Myocardial blood flow and cardiac sympathetic innervation in young adults late after arterial switch operation for transposition of the great arteries.

BACKGROUND: The arterial switch operation (ASO) for repair of transposition of the great arteries (TGA) requires transection of the great arterial trunks and re-implantation of the coronary arteries into the neoaortic root resulting in cardiac sympathetic denervation which may affect myocardial blood flow (MBF) regulation. The aims of the present study were to evaluate sympathetic (re-)innervation in young adults after ASO and its impact on MBF. METHODS: Twelve patients (age 22.5 ±â€¯2.6 years) after ASO for TGA in the neonatal period and ten healthy controls (age 22.0 ±â€¯1.7 years) were included. Positron emission tomography (PET) was used for measuring cardiac sympathetic innervation with [11C]meta-hydroxyephedrine (mHED) and MBF with [15O]H2O PET at rest, during adenosine stimulation, and during sympathetic stimulation with cold pressor test. Cold pressor-induced MBF response capacity was calculated as maximal global MBF over peak rate-pressure product multiplied by 10'000. RESULTS: Global [11C]mHED uptake was significantly lower in patients compared to controls (7.0 ±â€¯2.3 versus 11.8 ±â€¯2.1%/min, p < 0.001). Global MBF was lower in patients compared to controls at rest and during adenosine-induced hyperemia (0.66 ±â€¯0.08 versus 0.82 ±â€¯0.15 ml/min/g, p = 0.005; 2.23 ±â€¯1.19 versus 3.36 ±â€¯1.04 ml/min/g, p = 0.030, respectively). Interestingly, MBF during cold pressor test did not differ between patients and controls (0.99 ±â€¯0.20 versus 1.07 ±â€¯0.16 ml/min/g, p = 0.330). However, cold pressor-induced MBF response capacity was significantly lower for patients as compared to controls (1.09 ±â€¯0.35 versus 1.44 ±â€¯0.39 ml/g/10,000 mmHg, p = 0.040). CONCLUSIONS: With only partial sympathetic re-innervation of the coronary arteries, maximal dilator capacity of the coronary microvasculature and cold pressor-induced MBF response capacity remain substantially impaired in young adults after ASO compared to healthy controls.

Heart rate response during exercise predicts exercise tolerance in adults with transposition of the great arteries and atrial switch operation.

BACKGROUND: To assess the relationship between heart rate response and exercise tolerance in adults with systemic right ventricle (sRV) after atrial switch repair for Transposition of the Great Artery (TGA) in addition to other physiological parameters. METHODS: All patients with a sRV after atrial switch repair for TGA followed in our institution between June 2015 and April 2018 who underwent cardiopulmonary exercise testing (CPET) were analyzed. Cardiac imaging performed within a six-month time period of the CPET were also collected. Chronotropic incompetence was defined as the inability to achieve 80% of age-predicted maximal heart rate reserve (HRR) and <62% on a beta-blocker regimen. Patient characteristics were assessed according to tertiles of the percentage of predicted pVO2 (%ppVO2). RESULTS: We studied 70 patients (mean of age 32.4 ±â€¯7.6 years old, 51 males). Mean peak oxygen uptake was 21.5 ±â€¯5.8 mL/kg/min, corresponding to a %ppVO2 of 57 ±â€¯14.1% while mean VE/VCO2 slope was 37.1 ±â€¯8.2. There was a trend toward more exaggerated hyperventilation in patient with lower pVO2. Mean age-adjusted HRR was 68.5 ±â€¯19%. Chronotropic incompetence was observed in 65.7% and was correlated with %ppVO2 (r = 0.482; p < 0.001) as physical training evaluated with Ventilatory Anaerobic threshold (r = 0.571; p < 0.001), while no difference was found based on respiratory parameters. No echocardiographic or Magnetic Resonance Imaging parameters assessing sRV systolic function at rest were correlated with %ppVO2. CONCLUSIONS: Exercise limitation is related to the inability to increase cardiac output during exercise and is notably due to the degree of chronotropic incompetence.

Aortic angle is associated with neo-aortic root dilatation and regurgitation following arterial switch operation.

INTRODUCTION: Neo-aortic root dilatation and regurgitation are common progressive long-term complications of the arterial switch operation (ASO) for transposition of the great arteries (TGA) with increasing clinical burden. While several risk factors have been identified, most are constitutional. The acute aortic angle commonly seen after ASO might alter aortic dynamics and facilitate progression of the neo-aortic root dilatation and aortic regurgitation, but insufficient data is available. We intend to assess the effect of the aortic angle in the extent of neo-aortic root dilatation and presence of regurgitation. METHODS: Retrospective analysis of TGA patients undergoing CMR after ASO at a single tertiary centre from November 2010 to July 2017. RESULTS: 180 patients were analysed, 157 of which having adequate imaging of the aortic arch and root. Neo-aortic root Z score was normally distributed with 73% of patients having a Z score > 2. The aortic angle had a significant (p < 0,001) inverse relationship with the neo-aortic root Z score both in univariate and multivariate linear regression. Other significant associations were male gender and the concomitant presence of a VSD or a dysplastic neo-aortic valve. The presence of neo-aortic regurgitation was also inversely correlated with the aortic angle. The presence of a bicuspid neo-aortic valve was another significant association, further correlating with the more severe forms. CONCLUSIONS: Acute aortic angles associate more extensive neo-aortic root dilatation and higher incidence of regurgitation. We believe a surgical technique promoting less acute aortic angles has potential for ameliorating the long-term outcomes of TGA.

Role of myocardial collagen degradation and fibrosis in right ventricle dysfunction in transposition of the great arteries after atrial switch.

BACKGROUND: Heart failure is a serious event in patients with transposition of the great arteries (D-TGA) after atrial redirection surgery. We aimed to determine the association between myocardial fibrosis and systolic and diastolic systemic right ventricle (sRV) dysfunction. METHODS: Diastolic and systolic function of sRV was prospectively assessed using echocardiography and cardiac magnetic resonance imaging (CMR) in 48 patients with atrially switched D-TGA and 26 healthy subjects. Diastolic function of the subaortic ventricle was assessed by echocardiography Doppler and DTI. In CMR, ejection fraction of sRV and wall stress defined as the product of the systolic blood pressure and volume/mass ratio were assessed. Fibrosis extent within sRV myocardium was evaluated using gadolinium-enhanced magnetic resonance and serum collagen turnover biomarkers. RESULTS: Late gadolinium enhancement (LGE) was found in 35% of D-TGA patients, and the collagen degradation biomarker pro-MMP1:TIMP1 ratio was significantly increased in D-TGA patients compared to healthy subjects (1.0 × 10-2vs. 2.5 × 10-2, p = 0.04). Increase in sRV wall stress was significantly associated with LGE (p = 0.01) and pro-MMP1:TIMP1 ratio (r = 0.77, p < 0.01). After adjustment for age, sex, BMI, blood pressure and cardiac treatment, pro-MMP1:TIMP1 ratio was the strongest determinant of sRVEF (R2 = 0.85, p < 0.01). Pro-MMP1:TIMP1 ratio was also significantly correlated with the early diastolic filling parameter E/E' (r = 0.53, p = 0.02), but this was not anymore the case after adjustment. CONCLUSIONS: Diastolic and systolic sRV dysfunction is related to myocardial collagen degradation and fibrosis. Research in medical therapies that reduce systemic sRV afterload and limit collagen degradation is warranted in this setting.

Aortopulmonary collaterals in neonates with d-transposition of the great arteries - Clinical significance early after arterial switch operation.

OBJECTIVES: Purpose of this study is to evaluate the clinical significance of major aortopulmonary collateral arteries (MAPCAs) during the early postoperative course after arterial switch operation (ASO) in d-transposition of the great arteries (dTGA). METHODS: Clinical data of 98 patients with simple dTGA between January 2007 and December 2016 at the University Children's Hospital Zurich, Switzerland were analyzed retrospectively. RESULTS: 37 from 98 patients (38%) required cardiac catheterization (CC) due to an early complicated postoperative course or difficult coronary transfer due to special coronary anatomy. In 15 (15%) patients, hemodynamically relevant MAPCAs were found during CC and coil embolization was performed. Patients with relevant MAPCAs had a significantly longer PICU stay (7 versus 6 days, p = 0.021), longer hospital stay (41 versus 27 days, p = 0.005), longer mechanical ventilation time (5 versus 3 days, p = 0.005), longer need for inotropic support (5 versus 4 days, p = 0.001) and delayed chest closure time (3 versus 2 days, p = 0.030) in those in whom it was left open in comparison to all other patients. In patients having CC, pre-surgery oxygen saturation was significantly lower in patients with relevant MAPCAs (58% vs 70%, p 0.019). Echocardiography had a sensitivity of 53% and a specificity of 100% in detecting relevant MAPCAs, accurately. CONCLUSIONS: MAPCAs are frequently found in dTGA patients and can be associated with lower baseline oxygen saturation and a prolonged postoperative course after ASO. Transthoracic echocardiography cannot replace CC as diagnostic tool. If significant MAPCAs are suspected, early CC should be performed for diagnostic and therapeutic reasons.

Gothic aortic arch and cardiac mechanics in young patients after arterial switch operation for d-transposition of the great arteries.

BACKGROUND: In patients who have undergone arterial switch operation (ASO) for d-transposition of the great arteries a gothic aortic arch (GA) morphology has been found and it has been associated with abnormal aortic bio-elastic properties. HYPOTHESIS: GA is frequent in ASO patients and may have an impact on cardiac mechanics. Our study aims were to assess 1- the occurrence of GA in a large sample of patients after ASO; 2- the association between GA and aortic bio-elastic properties; and 3- the impact of GA on left ventricular (LV) function using speckle tracking echocardiography (STE). METHODS: We studied one hundred and five asymptomatic patients, who have undergone first stage ASO for d-TGA, with normal left ventricular ejection fraction (LVEF ≥53%). RESULTS: Forty-six (44%) patients showed a GA (mean age 11.5±7.2years, 26 males) while fifty-nine (56%) patients (mean age 9.6±6.7years, 37 males) did not present GA. The two groups were comparable for age, sex, BSA, and office blood pressure values. In group GA aortic root was significantly dilated (27.4±7.5mm vs. 21.2±6.9mm, p<0.0001), aortic stiffness index (Group GA=1.8±1.2 vs. 1.4±0.7, p=0.025) was significantly increased, left atrial volume was larger (p=0.0145), global longitudinal strain (Group GA=-18.4±2.5% vs. -20.1±3.3%, p=0.012) and basal LV longitudinal strains (Group GA=-16.9±4.8% vs. -20.4±7.0%, p=0.013) were significantly reduced. CONCLUSIONS: After ASO the presence of a GA is associated with a significantly dilated aortic root, stiffer aortic wall, larger left atrial volume, and worse LV longitudinal systolic deformations, well known predictors of cardiovascular morbidity and mortality.