1 patient, and 3 to 4+ in 1 patient.

CONCLUSION

Repair of the insufficient systemic semilunar valve offers acceptable 10-year freedom from reoperation and functional results, and should be considered for most children.

Towards the development of a pediatric ventricular assist device

The very limited options available to treat ventricular failure in children with congenital and acquired heart diseases have motivated the development of a pediatric ventricular assist device at the University of Pittsburgh (UoP) and University of Pittsburgh Medical Center (UPMC). Our effort involves a consortium consisting of UoP, Children's Hospital of Pittsburgh (CHP), Carnegie Mellon University, World Heart Corporation, and LaunchPoint Technologies, Inc. The overall aim of our program is to develop a highly reliable, biocompatible ventricular assist device (VAD) for chronic support (6 months) of the unique and high-risk population of children between 3 and 15 kg (patients from birth to 2 years of age). The innovative pediatric ventricular assist device we are developing is based on a miniature mixed flow turbodynamic pump featuring magnetic levitation, to assure minimal blood trauma and risk of thrombosis. This review article discusses the limitations of current pediatric cardiac assist treatment options and the work to date by our consortium toward the development of a pediatric VAD.

The PediaFlow pediatric ventricular assist device

The very limited options available to treat ventricular failure in patients with congenital and acquired heart diseases have motivated the development of a pediatric ventricular assist device (VAD). Our effort involves a consortium consisting of the University of Pittsburgh, Carnegie Mellon University, Children's Hospital of Pittsburgh, World Heart Corporation, and LaunchPoint Technologies, LLC. The overall aim of our program is to develop a highly reliable, biocompatible VAD for chronic support (6 months) of the unique and high-risk population of children between 3 kg and 15 kg (patients from birth to 2 years of age). The innovative pediatric VAD we are developing (PediaFlow) is based on a miniature mixed-flow turbodynamic pump featuring magnetic levitation, with the design goal being to assure minimal blood trauma and risk of thrombosis. This article discusses the limitations of current pediatric cardiac assist treatment options and the work to date by our consortium toward the development of a pediatric VAD.

Extracorporeal membrane oxygenation as a bridge to surgical treatment of flail tricuspid valve in a neonate

A term infant rapidly developed profound cyanosis and metabolic acidosis shortly after an uncomplicated vaginal delivery. Echocardiography identified a flail antero-superior leaflet of the tricuspid valve, which was producing severe tricuspid insufficiency. The clinical state deteriorated despite maximal medical management, and the patient was placed on venoarterial extracorporeal membrane oxygenation. Within twenty-four hours, the metabolic acidosis corrected, inotropic support was discontinued, and the patient was weaned to minimal ventilator settings. Successful repair of the tricuspid valve was performed two days later.

Complete versus partial atrioventricular canal: equal risks of repair in the modern era

OBJECTIVE

To assess the authors' hypothesis that with modern techniques, the current risks of repair for both complete and partial atrioventricular canal (AVC) are equal.

SUMMARY BACKGROUND DATA

Repair of complete AVC in infancy has traditionally carried a substantial mortality. In contrast, partial AVC has been considered low-risk for repair and can be performed later in childhood.

METHODS

This was a retrospective review of 63 infants and children who underwent complete (n = 40) or partial AVC repair (n = 23) from 1990 to 2001. Among complete AVC patients, the ventriculoseptal defect was repaired via an individualized approach according to each patient's specific anatomy: direct suturing without a patch (n = 5) and/or interposition of a small pericardial patch with a running suture (n = 35). In all 63 patients the left AV valve cleft was closed with interrupted sutures, and all atrial defects were closed with a pericardial patch. Data were analyzed with the Student test and Fisher exact test.

RESULTS

Results are expressed as the mean +/- SEM. Age at operation was 6.3 +/- 2.0 months for complete AVC and 47.5 +/- 6.1 months for partial AVC (P <.001). Bypass time was 65.2 +/- 2.3 minutes for complete AVC and 58.3 +/- 3.9 minutes for partial AVC ( P=.1). Reoperation rate was 7.5% (3/40) for complete AVC and 13.0% (3/23) for partial AVC ( P=.6). Early mortality was 2.5% (1/40) for complete AVC and 0% (0/23) for partial AVC ( P=.6).

CONCLUSIONS

Compared to partial AVC, patients presenting for complete AVC repair are significantly younger and manifest more complex anatomy and pathophysiology. However, utilizing modern techniques, including an individualized surgical approach to the ventricular component, repair of complete AVC yields reoperation and early mortality rates similar to those of partial AVC.

Role of nitric oxide in heparin-induced attenuation of hypoxic pulmonary vascular remodeling

Heparin and nitric oxide (NO) attenuate changes to the pulmonary vasculature caused by prolonged hypoxia. Heparin may increase NO; therefore, we hypothesized that heparin may attenuate hypoxia-induced pulmonary vascular remodeling via a NO-mediated mechanism. In vivo, rats were exposed to normoxia (N) or hypoxia (H; 10% O(2)) with or without heparin (1,200 U x kg-1 x day-1) and/or the NO synthase (NOS) inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME; 20 mg x kg-1 x day-1) for 3 days or 3 wk. Heparin attenuated increases in pulmonary arterial pressure, the percentage of muscular pulmonary vessels, and their medial thickness induced by 3 wk of H. Importantly, although L-NAME alone had no effect, it prevented these effects of heparin on vascular remodeling. In H lungs, heparin increased NOS activity and cGMP levels at 3 days and 3 wk and endothelial NOS protein expression at 3 days but not at 3 wk. In vitro, heparin (10 and 100 U x kg-1 x ml-1) increased cGMP levels after 10 min and 24 h in N and anoxic (0% O2) endothelial cell-smooth muscle cell (SMC) coculture. SMC proliferation, assessed by 5-bromo-2'-deoxyuridine incorporation during a 3-h incubation period, was decreased by heparin under N, but not anoxic, conditions. The antiproliferative effects of heparin were not altered by L-NAME. In conclusion, the in vivo results suggest that attenuation of hypoxia-induced pulmonary vascular remodeling by heparin is NO mediated. Heparin increases cGMP in vitro; however, the heparin-induced decrease in SMC proliferation in the coculture model appears to be NO independent.

Deletion of endothelial nitric oxide synthase exacerbates myocardial stunning in an isolated mouse heart model

BACKGROUND

While endothelial nitric oxide synthase (eNOS) is an important regulator of vascular tone, it is also constitutively expressed in cardiac myocytes and contributes to the regulation of myocardial function. The role of eNOS in ischemia-reperfusion is uncertain, however, with some studies showing beneficial effects while other studies demonstrate increased cardiac injury. We hypothesized that the beneficial effects of eNOS would predominate, and thus that targeted deletion of eNOS would exacerbate myocardial dysfunction following ischemia-reperfusion.

MATERIALS AND METHODS

ENOS knockout and wild-type mouse hearts were Langendorff-perfused using Krebs bicarbonate buffer and subjected to 20 min of global normothermic ischemia followed by 30 min of reperfusion. Myocardial function was measured using a ventricular balloon to determine time to onset of contracture, left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), and rate-pressure product (RPP). RESUKTS: Heart rate and coronary resistance were similar in both groups during baseline and reperfusion periods. Diastolic function as determined by peak LVEDP during ischemia and final LVEDP after reperfusion were worse in the eNOS knockout group vs wild-type (114 and 31 mmHg vs 92 and 18 mmHg, P <.05). Although RPP (heart rate x LVDP), measured as an index of systolic function, was initially better in eNOS knockouts (24216 vs 16353), wild-type hearts recovered more function than did eNOS knockout hearts by the end of 30 min of reperfusion (30892 vs 20522, P <.05).

CONCLUSIONS

These data suggest that the deletion of eNOS results in increased myocardial dysfunction following ischemia-reperfusion in an isolated heart model.

Nonanticoagulant heparin prevents coronary endothelial dysfunction after brief ischemia-reperfusion injury in the dog

BACKGROUND

Coronary endothelial dysfunction after brief ischemia-reperfusion (IR) remains a clinical problem. We investigated the role of heparin and N-acetylheparin, a nonanticoagulant heparin derivative, in modulating coronary endothelial function after IR injury, with an emphasis on defining the role of the nitric oxide (NO)-cGMP pathway in the heparin-mediated effect.

METHODS AND RESULTS

Male mongrel dogs were surgically instrumented, and the effects of both bovine heparin and N-acetylheparin on coronary endothelial vasomotor function, expressed as percent change from baseline flow after acetylcholine challenge, were studied after 15 minutes of regional ischemia of the left anterior descending artery (LAD) followed by 120 minutes of reperfusion. In dogs treated with placebo (saline), coronary vasomotor function was significantly (P</=0.03) decreased after 15 and 30 minutes of reperfusion (65+/-12% and 73+/-12%) compared with preischemia (103+/-6%). In contrast, the vasodilatory response to the endothelium-independent vasodilator sodium nitroprusside was maintained during reperfusion. Preischemic administration of both bovine heparin and N-acetylheparin (6.0 mg/kg IV) preserved coronary endothelial function throughout reperfusion. In a parallel group of dogs, nitrate/nitrite (NOx) and cGMP levels in the LAD were measured after treatment and during 15-minute reperfusion. Preischemic administration of N-acetylheparin caused a significant increase in basal NOx and cGMP levels compared with saline controls. Pretreatment with N-acetylheparin also caused a significant increase in NOx and cGMP levels in the LAD after 15 minutes of reperfusion compared with IR alone.

CONCLUSIONS

These results suggest that heparin preserves coronary endothelial function after brief IR injury by a mechanism independent of its anticoagulant activity and that the effect of heparin may be mediated in part by activation of the NO-cGMP pathway.

Non-anticoagulant heparin increases endothelial nitric oxide synthase activity: role of inhibitory guanine nucleotide proteins

Heparin, which is widely used clinically, has recently been shown to have specific properties affecting the vascular endothelium. We hypothesized that heparin stimulates endothelial nitric oxide synthase (eNOS) activity by a mechanism independent of its anticoagulant properties and dependent on an inhibitory guanine nucleotide regulatory protein (Gi). We determined the effect of both heparin and N-acetyl heparin (Non-Hep), a heparin derivative without anticoagulant properties, on eNOS activity in cultured bovine aortic endothelial cells and on endothelium-dependent relaxation in isolated vascular rings. The eNOS activity was determined by measuring both citrulline and nitric oxide (NO) metabolite formation. Heparin and Non-Hep dose-dependently increased basal eNOS activity (ED50 1.0 microgram/ml or 0.15 U/ml), an effect that was significantly inhibited by pertussis toxin (100 ng/ml), a Gi-protein inhibitor. Agonist-stimulated (acetylcholine, 10 microM) eNOS activity was potentiated following pre-treatment with both heparin and Non-Hep and reversed by pertussis toxin. Heparin and Non-Hep induced a dose-dependent relaxation in preconstricted thoracic aortic rings, an effect that was significantly inhibited by pertussis toxin, endothelial inactivation (following treatment with sodium deoxycholate) and NG-nitro-L-arginine-methyl ester (L-NAME). We conclude that heparin and non-anticoagulant heparin induce endothelium-dependent relaxation following activation of eNOS by a mechanism involving a Gi-protein. Administration of heparin derivatives without anticoagulant properties may have therapeutic implications for the preservation of eNOS in conditions characterized by endothelial dysfunction.

Heparin preserves nitric oxide activity in coronary endothelium during ischemia-reperfusion injury

BACKGROUND

Brief episodes of ischemia followed by reperfusion adversely affect endothelial vasomotor function. We hypothesized that heparin may impart a protective effect on the coronary endothelium during ischemia-reperfusion injury possibly via the nitric oxide pathway.

METHODS

Eighteen anesthetized dogs were randomly assigned to one of two treatment groups: saline solution or bovine heparin (6.0 mg x kg intravenously). A flow probe and cannula were placed in the left anterior descending artery. Functional recovery of the coronary endothelium was assessed after 15 minutes of ischemia and during 120 minutes of reperfusion after acetylcholine and nitroprusside challenge. In a separate group (n = 10), nitric oxide activity was measured as nitrate/nitrite levels and cyclic guanosine monophosphate levels in the left anterior descending artery.

RESULTS

Control dogs displayed a significant decrease in percent change of left anterior descending artery flow at 15, 30, and 60 minutes of reperfusion (67%+/-8%, 76% +/-11%, and 84%+/-8%) when compared with preischemic values (108+/-6; p < 0.01). Heparinized dogs, however, showed preservation of coronary endothelial function after acetylcholine challenge throughout reperfusion. Heparin-treated dogs also displayed a significant increase in nitrate/nitrite levels during reperfusion (37.3+/-4.1 micromol/L) when compared with the saline group (24.3+/-0.8 micromol/L; p < 0.03). Left anterior descending artery levels of cyclic guanosine monophosphate were also significantly increased after heparin administration (3.0+/-0.3 pmol/mg) when compared with ischemia-reperfusion alone (0.7+/-0.1 pmol/mg; p < 0.03).

CONCLUSIONS

Heparin preserves the vasoregulatory function of the coronary endothelium during brief episodes of ischemia-reperfusion injury, in part, via the nitric oxide pathway. Administration of heparin may have important therapeutic implications in the prevention of coronary endothelial dysfunction associated with reperfusion injury.

Early discharge of patients with new-onset atrial fibrillation after cardiovascular surgery

BACKGROUND

Atrial fibrillation is one of the most frequent complications after cardiovascular surgery. It may result in thromboembolic events, hemodynamic deterioration, and an increased length and cost of hospitalization.

METHODS

We retrospectively studied 504 consecutive adult patients undergoing cardiovascular surgery to determine whether patients with new-onset postoperative atrial fibrillation could be safely discharged in atrial fibrillation after ventricular rate had been controlled and anticoagulation initiated.

RESULTS

Postoperative atrial fibrillation occurred in 79 (16.2%) of the 487 survivors. Of these patients, 67 were discharged in sinus rhythm, whereas the remaining 12 were discharged in atrial fibrillation. Patients discharged in atrial fibrillation tended to be older, have higher Parsonnet risk scores, and have an increased incidence of valvular heart surgery. Despite this result, this cohort had a shorter length of hospital stay (7.3+/-2.0 days vs 10.9+/-9.3 days, p = 0.006), decreased hospital costs ($14,188+/-$2635 vs $23,016+/-$21,963, p = 0.002), and decreased hospital charges ($37,878+/-$7420 vs $58,289+/-$50,980, p = 0.003) compared with patients with atrial fibrillation discharged in sinus rhythm. In the 12 persons discharged home in atrial fibrillation, no repeat hospitalizations, bleeding complications, or thromboembolic events occurred.

CONCLUSION

A strategy of early discharge of patients with persistent postoperative atrial fibrillation appears promising and deserves prospective testing on a larger scale.

Heparin and nonanticoagulant heparin preserve regional myocardial contractility after ischemia-reperfusion injury: role of nitric oxide

OBJECTIVES

These studies were performed to determine the effect of heparin and nonanticoagulant heparin on myocardial function after ischemia-reperfusion and to further evaluate the role that the nitric oxide-cyclic guanosine monophosphate pathway plays in mediating the effect of heparin.

METHODS

Fifteen dogs were subjected to 15 minutes ischemia followed by 120 minutes reperfusion and pretreated with either saline solution, bovine heparin (6.0 mg/kg intravenously), or N-acetyl heparin (6.0 mg/kg intravenously), a heparin derivative without anticoagulant properties. The left anterior descending artery was occluded for 15 minutes and regional systolic shortening, a unitless measure of myocardial contractility, assessed during reperfusion. To evaluate the role of nitric oxide, the inhibitor N(omega)-nitro-L-arginine, 1.5 mg/kg intracoronary, was given before heparin administration. Myocardial levels of cyclic guanosine monophosphate, the second messenger of nitric oxide, were also measured in the N-acetyl heparin group using radioimmunoassay.

RESULTS

Regional systolic shortening was significantly decreased in the saline group during 60 and 120 minutes compared with before ischemia (9.2 +/- 1.0 and 9.0 +/- 0.9 vs 12.2 +/- 1.2, p < or = 0.0003). Heparin and N-acetyl heparin-treated dogs, however, showed preservation of systolic shortening throughout reperfusion. Administration of nitro-L-arginine significantly attenuated the protective effect of heparin (9.2 +/- 1.2 vs 12.7 +/- 1.1, p < or = 0.0001) and N-acetyl heparin (9.3 +/- 0.3 vs 12.8 +/- 0.4, p < or = 0.0001) during 120 minutes reperfusion. Myocardial levels of cyclic guanosine monophosphate were also significantly increased in the N-acetyl heparin group compared with saline (199.1 +/- 7.1 vs 103.5 +/- 4.5 pmol/mg, p < or = 0.0001).

CONCLUSIONS

Heparin preserves myocardial contractility after ischemia-reperfusion independent of its anticoagulant properties. Furthermore, the protective effects of heparin during ischemia-reperfusion are mediated, at least in part, through a nitric oxide-cyclic guanosine monophosphate pathway.

Maturation alters the pulmonary arterial response to hypoxia and inhaled nitric oxide in the presence of endothelial dysfunction

Surgical intervention in ever younger patients has led to a new appreciation of the unique physiology of the neonate. Specifically, newborn patients may respond very differently to hypoxic episodes and subsequent treatment with inhaled nitric oxide than older infants. In the current study, we examined differences in the pulmonary arterial response to hypoxia and inhaled nitric oxide in 48-hour-old (n = 8) and 14-day-old (n = 8) Yorkshire pigs in a model of nitric oxide synthase inhibition, as might be seen with endothelial dysfunction. Data were acquired after treatment with the nitric oxide synthase inhibitor N omega-nitro-L-arginine during hypoxia (inspired oxygen fraction = 0.10) and during inhalation of nitric oxide (100 ppm). Input mean impedance, reflecting distal arteriolar vasoconstriction, and characteristic impedance, reflecting proximal arterial geometry and distensibility, were calculated. The modulus of elasticity, a measure of the "stiffness" of the proximal vessels, was also calculated. Hypoxia caused a large increase in input mean impedance in both 48-hour-old and 14-day-old pigs (4826 +/- 272 versus 8744 +/- 488 dyne.cm.sec-5 and 3129 +/- 73 versus 6000 +/- 134 dyne.cm.sec-5, respectively; p = 0.0078). Characteristic impedance was not altered in the younger animals (1171 +/- 76 dyne.cm.sec-5) but increased in the older animals (419 +/- 15 versus 797 +/- 20 dyne.cm.sec-5. p = 0.0078). Older animals also experienced an increase in the modulus elasticity (1.92E06 +/- 3.2E05 versus 1.05E07 +/- 3.9E05 dyne/cm2, p = 0.0078). These data show that inhibited nitric oxide production, as might be seen in endothelial dysfunction, potentiates the profound hypoxic vasoconstriction observed at the level of the distal pulmonary arterioles in both neonatal and infant animals. In contrast, only older animals had a stiffening of the larger, more proximal vessels with hypoxia. In both age groups, inhaled nitric oxide effectively reduced the increases in impedance.

Pulmonary arterial endothelial dysfunction potentiates hypercapnic vasoconstriction and alters the response to inhaled nitric oxide

BACKGROUND

Pulmonary hypertensive crisis can be initiated by episodes of hypercapnic acidosis. Hypercapnic vasoconstriction in the newborn pulmonary arterial circulation may be modulated by endogenous production of nitric oxide (NO) by the endothelial cell and effectively treated with inhalation of NO.

METHODS

Sixteen 48-hour-old piglets were randomized to receive a hypercapnic challenge after administration of either saline vehicle or the NO synthase inhibitor N-omega-nitro-L-arginine (L-NA). Pulmonary arterial pressure, flow, and radius measurements were taken at baseline, after infusion of vehicle or L-NA, during hypercapnia (inspired fraction of carbon dioxide, 0.15), and during inhalation of NO (100 ppm). Fourier analysis was used to calculate input mean impedance, reflecting distal arteriolar vasoconstriction, and characteristic impedance, reflecting proximal arterial geometry and distensibility.

RESULTS

Input mean impedance was increased with L-NA administration. Animals pretreated with L-NA also underwent a much larger increase in input mean impedance with exposure to hypercapnia than untreated animals. Characteristic impedance increased in the treated animals, but not in the controls.

CONCLUSIONS

In the newborn pulmonary arterial circulation, endogenous NO production by the endothelial cell modulates resting tone distally, but not proximally. In addition, lack of a functional endothelium markedly potentiates the distal vasoconstrictor response to hypercapnia and produces proximal vasoconstriction. Despite impaired endothelial function, inhaled NO remains an effective vasodilator in hypercapnic pulmonary vasoconstriction.