Phosphodiesterase 5 inhibitor treatment and survival in interstitial lung disease pulmonary hypertension: A Bayesian retrospective observational cohort study.

BACKGROUND AND OBJECTIVE: Pulmonary hypertension is a life-limiting complication of interstitial lung disease (ILD-PH). We investigated whether treatment with phosphodiesterase 5 inhibitors (PDE5i) in patients with ILD-PH was associated with improved survival. METHODS: Consecutive incident patients with ILD-PH and right heart catheterisation, echocardiography and spirometry data were followed from diagnosis to death, transplantation or censoring with all follow-up and survival data modelled by Bayesian methods. RESULTS: The diagnoses in 128 patients were idiopathic pulmonary fibrosis (n = 74, 58%), hypersensitivity pneumonitis (n = 17, 13%), non-specific interstitial pneumonia (n = 12, 9%), undifferentiated ILD (n = 8, 6%) and other lung diseases (n = 17, 13%). Final outcomes were death (n = 106, 83%), transplantation (n = 9, 7%) and censoring (n = 13, 10%). Patients treated with PDE5i (n = 50, 39%) had higher mean pulmonary artery pressure (median 38 mm Hg [interquartile range, IQR: 34, 43] vs. 35 mm Hg [IQR: 31, 38], p = 0.07) and percentage predicted forced vital capacity (FVC; median 57% [IQR: 51, 73] vs. 52% [IQR: 45, 66], p=0.08) though differences did not reach significance. Patients treated with PDE5i survived longer than untreated patients (median 2.18 years [95% CI: 1.43, 3.04] vs. 0.94 years [0.69, 1.51], p = 0.003) independent of all other prognostic markers by Bayesian joint-modelling (HR 0.39, 95% CI: 0.23, 0.59, p < 0.001) and propensity-matched analyses (HR 0.38, 95% CI: 0.22, 0.58, p < 0.001). Survival difference with treatment was significantly larger if right ventricular function was normal, rather than abnormal, at presentation (+2.55 years, 95% CI: -0.03, +3.97 vs. +0.98 years, 95% CI: +0.47, +2.00, p = 0.04). CONCLUSION: PDE5i treatment in ILD-PH should be investigated by a prospective randomized trial.

Perioperative management of patients with pulmonary hypertension undergoing non-cardiothoracic, non-obstetric surgery: a systematic review and expert consensus statement.

BACKGROUND: The risk of complications, including death, is substantially increased in patients with pulmonary hypertension (PH) undergoing anaesthesia for surgical procedures, especially in those with pulmonary arterial hypertension (PAH) and chronic thromboembolic PH (CTEPH). Sedation also poses a risk to patients with PH. Physiological changes including tachycardia, hypotension, fluid shifts, and an increase in pulmonary vascular resistance (PH crisis) can precipitate acute right ventricular decompensation and death. METHODS: A systematic literature review was performed of studies in patients with PH undergoing non-cardiac and non-obstetric surgery. The management of patients with PH requiring sedation for endoscopy was also reviewed. Using a framework of relevant clinical questions, we review the available evidence guiding operative risk, risk assessment, preoperative optimisation, and perioperative management, and identifying areas for future research. RESULTS: Reported 30 day mortality after non-cardiac and non-obstetric surgery ranges between 2% and 18% in patients with PH undergoing elective procedures, and increases to 15-50% for emergency surgery, with complications and death usually relating to acute right ventricular failure. Risk factors for mortality include procedure-specific and patient-related factors, especially markers of PH severity (e.g. pulmonary haemodynamics, poor exercise performance, and right ventricular dysfunction). Most studies highlight the importance of individualised preoperative risk assessment and optimisation and advanced perioperative planning. CONCLUSIONS: With an increasing number of patients requiring surgery in specialist and non-specialist PH centres, a systematic, evidence-based, multidisciplinary approach is required to minimise complications. Adequate risk stratification and a tailored-individualised perioperative plan is paramount.

Growth/differentiation factor 15 causes TGFß-activated kinase 1-dependent muscle atrophy in pulmonary arterial hypertension.

INTRODUCTION: Skeletal muscle dysfunction is a clinically important complication of pulmonary arterial hypertension (PAH). Growth/differentiation factor 15 (GDF-15), a prognostic marker in PAH, has been associated with muscle loss in other conditions. We aimed to define the associations of GDF-15 and muscle wasting in PAH, to assess its utility as a biomarker of muscle loss and to investigate its downstream signalling pathway as a therapeutic target. METHODS: GDF-15 levels and measures of muscle size and strength were analysed in the monocrotaline (MCT) rat, Sugen/hypoxia mouse and in 30 patients with PAH. In C2C12 myotubes the downstream targets of GDF-15 were identified. The pathway elucidated was then antagonised in vivo. RESULTS: Circulating GDF-15 levels correlated with tibialis anterior (TA) muscle fibre diameter in the MCT rat (Pearson r=-0.61, p=0.003). In patients with PAH, plasma GDF-15 levels of <564 pg/L predicted those with preserved muscle strength with a sensitivity and specificity of ≥80%. In vitro GDF-15 stimulated an increase in phosphorylation of TGFß-activated kinase 1 (TAK1). Antagonising TAK1, with 5(Z)-7-oxozeaenol, in vitro and in vivo led to an increase in fibre diameter and a reduction in mRNA expression of atrogin-1 in both C2C12 cells and in the TA of animals who continued to grow. Circulating GDF-15 levels were also reduced in those animals which responded to treatment. CONCLUSIONS: Circulating GDF-15 is a biomarker of muscle loss in PAH that is responsive to treatment. TAK1 inhibition shows promise as a method by which muscle atrophy may be directly prevented in PAH. TRIAL REGISTRATION NUMBER: NCT01847716; Results.

The patient experience of pulmonary hypertension: a large cross-sectional study of UK patients.

BACKGROUND: Pulmonary Hypertension Association UK (PHA-UK) is the only charity in the UK especially for people affected by pulmonary hypertension (PH). To better understand the impact of PH on patients and carers beyond clinical symptoms, the PHA-UK carried out a cross-sectional survey on the effect of PH on daily living, along with a follow-up survey assessing the financial impact of PH. METHODS: This is a descriptive cross-sectional survey of adult patients with PH in the UK. A quantitative survey of four key topics (time to diagnosis, quality of life [QoL], financial impact and specialist treatment), was made available to PHA-UK members and patients on PH therapy, with a follow-up financial impact survey sent to those responders who agreed to be contacted further. Data collection was carried out in January and February 2017 for the main survey, and November and December 2017 for the financial impact survey. RESULTS: The main survey was completed by 567 individuals, and the financial follow-up survey by 171. Mean age of responders was 69 ± 17 years with 70% female. 60% of respondents said PH had a major impact on their QoL, with 45% reporting that treatment and management improves their QoL 'a lot'. The time between first experiencing symptoms and diagnosis was ≥1 year for 48% of patients, with 40% seeing 4+ doctors before diagnosis. 63% of patients reported financial worries. Patients in part-time and full-time work reported the greatest financial burden, with a 13 and 33% fall in monthly income respectively. Patients had positive experiences of treatment in specialist centres, with 62% rating their care 'excellent', and 92% saying they preferred travelling to a specialist centre rather than seeing a local non-specialist. CONCLUSIONS: This study reports the largest UK survey exploring issues affecting patients with PH. The study shows that despite the availability of new therapies, patients are still experiencing delays prior to diagnosis, and experiencing both emotional and financial impacts from the disease. By identifying the areas patients find most important in their treatment, this research can inform future care policies and long-term management to support patients living with PH and their families.

emPHasis-10: development of a health-related quality of life measure in pulmonary hypertension.

The aim of this study was to develop a measure of the impact of pulmonary hypertension (PH) on health-related quality of life (HRQoL) as there is a need for a short, validated instrument that can be used in routine clinical practice. Interviews were conducted with 30 PH patients to derive 32 statements, which were presented as a semantic differential six-point scale (0-5), with contrasting adjectives at each end. This item list was completed by patients attending PH clinics across the UK and Ireland. Rasch analysis was applied to identify items fitting a uni-dimensional model. 226 patients (mean age 55.6±14 years; 70% female) with PH (82% had pulmonary arterial hypertension) completed the study questionnaires. 10 of the 32 items demonstrated fit to the Rasch model (Chi-squared 16; p>0.05) and generated the emPHasis-10 questionnaire. Test-retest (intraclass correlation coefficient 0.95, n=33) and internal consistency (Chronbach's α=0.9) were strong. emPHasis-10 scores correlated consistently with other relevant measures and discriminated subgroups of patients stratified by World Health Organization functional class (ANOVA F=1.73; p<0.001). The emPHasis-10 is a short questionnaire for assessing HRQoL in pulmonary arterial hypertension. It has excellent measurement properties and is sensitive to differences in relevant clinical parameters. It is freely available for clinical and academic use.

Patient information that promotes healt literacy.

Health literacy is the ability to make informed health decisions in everyday life. For many patients and carers, decision-making is made more difficult by the fact that high-quality information is unavailable to them. The Pulmonary Hypertension Association has created patient materials that promote health literacy to help patients and their families make decisions that are well informed.

The use of sildenafil to treat pulmonary hypertension associated with interstitial lung disease.

BACKGROUND AND OBJECTIVE: Limited data suggest a benefit following sildenafil treatment in patients with pulmonary hypertension (PH) and interstitial lung disease (ILD). The role of sildenafil in the management of PH in ILD is not clear. We report our experience of ILD patients with PH after 6-month sildenafil therapy. METHODS: We reviewed 15 patients (mean age 55 ± 15 years; 8 men) with ILD (mean FVC 52.6 ± 15.4%) and PH (mean right ventricular systolic pressure 73.8 ± 17.8 mm Hg). Median brain natriuretic peptide: 37 (5-452) pmol/L; mean 6MWD: 156 ± 101 m. RESULTS: Following 6-month treatment with sildenafil, brain natriuretic peptide levels were lower (n = 12, P = 0.03), 6MWD was higher (n = 6, P < 0.05), but no change in right ventricular systolic pressure (n = 11) was demonstrated. CONCLUSIONS: Our observations suggest that sildenafil may be useful in the management of PH in ILD. Controlled trials are warranted before therapeutic recommendations can be made.

A single-centre, placebo-controlled, double-blind randomised cross-over study of nebulised iloprost in patients with Eisenmenger syndrome: A pilot study.

BACKGROUND: Pulmonary arterial hypertension (PAH), is a rare and progressive disease with a high morbidity and mortality. Prostanoid pulmonary vasodilators are the most effective treatment for idiopathic and connective tissue associated PAH. Nonetheless, data examining their safety and efficacy in patients with Eisenmenger syndrome the most severe form of PAH, that is, related to cyanotic congenital heart disease (CHD-PAH) remains limited. AIM: To evaluate safety and the clinical efficacy of nebulised iloprost in patients with Eisenmenger syndrome who are on maximum background oral PAH therapy. METHODS: This pilot study was a randomised, double-blind, placebo-controlled, cross-over study. Patients were randomised to receive nebulised placebo or iloprost for 12 weeks and were then crossed over, with a 7-14-day washout. The primary endpoint was a change in 6-minute walk distance (6MWD). RESULTS: Sixteen patients (11 females, aged 47.3 ±â€¯9.8 year) were recruited, twelve completed the study. All were in WHO-FC III, with a resting oxygen saturation of 84 [81-87] % and a median 6MWD of 290 [260-300] m. There was no significant difference in the primary endpoint between nebulised iloprost (0[-4-9]m) and placebo (10 [-15-51]m), p = 0.58. There were no safety concerns with nebulised iloprost. CONCLUSIONS: Our pilot study provides preliminary evidence that the addition of nebulised iloprost to maximum oral PAH therapy did not improve the primary endpoint of 6MWD. Nebulised iloprost was well tolerated with no significant safety concerns in CHD-PAH.

Chronic thromboembolic pulmonary hypertension following long-term peripherally inserted central venous catheter use.

A 36-year-old woman presented with recurrent pulmonary emboli (PE) despite oral anticoagulation. She was a type I diabetic with severe gastroparesis requiring insertion of multiple long-term peripherally inserted central catheters (PICC) over a 10-year period. Imaging at presentation demonstrated a PICC-associated mobile mass in the right atrium and signs of pulmonary hypertension (PH). She was thrombolyzed and fully anticoagulated, and diabetic management without PICC strongly recommended. PH persisted, however, and she developed chronic thromboembolic pulmonary hypertension (CTEPH), for which successful pulmonary endarterectomy (PEA) surgery led to symptomatic and hemodynamic improvement. This was the first case of CTEPH reported related to long-term PICC use outside the setting of malignant disease, and a novel observation that the PEA specimen contained multiple plastic fragments. Long-term PICC placement increases the risk of CTEPH, a life-threatening, albeit treatable, complication.

Safety and tolerability of bosentan in adults with Eisenmenger physiology.

BACKGROUND: Bosentan, a dual-endothelin receptor antagonist, is an established treatment for pulmonary arterial hypertension. We hypothesized that bosentan is safe and well tolerated in patients with Eisenmenger physiology. METHODS: In this pilot open-label study, we primarily examined safety and tolerability of oral bosentan. Patients were recruited from our adult congenital heart clinic following informed consent. Baseline and 3-month assessment included WHO functional class, resting oxygen saturations, 6-min walk test, transthoracic echocardiography and respiratory mass spectrometry. Patient clinical status and liver enzymes were closely monitored throughout. RESULTS: All 10 study patients (42+/-4 years; eight female) tolerated bosentan well. No major adverse events or significant liver enzyme elevations were observed. All but one patient felt better; none felt worse. Four patients experienced transient leg oedema. Resting oxygen saturations (83+/-5 versus 80+/-5%; P=0.011) and the distance travelled in the 6-min walk test (348+/-112 versus 249+/-117 m; P=0.004) increased relative to baseline. Changes in echocardiographic parameters (maximum aortic forward flow velocity 1.3+/-0.1 versus 1.1+/-0.2 ms, P=0.013; pulmonary arterial acceleration time 66+/-10 versus 58+/-12 m/s, P=0.02) and pulmonary blood flow (3.45+/-1.2 versus 2.58+/-1.0 L/min, P=0.008) suggested improved pulmonary haemodynamics by study end. Other echocardiographic changes suggested improved right ventricular systolic function (septal amplitude 1.0 versus 1.1 cm, P=0.048; systolic tissue Doppler velocity 4.8 versus 2.3 cm s(-1), P=0.002) by study end. CONCLUSIONS: Bosentan was safe and well tolerated in adults with Eisenmenger physiology both at initiation and after 3 months of oral therapy. Clinical status of patients and pulmonary haemodynamics appeared to improve, and this warrants further investigation.

Disease targeting therapies in patients with Eisenmenger syndrome: response to treatment and long-term efficiency.

OBJECTIVES: To examine long-term efficacy of disease targeting therapies (DTT) in patients with Eisenmenger syndrome. METHODS: All adult patients with Eisenmenger syndrome treated with DTT at our institution were included. Functional class (FC), oxygen saturation and 6-minute walk test distance (6 MWTd) were analysed retrospectively. RESULTS: Between 2002 and 2010, 79 Eisenmenger patients (21 males, 16 with Down syndrome) aged 34 ± 10 years (range 17-68 years) were included. Median follow-up was 3.3 years (range 0.2 to 8.9 years). 6 MWTd increased early after initiation of DTT, with a plateau after approximately 3 years and no obvious trend towards a deterioration on average during longer-term follow-up. Two patients died during follow-up and escalation of treatment was required in 18 patients after a median period of 2.5 years. Escalation of therapy was also associated with an increase in 6 MWTd. In addition, FC improved on DTT and oxygen saturation, increased, both at rest and peak exercise. This effect was more pronounced in the patients with the lowest baseline oxygen saturation at rest. CONCLUSIONS: Long-term DTT is safe and improves objective exercise capacity and subjective symptoms. Response to DTT was typically observed early after initiation of DTT and was, on average, maintained longer-term. However, 1 in 5 patients required escalation of DTT, with time, due to symptomatic deterioration and this was associated with an afresh improvement in 6 MWTd.

A review of the management of pulmonary arterial hypertension associated with congenital heart disease.

Approximately 5-10% of adolescent and adult patients with congenital heart disease (CHD) will develop pulmonary arterial hypertension (PAH). Patients with PAH associated with CHD (PAH-CHD) exhibit several similarities to those with idiopathic and other associated forms of PAH, especially with regards to their non-specific, cardinal symptoms. The development of PAH-CHD can lead to lifelong impairment although, paradoxically, survival may be better versus idiopathic PAH. Patients with PAH-CHD may experience social limitations, and emotional and psychological issues, arising from their disease burden. Nurses and other allied healthcare professionals are well placed to deliver the individually-tailored care that patients with PAH-CHD require. Activities known to be of particular benefit include patient engagement and education, patient empowerment, colleague training, and ensuring effective communication across the multidisciplinary team. Recent developments in the management of PAH-CHD have led to changes in the medical needs and optimal care of this patient population. This review aims to provide an overview of the natural course, diagnosis, symptoms and impact of PAH-CHD. We also aim to communicate the current standards in management of patients with PAH-CHD, and how their outlook can be improved in the future.

The trajectory to diagnosis with pulmonary arterial hypertension: a qualitative study.

OBJECTIVES: To investigate the patient's experience of the trajectory to receiving a diagnosis of pulmonary arterial hypertension (PAH) and inform the provision of care for this patient group. DESIGN: Qualitative study using in-depth one-to-one interviews and pictorial representations. Data were analysed using thematic analysis. SETTING: Participants were interviewed in their own homes across England. PARTICIPANTS: 30 patients with a diagnosis of pulmonary hypertension (18 participants were women, mean age 56 and range 26-80 years and time since diagnosis ranged from a few months to more than 12 years) participated. RESULTS: All participants, regardless of the time since diagnosis, vividly described the process from manifestation of symptoms to receiving a confirmed diagnosis. The authors present data using three major themes: (i) making sense of symptoms, (ii) process of elimination and (iii) being diagnosed with PAH. Making sense of symptoms represented an early period of perseverance-people tried to carry-on as usual despite 'unexplained breathlessness'. As time progressed, this period was punctuated by critical events that triggered seeking medical advice. Once medical contact had been made, patients described a period of 'elimination' and convoluted contact with the medical profession. Dyspnoea misdiagnosis was a key factor that delayed the PAH diagnosis. Diagnosis disclosure by some medical professionals was also viewed as lacking empathy. More positive experiences were relayed when the medical team disclosing the diagnosis acknowledged previous limitations. CONCLUSIONS: A lack of awareness of this illness from both the sufferer themselves and the medical profession emerged as a central theme and led to prolonged periods of being misdiagnosed. The application of a diagnostic pathway for unexplained dyspnoea that alerts practitioners to rare conditions could expedite the process of correct diagnosis.

Quality of life and functional capacity can be improved in patients with Eisenmenger syndrome with oral sildenafil therapy.

BACKGROUND: Patients with Eisenmenger syndrome (ES) have a decreased exercise capacity and poor quality of life (QoL). While patients may survive to middle adulthood, the burden of disease is disabling. Sildenafil seems to improve exercise tolerance and hemodynamics, but there is no data to date on its impact on QoL. METHODS: Eisenmenger patients in New York Heart Association (NYHA) class III were recruited in a prospective study of efficacy and safety of oral sildenafil. The QoL endpoint was assessed using a disease-specific questionnaire (CAMPHOR). Exercise capacity was assessed by means of six minute walk test (6MWT). All patients underwent comprehensive assessment at baseline and after 3months of treatment. RESULTS: Twelve patients (mean age was 34.3±10.2, 83% female) with various cardiac anatomies were recruited. No major adverse events during the follow-up or significant drop in resting oxygen saturation were recorded. After 3months of oral sildenafil therapy, all patients improved to NYHA II with a concomitant improvement in 6MWT distance (347.3±80.7 to 392.5±82.0m, p=0.002). All components of the CAMPHOR score, relating to symptoms, activity and QoL, improved significantly resulting in substantial improvement in the total CAMPHOR score (27.6±10.5 to 15.8±10.4, p=0.002). CONCLUSIONS: Three months of sildenafil therapy in adults with ES was well tolerated and associated with significant improvement in the QoL CAMPHOR questionnaire and in NYHA class and exercise capacity. Larger studies are warranted to assess long term efficacy of oral sildenafil and potential impact on survival.

Long-term safety, tolerability and efficacy of bosentan in adults with pulmonary arterial hypertension associated with congenital heart disease.

OBJECTIVE: To examine long-term safety and efficacy of bosentan--an oral dual endothelin receptor antagonist--in patients with pulmonary hypertension associated with congenital heart disease or Eisenmenger's syndrome. DESIGN: Retrospective study. SETTING: Tertiary cardiology referral centre. PATIENTS: All adult patients with pulmonary arterial hypertension associated with congenital heart disease treated with bosentan at the Royal Brompton Adult Congenital Heart Centre were included. MAIN OUTCOME MEASURES: Oxygen saturation, functional (WHO) class, 6-minute walk test distance and liver enzymes were analysed. RESULTS: Eighteen patients (14 female) with pulmonary arterial hypertension associated with congenital heart disease (15 patients with Eisenmenger's syndrome) with a mean (SD) age of 41 (9) years (range 23-69) were included. Median follow-up was 29 months (range 1-39). One patient died during follow-up. Patients tolerated bosentan well and no significant rise in liver transaminases was seen. Arterial oxygen saturation remained stable throughout follow-up. Mean (SD) functional class (p = 0.001) and the 6-minute walk test distance improved compared with baseline (284 (144) vs 363 (124) m, 380 (91) m and 408 (114) m at baseline, 0-6 months, 6-12 months and 1-2 years of treatment, respectively; p<0.05 for each). CONCLUSIONS: Bosentan appears to be safe and well tolerated in adults with pulmonary arterial hypertension associated with congenital heart disease or Eisenmenger's syndrome during mid- to long-term follow-up. In addition, functional class and the 6-minute walk test distance improved and this effect was maintained for up to 2 years of bosentan treatment.

Presentation, survival prospects, and predictors of death in Eisenmenger syndrome: a combined retrospective and case-control study.

AIMS: To characterize contemporary Eisenmenger patients at a large centre for adult congenital heart disease, assess survival prospects, and identify predictors of death in this population. METHODS AND RESULTS: All Eisenmenger patients under follow-up at our centre since 2000 (n=171, mean age 37+/-12 years) were included. To identify predictors of mortality, a case-control study was performed. Data including symptoms, functional class, medication, laboratory, and electrocardiographic and echocardiographic parameters are presented. Iron deficiency was common and strongly related to phlebotomy (relative risk 4.1, P<0.0001). Haemoglobin concentration was inversely related to arterial oxygen saturations in iron-replete patients (P<0.001) but not in iron-deficient patients. During a median follow-up of 67 months, 20 patients died. Survival at 40, 50, and 60 years of age was 94, 74, and 52%, respectively. When compared with healthy individuals, median survival was reduced by approximately 20 years in Eisenmenger patients and was worst in those with complex lesions. Predictors of mortality included functional class, signs of heart failure, history of clinical arrhythmia, QRS duration and QTc interval, and low serum albumin and potassium levels. CONCLUSION: Despite good short-term prognosis, life expectancy is markedly reduced in Eisenmenger patients. Markers of heart failure and parameters associated with arrhythmia are of prognostic value in terms of mortality and may guide clinicians caring for Eisenmenger patients.

Blood viscosity and its relationship to iron deficiency, symptoms, and exercise capacity in adults with cyanotic congenital heart disease.

OBJECTIVES: This study sought to determine the relationship between blood viscosity and iron deficiency and their impact on symptoms and exercise function in adults with cyanotic congenital heart disease. BACKGROUND: Iron deficiency is believed to raise whole blood viscosity in cyanotic congenital heart disease, although available data are inconsistent. METHODS: Thirty-nine cyanotic adults were prospectively assessed for iron deficiency (transferrin saturation < or =5%), hyperviscosity symptoms, and exercise capacity. Same-day measurement of whole blood viscosity and hematocrit (Hct) adjusted viscosity (cells resuspended in autologous plasma to Hct of 45%) was performed at shear rates ranging from 0.277 s(-1) to 128.5 s(-1). RESULTS: Viscosity did not differ between patients with iron deficiency (n = 14) and those without (n = 25). Whole blood viscosity correlated with Hct (r = 0.63, p < 0.001 at low shear and r = 0.84, p < 0.001 at high shear) but not with red blood cell size or iron indices. Hyperviscosity symptoms were independent of iron indices but directly correlated with increased Hct-adjusted viscosity (r = 0.41, p = 0.01). Exercise capacity did not differ in iron-deficient patients. However, peak oxygen consumption was higher in those with Hct > or = 65% (12.6 +/- 3.4 ml/kg/m2 vs. 9.8 +/- 2.6 ml/kg/m2, mean +/- SD, p = 0.036) despite higher whole blood viscosity in these same individuals (p < 0.01 for all shear rates). CONCLUSIONS: Iron deficiency is common in cyanotic adults but does not alter viscosity. Hyperviscosity symptoms are associated with a higher Hct-adjusted viscosity independent of cell size or iron stores. Higher Hct is associated with better exercise capacity. Further work to understand the origin of hyperviscosity symptoms is warranted.