Congenital heart disease-associated pulmonary arterial hypertension: preliminary results from a novel registry

BACKGROUND/AIMS

Pulmonary arterial hypertension (PAH) frequently accompanies childhood congenital heart disease (CHD) and may persist into adult life. The advent of specific PAH therapies for PAH prompted formation of a national Australian and New Zealand registry in 2010 to document the incidence, demographics, presentation and outcomes for these patients.

METHODS

This multicentre, prospective, web-based registry enrols patients with CHD-associated PAH being followed in a tertiary centre. The inclusion criteria stipulated patient age ≥16 years, a measured mean pulmonary arterial pressure >25 mmHg at rest or echocardiographical evidence of PAH or a diagnosis of Eisenmenger syndrome, and followed since 1 January 2000. A single observer collected standardised data during a series of site visits.

RESULTS

Of the first 50 patients enrolled, 30 (60%) were female. The mean age (standard deviation (SD)) at the time of PAH diagnosis or confirmation in an adult centre was 27.23 (10.07) years, and 32 (64%) patients are currently aged >30 years. Fourteen (28%) patients were in World Health Organization Functional Class II and 36 (72%) in Class III at the time of diagnosis. Forty-seven of 50 (94%) had congenital systemic-pulmonary shunts, and 36 (72%) never underwent intervention. Thirteen (26%) had Down syndrome. Confirmation of PAH by recent cardiac catheterisation was available in 30 (60%) subjects. During follow up, a total of 32 (64%) patients received a PAH-specific therapy.

CONCLUSIONS

CHD associated with PAH in adult life has resulted in a new population with unique needs. This registry will allow documentation of clinical course and long-term outcomes for these patients.

Screening and treating pulmonary arterial hypertension in a tertiary hospital-based multidisciplinary clinic: the first 200 patients

BACKGROUND

Pulmonary arterial hypertension (PAH) is an increasingly recognised serious illness with insidious onset, delayed diagnosis, complex diagnostic algorithms and poor prognosis, but with recently available effective treatments.

AIMS

To efficiently diagnose and to offer treatment for PAH, we established a multidisciplinary service in 2005, where patients attend a clinic staffed by specialists in cardiology, respiratory medicine, rheumatology and immunology in a tertiary referral hospital setting.

METHODS

We studied the first 200 patients referred. Serology, echocardiography, lung function tests, high-resolution computed tomography, World Health Organisation Class determination and 6-min walk tests and/or right heart catheterisation were performed, as clinically indicated.

RESULTS

Of the 200 patients seen, 66 had confirmed pulmonary hypertension (mean pulmonary artery pressure > 25 mmHg) diagnosed on echocardiography ± right heart catheterisation. Of these patients, 58 had catheter-proven PAH (mean pulmonary artery pressure > 25 mmHg with mean wedge pressure < 15 mmHg). Underlying diagnoses for the confirmed PAH patients were idiopathic (32), scleroderma-associated (14), other connective tissue disease (4) and associated with congenital heart disease (8). Patients with confirmed PAH were commenced on PAH-specific therapy--initially bosentan in the majority but sildenafil, and iloprost were occasionally used initially for patient-specific reasons. Median time from when the patient first called the clinic to prescription of therapy was 16 days (interquartile range; 0-31 days). All surviving patients with PAH have attended for regular 6-monthly follow-up visits with a 100% retention rate up to 4 years.

CONCLUSION

A multidisciplinary clinic can provide efficient diagnosis and rapid triage to PAH-specific therapy, if appropriate. Retention rates remain high, at follow up.

Ironic case of hepatic dysfunction following the global withdrawal of sitaxentan

A patient with pulmonary arterial hypertension secondary to systemic sclerosis was successfully treated with sitaxentan prior to its worldwide withdrawal (because of hepatotoxicity concerns), but then ironically experienced acute hepatic dysfunction during substitute bosentan therapy, and was eventually stabilised on a phosphodiesterase-5 inhibitor.

Vitamin B-12 supplementation improves arterial function in vegetarians with subnormal vitamin B-12 status

OBJECTIVE

Vegetarians are more vascular-healthy but those with subnormal vitamin B-12 status have impaired arterial endothelial function and increased intima-media thickness. We aimed to study the impact of vitamin B-12 supplementation on these markers, in the vegetarians.

DESIGN

Double-blind, placebo controlled, randomised crossover study.

SETTING

Community dwelling vegetarians.

PARTICIPANTS

Fifty healthy vegetarians (vegetarian diet for at least 6 years) were recruited.

INTERVENTION

Vitamin B-12 (500 µg/day) or identical placebo were given for 12 weeks with 10 weeks of placebo-washout before crossover (n=43), and then open label vitamin B-12 for additional 24 weeks (n=41).

MEASUREMENT

Flow-mediated dilation of brachial artery (FMD) and intima-media thickness (IMT) of carotid artery were measured by ultrasound.

RESULTS

The mean age of the subjects was 45±9 years and 22 (44%) were male. Thirty-five subjects (70%) had serum B-12 levels <150 pmol/l. Vitamin B-12 supplementation significantly increased serum vitamin B-12 levels (p<0.0001) and lowered plasma homocysteine (p<0.05). After vitamin B-12 supplementation but not placebo, significant improvement of brachial FMD (6.3±1.8% to 6.9±1.9%; p<0.0001) and in carotid IMT (0.69±0.09 mm to 0.67±0.09 mm, p<0.05) were found, with further improvement in FMD (to 7.4±1.7%; p<0.0001) and IMT (to 0.65±0.09 mm; p<0.001) after 24 weeks open label vitamin B-12. There were no significant changes in blood pressures or lipid profiles. On multivariate analysis, changes in B-12 (β=0.25; p=0.02) but not homocysteine were related to changes in FMD, (R=0.32; F value=3.19; p=0.028).

CONCLUSIONS

Vitamin B-12 supplementation improved arterial function in vegetarians with subnormal vitamin B-12 levels, proposing a novel strategy for atherosclerosis prevention.

Therapeutic approaches in adults with congenital heart disease-associated pulmonary arterial hypertension

Pulmonary arterial hypertension is a major contributor to reduced functional capacity in patients with congenital heart disease. Expert care is essential. Whilst careful supportive management has traditionally been the mainstay for these patients, in recent times significant improvements in exercise capacity and even survival have been observed with the use of disease-targeted therapy, including endothelin receptor antagonists, phosphodiesterase inhibitors and prostanoids. In this review we will discuss current therapeutic options and summarise the recent literature on disease-targeted therapy.

Risk factors for cardiovascular disease do not fully explain differences in carotid intima-media thickness between Indigenous and European Australians without diabetes

OBJECTIVE

To investigate whether cardiovascular risk factors can explain the higher carotid intima-media thickness (CIMT) in Indigenous compared with European Australians.

DESIGN

Cross-sectional study in three subgroups.

PATIENTS

Non-diabetic urban European (n = 86), urban Indigenous (n = 69), and remote Indigenous (n = 60) Australians aged 25-64 years.

MEASUREMENTS

CIMT, age, sex, anthropometry, blood pressure, smoking status, fasting glucose and insulin, haemoglobin (Hb)A1c, homocysteine, C-reactive protein (CRP), lipids, urinary albumin and creatinine.

RESULTS

CIMT and levels of risk factors, except fasting glucose and total cholesterol, worsened across the three groups. Log(n) fasting insulin [beta = 0.022, 95% confidence interval (CI) 0-0.0439], age (beta = 0.006, 95% CI 0.004-0.007), gender (female beta = -0.005 vs. male, 95% CI -0.084 to -0.026), mean arterial pressure (MAP) (beta = 0.001, 95% CI 0.001-0.002) and ethnicity/location [urban Indigenous (beta = 0.027, 95% CI -0.010 to 0.064 vs. European); remote Indigenous (beta = 0.083, 95% CI 0.042-0.123 vs. European)] explained 41% of variance in CIMT. Significant interactions were seen for ethnicity/location with age (P = 0.014) and MAP (P = 0.018). Age was consistently associated with CIMT across the three populations, and was associated with larger increments in CIMT for the Indigenous subgroups (beta = 0.007, 95% CI 0.005-0.009 urban; beta = 0.007, 95% CI 0.004-0.010 remote) compared with Europeans (beta = 0.003, 95% CI 0.002-0.006) in models including age, sex and MAP. MAP was only associated with CIMT in the remote Indigenous subgroup.

CONCLUSION

After adjusting for selected risk factors, CIMT in remote Indigenous participants was still higher than in Europeans. The slope of the association between age and CIMT steepened from urban Europeans to remote Indigenous.

The "atheroprotective" mediators apolipoprotein A-I and Foxp3 are over-abundant in unstable carotid plaques

OBJECTIVE

Inflammation is important in plaque vulnerability but the role of atheroprotective mediators in unstable plaques is not defined. The apolipoproteinA-I (apoA-I) component of HDL, and CD4+/CD25+ regulatory T cells (with their major transcription factor, Foxp3), have been implicated in the suppression of vascular inflammation. Our aim was to characterise the presence of these novel "protective" markers (apoA-I and Foxp3) in carotid plaques from symptomatic and asymptomatic subjects.

METHODS AND RESULTS

Plaques from 57 patients (25 symptomatic, 32 asymptomatic) were stained immunohistochemically for macrophages (CD68), T cells (CD3), monocyte chemotactic protein-1 (MCP-1), matrix metalloproteinase-2 (MMP-2), myeloperoxidase (MPO), apoA-I and Foxp3. Twelve randomly selected plaques (6 asymptomatic, 6 symptomatic) were immunostained for interleukin-10 (IL-10) and interleukin-17 (IL-17). Staining was quantified using Image-Pro Plus software. Significantly greater areas of positive immunostaining for CD68, CD3, MCP-1, MMP-2, IL-17 and MPO were found in plaques from symptomatic patients compared with asymptomatic patients (p<0.05 for all). Furthermore, significantly greater areas of positive immunostaining for apoA-I, Foxp3 and IL-10 were found in symptomatic versus asymptomatic plaques (p<0.05 for all). The presence of apoA-I was correlated significantly and co-localised with CD3, CD68, MCP-1, MMP-2 and MPO immunostaining (R=0.70, 0.63, 0.52, 0.55 and 0.79, respectively; p<0.01 for all). Foxp3 immunostaining also correlated significantly with CD3 (R=0.42), CD68 (R=0.47), MCP-1 (R=0.55) and MMP-2 (R=0.44) immunostaining (p<0.05 for all).

CONCLUSIONS

ApoA-I and Foxp3 are over-abundant in plaques from symptomatic subjects and co-localise with key inflammatory mediators. These data suggest ineffective/insufficient protection against atherosclerosis-mediated inflammation by these "atheroprotective" moieties.

Recalibration of a Framingham risk equation for a rural population in India

BACKGROUND

Coronary heart disease (CHD) risk estimation tools are a simple means of identifying those at high risk in a community and hence a potentially cost-effective strategy for CHD prevention in resource-poor countries. Since India has few local data upon which to develop such a tool de novo, in this study a Framingham risk equation has been recalibrated to estimate CHD risks in a population from rural India and the sensitivity of the method to information resources examined. Recent surveys of this population have found high levels of cardiovascular risk factors, particularly metabolic risk factors and a high proportion of mortality due to cardiovascular diseases.

METHODS

The proportion of a rural Indian population at high risk of CHD using three risk estimation equations was estimated. The first a published version of the Framingham risk equation, the second a recalibrated equation using local mortality surveillance data and local risk factor data, and the third a recalibrated equation using national mortality data and local risk factor data.

RESULTS

The mean 10-year probability of CHD for adults >30 years was 10.4% (9.6% to 11.1%) for men and 5.3% (4.9% to 5.7%) for women using the Framingham equation; 10.7% (9.9% to 11.5%) for men and 4.2% (3.9% to 4.5%) for women using the local recalibration; and 18.9% (17.7% to 20.1%) for men and 8.2% (7.6% to 8.8%) for women using the national recalibration.

CONCLUSION

These findings indicate that in India, equations recalibrated to summary national data are unlikely to be relevant to all regions of India and demonstrate the importance of local data collection to enable development of relevant CHD risk tools.

Diastolic dysfunction and abnormalities of the microcirculation in type 2 diabetes

AIM

Diabetic cardiomyopathy is an increasingly recognized entity. The pathogenic factors that may contribute to its development, especially the earliest changes of diastolic dysfunction (DD), have not been clearly defined. Microvessel dysfunction and upregulation of profibrotic growth factors have been described as possible causes. The aim of this study was therefore to determine whether microvascular dysfunction and/or upregulation of the profibrotic connective tissue growth factor (CTGF) are associated with subclinical DD in subjects with type 2 diabetes.

METHODS

Forty subjects with type 2 diabetes and 20 age-matched non-diabetic controls, all of whom had no clinical evidence of ischaemic heart disease, cardiac failure or echo evidence of systolic ventricular dysfunction, were recruited. Microvascular function was measured by laser Doppler velocimetry, with examination of endothelium-dependent increase in blood flow following iontophoresis of acetylcholine (ACh) and endothelium-independent increase in blood flow in response to the nitric oxide donor sodium nitroprusside (SNP). CTGF levels were determined by Western immunoblotting.

RESULTS

DD determined on the basis of traditional echocardiographic criteria was similar in diabetic subjects compared with controls (28 vs. 20%, p = 0.5). Using left ventricular myocardial tissue Doppler-based indices for DD, the E/E' and the E'/A' ratios (where E is the flow related to early ventricular filling and E' and A' are early and late diastolic velocities, respectively) in diabetic subjects revealed evidence of more DD than controls (p = 0.046 and p = 0.007 respectively) . Comparing controls with no DD by conventional echocardiographic criteria (Group I), diabetes and no DD (Group II) and diabetes with DD (Group III), there was a significant trend in reduction of both endothelium-dependent (ACh fold change; p = 0.04) and endothelium-independent (SNP fold change; p = 0.0004) blood flow across the groups. The ACh and SNP responses, however, were not correlated significantly with quartiles of the E/E' ratio or the E'/A' ratio. CTGF plasma levels did not differ across the groups and CTGF did not correlate with parameters of microvascular function.

CONCLUSIONS

This study indicates that while there is a significant association between DD and measures of microvascular function, the relationship between endothelial dysfunction, CTGF and subtle measures of DD is not strong. Other factors are therefore likely to play an important role in the early pathogenesis of subclinical cardiac DD in type 2 diabetes.

The effects of obesity and non-pharmacological weight loss on vascular and ventricular function and structure

AIMS

The mechanisms by which obesity confers increased cardiovascular risk and the effects of moderate weight loss on cardiovascular health are incompletely understood. We sought to characterize the preclinical changes in cardiac and vascular health that accompany obesity and the influence of lifestyle modification on these parameters.

METHODS

Preclinical markers of vasculopathy in resistance vessels and conduit arteries and left ventricular structure and function were assessed in 39 obese subjects (BMI > 30 kg/m(2)) and 11 healthy weight controls. The influence of serum on cellular adhesion molecule (CAM) expression on human endothelial cells was studied ex vivo in a subgroup of 13 obese and nine healthy weight subjects. These analyses were repeated in all 17 of the obese subjects who complied with 4-9 months of lifestyle modification treatment (six with weight loss >5% and 11 with weight loss <5%).

RESULTS

Compared with healthy weight controls, obese subjects had decreased peak hyperaemic forearm blood flow (p = 0.015), increased carotid intima-media thickness (p = 0.009), increased left ventricular wall thickness and volume and evidence of systolic and diastolic dysfunction as assessed using tissue Doppler imaging (S', p = 0.09; E'/A', p = 0.02), and serum from obese subjects increased the intercellular CAM-1 expression on human endothelial cells (p = 0.009). However, arterial endothelial function assessed by flow-mediated dilatation was not altered (p = 0.99). Lifestyle modification treatment resulted in potentially beneficial changes in fibrinogen (p = 0.003), HDL cholesterol (p = 0.05) and soluble vascular CAM-1 (p = 0.06). In subjects with weight loss greater than 5% of body weight, there was also a decrease in low-level inflammation (high-sensitivity C-reactive protein, p = 0.05), lipid peroxidation (thiobarbituric acid-reactive substances, p = 0.05) and triglycerides (p = 0.07).

CONCLUSIONS

Obesity is associated with widespread alterations in cardiac and vascular structure and function. Moderate short-term weight loss by lifestyle modification results in some beneficial changes in serum profile; however, these are not accompanied by significant alterations to either cardiac or vascular structure and function.

Increased carotid intima-media thickness in remote and urban Indigenous Australians: impact of diabetes and components of the metabolic syndrome

OBJECTIVE

Indigenous Australians have rates of cardiovascular (CVD) mortality some seven to 10-fold higher than non-Indigenous Australians aged 25-64 years. We aimed to evaluate the impact of type 2 diabetes and components of the metabolic syndrome on carotid intima-media thickness (CIMT) as a marker of cardiovascular risk in Indigenous Australians living in remote and urban environments and in Australians of European ancestry.

DESIGN, PATIENTS AND MEASUREMENTS

CIMT was measured by high-resolution B-mode ultrasound imaging of the common carotid artery in 119 remote Indigenous, 144 urban Indigenous and 122 urban European Australians with and without diabetes.

RESULTS

In nondiabetic participants, CIMT was lowest in Europeans (mean (SD) 0.64 mm (0.10)), higher in urban Indigenous Australians (0.67 mm (0.12)) and highest in remote Indigenous Australians (0.73 mm (0.15), P < 0.001). CIMT was higher with diabetes with the same pattern observed between populations: 0.73 mm, 0.79 mm and 0.82 mm, respectively (P < 0.001). Traditional risk factors (age, male gender, blood pressure and HbA1c) explained 35-45% of the variance of CIMT within each population group. However, differences in CIMT between population groups were maintained after adjustment for these cardiovascular risks plus cholesterol and smoking (P < 0.001). Factor analysis revealed that variables of the metabolic syndrome, together with smoking and elevated C-reactive protein (CRP) and urinary albumin-creatinine ratio (ACR), are likely to explain the higher CIMT in Indigenous Australians (and the urban-remote gradient). Unmeasured variables (genetic, psychosocial and socioeconomic) may also contribute to higher CIMT in these populations.

CONCLUSION

Glycaemic control and metabolic syndrome components contribute significantly to premature atherogenesis in Indigenous Australians and we recommend that therapy should be targeted accordingly.

Endothelial dysfunction and arterial abnormalities in childhood obesity

Rates of overweight and obesity in both adults and children have risen sharply during the past 20 years. The reasons for this escalation in obesity are not fully determined, however, sedentary lifestyle and dietary changes in combination with genetic predisposition are probably involved. Clinical cardiovascular disease, including myocardial infarction and stroke, are usually only manifest in the fifth decade of life or beyond. However, the earliest physical signs of atherosclerosis, the underlying disease process that leads to these events, may be present from early childhood. There are now a variety of noninvasive tests used to assess both the structural and functional properties of the vasculature and in vivo changes suggestive of 'early atherosclerosis' have now been characterised. These have allowed not only an increased understanding of the atherosclerotic changes to the vasculature that accompany overweight and obesity in children, but have also allowed serial study of the effects of diet and exercise interventions on early atherosclerosis changes, in childhood obesity.

Treatment of obstructive sleep apnoea leads to improved microvascular endothelial function in the systemic circulation

BACKGROUND

Obstructive sleep apnoea (OSA) is a common and potentially reversible cause of systemic hypertension. The mechanisms whereby OSA leads to hypertension and the effects of treatment on arterial function, however, are not well established. Microvascular arterial endothelial and smooth muscle function was assessed in subjects with OSA before and after treatment with continuous positive airways pressure (CPAP).

METHODS

Ten subjects of mean (SE) age 49 (8) years with at least moderately severe OSA had detailed forearm vascular reactivity studies before and after 3 months of CPAP treatment. The systemic circulation was assessed by measuring brachial artery pressure, flow and resistance responses to intra-arterial infusions of acetylcholine (ACh; an endothelium dependent vasodilator), sodium nitroprusside (SNP; an endothelium independent vasodilator), L-NMMA (a nitric oxide (NO) antagonist), and L-arginine (the substrate for NO).

RESULTS

Before CPAP, ACh and SNP infusions increased forearm blood flow in a dose dependent manner (p<0.01). After CPAP, endothelium dependent dilation to ACh was significantly increased (434 (23)% of baseline after CPAP v 278 (20)% before CPAP, p<0.001), whereas SNP induced dilation was unchanged. Resting NO production was higher after CPAP, evidenced by a significantly greater reduction in basal flow by L-NMMA (p=0.05). L-Arginine reversed the effect of L-NMMA in all cases.

CONCLUSION

In patients with OSA, treatment with CPAP improves baseline endothelial NO release and stimulates endothelium dependent vasorelaxation in the systemic circulation. This is a potential mechanism for improving systemic and vascular function in patients with OSA treated with CPAP.