Rachael Cordina

Resistance training improves cardiac output, exercise capacity and tolerance to positive airway pressure in Fontan physiology☆

BACKGROUND Subjects with Fontan-type circulation have no sub-pulmonary ventricle and thus depend exquisitely on the respiratory bellows and peripheral muscle pump for cardiac filling. We hypothesised that resistance training to augment the peripheral muscle pump might improve cardiac filling, reduce inspiratory-dependence of IVC return to the heart and thus improve exercise capacity and cardiac output on constant positive airway pressure (CPAP). METHODS Eleven Fontan subjects (32+/-2 years, mean+/-SEM) had cardiac magnetic resonance imaging (MRI) and exercise testing (CPET); six underwent 20 weeks of high-intensity resistance training; others were non-exercising controls. After training, CPET was repeated. Four trainers had MRI with real-time flow measurement at rest, exercise and on CPAP in the trained state and following a 12-month detrain. RESULTS In the trained state, muscle strength increased by 43% (p=0.002), as did total muscle mass (by 1.94 kg, p=0.003) and peak VO2 (by 183 ml/min, p=0.02). After detraining, calf muscle mass and peak workload had fallen significantly (p<0.03 for both) as did peak VO2 (2.72 vs. 2.18 l/min, p<0.001) and oxygen pulse, a surrogate for SV (16% lower, p=0.005). Furthermore after detraining, SV on MRI decreased at rest (by 11 ml, p=0.01) and during moderate-intensity exercise (by 16 ml, p=0.04); inspiratory-dependent IVC blood return during exercise was 40% higher (p=0.02). On CPAP, cardiac output was lower in the detrained state (101 vs. 77 ml/s, p=0.03). CONCLUSIONS Resistance muscle training improves muscle mass, strength and is associated with improved cardiac filling, stroke volume, exercise capacity and cardiac output on CPAP, in adults with Fontan-type circulation.

Skeletal muscle abnormalities and exercise capacity in adults with a Fontan circulation

Objectives The peripheral muscle pump is key in promoting cardiac filling during exercise, especially in subjects who lack a subpulmonary ventricle (the Fontan circulation). A muscle-wasting syndrome exists in acquired heart failure but has not been assessed in Fontan subjects. We sought to investigate whether adults with the Fontan circulation exhibit reduced skeletal muscle mass and/or metabolic abnormalities. Design and patients Sixteen New York Heart Association Class I/II Fontan adults (30±2 years) underwent cardiopulmonary exercise testing and lean mass quantification with dual x-ray absorptiometry (DXA); eight had calf muscle 31P magnetic resonance spectroscopy as did eight healthy age-matched and sex-matched controls. DXA results were compared with Australian reference data. Setting Single tertiary referral centre. Results Peak VO2 was 1.9±0.1 L/min (66±3% of predicted values). Skeletal muscle mass assessed by relative appendicular lean mass index was significantly reduced compared with age-matched and sex-matched reference values (Z-score −1.46±0.22, p<0.0001). Low skeletal muscle mass correlated with poorer VO2 max (r=0.67, p=0.004). Overall, skeletal muscle mass T-score (derived from comparison with young normal reference mean) was −1.47±0.21; 4/16 Fontan subjects had sarcopenic range muscle wasting (T-score <−2.0) and 9/16 had less marked, but clinically significant wasting (T-score <−1.0 but ≥−2.0). Muscle aerobic capacity, measured by the rate constant (k) of postexercise phosphocreatine resynthesis, was significantly impaired in Fontan adults versus controls (1.48±0.13 vs 2.40±0.33 min−1, p=0.02). Conclusions Fontan adults have reduced skeletal muscle mass and intrinsic muscle metabolic abnormalities.

Treatment of segmental pulmonary artery hypertension in adults with congenital heart disease.

INTRODUCTION Pulmonary arterial hypertension (PAH) in patients with congenital heart disease (CHD) usually has a homogeneous pressure distribution. More rarely, complex CHD patients have segmental PAH. This is often post-surgically. The characteristics of these patients and their responsiveness to specific pulmonary vasodilator therapy have not been described. METHODS Seven adults with segmental PAH complicating CHD were treated at 3 specialized adult CHD centers between January 2006 and December 2010. Clinical characteristics, six minute walking distances (6 MWD), laboratory tests and images were obtained from medical records and the responses to Bosentan, an endothelin-1 receptor antagonist, were assessed. RESULTS All patients (mean age 32 (23-42) years, five females) had a primary diagnosis pulmonary atresia (PA), four with major aortopulmonary collateral arteries (MAPCAs). Four segmental PAH patients had a right pulmonary artery stenosis, two a left pulmonary artery stenosis and one a unilateral MAPCA stenosis. All patients were symptomatic (functional class II or III) and bosentan was started empirically. Bosentan treatment led to a significant improvement in functional class compared to baseline (1.7 ± 0.5 versus 2.4 ± 0.5; p<0.01). Mean 6 MWD (available in 6 patients) increased by 62 m (22-150 m) from 386 ± 135 to 448 ± 133 m (p=0.03) after 12 months treatment. Most improvement was seen in patients with low baseline 6 MWD. Higher baseline exercise heart rate was significantly associated with lesser improvement in 6 MWD (r=-0.91 p=0.01). Laboratory results did not change after initiation of bosentan treatment. CONCLUSION This small retrospective case series suggested a significant improvement of functional class and exercise capacity after bosentan treatment in patients with segmental PAH. These findings warrant a prospective study of the potential benefit of selective pulmonary vasodilator therapy in these complex patients. Therefore, we call on treating physicians to share similar cases.

Late-onset pulmonary arterial hypertension after a successful atrial or arterial switch procedure for transposition of the great arteries.

Common complications after surgery for transposition of the great arteries (TGA) include systemic ventricular dysfunction and arrhythmia after atrial baffle repair (AB) and outflow tract stenosis or regurgitation after the arterial switch (AS). Severe pulmonary hypertension (PHT) is a rarely reported problem after AB and AS. In this study we sought to evaluate the frequency of late onset severe PHT following surgical repair for TGA. We report 3 cases, 2 after AB and 1 after AS, describe the frequency of this complication and treatment response, by comparing the response to pulmonary vasodilators in this group of patients to that of idiopathic or connective tissue disease (CTD) related PHT. We currently follow 85 patients ≥17 years of age with repaired TGA; 77 after AB and 8 after AS. 3.5% of our adult congenital heart disease patients with TGA have developed late severe PHT. None of these patients demonstrated clinical improvement with Bosentan at 6 months, however 2 of 3 were stabilised with the addition of Sildenafil to initial therapy. The third patient died 4 months after the diagnosis of severe PHT, whilst waiting for heart-lung transplantation, despite Bosentan, Sildenafil and inotropic support. By contrast, of 37 patients with idiopathic or CTD related PHT commenced on Bosentan as initial therapy, 32 (86.5%) demonstrated a clinical response at 6 months; the other patients had Sildenafil as added therapy after 6 months. Our data suggest that patients with TGA and late onset PHT are less likely to achieve a clinical response on pulmonary vasodilator monotherapy (P = 0.006). Whilst more investigation is needed, our experience suggests an aggressive clinical course, often requiring combination PHT treatment.

Chronic cyanosis and vascular function: implications for patients with cyanotic congenital heart disease.

In patients with cyanotic congenital heart disease, chronic hypoxaemia leads to important changes in blood vessel function and structure. Some of these alterations are maladaptive and probably contribute to impaired cardiopulmonary performance and an increased incidence of thrombotic and embolic events. Recent evidence suggests that deranged endothelial function, a sequel of chronic cyanosis, could be an important factor in the pathogenesis of cyanosis-associated cardiovascular risk. In this article, we discuss the physiological and mechanical consequences of compensatory erythrocytosis and possible pathophysiological mechanisms of vascular dysfunction in chronic cyanosis.

Three decades later: the fate of the population of patients who underwent the Atriopulmonary Fontan procedure

OBJECTIVE To review our experience of patients with an atrio-pulmonary Fontan circulation to determine their long-term outcomes. METHODS AND RESULTS A retrospective analysis of long-term follow-up data using the Australia and New Zealand Fontan Registry was performed. There were 215 patients surviving hospital discharge after an atrio-pulmonary Fontan completion. A total of 163 patients were alive at latest follow-up, with 52 deaths. Twelve patients had required heart transplantation and 95 had Fontan failure (death, transplantation, Fontan takedown, Fontan conversion, severe systemic ventricular dysfunction or NYHA≥3). Twenty-eight year freedom from death, death and transplantation and Fontan failure were 69% (95% CI 61-78%), 64% (95% CI 56-74%) and 45% (95% CI 36-55%) respectively. One hundred and thirty patients developed atrial arrhythmias. Freedom from arrhythmia at 28years post Fontan was 22.9% (95% CI: 15.1-30.8). Development of arrhythmia increased the likelihood of death (HR:2.97, 95%CI 1.50-5.81; p=0.002), death and heart transplantation (HR:3.11, 95%CI 1.64-5.87; p<0.001) and Fontan failure (HR:4.78 95%CI 2.95-7.74; p<0.001). There were 42 patients who had thromboembolic events, of which only 12 were therapeutically anti-coagulated. Two-thirds of the surviving patients (86/126) with an intact atrio-pulmonary Fontan were regularly reviewed. Patients receiving follow-up care with general cardiologists without specialised training were more likely to face Fontan failure than those managed by cardiologists with specialist training in congenital heart disease (HR: 1.94, 95% CI 1.16-3.24; p=0.02). The majority of the surviving patients (81/86) remained physically active and almost two-thirds (54/86) were currently employed. CONCLUSION Two-thirds of the patients who underwent a classical atrio-pulmonary Fontan are still alive 3 decades later. The majority are affected by the burden of arrhythmias but remain functionally active today. These challenging patients should only receive follow-up care from cardiologists with specialised training.

Widespread endotheliopathy in adults with cyanotic congenital heart disease.

INTRODUCTION Cyanotic congenital heart disease is associated with functional limitation and vascular events. The nature and extent of endothelial dysfunction in cyanotic adults is poorly understood. We sought to characterise endothelial function in this setting. METHODS A total of fourteen adults with cyanotic congenital heart disease (40±3 years) together with age- and sex-matched healthy controls underwent assessment of nitric oxide-dependent vascular responses, including flow-mediated dilatation of the brachial artery and dynamic vessel analysis of the retina in response to flickering light. Plasma levels of the endothelium-derived vasoconstrictor endothelin-1 and the nitric oxide antagonist, asymmetric dimethylarginine, were measured. Circulating endothelial progenitor cells were assessed by flow cytometry. RESULTS Flow-mediated dilatation was significantly lower in cyanosed adults than controls (4.0±0.8 versus 7.2±1.0%, p=0.019, n=11 per group). Retinal arterial and venous dilatory responses were also impaired (2.9±0.8 versus 5.0±0.6%, p=0.05 and 3.4±0.3 versus 5.2±0.7%, p=0.04, n=13). Serum levels of endothelin-1 and asymmetric dimethylarginine were higher in cyanosed adults (3.0±0.6 versus 1.1±0.1 pg/ml, p=0.004 and 0.68±0.05 versus 0.52±0.02 μmol/L, p=0.03, n=11). Endothelial progenitor cells (CD34+CD45dimCD133+KDR+) were reduced in those with chronic cyanosis (17±4 versus 40±6 per million white blood cells, p=0.005, n=11). CONCLUSIONS Endothelial function is impaired in the systemic arteries and retinal vessels in adults with cyanotic congenital heart disease, suggesting a widespread endotheliopathy. Diminished numbers of endothelial progenitor cells might potentially contribute to these observations.

Maternal cardiac arrhythmias during pregnancy and lactation

Arrhythmias occurring during pregnancy can cause significant symptoms and even death in mother and fetus. The management of these arrhythmias is complicated by the need to avoid harm to the fetus and neonate. It is useful to classify patients with arrhythmias into those with and without structural heart disease. Those with a primary electrical problem, but an otherwise normal heart, often tolerate rapid heart rates without compromise whereas patients with problems such as rheumatic heart disease, congenital heart disease or cardiomyopathy may quickly decompensate during an arrhythmia.

Brain Volumetrics, Regional Cortical Thickness and Radiographic Findings in Adults with Cyanotic Congenital Heart Disease

Background Chronic cyanosis in adults with congenital heart disease (CHD) may cause structural brain changes that could contribute to impaired neurological functioning. The extent of these changes has not been adequately characterized. Hypothesis We hypothesized that adults with cyanotic CHD would have widespread changes including abnormal brain volumetric measures, decreased cortical thickness and an increased burden of small and large vessel ischemic changes. Methods Ten adults with chronic cyanosis from CHD (40 ± 4 years) and mean oxygen saturations of 82 ± 2% were investigated using quantitative MRI. Hematological and biochemical parameters were also assessed. All subjects were free from major physical or intellectual impairment. Brain volumetric results were compared with randomly selected age- and sex-matched controls from our database of normal subjects. Results Five of 10 cyanotic subjects had cortical lacunar infarcts. The white matter (WM) hyperintensity burden was also abnormally high (Scheltens Scale was 8 ± 2). Quantitative MRI revealed evidence of extensive generalized WM and gray matter (GM) volumetric loss; global GM volume was reduced in cyanosed subjects (630 ± 16 vs. 696 ± 14 mL in controls, p = 0.01) as was global WM volume (471 ± 10 vs. 564 ± 18 mL, p = 0.003). Ventricular cerebrospinal fluid volume was increased (35 ± 10 vs. 26 ± 5 mL, p = 0.002). There were widespread regions of local cortical thickness reduction observed across the brain. These changes included bilateral thickness reductions in the frontal lobe including the dorsolateral prefrontal cortex and precentral gyrus, the posterior parietal lobe and the middle temporal gyrus. Sub-cortical volume changes were observed in the caudate, putamen and in the thalamus (p ≤ 0.005 for all regions). Cortical GM volume negatively correlated with brain natriuretic peptide (R = − 0.89, p = 0.009), high sensitivity C-reactive protein (R = − 0.964, p < 0.0001) and asymmetric dimethylarginine (R = − 0.75, p = 0.026) but not with oxygen saturations, packed cell volume or viscosity. Conclusions We present the first comprehensive analysis of brain structure in adults with chronic neurocyanosis due to congenital heart disease. We demonstrate clear evidence for marked macro- and microvascular injury. Cyanotic patients show global evidence for reduced brain volume as well as specific foci of cortical thickness reduction. The GM volume loss correlated with hsCRP, BNP and ADMA suggesting that inflammation, neurohormonal activation and endothelial dysfunction may have important roles in its pathogenesis.

Echocardiographic Predictors of Mortality in Adults With a Fontan Circulation

Adults with univentricular physiology repaired with a Fontan-type procedure are at increased risk of premature death. We investigated echocardiographic indexes that are predictive of mortality in this setting because the prognostic utility of such imaging is not well characterized. Adults who had