Cardiac Function and Serum Biomarkers throughout Staged Fontan Palliation: A Prospective Observational Study.

Fontan patients undergo multiple cardiothoracic surgeries in childhood. Following these procedures, ventricular function is temporarily decreased, and recovers over months. This is presumably related to cardiopulmonary bypass, but this is incompletely understood. Throughout the Fontan palliation, cardiac function is also affected by volume unloading. We aimed to gain insight into the biological processes related to impaired ventricular function and recovery following Fontan palliations using a panel of biomarkers. Furthermore, we described changes in ventricular function across the Fontan palliation due to volume unloading. We performed a prospective multicenter observational study in patients undergoing partial (PCPC) or total cavo-pulmonary connection (TCPC). Patients underwent assessment-including echocardiography and blood sampling-before surgery (T1), at first follow-up (T2), and 1 year after their procedures (T3). Blood samples were analyzed using a biomarker panel (OLINK CVD-III). Ninety-two biomarkers were expressed as principal components (PC) to limit multiple statistical testing. We included 32 PCPC patients aged 7.2 [5.3-10.3] months, and 28 TCPC patients aged 2.7 [2.2-3.8] years. The single ventricular longitudinal strain (SV GLS) temporarily decreased for PCPC patients at T2 (-15.1 ± 5.6 (T1) to -13.5 ± 5.2 (T2) to -17.3 ± 4.5 (T3), p < 0.047 for all differences), but not following TCPC. The serum biomarkers were expressed as 4 PCs. PC1, including biomarkers of cell-cell adhesion, was not related to any patient characteristic. PC2, including biomarkers of superoxide anion regulation, increased at T2. PC3, including biomarkers of cardiovascular development, related to the stage of Fontan palliation. PC4 was of uncertain biological or clinical significance. No PC was found that related to ventricular performance. The SV GLS was temporarily diminished following PCPC, but not following TCPC. Several biomarkers were related to post-operative stress and adaptation to the PCPC or TCPC circulation, but none were related to the outcome.

Improvement of physical activity levels in children and adolescents after surgery for congenital heart disease: preferences and use of physical therapy.

PURPOSE: After surgery for congenital heart disease in children and adolescents, an active lifestyle is important to achieve and maintain good physical fitness. This study aimed to describe physical activity, as well as the use of patients' and parents' preferences for rehabilitative care after surgery for congenital heart disease. METHODS: This cross-sectional study included patients aged 4-16 years old, who had undergone surgery for congenital heart disease 2 years prior to the study onset. Patients and/or parents were invited to complete questionnaires on physical activity, and on their preferences for, and -use of, rehabilitative care after surgery. RESULTS: Forty-five of the 92 eligible patients and/or parents completed the questionnaires. The median age of the children was 12.2 years (IQR 7.8-16.1). Two children (4%) met the recommendations for taking part in moderate physical activity and 13 (29%) having done so for vigorous physical activity. Postoperatively 15 children (33%) had had physical therapy in primary care. More than 50% of the patients/parents would have preferred to have had more information on physical activity and to have taken part in an individual exercise program delivered during their primary care. CONCLUSION: The majority of eligible patients do not meet public health recommendations for engaging in physical activity and do not use physical therapy after surgery for congenital heart disease. The majority of patients and parents preferred more information as well as individual physical therapy treatments.Implications for rehabilitationsTwo years after surgery for congenital heart disease children and adolescents are less active compared to typically developing peers.Patients with a congenital heart disease and their parents need more information and support regarding stimulation of physical activity and physical fitness after heart surgery.In the postoperative process, a well-structured and supportive (individual) rehabilitation program should be introduced to improve physical activity and physical fitness.

A low incidence of preoperative neurosonographic abnormalities in neonates with heart defects.

BACKGROUND AND AIM: To investigate whether neonates with prenatally detected congenital heart defects (CHD) demonstrate cerebral abnormalities on early preoperative cranial ultrasound (CUS), compared to healthy neonates, and to measure brain structures to assess brain growth and development in both groups. STUDY DESIGN, SUBJECTS AND OUTCOME MEASURES: Prospective cohort study with controls. Between September 2013 and May 2016 consecutive cases of prenatally detected severe isolated CHD were included. Neonatal CUS was performed shortly after birth, before surgery and in a healthy control group. Blinded images were reviewed for brain abnormalities and various measurements of intracranial structures were compared. RESULTS: CUS was performed in 59 healthy controls and 50 CHD cases. Physiological CUS variants were present in 54% of controls and in 52% of CHD cases. Abnormalities requiring additional monitoring (both significant and minor) were identified in four controls (7%) and five CHD neonates (10%). Significant abnormalities were only identified in four CHD neonates (8%) and never in controls. A separate analysis of an additional 8 CHD neonates after endovascular intervention demonstrated arterial stroke in two cases that underwent balloon atrioseptostomy (BAS). Cerebral measurements were smaller in CHD neonates, except for the cerebrospinal fluid measurements, which were similar to the controls. CONCLUSIONS: The prevalence of significant preoperative CUS abnormalities in CHD cases was lower than previously reported, which may be partially caused by a guarding effect of a prenatal diagnosis. Arterial stroke occurred only in cases after BAS. As expected, neonates with CHD display slightly smaller head size and cerebral growth.

Longitudinal Myocardial Deformation Does Not Predict Single Ventricle Ejection Fraction Assessed by Cardiac Magnetic Resonance Imaging in Children with a Total Cavopulmonary Connection.

Survival of children with single ventricle heart defects after the total cavopulmonary connection (TCPC) has improved, but impaired cardiac function remains a major cause of morbidity and mortality. Cardiac magnetic resonance imaging (cMRI) is the gold standard in assessing single ventricle volume and function, but high costs and limited availability hamper its routine use. A cheaper and more available alternative is echocardiography. Myocardial function can be studied in more detail using speckle tracking echocardiography (STE). The purpose of the study was to describe the association between myocardial deformation assessed by speckle tracking echocardiography (STE) and single ventricle function assessed by cMRI and to evaluate differences in myocardial deformation in children with single left and single right ventricular morphology. Cross-sectional, multicenter study in 77 children after TCPC was conducted. STE segmental and global longitudinal peak strain and systolic strain rate (SR) of the dominant ventricle were measured. Impaired SV function by cMRI was defined as ejection fraction (EF) < 45%. Mean age was 11.8 (range 9.7-14.3) years. Pearson R for cMRI EF versus global longitudinal strain and SR was - 0.25 (p = 0.06) and - 0.03 (p = 0.82), respectively. Global single ventricle longitudinal strain and SR was similar in patients after TCPC with single left and single right ventricular morphology (- 19.0 ± 3.1% vs 19.2 ± 3.2%, p = 0.94). STE myocardial deformation parameters do not correlate with single ventricle ejection fraction assessed by cMRI.

Right ventricular outflow tract obstruction in complicated monochorionic twin pregnancy.

OBJECTIVES: Severe right ventricular outflow tract obstruction (RVOTO) is a potential complication in recipient twins of twin-to-twin transfusion syndrome (TTTS) that requires postnatal follow-up or treatment. We aimed to evaluate pregnancy characteristics of neonates with RVOTO from complicated monochorionic twin pregnancies, determine the incidence of RVOTO in TTTS cases and construct a prediction model for its development. METHODS: This was an observational cohort study of all complicated monochorionic twin pregnancies with a postnatal diagnosis of RVOTO examined at our center. Cases were referred for evaluation of the need for fetal therapy or intervention because of TTTS, selective intrauterine growth restriction (sIUGR) or multiple congenital malformations in one of the twins. Ultrasound data were retrieved from our monochorionic twin database. Among liveborn TTTS recipients treated prenatally with laser therapy, those with RVOTO were compared with those without RVOTO (controls). We describe four additional cases with RVOTO that were not TTTS recipients. RESULTS: A total of 485 twin pregnancies received laser therapy for TTTS during the study period. RVOTO was diagnosed in 3% (11/368) of liveborn TTTS recipients, of whom two showed mild Ebstein's anomaly. Before laser therapy, pericardial effusion was seen in 45% (5/11) of RVOTO cases (P < 0.01) and abnormal A-wave in the ductus venosus (DV) in 73% (8/11) (P = 0.03), significantly higher proportions than in controls. Mean gestational age at laser therapy was 17 + 3 weeks in RVOTO cases compared with 20 + 3 weeks in controls (P = 0.03). A prediction model for RVOTO was constructed incorporating these three significant variables. One TTTS donor had RVOTO after the development of transient hydrops following laser therapy. Three larger twins in pregnancies complicated by sIUGR developed RVOTO, the onset of which was detectable early in the second trimester. CONCLUSIONS: RVOTO occurs in TTTS recipient twins but can also develop in TTTS donors and larger twins of pregnancies complicated by sIUGR. Abnormal flow in the DV, pericardial effusion and early gestational age at onset of TTTS are predictors of RVOTO in TTTS recipients, which suggests increased vulnerability to hemodynamic imbalances in the fetal heart in early pregnancy. These findings could guide diagnostic follow-up protocols after TTTS treatment. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Ventricular function and cardiac reserve in contemporary Fontan patients.

BACKGROUND/OBJECTIVE: Total cavopulmonary connection (TCPC) has been the preferred treatment for patients with univentricular hearts. Current TCPC-techniques are the intra-atrial lateral tunnel (ILT) and the extracardiac conduit (ECC). We aimed to determine ventricular function during rest and stress, and to compare results for both techniques and for left (LV) versus right ventricular (RV) dominance. METHODS: 99 patients, aged 12.5 ± 4.0 years underwent echocardiography and magnetic resonance imaging (MRI), and 69 patients underwent stress MRI. RESULTS: Echocardiography showed impaired systolic and diastolic function. MRI parameters were comparable between ILT and ECC at rest. During dobutamine there was a decrease in end-diastolic volume (EDVi) (91 ± 21 vs. 80 ± 20 ml/m(2) p<0.001). Ejection fraction (EF) and cardiac index (CI) during dobutamine were lower for ILT patients (59 ± 11 (ILT) vs. 64 ± 7% (ECC), p=0.027 and 4.2 ± 1.0 (ILT) vs. 4.9 ± 1.0L/min/m(2) (ECC), p=0.006), whereas other parameters were comparable. TEI-index was higher in ILT-patients (0.72 ± 0.27 (ILT) vs. 0.56 ± 0.22 (ECC), p=0.002). Diastolic function was frequently impaired in patients with a dominant RV (67% (RV) vs. 39% (LV), p=0.011). Patients with dominant LV's had smaller end-systolic volume (ESVi) (40 ± 13 (LV) vs. 47 ± 16 (RV) ml/m(2), p=0.030) and higher EF (55 ± 8 (LV) vs. 49 ± 9 ml/m(2) (RV), p=0.001) and contractility (2.3 ± 0.8 (LV) vs. 1.9 ± 0.7 mmHg/ml/m(2) (RV), p=0.050) during rest and higher EF during dobutamine (63 ± 8 (LV) vs. 58 ± 10 ml/m(2) (RV), p=0.043). CONCLUSION: Ventricular function is relatively well preserved in modern-day Fontan patients. With dobutamine stress there is a decrease in EDVi. ECC patients have higher CI and EF during stress. Patients with a dominant RV have lower systolic, including impaired contractility, and diastolic function.

Umbilical blood flow patterns directly after birth before delayed cord clamping.

BACKGROUND: Delayed umbilical cord clamping (DCC) affects the cardiopulmonary transition and blood volume in neonates immediately after birth. However, little is known of blood flow in the umbilical vessels immediately after birth during DCC. The objective is to describe the duration and patterns of blood flow through the umbilical vessels during DCC. METHODS: Arterial and venous umbilical blood flow was measured during DCC using Doppler ultrasound in uncomplicated term vaginal deliveries. Immediately after birth, the probe was placed in the middle of the umbilical cord, pattern and duration of flow in vein and arteries were evaluated until cord clamping. RESULTS: Thirty infants were studied. Venous flow: In 10% no flow was present, in 57% flow stopped at 4:34 (3:03-7:31) (median (IQR) min:sec) after birth, before the cord was clamped. In 33%, flow continued until cord clamping at 5:13 (2:56-9:15) min:sec. Initially, venous flow was intermittent, increasing markedly during large breaths or stopping and reversing during crying, but then became continuous. Arterial flow: In 17% no flow was present, in 40% flow stopped at 4:22 (2:29-7:17) min:sec, while cord pulsations were still palpable. In 43% flow continued until the cord was clamped at 5:16 (3:32-10:10) min:sec. Arterial flow was pulsatile, unidirectional towards placenta or bidirectional to/from placenta. In 40% flow became continuous towards placenta later on. CONCLUSIONS: During delayed umbilical cord clamping, venous and arterial umbilical flow occurs for longer than previously described. Net placental transfusion is probably the result of several factors of which breathing could play a major role. Umbilical flow is unrelated to cessation of pulsations.

Evaluation of the diagnostic work-up in children with myocarditis and idiopathic dilated cardiomyopathy.

The underlying etiology of dilated cardiomyopathy (DCM) in children varies, 14-22% is secondary to myocarditis, and the majority remains idiopathic. Etiology has prognostic value; however, 'a clinical diagnosis of myocarditis' has been frequently used because the gold standard [endomyocardial biopsy (EMB)] is often not performed. Therefore, a consistent diagnostic approach and interpretation is needed. In this multicenter study, we evaluated the diagnostic approach and interpretation of the viral results in children with myocarditis and idiopathic DCM. We included 150 children with DCM, of whom 103 were assigned the diagnosis myocarditis (n = 21) or idiopathic DCM (n = 82) by the attending physician. Viral tests were performed in 97/103 patients, in only 34% (n = 35) some of the tests were positive. Of those patients, we evaluated the probability of the assigned diagnosis using the viral test results. We classified viral test results as reflecting definite or probable myocarditis in 14 children and possible or unlikely myocarditis in 21 children. Based on this classification, 23% of patients were misclassified. We found that in children with DCM, the diagnostic approach varied and the interpretation was mainly based on viral results. Since a 'clinical diagnosis of myocarditis' has been frequently used in daily practice because of the lack of EMB results, a uniform protocol is needed. We propose to use viral test results in several steps (blood PCR, serology, PCR and/or cultures of the gastro-intestinal and respiratory tract, and EMB results) to estimate the probability of myocarditis.

Systematic review of the effects of physical exercise training programmes in children and young adults with congenital heart disease.

BACKGROUND: Most patients with congenital heart disease (ConHD) do not perform regular physical exercise. Consensus reports have stated that exercise should be encouraged and regularly performed in these patients, but this is not common practise. We reviewed the literature on actual evidence for either negative or positive effects of physical exercise training programmes in children and young adults with ConHD. METHODS: Using the Medline database, we systematically searched for articles on physical exercise training programmes in ConHD. RESULTS: A total of 31 articles met all inclusion criteria; in total, 621 subjects (age range 4 to 45 years) were included. Most studies used training programmes with a duration of 12 weeks. On average, the number of training sessions was 3 times per week. In 12 studies, training intensity was set at a percentage of peak heart rate. Outcome measures reported were PeakVO2, activity levels and muscle strength. Twenty-three studies (72%) found a significant positive change in the main outcome measure after the physical exercise training period. None of the studies reported negative findings related to physical exercise training in ConHD. Cardiac effects have hardly been studied. CONCLUSION: In most studies, participation in a physical exercise training programme was safe and improved fitness in children and young adults with ConHD. We recommend that patients with ConHD participate in physical exercise training. Cardiac effects need to be studied more extensively.

Psychological functioning and disease-related quality of life in pediatric patients with an implantable cardioverter defibrillator.

The objective of this multicenter study was to evaluate psychological functioning and disease-related quality of life (DRQoL) in pediatric patients with an implantable cardioverter defibrillator (ICD) in The Netherlands. Thirty patients were investigated; the mean age was 16.3 years, and the mean duration of implantation was 3.6 years. To assess psychological problems, three domains of the Symptom Checklist (SCL-90-R) were administered to the 25 patients[13 years old. DRQoL was assessed with a disease-specific pediatric questionnaire, the short-form 11-item Worries About (WA)ICDs Scale. Patients C13 years old scored significantly higher than the reference group on the domains of anxiety, depression, and sleeping problems of the SCL-90-R (T = 7.5, p\0.001; T = 5.4, p\0.001; and T = 7.8, p\0.001, respectively). Patients who had received an (in)appropriate shock reported more depressive symptoms (T = 2.1, p\0.03). Patients with [2 years implant duration (N = 19) or who had received an (in)appropriate shock (N = 13) showed lower DRQoL scores on the modified WAICD (T = 2.1, p\0.04; T = 2.1, p\0.5, respectively). Age at implantation or underlying disease did not influence psychological problems or DRQoL. Young ICD patients showed more anxiety, depression, and sleeping disorders. Worries were increased among patients with ICD shocks and in those who had their ICD implanted for[2 years. To determine psychological problems and help children to learn to cope with shocks, proper guidance and monitoring of young ICD patients are recommended.

Dilatation of the great arteries in an infant with marfan syndrome and ventricular septal defect.

We describe an infant presenting with contractures of the fingers, a large ventricular septal defect (VSD), and severe pulmonary artery dilatation. He had clinical and echocardiographic features of both neonatal or infantile Marfan syndrome (MFS) and congenital contractural arachnodactyly. After surgical VSD closure, the aortic root developed progressive dilatation while the size of pulmonary artery returned to normal limits. Eventually the diagnosis of MFS was confirmed by DNA analysis.

Exercise testing and prescription in patients with congenital heart disease.

The present paper provides a review of the literature regarding exercise testing, exercise capacity, and the role of exercise training in patients with congenital heart disease (CHD). Different measures of exercise capacity are discussed, including both simple and more advanced exercise parameters. Different groups of patients, including shunt lesions, pulmonary valvar stenosis, patients after completion of Fontan circulation, and patients with pulmonary arterial hypertension are discussed separately in more detail. It has been underscored that an active lifestyle, taking exercise limitations and potential risks of exercise into account is of utmost importance. Increased exercise capacity in these patients is furthermore correlated with an improvement of objective and subjective quality of life.

Real-time transthoracic three dimensional echocardiography: normal reference data for left ventricular dyssynchrony in adolescents.

BACKGROUND: Since the introduction of cardiac resynchronization therapy, the assessment of left ventricular (LV) dyssynchrony has become increasingly important. Real-time three-dimensional echocardiography (RT-3DE) is one of the methods that is increasingly used. However, normal reference data in a young population are scarce. METHODS: RT-3DE was performed in 73 healthy adolescents aged 12 to 18 years. A systolic dyssynchrony index was derived from the dispersion of time to minimum regional volume for all 16 LV segments. RESULTS: Acquisition of RT-3DE data sets was feasible in 67 of 73 subjects (92%). LV end-diastolic volume and LV end-systolic volume were 99+/-25 and 41+/-15 mL, respectively. All controls had highly synchronized segmental function (systolic dyssynchrony index, 1.26+/-0.53%). Dyssynchrony was independent of age, weight, or length. Interobserver variability for the dyssynchrony index was 2+/-2 ms and 0.3+/-0.2% for the absolute and heart rate-corrected values, respectively. Intraobserver variability was 2.0+/-0.07 ms and 0.0+/-0.27%, respectively. CONCLUSIONS: RT-3DE could be performed in most healthy adolescents with good interobserver and intraobserver variability. Highly synchronized segmental function was present and was independent of age, weight, or length.

Fetal dilated cardiomyopathy caused by persistent junctional reciprocating tachycardia.

Ultrasound examination of a fetus at 32 weeks' gestation revealed dilated cardiomyopathy and a heart rate of 170 beats per minute. Prenatally, this mild tachycardia was not primarily suspected to be the cause of the myocardial changes. Postnatal electrocardiography revealed a persistent junctional reciprocating tachycardia (PJRT) and the diagnosis of tachycardia-induced cardiomyopathy (TICM) became apparent. After conversion to a sinus rhythm under digoxin and amiodarone, the cardiac changes regressed. PJRT is a rare form of supraventricular tachycardia. The prenatal findings in the condition have previously been described retrospectively, but it can only be diagnosed postnatally by its characteristic electrocardiographic properties. This case indicates that TICM can occur at lower heart rates than previously assumed. Even severe prenatal cardiomyopathy may be reversible once sinus rhythm has been restored.

Congenital valvular aortic stenosis: limited progression during childhood.

OBJECTIVE: Congenital valvular aortic stenosis is a common congenital heart malformation. The rate of progression in childhood, however, remains to be established. We assessed the progression of peak aortic velocity before intervention as well as the frequency of intervention in paediatric patients with isolated congenital valvular aortic stenosis. METHODS: A retrospective cohort study was performed in 245 consecutive patients with aortic stenosis. Both clinical and echocardiographic data were obtained. RESULTS: Over a period of 9.0 (SD 5.2) years (range 0.1-19.4), the mean annual increase in peak systolic velocity was 0.04 m/s/year (95% CI 0.028 to 0.056 m/s/year; p<0.001) as shown by ANOVA. 40 patients underwent a cardiac intervention shortly after their first echocardiogram. Another 33 patients underwent intervention during follow-up. Interventions were performed significantly more often in patients diagnosed at a younger age and/or with a higher peak velocity at diagnosis (p<0.001). Mortality was considerable in those diagnosed in infancy (5-year survival rate of 73% (SD 9%), whereas it was nearly absent in patients diagnosed after infancy. Most patients who died during infancy had progressive left ventricular dysfunction despite adequate relief of left ventricular outflow obstruction. CONCLUSIONS: Valvular aortic stenosis in the paediatric age group usually has a good prognosis beyond the neonatal period. Progression over time is usually limited, although a considerable proportion of patients need intervention shortly after initial diagnosis. Mortality, except for the neonatal age group, is nearly absent.

Fludrocortisone and sleeping in the head-up position limit the postural decrease in cardiac output in autonomic failure.

Treatment with head-up tilt sleeping and low-dose fludrocortisone effectively minimizes orthostatic symptoms and increases orthostatic blood pressure in patients with neurogenic orthostatic hypotension. The aim of the present study was to examine whether the improvement in orthostatic blood pressure during combined treatment with low-dose fludrocortisone and nocturnal head-up tilt in patients with neurogenic orthostatic hypotension can be attributed to expansion of plasma volume or to increased total peripheral resistance. The effects of a 3-week treatment with fludrocortisone and nocturnal head-up tilting on the postural changes in arterial pressure, heart rate, and cardiac output (pulse contour) were evaluated in eight consecutive patients with orthostatic hypotension. The period during which the patients were able to remain in the standing position without orthostatic complaints increased minimally from 3 to 10 minutes. The decrease in arterial pressure after 1 minute of standing--(means with standard deviations in parentheses) systolic, 49 (20) mm Hg; diastolic, 18 (11) mm Hg--before treatment was produced by a greater than normal decrease in cardiac output: 37% (10%) in patients with neurogenic orthostatic hypotension versus -14% (8%) in control subjects. Treatment increased upright arterial pressure from 83 (19) mm Hg systolic and 55 (13) mm Hg diastolic to 114 (22) mm Hg systolic and 60 (16) mm Hg diastolic by limiting the decrease in cardiac output. Body weight increased but hematocrit did not change. Leg pressure-volume relationship decreased in the two patients studied. The responses of plasma renin activity and aldosterone to orthostatic stress prior to treatment were subnormal and became even lower after treatment. The improvement in upright blood pressure in orthostatic hypotension during treatment with fludrocortisone and nocturnal head-up sleeping is the result of a reduction in the orthostatic decrease in cardiac output. Preliminary data suggest that the expanded body fluid volume is allocated to the perivascular space rather than to the intravascular space.

Dynamics of circulatory adjustments to head-up tilt and tilt-back in healthy and sympathetically denervated subjects.

1. The initial circulatory adjustments induced by head-up tilt and tilt-back were investigated in six healthy subject (aged 30-58 years) and six patients with orthostatic hypotension due to pure autonomic failure (aged 33-65 years). 2. Continuous responses of finger arterial pressure and heart rate were recorded by Finapres. A pulse contour algorithm applied to the arterial pressure waveform was used to compute stroke volume responses. 3. In the healthy subjects, head-up tilt induced gradual circulatory adjustments. After 1 min upright stroke volume and cardiac output had decreased by 39 +/- 9% and 26 +/- 10% respectively. Little change in mean blood pressure at heart level (+1 +/- 7 mmHg) indicated that systemic vascular resistance had increased by 39 +/- 24%. The gradual responses to head-up tilt contrasted with the pronounced and rapid circulatory responses upon tiltback. After 2-3 s a rapid increase in stroke volume (from 62 +/- 8% to 106 +/- 10%) and cardiac output (from 81 +/- 11% to 118 +/- 20%) was observed with an overshoot of mean arterial pressure above supine control values of 16 +/- 3 mmHg at 7 s. In the patients a progressive fall in blood pressure on head-up tilt was observed. After 1 min upright mean blood pressure had decreased by 59 +/- 8 mmHg. No change in systemic vascular resistance and a larger decrease in stroke volume (60 +/- 7%) and cardiac output (53 +/- 8%) were found. On tilt-back a gradual recovery of blood pressure was observed. 4. In healthy humans upon head-up tilt neural compensatory mechanisms are very effective in maintaining arterial pressure at heart level. The gradual circulatory adjustments to head-up tilt in healthy subjects contrast with the pronounced and abrupt circulatory changes on tilt-back. In patients with a lack of neural circulatory reflex adjustments, gradual blood pressure decreases to head-up tilt and gradual increases to tilt-back are observed.