High-sensitive troponinT, interleukin-8, and interleukin-6 link with post-surgery risk in infant heart surgery

BACKGROUND

This study focuses on biomarkers in infants after open heart surgery, and examines the association of high-sensitive troponin T (hs-cTnT), interleukin-6 (IL-6), and interleukin-8 (IL-8) with postoperative acute kidney injury (AKI), ventilatory support time and need of vasoactive drugs.

METHODS

Secondary exploratory study from a double-blinded clinical randomized trial (Mile-1) on 70 infants undergoing open heart surgery with cardiopulmonary bypass (CPB). In this sub-study, the entire study population was examined without considering the study drugs. The biomarkers' peak concentration (highest concentration at 2 or 6 h post-CPB) were used for statistical analyses.

RESULTS

Peak IL-8, hs-cTnT, and IL-6 occurred at 2 h post-CPB for 96%, 79%, and 63% of the patients, respectively. The odds ratio of developing AKI2-3 for IL-6 > 293 pg/mL was 23.4 (95% CI 5.3;104.0), for IL-8 > 100 pg/mL it was 11.5 (3.0;44.2), and for hs-cTnT >5597 pg/mL it was 6.1 (1.5; 24.5). In more than two third of the patients with the highest peak concentrations of IL-8, IL-6, and hs-cTnT, there was a need for ventilatory support for >24 h and use of vasoactive drugs at 24 h post-CPB, while in less than one third of the patients with the lowest peak concentrations of IL-8 and hs-cTnT such requirements were observed.

CONCLUSIONS

The peak biomarker concentrations and CPB-time strongly predicted AKI2-3, with IL-6 and IL-8 emerging as strongest predictors. Furthermore, our findings suggest that measuring hs-cTnT and IL-8 just 2 h post-CPB-weaning may assist in identifying infants suitable for early extubation and highlight those at risk of prolonged ventilation.

Outcomes of transcatheter pulmonary SAPIEN 3 valve implantation: an international registry

BACKGROUND AND AIMS

Transcatheter pulmonary valve implantation (TPVI) is indicated to treat right-ventricular outflow tract (RVOT) dysfunction related to congenital heart disease (CHD). Outcomes of TPVI with the SAPIEN 3 valve that are insufficiently documented were investigated in the EUROPULMS3 registry of SAPIEN 3-TPVI.

METHODS

Patient-related, procedural, and follow-up outcome data were retrospectively assessed in this observational cohort from 35 centres in 15 countries.

RESULTS

Data for 840 consecutive patients treated in 2014-2021 at a median age of 29.2 (19.0-41.6) years were obtained. The most common diagnosis was conotruncal defect (70.5%), with a native or patched RVOT in 50.7% of all patients. Valve sizes were 20, 23, 26, and 29 mm in 0.4%, 25.5%, 32.1%, and 42.0% of patients, respectively. Valve implantation was successful in 98.5% [95% confidence interval (CI), 97.4%-99.2%] of patients. Median follow-up was 20.3 (7.1-38.4) months. Eight patients experienced infective endocarditis; 11 required pulmonary valve replacement, with a lower incidence for larger valves (P = .009), and four experienced pulmonary valve thrombosis, including one who died and three who recovered with anticoagulation. Cumulative incidences (95%CI) 1, 3, and 6 years after TPVI were as follows: infective endocarditis, 0.5% (0.0%-1.0%), 0.9% (0.2%-1.6%), and 3.8% (0.0%-8.4%); pulmonary valve replacement, 0.4% (0.0%-0.8%), 1.3% (0.2%-2.4%), and 8.0% (1.2%-14.8%); and pulmonary valve thrombosis, 0.4% (0.0%-0.9%), 0.7% (0.0%-1.3%), and 0.7% (0.0%-1.3%), respectively.

CONCLUSIONS

Outcomes of SAPIEN 3 TPVI were favourable in patients with CHD, half of whom had native or patched RVOTs.

Absolute Quantification of Donor-Derived Cell-Free DNA in Pediatric and Adult Patients After Heart Transplantation: A Prospective Study

In this prospective study we investigated a cohort after heart transplantation with a novel PCR-based approach with focus on treated rejection. Blood samples were collected coincidentally to biopsies, and both absolute levels of dd-cfDNA and donor fraction were reported using digital PCR. 52 patients (11 children and 41 adults) were enrolled (NCT03477383, clinicaltrials.gov), and 557 plasma samples were analyzed. 13 treated rejection episodes >14 days after transplantation were observed in 7 patients. Donor fraction showed a median of 0.08% in the cohort and was significantly elevated during rejection (median 0.19%, p < 0.0001), using a cut-off of 0.1%, the sensitivity/specificity were 92%/56% (AUC ROC-curve: 0.78). Absolute levels of dd-cfDNA showed a median of 8.8 copies/mL and were significantly elevated during rejection (median 23, p = 0.0001). Using a cut-off of 7.5 copies/mL, the sensitivity/specificity were 92%/43% for donor fraction (AUC ROC-curve: 0.75). The results support the feasibility of this approach in analyzing dd-cfDNA after heart transplantation. The obtained values are well aligned with results from other trials. The possibility to quantify absolute levels adds important value to the differentiation between ongoing graft damage and quiescent situations.

Five year risk assessment and treatment patterns in patients with chronic thromboembolic pulmonary hypertension

AIMS

Repeated risk assessments and treatment patterns over long time are sparsely studied in chronic thromboembolic pulmonary hypertension (CTEPH); thus, we aimed to investigate changes in risk status and treatment patterns in incident patients with CTEPH over a 5 year period.

METHODS AND RESULTS

Descriptive and explorative study including 311 patients diagnosed with CTEPH 2008-2019 from the Swedish pulmonary hypertension registry, stratified by pulmonary endarterectomy surgery (PEA). Risk and PH-specific treatment were assessed in surgically treated (PEA) and medically treated (non-PEA) patients at diagnosis and up to 5 years follow-up. Data are presented as median (Q1-Q3), count or per cent. Prior to surgery, 63% in the PEA-group [n = 98, age 64 (51-71) years, 37% female] used PH-specific treatment and 20, 69, and 10% were assessed as low, intermediate or high risk, respectively. After 1 year post-surgery, 34% had no PH-specific treatment or follow-up visit registered despite being alive at 5 years. Of patients with a 5 year visit (n = 23), 46% were at low and 54% at intermediate risk, while 91% used PH-specific treatment. In the non-PEA group [n = 213, age 72 (65-77) years, 56% female], 28% were assessed as low, 61% as intermediate and 11% as high risk. All patients at high risk versus 50% at low risk used PH-specific treatment. The 1 year mortality was 6%, while the risk was unchanged in 57% of the patients; 14% improved from intermediate to low risk, and 1% from high to low risk. At 5 years, 27% had a registered visit and 28% had died. Of patients with a 5 year visit (n = 58), 38% were at low, 59% at intermediate and 1% at high risk, and 86% used PH-specific treatment.

CONCLUSIONS

Risk status assessed pre-surgery did not foresee long-term post-PEA risk and pre-surgery PH-specific treatment did not foresee long-term post-PEA treatment. Medically treated CTEPH patients tend to remain at the same risk over time, suggesting a need for improved treatment strategies in this group.

DOSE EVALUATION AND PROPOSAL OF LOCAL DIAGNOSTIC REFERENCE LEVELS FOR PAEDIATRIC CARDIAC CATHETERIZATIONS PERFORMED ON A HIGH-SENSITIVITY ANGIOGRAPHIC SYSTEM ALLOWING LOW-DOSE IMAGING

Radiation doses from paediatric cardiac catheterizations were analysed based on procedure type and patient weight, and local diagnostic reference levels (LDRLs) were proposed. The procedures were performed on a Siemens Artis Q.zen biplane system with high-sensitivity detectors allowing low-dose imaging. Good radiological practice, e.g. adapting dose level and frame rate continuously and minimizing the x-ray field with collimators, was routine during procedures. The median total dose-area-product (DAP) value was 58 μGym2 for diagnostic catheterizations, 48 μGym2 for interventional catheterizations and 33 μGym2 for myocardial biopsies. The median DAP per body weight was 4.0 μGym2 kg-1. The median total fluoroscopy time varied from 6.0 min for myocardial biopsies, to 9.7 and 10.5 min, respectively, for diagnostic and interventional catheterizations. The third quartile of the DAP values in each weight group was proposed as LDRL. LDRLs for fluoroscopy time were determined solely based on procedure type, due to the absence of weight dependence.

Levosimendan Versus Milrinone and Release of Myocardial Biomarkers After Pediatric Cardiac Surgery: Post Hoc Analysis of Clinical Trial Data

OBJECTIVES

We compared the effect of two inodilators, levosimendan and milrinone, on the plasma levels of myocardial injury biomarkers, that is, high-sensitivity troponin T and heart-type fatty acid binding protein, and on N-terminal prohormone of brain natriuretic peptide as a biomarker of ventricular function. We hypothesized that levosimendan could attenuate the degree of myocardial injury when compared with milrinone.

DESIGN

A post hoc, nonprespecified exploratory secondary analysis of the Milrinone versus Levosimendan-1 trial (ClinicalTrials.gov Identifier: NCT02232399).

SETTING

Two pediatric tertiary university hospitals.

PATIENTS

Infants 1-12 months old, diagnosed with ventricular septal defect, complete atrioventricular septal defect, or Tetralogy of Fallot undergoing corrective surgery with cardiopulmonary bypass.

INTERVENTIONS

Seventy patients received a loading dose of either levosimendan or milrinone at the start of cardiopulmonary bypass followed by an infusion of the respective drug, which continued for 26 hours.

MEASUREMENTS AND MAIN RESULTS

Plasma levels of the three cardiac biomarkers were measured prior to the initiation of cardiopulmonary bypass and 2, 6, and 24 hours after weaning from cardiopulmonary bypass. In both groups, the levels of high-sensitivity troponin T and heart-type fatty acid binding protein were highest at 2 hours post cardiopulmonary bypass, whereas the highest level of N-terminal prohormone of brain natriuretic peptide occurred at 24 hours post cardiopulmonary bypass. There was no significant difference in the biomarkers' plasma levels between the study groups over time. Neither was there a significant difference in the postoperative peak plasma levels of the cardiac biomarkers.

CONCLUSIONS

In this post hoc analysis of the MiLe-1 trial, there was no demonstrable difference in the postoperative cardiac biomarker profile of myocardial injury and ventricular function when comparing infants managed in the perioperative period with levosimendan versus milrinone.

Clinical course and outcome after treatment with ventricular assist devices in paediatric patients: A single-centre experience

BACKGROUND

Heart failure is a rare condition in the paediatric population, associated with high morbidity and mortality. When medical therapy is no longer sufficient, mechanical circulatory support such as a ventricular assist device can be used to bridge these children to transplant or recovery. Coagulation-related complications such as thrombi, embolism and bleeding events represent the greatest challenge in paediatric patients on mechanical support. We aimed to describe the outcomes and coagulation-related complications in this patient population at our institution.

METHODS

A total of 20 patients with either Berlin Heart EXCOR® or HeartWare® implantation were reviewed in this retrospective study. Study endpoints were survival to heart transplant, weaning due to recovery or death. Thrombotic events were defined as thrombus formation in the device or in the patient, or cardioembolic strokes. Bleeding events were defined as events requiring interventional surgery or transfusion of red blood cells.

RESULTS

The aetiology of heart failure included cardiomyopathy (n = 12), end-stage congenital heart disease (n = 6) and myocarditis (n = 2). Of the 20 patients, 12 were bridged to transplant, 7 recovered and could be weaned and 1 died. The median duration of mechanical support was 84 days (range: 20-524 days). At least one major or minor bleeding event occurred in 45% of the patients. Thrombotic events occurred 21 times in 10 patients. Four of the patients (20%) had no bleeding or thromboembolic event.

CONCLUSION

In all, 95% of the patients were successfully bridged to transplant or recovery. Bleeding events and thrombotic events were common.

Evidence of support used for drug treatments in pediatric cardiology

BACKGROUND AND AIMS

Clinical support systems are widely used in pediatric care. The aim of this study was to assess the support for drug treatments used at pediatric cardiac wards and intensive care units in Sweden.

METHODS

Drug information, such as type of drug, indication, dose, and route of administration, for all in-hospital pediatric cardiac patients, was included in the study. Treatments were classified as either on-label (based on product information) or off-label. Support for off-label treatment was stratified by the use of clinical support systems (the national database on drugs, local, or other clinical experience guidelines).

RESULTS

In all, 28 patients were included in the study. The total number of drug treatments was 233, encompassing 65 different drugs. Overall, 175 (75%) treatments were off-label. A majority of off-label drug treatments were supported by other sources of information shared by experts. A total of 7% of the drug treatments were used without support.

CONCLUSION

Off-label drug treatment is still common in Swedish pediatric cardiac care. However, the majority of treatments were supported by the experience shared in clinical support systems.

KEY POINTS

Seventy-five percent of all prescriptions in pediatric cardiology care were off-label.A majority of patients received three or more drug treatments off-label.Use of clinical support systems and guidelines was common, but in 7% of all drug treatments, no support was found for the chosen treatment.

Survival in Children With Congenital Heart Disease: Have We Reached a Peak at 97%?

Background

Despite advances in pediatric health care over recent decades, it is not clear whether survival in children with congenital heart disease (CHD) is still increasing.

Methods and Results

We identified all patients with CHD using nationwide Swedish health registries for 1980 to 2017. We examined the survival trends in children with CHD; we investigated the mortality risk in patients with CHD compared with matched controls without CHD from the general population using Cox proportional regression models and Kaplan–Meier survival analysis. Among 64 396 patients with CHD and 639 012 matched controls without CHD, 3845 (6.0%) and 2235 (0.3%) died, respectively. The mean study follow‐up (SD) was 11.4 (6.3) years in patients with CHD. The mortality risk was 17.7 (95% CI, 16.8–18.6) times higher in children with CHD compared with controls. The highest mortality risk was found during the first 4 years of life in patients with CHD (hazard ratio [HR], 19.6; 95% CI, 18.5–20.7). When stratified by lesion group, patients with non‐conotruncal defects had the highest risk (HR, 97.2; 95% CI, 80.4–117.4). Survival increased substantially according to birth decades, but with no improvement after the turn of the century where survivorship reached 97% in children with CHD born in 2010 to 2017.

Conclusions

Survival in children with CHD has increased substantially since the 1980s; however, no significant improvement has been observed this century. Currently, >97% of children with CHD can be expected to reach adulthood highlighting the need of life‐time management.

Durable circulatory support with a paracorporeal device as an option for pediatric and adult heart failure patients

OBJECTIVES

Not all patients in need of durable mechanical circulatory support are suitable for a continuous-flow left ventricular assist device. We describe patient populations who were treated with the paracorporeal EXCOR, including children with small body sizes, adolescents with complex congenital heart diseases, and adults with biventricular failure.

METHODS

Information on clinical data, echocardiography, invasive hemodynamic measurements, and surgical procedures were collected retrospectively. Differences between various groups were compared.

RESULTS

Between 2008 and 2018, a total of 50 patients (21 children and 29 adults) received an EXCOR as bridge to heart transplantation or myocardial recovery. The majority of patients had heart failure compatible with Interagency Registry for Mechanically Assisted Circulatory Support profile 1. At year 5, the overall survival probability for children was 90%, and for adults 75% (P = .3). After we pooled data from children and adults, the survival probability between patients supported by a biventricular assist device was similar to those treated with a left ventricular assist device/ right ventricular assist device (94% vs 75%, respectively, P = .2). Patients with dilated cardiomyopathy had a trend toward better survival than those with other heart failure etiologies (92% vs 70%, P = .05) and a greater survival free from stroke (92% vs 64%, P = .01). Pump house exchange was performed in nine patients due to chamber thrombosis (n = 7) and partial membrane rupture (n = 2). There were 14 cases of stroke in eleven patients.

CONCLUSIONS

Despite severe illness, patient survival on EXCOR was high, and the long-term overall survival probability following heart transplantation and recovery was advantageous. Treatment safety was satisfactory, although still hampered by thromboembolism, mechanical problems, and infections.

Case Report: Disseminated Systemic Embolism of Lipiodol After Lymphography for Plastic Bronchitis After Fontan Repair

Lipiodol-based lymphangiography is not only a diagnostic tool for visualization of lymphatic disorders such as plastic bronchitis (PB), but also aims a therapeutic effect by embolizing lymph leakages. We performed such percutaneous lymphatic embolization for PB in a Fontan patient with proven absence of right-to-left shunt, and demonstrated important lymphatic abnormalities in the mediastinum. Shortly after the procedure, the patient developed severe convulsive seizures, revealing multiple cerebral embolisms of Lipiodol. Radiological images were impressive, yet the clinical neurological outcome was favorable. Lipiodol-based lymphography in Fontan patients with plastic bronchitis should be avoided as this subgroup is more likely to have developed lympho-pulmonary venous connections which allow systemic emboli.

2019 updated consensus statement on the diagnosis and treatment of pediatric pulmonary hypertension: The European Pediatric Pulmonary Vascular Disease Network (EPPVDN), endorsed by AEPC, ESPR and ISHLT

The European Pediatric Pulmonary Vascular Disease Network is a registered, non-profit organization that strives to define and develop effective, innovative diagnostic methods and treatment options in all forms of pediatric pulmonary hypertensive vascular disease, including pulmonary hypertension (PH) associated with bronchopulmonary dysplasia, PH associated with congenital heart disease (CHD), persistent PH of the newborn, and related cardiac dysfunction. The executive writing group members conducted searches of the PubMed/MEDLINE bibliographic database (1990-2018) and held face-to-face and web-based meetings. Ten section task forces voted on the updated recommendations, based on the 2016 executive summary. Clinical trials, meta-analyses, guidelines, and other articles that include pediatric data were searched using the term "pulmonary hypertension" and other keywords. Class of recommendation (COR) and level of evidence (LOE) were assigned based on European Society of Cardiology/American Heart Association definitions and on pediatric data only, or on adult studies that included >10% children or studies that enrolled adults with CHD. New definitions by the World Symposium on Pulmonary Hypertension 2018 were included. We generated 10 tables with graded recommendations (COR/LOE). The topics include diagnosis/monitoring, genetics/biomarkers, cardiac catheterization, echocardiography, cardiac magnetic resonance/chest computed tomography, associated forms of PH, intensive care unit/lung transplantation, and treatment of pediatric PH. For the first time, a set of specific recommendations on the management of PH in middle- and low-income regions was developed. Taken together, these executive, up-to-date guidelines provide a specific, comprehensive, detailed but practical framework for the optimal clinical care of children and young adults with PH.

Perioperative monitoring of platelet function in paediatric cardiac surgery by thromboelastometry, or platelet aggregometry?

BACKGROUND

Impaired platelet function increases the risk of bleeding complications in cardiac surgery. Reliable assessment of platelet function can improve treatment. We investigated whether thromboelastometry detects clinically significant preoperative, perioperative, and postoperative adenosine diphosphate (ADP)-dependent platelet dysfunction in paediatric cardiac surgery patients.

METHODS

Fifty-seven children were included in a single-centre prospective observational study. Clot formation (modified rotational thromboelastometry with heparinase, HEPTEM) and platelet aggregation (multiple electrode aggregometry) were analysed at five time points before, during, and after surgery. The accuracy of thromboelastometric indices of platelet function [maximal clot firmness (MCF) and clot formation time (CFT)] to detect ADP-dependent platelet dysfunction (defined as ADP-induced aggregation ≤30 units) was calculated with receiver operating characteristics analysis, which also identified optimal cut-off levels. Positive and negative predictive values for the identified cut-off levels (CFT≥166 s; MCF≤43 mm) to detect platelet function were determined.

RESULTS

The MCF and CFT were highly accurate in predicting platelet dysfunction during cardiopulmonary bypass [CPB; area under the aggregation curve 0.89 (95% confidence interval 0.80-0.97) and 0.86 (0.77-0.96), respectively] but not immediately after CPB [0.64 (0.48-0.79) and 0.67 (0.52-0.82), respectively] or on arrival at the intensive care unit [0.53 (0.37-0.69) and 0.60 (0.44-0.77), respectively]. The positive and negative predictive values were acceptable during CPB (87 and 67%, respectively, for MCF≤43 mm; 80 and 100% for CFT≥166 s) but markedly lower after surgery.

CONCLUSION

In paediatric cardiac surgery, thromboelastometry has acceptable ability to detect ADP-dependent platelet dysfunction during, but not after, CPB.

The highest mortality rates in childhood dilated cardiomyopathy occur during the first year after diagnosis

Aim

The aim of the study was to assess the incidence, mortality and morbidity of dilated cardiomyopathy (DCM) and noncompaction of the left ventricle (LVNC) in Swedish children.

Methods

We reviewed hospital records of all children with dilated cardiomyopathy (DCM) or left ventricular noncompaction cardiomyopathy (LVNC) up to the age of 18 in the healthcare region of western Sweden from 1991 to 2015.

Results

In total, 69 cases (61% males) were identified. The combined incidence of DCM and LVNC was 0.77 (95% CI 0.59‐0.96) per 100 000 person years. Children were divided into six groups, and their outcomes were analysed depending on their aetiology. Idiopathic DCM was reported in 43%, and familial dilated and left ventricular noncompaction aetiology was present in 32%. DCM due to various diseases occurred in 8%. DCM associated with neuromuscular diseases was present in 16%. The overall risk of death or receiving transplants in children with idiopathic and familial DCM was 30% over the study period, and 21% died in the first year after diagnosis.

Conclusion

The combined incidence of DCM and LVNC was similar to previous reports. Most children with idiopathic DCM presented during infancy, and mortality was highest during the first year after diagnosis.

Earlier detection of coagulopathy with thromboelastometry during pediatric cardiac surgery: a prospective observational study

OBJECTIVE

Earlier detection of coagulopathy in pediatric cardiac surgery patients.

AIM

To determine whether thromboelastometry (TEM) analysis before weaning from cardiopulmonary bypass (CPB) and hemoconcentration is predictive of post-CPB results and whether analysis of clot firmness already after 10 min yields reliable results.

BACKGROUND

Cardiac surgery with CPB induces a coagulopathy that may contribute to postoperative complications. Earlier detection increases the possibility of initiating countermeasures. METHODS/MATERIAL: Fifty-six pediatric cardiac surgery patients were included in a prospective observational study. HEPTEM and FIBTEM clotting time (CT), clot formation time (CFT), and clot firmness after 10 min (A10) and at maximum (MCF) were analyzed during CPB and after CPB and ultrafiltration with modified rotational thromboelastometry (ROTEM). The analyses were compared, and correlations and differences were calculated.

RESULTS

Hemoconcentration with modified ultrafiltration increased hematocrit from 28 ± 3 to 37 ± 4% (P < 0.001). Correlation coefficients of the TEM variables during and after CPB ranged from 0.61 to 0.82 (all P < 0.001). HEPTEM-CT and HEPTEM-MCF differed significantly but the differences were marginal. Both HEPTEM and FIBTEM A10 measurements during CPB were significantly less than MCF (P < 0.001 for both), but the correlations were highly significant (HEPTEM: r = 0.95, P < 0.001; FIBTEM: r = 0.96, P < 0.001), and the differences were predictable, with narrow confidence intervals (HEPTEM: -8.2 mm (-8.9 to -7.5); FIBTEM: -0.5 mm (-0.7 to -0.3).

CONCLUSION

The results suggest that intraoperative TEM analyses can be accelerated by analyzing HEPTEM/FIBTEM on CPB before hemoconcentration and by analyzing clot firmness already after 10 min.

First two decades of paediatric heart transplantation in Sweden - outcome of listing and post-transplant results

AIMS

To evaluate outcome in the first generation of children with end-stage heart disease to whom heart transplantation was available.

METHODS

Retrospective review of all 135 Swedish children <18 years old listed for heart transplantation 1989-2009, followed to December 31, 2009, including 74 (55%) with cardiomyopathy and 61 (45%) with congenital heart disease; 34 (25%) were infants (<1 year). Cumulative risk of requiring heart transplantation was 1:17,300 (11 patients who improved were omitted from outcome analysis).

RESULTS

Waiting-list mortality was 31% (44% in infants). Median waiting time in 82 transplanted patients was 57 days (0-585 days). Post-transplant follow-up time was median 5.9 years (0.03-20.1 years), and actuarial survival was 92% at 1 year, 82% at 5 years, 76% at 10 years and 58% at 15 years. Survival after listing was 64% at 1 year, 58% at 5 years, 52% at 10 years and 40% at 15 years. Post-transplant complications included rejections (34%), malignancies (12%), renal failure (8%), coronary artery vasculopathy (6%) and re-transplantation (5%). Among 64 survivors, 84% were free of complications affecting prognosis.

CONCLUSION

High waiting-list mortality and post-transplant attrition precluded 60% of this pioneer population from reaching adulthood. Functional status in survivors is generally good.

Intraoperative thromboelastometry is associated with reduced transfusion prevalence in pediatric cardiac surgery

BACKGROUND

The majority of pediatric cardiac surgery patients receive blood transfusions. We hypothesized that the routine use of intraoperative thromboelastometry to guide transfusion decisions would reduce the overall proportion of patients receiving transfusions in pediatric cardiac surgery.

METHODS

One hundred pediatric cardiac surgery patients were included in the study. Fifty patients (study group) were prospectively included and compared with 50 procedure- and age-matched control patients (control group). In the study group, thromboelastometry, performed during cardiopulmonary bypass, guided intraoperative transfusions. Intraoperative and postoperative transfusions of packed red blood cells, fresh frozen plasma, platelets, and fibrinogen concentrates, and postoperative blood loss and hemoglobin levels were compared between the 2 groups.

RESULTS

The proportion of patients receiving any intraoperative or postoperative transfusion of packed red blood cells, fresh frozen plasma, platelets, or fibrinogen concentrates was significantly lower in the study group than in the control group (32 of 50 [64%] vs 46 of 50 [92%], respectively; P < 0.001). Significantly fewer patients in the study group received transfusions of packed red blood cells (58% vs 78%, P = 0.032) and plasma (14% vs 78%, P < 0.001), whereas more patients in the study group received transfusions of platelets (38% vs 12%, P = 0.002) and fibrinogen concentrates (16% vs 2%, P = 0.015). Neither postoperative blood loss nor postoperative hemoglobin levels differed significantly between the study group and the control group.

CONCLUSIONS

The results suggest that routine use of intraoperative thromboelastometry in pediatric cardiac surgery to guide transfusions is associated with a reduced proportion of patients receiving transfusions and an altered transfusion pattern.

Influence of Early Antihypertensive Treatment on Vascular and Cardiac Design in SHR with and without Renal Hypertension

The present study was designed to explore to what extent pressure reduction by antihypertensive therapy and pressure elevation by renal hypertension are able to affect structural vascular and cardiac changes in young spontaneously hypertensive rats (SHR). Pressure elevation in SHR was induced by means of superimposing 2 kidney, 1 clip renal hypertension (2K1C). Pressure reduction was achieved by means of the vasoselective calcium antagonist felodipine from 6 to 13 weeks of age in both clipped and unclipped SHR. Vascular structure of the skeletal muscle was assessed hemodynamically by perfusing a hindlimb preparation and left ventricular dimensions were calculated from pressure-volume relationships of isolated hearts arrested in diastole. Induction of renal hypertension in SHR resulted, besides augmentation of arterial pressure in a marked concentric left ventricular hypertrophy, i.e. elevations of wall thickness to internal radius ratio. Likewise, in renal hypertensive SHR, a structural adaptation of the skeletal muscle vascular bed occurred, reflected as elevations of minimal vascular resistance and maximal generated perfusion pressure. Antihypertensive treatment for 8 weeks with felodipine reduced and also prevented mean arterial pressure from increasing further in SHR, and in SHR with superimposed renal hypertension by approximately 15% (p < 0.001 for both). In renal hypertensive SHR, felodipine partly prevented the development of exaggerated structural changes, both in the heart and in the skeletal muscle vascular bed, as reflected by reduced wall thickness to internal radius ratio and reduced minimal vascular resistance by 22% and maximal pressure response by 10% respectively (p < 0.01 for both parameters).(ABSTRACT TRUNCATED AT 250 WORDS)

Brain natriuretic peptide assessed at long-term follow-up before and after maximal exercise in surgically palliated patients with functionally univentricular hearts

We evaluated the concentrations of brain natriuretic peptide in the plasma as a marker of systolic ventricular function before and after maximal exercise in 15 surgically palliated patients with functionally univentricular hearts, with apparently good ventricular function. Of the patients, 6 with median age of 14.6 years, and a range from 12.5 to 17.9 years, had been palliated by construction of a total cavopulmonary connection, while the other 9 patients, with a median age of 32.1 years, and a range from 15.6 to 54.2 years, had undergone the classical Fontan procedure. We used 8 healthy individuals, with a median age of 13.9 years, and a range from 12.8 to 14.2 years, as a control group for the measurements of brain natriuretic peptide. The values of the peptide were significantly higher in those with the classical Fontan procedure, both before, when the median value was 131.8 nanogram per litre, with a range from 0.5 to 296.4, and after maximal exercise, when the median value was 108.1, with a range from 0.1 to 235.9. The comparable values in those with a total cavopulmonary connection were a median of 12.8, and a range from 0.5 to 39.1 before, and a median of 9.7, with a range from 2.7 to 26.2 after maximal exercise. The median value for the control group was 13.1, with a range from 2.6 to 38.7 before exercise (p = 0.016), and a median of 24.1, with a range from 5.8 to 66.7 after maximal exercise (p = 0.03), respectively. In the control subjects, the level of the peptide increased by a median of 9.7 nanograms per litre, with a range from 1.2 to 28.0 after maximal exercise (p = 0.008). The level was unchanged after maximal exercise in those with classical Fontan procedures and total cavopulmonary connections, with a difference between levels before and after exercise of a median of 5.9 nanogram per litre, and a range from -23.7 to 31.0 (p = 0.96), and a median of -1.0 nanogram per litre, with a range from -12.0 to 3.9 (p > 0.99), respectively. We conclude that maximal exercise did not increase the level of brain natriuretic peptide level in those patients with the classical Fontan procedure, nor those with a total cavopulmonary connection, findings which may indicate that systolic ventricular dysfunction is not the major cause of the decreased working capacity observed in patients with well functioning palliated functionally univentricular hearts.

Increased plasma levels of natriuretic peptide type B and A in children with congenital heart defects with left compared with right ventricular volume overload or pressure overload

AIM

Natriuretic peptide levels B (BNP) and A (ANP) have been described in children with congenital heart defects (CHD) with pressure and volume overload. However, the impact of ventricular morphology per se on natriuretic peptide levels has not been reported. The aim of the present study was to evaluate plasma BNP and ANP in children with CHD with left or right ventricular volume or pressure overload.

METHODS AND RESULTS

Plasma BNP and ANP were analysed in 61 children, median age 3.1 (0.3-16.2) years. Haemodynamic load was evaluated by echo-Doppler and/or catheterization measurements and classified as: pressure overload of the right (RV pressure) or left (LV pressure) ventricle, or volume overload of the right (RV volume) or left (LV volume) ventricle, of a sufficient degree to indicate surgery/catheter intervention. Twenty-three children, with a median age of 1.1 (0.1-8.3) years, without heart disease, served as controls for the natriuretic peptide measurements. Children in the LV volume group had significantly higher BNP and ANP values, 55.4 ng l-1 (10.7-352) and 164 (31.8-346), than children in the RV volume, 15.6 (0.0-105.1) and 57.2 (11.3-234.1), LV pressure, 6.8 (0.7-170) and 40.8 (12.6-210), and RV pressure, 18.0 (5.0-29.1) and 69.3 (8.7-182), groups respectively (P<0.0001). The values in the LV pressure group were close to the values in the Control group, 4.7 (0.0-17.7) and 32.9 (11.7-212.1), respectively (P=0.051 and P=0.378, respectively).

CONCLUSIONS

Plasma concentrations of BNP and ANP were higher in children with CHD with left ventricular volume overload compared with right ventricular volume overload or pressure overload.

Creation and enlargement of atrial defects in congenital heart disease

Transcatheter creation and enlargement of interatrial defects (IAD) may improve hemodynamics; however, procedural outcomes have not been well defined. Hospital records were reviewed for children who underwent percutaneous procedures to create and enlarge an IAD and were grouped as follows: (1) right and (2) left heart obstructive lesions, (3) left atrial (LA) decompression during left heart assist, (4) failing Fontan circulation, and (5) miscellaneous. Forty-five children (mean age, 3.4 +/- 4.7 years; 30 (67%) male) were identified. In group 1 (n = 6), all achieved endpoints of right atrial (RA) decompression (n = 2), improved left ventricular filling (n = 3), or improved arterial saturations (n = 1). In group 2 (n = 18), mean LA pressure decreased (21 +/- 6 to 13 +/- 5 mmHg, p < 0.001) and arterial saturations increased (61 +/- 13% to 78 +/- 11%, p < 0.001). All except 2 patients achieved definitive repair, further palliation (n = 9), or heart transplantation (HTX) (n = 7). In group 3 (n = 5), the LA was decompressed (21 to 13 mmHg, p = 0.03) in all, and all except 1 patient survived to HTX (n = 2) or full recovery (n = 2). In group 4 (n = 11), of 7 patients with a low cardiac output syndrome after surgery, despite improved atrial shunting, 3 died and 1 required a HTX. In group 5 (n = 5), RA decompression (n = 1) or improved arterial saturation (n = 4) was achieved in all. Overall, 5-year HTX free survival was 75%. Mechanical ventilation before the procedure (p < 0.001), the need for a blade septostomy (p = 0.002), and higher LA pressures after the procedure (p = 0.04) independently predicted mortality or the requirement for HTX. Transcatheter optimization of an atrial communication can help optimize treatment strategies and has a low procedural risk.

Clinical signs of heart failure are associated with increased levels of natriuretic peptide types B and A in children with congenital heart defects or cardiomyopathy

AIM

To study whether natriuretic peptide types B (BNP) and A (ANP) reflect clinical signs of heart failure (CSHF) in children with congenital heart defects or cardiomyopathy resulting in different types of haemodynamic situations, such as pressure overload in coarctation of the aorta (CoA), volume overload in ventricular septal defect (VSD) or systolic dysfunction in dilated cardiomyopathy (DCM).

METHODS

Blood samples for plasma P-BNP and P-ANP were taken before procedures during regular investigation from 26 children (9 CoA, 11 VSD and 6 DCM). The ordinary paediatric cardiologist performed the cardiac evaluation and the data were retrieved from medical charts. CSHF was considered positive if two of the following criteria were fulfilled: reduced physical capacity, feeding disorders, dyspnoea, tachypnoea, hepatomegaly and oedema. The statistical methods were non-parametric.

RESULTS

0/9 children with CoA, 5/11 with VSD and 6/6 with DCM had CSHF. In children with CSHF, P-BNP and P-ANP were higher, 263 ng l(-1) (range 47.5-1300) and 303 ng l(-1) (range 168-466), than in those without CSHF, 12.3 ng l(-1) (range 4.8-30.8) and 42.9 ng l(-1) (range 13.7-189), respectively (p < 0.001, Mann-Whitney U-test), irrespective of the diagnosis. The same relationship was also found in the group of children with VSD.

CONCLUSION

Plasma levels of ANP and BNP increase in children with CSHF. This increase is seen irrespective of whether it is due to systolic dysfunction, as in children with DCM, or to a volume overload with a normal systolic function, as in children with VSD.

Increased left ventricular mass in obese adolescents*1

AIMS

An increase of left ventricular mass (LVM) has been reported in obese adolescents in previous studies using echocardiography. The aim of our study was to determine the extent of the increase in LVM and correlation to other risk factors using cardiac magnetic resonance imaging in obese and lean adolescents.

METHODS AND RESULTS

Nineteen obese and 20 lean adolescents were recruited. Following resting blood pressure measurements and blood sampling for insulin, triglycerides, and cholesterol levels, all subjects underwent cardiac magnetic resonance examination to assess LVM. LVM adjusted for body height was 16% greater in obese compared to lean adolescents (median 66 g/m, p = 0.0042). Obese subjects had higher resting systolic blood pressures than controls (median 115 vs. 110 mmHg, p = 0.0077) and higher fasting triglyceride and insulin levels. HDL-cholesterol levels were lower in the obese group compared with the lean group.

CONCLUSIONS

Obese adolescents had a higher LVM than age-matched lean subjects, which correlated mainly with body mass index and systolic blood pressure. These findings add to the established cardiovascular risk profile of obese adolescents.

Increased levels of brain and atrial natriuretic peptides after the first palliative operation, but not after a bidirectional glenn anastomosis, in children with functionally univentricular hearts

We evaluated the concentrations of the brain and atrial natriuretic peptides in the plasma as markers of ventricular function and volume load in children with functionally univentricular hearts. We studied 7 children aged from 0.5 to 0.7 years with functionally univentricular hearts who had undergone a first palliative operation, and 10 children aged from 1.8 to 3.7 years who had undergone a bidirectional Glenn anastomosis at ages ranging from 0.4 to 1.0 year. As a control group, we studied 14 children without heart defects aged from 0.1 to 4.5 years. Levels of the brain natriuretic peptide were measured at 8.3 to 122 ng/l, with a mean of 52.8 ng/l, after the first palliative operation, compared to 0 to 16 ng/l, with a mean of 7.3 ng/l, after a bidirectional Glenn anastomosis, and 0 to 13.8 ng/l, with a mean of 5.9 ng/l, in the children serving as controls. Corresponding values for atrial natriuretic peptide were 17 to 203 ng/l, with a mean of 103 ng/l, after the first palliative operation, compared to 16 to 54 ng/l, with a mean of 29 ng/l, after the bidirectional Glenn anastomosis, and 12 to 52 ng/l, with a mean of 32 ng/l in the controls. Echocardiography showed that all the children with functionally univentricular hearts had normal ventricular function. Blood presssure, pulmonary arterial pressure, and arterial saturations of oxygen did not differ between the groups. We conclude, that in children with functionally univentricular hearts, the volume overload imposed on the heart after the first palliative operation is associated with increased production of brain and atrial natriuretic peptides, while after ventricular unloading, levels of the natriuretic peptides return to control values.

Syncope--an unusual presentation of ventricle dysfunction in a patient with Fontan circulation

We report a case of recurrent syncope in association with moderate ventricular dysfunction and mild AV-valve regurgitation in an 18-year-old girl, 4 years after she underwent total cavopulmonary connection surgery. Cardiac catheterization revealed a transpulmonary gradient of 1-2 mmHg. During exercise, a dramatic fall in blood pressure and blood oxygenation was observed, paralleled by an increase in heart rate and central venous pressure. Although a slight increase in pulmonary vascular resistance could not be excluded, the reaction was interpreted in terms of an extremely low transpulmonary gradient in association with ventricular dysfunction. Five months after heart transplantation, the patient has been completely free from syncope. Fontan circulation usually involves a delicate haemodynamic situation which may necessitate haemodynamic re-evaluations, including dynamic measurements of the central venous pressure during exercise. Also a moderate ventricular dysfunction may result in compromised pulmonary circulation which in turn may lead to syncope during exercise as a result of insufficient systemic circulation.

Cardiomyopathy in children with mitochondrial disease; clinical course and cardiological findings

AIMS

To determine the frequency of cardiomyopathy in children with mitochondrial disease and describe their clinical course, prognosis and cardiological manifestations.

METHODS AND RESULTS

Of 301 children with CNS and neuromuscular disease referred to our institution in 1984 to 1999, 101 had mitochondrial disease. Seventeen patients had cardiomyopathy, diagnosed by echo-Doppler investigations, all of the hypertrophic, non-obstructive type. The onset of symptomatic mitochondrial disease ranged from birth to 10 years of age. Eight children had cytochrome-c oxidase deficiency, while the remaining nine had various defects. Cardiomyopathy was diagnosed from birth to 27 years. Left ventricular posterior wall and septal thickness were both increased: z-scores +4.6+/-2.6 and +4.3+/-1.6 (mean+/-SD), respectively. The left ventricular diastolic diameter z-score, +1.3+/-3.4, and fractional shortening, 24+/-13%, displayed marked variations. Nine patients developed heart failure. Eleven patients with cardiomyopathy died, including all eight with cytochrome-c oxidase deficiency, and one patient underwent a heart transplantation. Mortality in children with mitochondrial disease was higher in those with cardiomyopathy (71%) than those without (26%) (P<0.001).

CONCLUSIONS

In children with mitochondrial disease, cardiomyopathy was common (17%) and was associated with increased mortality. The prognosis for children with cytochrome-c oxidase deficiency and cardiomyopathy appeared to be particularly unfavorable.

Sustained elevated concentrations of cardiac troponin T during acute allograft rejection after heart transplantation in children

BACKGROUND

The diagnosis of acute rejection after heart transplantation is made on the basis of endomyocardial biopsy. In children, where the method may be associated with complications, a noninvasive alternative would be desirable. We evaluated the myocardial damage marker cardiac troponin T (cTnT) as a marker of rejection in children who have undergone heart transplantation.

METHODS

Peripheral venous blood was collected in 124 endomyocardial biopsies in 14 children who had undergone heart transplantation (1-20 years of age). Serum levels of cTnT were compared with histologic rejection according to the International Society of Heart and Lung Transplantation (ISHLT) (grades 0-4).

RESULTS

Seven children experienced nine episodes of acute rejection. During rejection, cTnT increased from 0.05+/-0.07 (mean+/-SD) microg/L to 0.26+/-0.27 microg/L and remained elevated 7 and 30 days thereafter (0.10+/-0.11 and 0.36+/-0.38 microg/L, respectively) before returning to normal after 50 to 430 days. In surveillance biopsies, cTnT displayed considerable variation at all rejection grades: ISHLT grade 0, median 0.03 microg/L (range 0.01-2.04 microg/L); ISHLT grade 1, median 0.06 microg/L (range 0.01-0.67 microg/L); ISHLT grade 2, median 0.10 microg/L (range 0.01-1.42 microg/L); and ISHLT grade 3, median 0.17 microg/L (range 0.01-0.93 microg/L). A receiver operating characteristics analysis for cTnT versus rejection grade revealed an area under the curve of 0.69, indicating a moderate predictive value for cTnT. However, a cutoff of 0.015 microg/L yielded a specificity of only 36%, with a sensitivity of 89%, whereas a cutoff of 0.1 microg/L resulted in sensitivity and specificity of 53% and 77%, respectively.

CONCLUSIONS

Cardiac troponin T increased and remained elevated for at least 1 month during acute rejection. The diagnostic power of a single cTnT measurement was not sufficient to replace endomyocardial biopsy.

Reversal of protein-losing enteropathy in a child with Fontan circulation is correlated with central venous pressure after heart transplantation

We report on the reversal of protein-losing enteropathy (PLE) after heart transplantation (HTx) in a 10-yr-old boy with Fontan circulation, previously treated unsuccessfully with heparin for several months. The protein loss continued immediately after the Tx. During the following month, however, a gradual decrease in protein loss was observed, which correlated with a decrease in the inferior vena cava (IVC) pressure. The patient is doing well with a normal serum albumin level and a normal IVC pressure, 2 yr after Tx.

Interaction between the renin-angiotensin system and insulin-like growth factor I in aorto-caval fistula-induced cardiac hypertrophy in rats

The effects of angiotensin converting enzyme inhibition and angiotensin II receptor blockade on the development of cardiac hypertrophy and myocardial insulin-like growth factor I (IGF-I) in volume overload were studied in male Wistar rats with aorto-caval fistulas (ACF). Rats were treated with ramipril (RAM, 3 mg kg(-1) day(-1)) for 4-20 days or losartan (LOS, 10 mg kg(-1) day(-1)) for 2-7 days. Myocardial IGF-I and IGF-I receptor (IGF-I-R) mRNA were determined by solution hybridization. ACF caused hypertrophy of left (LV) and right ventricles (RV). Hypertrophy appeared on day 2 and reached maximal values of +60% in LV and +75% in RV at day 12. Systolic blood pressure was initially reduced 15% but recovered by day 12. RAM abolished the recovery of blood pressure. Furthermore, RAM attenuated RV hypertrophy by 17% on day 7 and on day 20, RV weights were close to values found in controls. Beginning on day 9, RAM reduced LV weight back to control levels in parallel to blood pressure. In contrast, LOS affected neither RV nor LV hypertrophy. RV IGF-I mRNA increased 60-100% on day 7 alone in RV in ACF. RAM potentiated the increase in RV IGF-I to +400% and induced an increase in RV IGF-I-R mRNA on day 7 (+90%) in ACF. LOS did not affect RV IGF-I. Development of cardiac hypertrophy in ACF seemed independent of angiotensin II. RV hypertrophy was associated with activation of IGF-I independent of the renin-angiotensin system. IGF-I was further potentiated when development of hypertrophy was attenuated, possibly indicative of a greater urge for compensational growth in a relatively thinner and more volume-distended chamber.

Increased expression of growth hormone receptor mRNA and insulin-like growth factor-I mRNA in volume-overloaded hearts

Recent results suggest that insulin-like growth factor-I (IGF-I) may be involved in the transition of a hemodynamic load into cardiac hypertrophy and that the expression of IGF-I seems to be coupled to increased wall stress. The present study investigated the role of growth hormone (GH) and IGF-I in myocardial hypertrophy induced by volume overload. An aortocaval fistula (ACF) was created in male Wistar rats, and experiments were performed 2, 4, and 7 days after the onset of volume overload. Right and left ventricular (RV and LV, respectively) myocardial expression of GH receptor mRNA and IGF-I mRNA were quantitated by a solution hybridization RNase protection assay. RV GH receptor mRNA content was elevated on the fourth and seventh days after the induction of the shunt, with peak levels (0.63 +/- 0.16 versus 0.14 +/- 0.03 amol/microgram DNA for the sham-operated animals; P < .01) after 4 days. Similarly, IGF-I mRNA was significantly increased in the RV of shunted animals (1.26 +/- 0.13 versus 0.56 +/- 0.05 amol/micrograms DNA; P < .01) 7 days after surgery. In the left ventricle, where systolic pressure was reduced in ACF rats, no differences could be detected in GH receptor and IGF-I mRNA content between ACF and sham-operated rats on any of the experimental days. There was no difference in the ratio of RV to LV weight during the experimental period. We have shown that the thin-walled right ventricle responds to volume overload with an increase of GH receptor mRNA content followed by elevated expression of IGF-I mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial capillary diffusion capacity in rat hearts with cardiac hypertrophy due to pressure and volume overload

The functional adaptation of the myocardial capillary bed in response to cardiac hypertrophy was studied in one volume overload (aortocaval fistula, ACF) and in one pressure overload model [left renal arterial stenosis, two-kidney, one-clip (2K,1C)]. Furthermore, a group where renal hypertension was reversed 1 wk before experimentation (UC-2K,1C) and a sham-operated (Sham) group were studied. Functional estimations of myocardial capillary diffusion capacity in terms of permeability surface area products (PS) per 100 g of myocardium were obtained by the single-injection indicator dilution technique in a Langendorff preparation. After 4 wk, ACF hearts, with 72% hypertrophy and normal minimal coronary vascular resistance (CVR), displayed an unchanged diffusion capacity, i.e., PS for Cr-EDTA and vitamin B12. This indicates a structural out-growth of the coronary vascular bed to match the increased demand of the tissue. 2K,1C hearts with marked elevations of minimal coronary vascular resistance and left ventricular hypertrophy (65%) showed higher PS values than Sham, implying that diffusion capacity was enhanced despite structural coronary vascular changes. These changes were completely reversed in UC-2K,1C. Thus the present data imply that myocardial capillary diffusion capacity was well maintained in volume overloaded cardiac hypertrophy and in contrast with earlier morphometric estimations, even enhanced in pressure overload hypertrophy.

Changes in myocardial capillary diffusion capacity during infusion of vasoactive drugs

The present study investigated how variations in coronary vascular resistance and metabolic demand affected myocardial capillary diffusion capacity. Hearts from Wistar rats were perfused with Krebs-Henseleit-albumin buffer in a Langendorff preparation, where heart rate (HR), contractility (dP/dtmax) and myocardial oxygen consumption (MVO2) were recorded continuously. Myocardial capillary diffusion capacity was measured as the permeability surface area product (PS) for Cr-EDTA and vitamin B12 by the single injection colorimetric indicator dilution method. After base-line recordings without drugs, angiotensin II+Arginine-vasopressin was infused, which increased coronary vascular resistance by 90%, stimulated HR by 11%, decreased dP/dtmax by 21% and reduced MVO2 by 4%. PSCr-EDTA and PSB12 decreased by 24 and 27%, respectively, leaving the ratio PSCr-EDTA/PSB12 unchanged indicating unaltered capillary permeability. Moreover, the reductions in MVO2 and PS correlated significantly. During vasodilation: (1) nitroprusside-NA stimulated HR by 7% and decreased dP/dtmax by 14%; (2) adenosine reduced dP/dtmax by 37% and decreased MVO2 by 9%; and (3) isoproterenol increased HR, dP/dtmax and MVO2 by 53, 76 and 9%, respectively. However, all three vasodilators reduced PSCr-EDTA and PSB12 in parallel by 7-25% leaving PSCR-EDTA/PSB12 unchanged. Thus, maximal estimated diffusion capacities were obtained during spontaneous coronary vascular tone, most likely reflecting maximal capillary recruitment in the Krebs-Henseleit-albumin perfused heart. The derecruiting effects of the vasoconstrictors were partly overridden by metabolic factors, while the reductions of PS after vasodilation more likely were due to increased heterogeneity in coronary flow.

Capillary diffusion capacity for Cr-EDTA and cyanocobalamine in spontaneously beating rat hearts

In order to obtain a functional estimate of the diffusional capacity of the myocardial capillary bed, the permeability surface area product (PS) for Cr-EDTA (mol. wt = 341) and cyanocobalamine (vitamin B12, mol. wt = 135) was determined in spontaneously beating Langendorff-perfused rat hearts over a wide range of coronary flow rates (700-3000 ml min-1 100 g-1). PS was determined by a single injection, colorimetric indicator dilution technique, allowing multiple, rapid and accurate determinations to be made in the same heart. During maximal vasodilation with nitroprusside Na PS averaged 535 +/- 33 and 220 +/- 22 ml min-1 100 g-1 for Cr-EDTA and vitamin B12 respectively at the highest flow (2917 +/- 74 ml min-1 100 g-1). The vasculature of the heart was found to be highly heterogeneous, since PS increased with flow and there were marked variations of extraction over transit times. A functional estimate of 'equivalent pore radius' was obtained from the ratio PSCr-EDTA/PSB12, which was 2.61 +/- 0.15 demonstrating a marked restriction to diffusion corresponding to a pore radius of 51 (41-75) A. This value is similar to that from skeletal muscle determined by the same method while PS-values are 40-45 times higher in the heart (Haraldsson & Rippe 1986). Taken together with morphological estimations of capillary surface area and endothelial path depth, these data indicate a 3-fold increase in the density of pores available for diffusion in the myocardium, compared to skeletal muscle.

Functional and stereologic estimations of myocardial capillary exchange capacity in treated and untreated spontaneously hypertensive rats

Myocardial capillary exchange capacity was investigated by stereologic and functional techniques in parallel during pressure-overload cardiac hypertrophy and after long-term antihypertensive therapy with the vasodilator felodipine. In 26-week-old female spontaneously hypertensive rats (SHR) blood pressure increased by 25% and left ventricular weight (LVW/BW) increased by 18% compared to Wistar-Kyoto rats (WKY). Myocardial capillary surface and volume densities normalized for organ weight were similar in both ventricles for both strains. Moreover, capillary surface density was higher sub-epicardially (EPI) than in the subendocardium (ENDO) in the left ventricle of SHR. Thirteen weeks of felodipine-therapy (SHR-Felo) normalized blood pressure without affecting LVW/BW although a transition from concentric to eccentric hypertrophy is known to occur. Myocardial capillary surface and volume densities and the left ventricular ENDO-EPI-gradient in surface density were similar to untreated SHR. However, felodipine-treatment increased right ventricular weight and capillary volume density. Functional capillary exchange was estimated in terms of permeability surface area products (PS) for Cr-EDTA and vitamin B12 and normalized for organ weight. PSCr-EDTA, PSB12 and the ratio PSCr-EDTA/PSB12 (an index of capillary permeability) were similar in SHR and WKY. Furthermore, the relation between functional and stereological indices of exchange capacity was investigated in a multiple linear regression analysis. However, no significant correlation between PS and neither capillary surface nor volume density was found. In conclusion, myocardial capillary exchange capacity was well adapted to the pressure overload cardiac hypertrophy present in female SHR. Despite induction of right ventricular hypertrophy, felodipine-treatment did not affect capillary exchange capacity. Furthermore, when functional and stereologic estimates were performed in parallel, the importance of dynamic factors for myocardial capillary exchange capacity (e.g. heterogeneity) was illustrated.

Left ventricular insulin-like growth factor I increases in early renal hypertension

Increasing interest has been directed toward the possible role of trophically acting molecules as modulators or initiators, or both, of myocardial hypertrophy. The aim of the present study was to investigate the possible role of one such molecule, namely, insulin-like growth factor I, in myocardial hypertrophy developed in response to renal artery stenosis. Two-kidney, one clip Goldblatt hypertension was induced in Wistar rats weighing 180 g, and sham-operated animals were used as controls. Blood pressure was increased as early as 2 days after clipping (133 +/- 4 versus 116 +/- 4 mm Hg, p less than 0.05), and the increase persisted 4 and 7 days after clipping (148 +/- 6 versus 129 +/- 3 mm Hg, p less than 0.01 and 171 +/- 5 versus 139 +/- 3 mm Hg, p less than 0.01, respectively). Left ventricular weight followed a similar pattern (373 +/- 7 versus 350 +/- 8 mg, NS, 415 +/- 11 versus 386 +/- 9 mg, p less than 0.01, and 466 +/- 11 versus 391 +/- 10 mg, p less than 0.01 at 2, 4, and 7 days after clipping, respectively), but no changes in body weight between the groups were observed. Insulin-like growth factor I messenger RNA (mRNA) was quantified using a solution hybridization assay. After 4 days of renal hypertension, there was a significant increase in left ventricular insulin-like growth factor I mRNA (2.0 x 10(-18) +/- 0.48 x 10(-18) versus 0.4 x 10(-18) +/- 0.07 x 10(-18) mol.microgram DNA-1), which was no longer detectable 7 days after clipping.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiological and mechanical characteristics of isolated hearts from spontaneously hypertensive (SHR) and normotensive (WKY) rats on very high- and low-sodium diets

Electrophysiological, mechanical, dimensional and coronary flow characteristics were studied on papillary strips and on isolated hearts, from spontaneously hypertensive (SHR) and normotensive (WKY) rats respectively, which from 5 to 15 weeks of age had been on either 'low' (LNa, 0.5 mmol 100 g-1 food), control (CNa, 5) 'high' (HNa, 50) or 'very high' (vHNa, 120) sodium diets. With respect to cardiac electrophysiological characteristics, contractility, and maximal stroke volume capacity only minor, if any, differences were observed between the various Na diet groups, both in WKY and SHR. This is in accordance with our earlier findings concerning vascular smooth muscle, where a largely unchanged sensitivity and responsiveness to, for example, noradrenaline was noted. Further, only to the extent that the various Na diets had also caused changes in average blood pressure levels, adaptations of cardiac and coronary resistance vessel design were observed, in general agreement with our earlier findings in other preparations and experimental designs. The largely unaffected functional characteristics of cardiac as well as vascular effector cells, despite 240-fold long-term variations in sodium intake, are in sharp contrast to the marked changes that have been shown to affect the adrenergic nerves, as here chronic low-Na intakes cause reductions of transmitter release/impulse, and vice versa at high Na intakes. This latter type of change seems to be by far the most important functional deviation affecting cardiovascular control during long-term alterations of sodium intake, as it can markedly affect both cardiac and vascular influences on haemodynamics, even though the respective effector functions seem to be surprisingly little influenced directly.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural and functional adaptations within the myocardium and coronary vessels after antihypertensive therapy in spontaneously hypertensive rats

The relationships between cardiac performance, coronary flow, minimal coronary vascular resistance and myocardial oxygen consumption (MVO2) were explored in isolated hearts from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) and in hearts from SHR given a combination of metoprolol and felodipine (selective calcium antagonist) for 35 weeks. Antihypertensive therapy markedly reduced arterial pressure and caused a substantial regression of left ventricular hypertrophy. An antegrade working-heart perfusion system was used, allowing measurements of stroke volume, coronary flow and MVO2 at varying pre- and afterloads. In untreated SHR cardiac function was reduced at low and enhanced at high perfusion pressure compared with WKY. Minimal coronary vascular resistance, which was greatly increased in SHR, was significantly reduced by treatment, allowing higher coronary flow for any given perfusion pressure and consequently a lower degree of oxygen extraction. In addition, at a given workload, MVO2 was reduced in both untreated and treated SHR. These results stress the importance of having adequate coronary perfusion within a hypertensive structurally redesigned coronary vascular bed in order to maintain cardiac performance. With antihypertensive therapy in SHR, an improved coronary flow capacity was created due to regression of the hypertensive vascular changes.

Cardiac design and pressure-volume characteristics of the left ventricle in normotensive (WKY) and hypertensive (SHR) rats after various dietary sodium treatments

Normotensive (WKY) and hypertensive rats (SHR) from 5 to 13-14 weeks of age were given 'low' (LNa; 0.5 mmol Na 100 g-1 food), 'control' (CNa; 5 or 12 mmol), 'high' (HNa; 50 mmol) and in SHR also 'medium low' (mLNa; 2 mmol) and 'very high' (vHNa; 120 mmol) sodium diets, to explore how such 240-fold variations in Na intake affect cardiac design. This was assessed in isolated perfused, temporarily-arrested hearts by recordings of left ventricular (LV) diastolic pressure-volume relationships (P/V), LV and RV weights, and by calculations of the ratio between LV wall thickness and internal radius (w/ri), after in vivo recordings of awake mean arterial pressure (MAP) and heart rate (HR). In WKY, where MAP was the same in all diet groups, the HNa group showed an increased w/ri due to a 20% reduction of LV diastolic volume, with signs of reduced wall compliance compared with CNa. The LNa WKY showed less marked changes in the same direction. In the SHR LNa group, where MAP was lowered about 20 mmHg, LV diastolic volume was reduced nearly 20% at a modest w/ri increase, while HNa and Cna SHR had equal MAP, LV weights, P/V and w/ri relationships. However, in vHNa SHR, where MAP was elevated about 25 mmHg, the LV showed a mainly eccentric hypertrophy with 15% increase of diastolic volume at a slight increase of w/ri. These differentiated, and in WKY and SHR partially differing structural cardiac adaptations consequent to changes in Na intake, can hardly be ascribed only to the respective pre- and afterload alterations, suggesting that also altered neuro-hormonal profiles may have contributed with 'trophic' influences.(ABSTRACT TRUNCATED AT 250 WORDS)