Tim Hornung

Myocardial perfusion defects and associated systemic ventricular dysfunction in congenitally corrected transposition of the great arteries

Background Patients with systemic ventricles of right ventricular morphology are at high risk of contractile dysfunction, the cause of which has not been fully elucidated. Objective To assess whether ischaemia or infarction contributes to ventricular impairment in unoperated patients with uncomplicated congenitally corrected transposition of the great arteries (TGA) by studying myocardial perfusion and function. Setting Paediatric and adult congenital cardiac clinics of a tertiary referral centre. Patients Five patients with congenitally corrected TGA but without associated structural cardiac defects (aged 3.5 to 34 years). Interventions Maximal exercise stress testing using standard or modified Bruce protocols. Sestamibi (technetium-99m methoxy isobutyl isonitrile) scanning after isotope injection at maximal exercise and rest. Main outcome measures Maximum exercise capacity; right ventricular myocardial perfusion, regional wall motion, and thickening; right ventricular ejection fraction. Results The two youngest patients (3.5 and 11 years) had normal exercise capacity for age, while the others had reduced exercise performance. Sestamibi scanning showed reversible myocardial ischaemia in four patients and fixed defects indicating infarction in five. Irreversible defects were mostly associated with impaired wall motion and thickening. The ejection fraction was normal (65%) in the youngest patient but < 55% in the others (mean (SD) 47(11)%). Conclusions Patients with unoperated congenitally corrected TGA have a high prevalence of myocardial perfusion defects, with consequent abnormalities of regional wall motion and thickening, and impaired ventricular contractility. These data suggest that ischaemia and infarction are important in the pathogenesis of ventricular failure in this condition.

Right ventricular dysfunction in congenitally corrected transposition of the great arteries

Although right ventricular (RV) dysfunction is an important complication in subjects with congenitally corrected transposition of the great arteries, its pathogenesis is poorly understood. We assessed the role of RV myocardial perfusion and found perfusion defects at rest in all 20 patients, involving 4.6 +/- 2.3 of a total of 12 segments; the extent of the resting perfusion defects correlated inversely with the RV ejection fraction.

Myocardial infarction complicating neonatal enterovirus myocarditis

Abstract: A 10‐week‐old, 31‐week gestation preterm boy re‐presented with heart failure after an initial episode of neonatal aseptic meningitis with positive CSF enterovirus polymerase chain reaction. Investigation demonstrated global myocardial dysfunction with left ventricle posterolateral myocardial infarction. The boy’s heart failure was controlled with medical treatment but his myocardial dysfunction persisted 9 months after presentation.

The Fontan epidemic: Population projections from the Australia and New Zealand Fontan Registry

BACKGROUND The number and age demographic of the future Fontan population is unknown. METHODS Population projections were calculated probabilistically using microsimulation. Mortality hazard rates for each Fontan recipient were calculated from survivorship of 1353 Fontan recipients in the Australia and New Zealand Fontan Registry, based on Fontan type, age at Fontan, gender and morphology. Projected rates of new Fontan procedures were generated from historical rates of Fontan procedures per population births. RESULTS At the end of 2014, the living Fontan population of Australia and New Zealand was 1265 people from an Australian and New Zealand regional population of 28 million (4.5 per 100,000 population). Of those, 165 (13%) received an atrio-pulmonary (AP) procedure, 262 (21%) a lateral tunnel (LT) procedure and 838 (66%) an extra-cardiac conduit (ECC) procedure. This population is expected to grow to 1917 (95% CI: 1846: 1986) by 2025 (5.8 per 100,000 population), with 149 (8%) AP procedures, 254 (13%) LT procedures, and 1514 (79%) ECC procedures. By 2045, the living Fontan population is expected to reach 2986 (95% CI: 2877: 3085; 7.2 per 100,000 population). The average age of the Fontan population is expected to increase from 18years in 2014 to 23years (95% CI: 22-23) by 2025, and 31years (95% CI: 30-31) by 2045. CONCLUSION The Australian and New Zealand population of patients alive after a Fontan procedure will double over the next 20years increasing the demand for heart-failure services and cardiac transplantation. Greater consideration for the needs of this mostly adult Fontan population will be necessary.

Ten-year outcomes of Fontan conversion in Australia and New Zealand demonstrate the superiority of a strategy of early conversion

OBJECTIVE To investigate the benefits of a strategy of early Fontan conversion. METHODS Using the Australia and New Zealand Fontan Registry, retrospective analysis of their long-term follow-up data was performed. RESULTS Between 1990 and 2014, a total of 39 patients underwent surgical conversion in 6 centres at a median age of 23.8 years (IQR: 19.3-28.2), 18.7 ± 5.0 years post-Fontan. One centre tended to perform conversion earlier: interval since first documented arrhythmia 2.9 ± 4.0 vs 4.0 ± 4.2 years, average NYHA Class 2 ± 0.4 vs 3 ± 0.9 (P = 0.008), mean number of preop anti-arrhythmics 1 ± 0.4 vs 2 ± 0.6 (P = 0.05). Two patients underwent conversion to an extracardiac conduit only, while 36 had concomitant right atrial cryoablation, of which 16 also had pacemaker implantation. Nine patients suffered major cardiac-related complications (7 low output syndrome, 3 ECMO, 3 acute renal failure, one stroke) (2/17 from the early conversion centre and 7/22 of the others; P = 0.14). Four patients died in hospital (10.3%) and 4 late after a median of 0.9 years [95% confidence interval (CI): 0.5-1] after conversion. An additional 2 patients needed transplantation at 1 and 8.8 years after conversion, respectively. The 10-year freedom from heart transplantation was 86% (95% CI: 51-97%). Outcomes from the centre with an early conversion strategy were significantly better: 8-year freedom from death or heart transplantation was 86% (95% CI: 53-96) vs 51% (95% CI: 22-74; log-rank P = 0.007). Eight additional patients required pacemaker implantation and 5 had arrhythmia recurrence. CONCLUSIONS Fontan conversion is associated with lasting survival outcomes up to 10 years after conversion. A strategy of surgical conversion at earlier stage of failure may be associated with better survival free from transplantation.

Systolic and Diastolic Abnormalities Reduce the Cardiac Response to Exercise in Adolescents With Type 2 Diabetes

OBJECTIVE To better understand the cardiac limitations during exercise in adolescents with type 2 diabetes mellitus (T2DM), we measured left ventricular performance with magnetic resonance imaging (MRI) during exercise in diabetic and nondiabetic adolescents. RESEARCH DESIGN AND METHODS Thirteen subjects with T2DM, 27 overweight/obese nondiabetic (ObeseND) subjects, and 19 nondiabetic nonobese control subjects were recruited. Cardiac (left ventricular) MRI scans were performed at rest and during submaximal exercise. RESULTS Vo2 peak indexed to fat-free mass was reduced in T2DM and ObeseND subjects compared with control subjects (P < 0.0001). Indexed cardiac output increased less during exercise and was 20% lower in T2DM subjects due to reduced stroke volume. This was a consequence of reduced ventricular filling with smaller end-diastolic volume, which decreased further during exercise in T2DM subjects, but not in ObeseND or control subjects. End-systolic volume was also smaller in T2DM subjects. These changes were associated with increased resting and exercise diastolic blood pressure, and total peripheral resistance in T2DM subjects. CONCLUSIONS Independently of obesity, T2DM impairs cardiac function during exercise in adolescents.

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.

Twin–twin transfusion syndrome, coarctation of the aorta and hypoplastic aortic arch: A case series report

Aim:  The twin–twin transfusion syndrome (TTTS) complicates 10–30% of monochorionic pregnancies. The incidence of pulmonary stenosis and endocardial fibroelastosis is especially high in the recipient twin. We report a novel finding of four cases of coarctation of the aorta and hypoplastic aortic arch in the donor to raise awareness of cardiac lesions in twins affected by TTTS.

Exercise Training Improves but Does Not Normalize Left Ventricular Systolic and Diastolic Function in Adolescents With Type 1 Diabetes

OBJECTIVE To determine the impact of 20 weeks of exercise training in aerobic capacity on left ventricular function and glycemic control in adolescents with and without type 1 diabetes. RESEARCH DESIGN AND METHODS Fifty-three adolescents with type 1 diabetes (aged 15.6 years) were divided into two groups: exercise training (n = 38) and nontraining (n = 15). Twenty-two healthy adolescents without diabetes (aged 16.7 years) were included and, with the 38 participants with type 1 diabetes, participated in a 20-week exercise-training intervention. Assessments included VO2max and body composition. Left ventricular parameters were obtained at rest and during acute exercise using MRI. RESULTS Exercise training improved aerobic capacity (10%) and stroke volume (6%) in both trained groups, but the increase in the group with type 1 diabetes remained lower than trained control subjects. Increased stroke volume in adolescents with type 1 diabetes resulted from greater left ventricular contractility (9% increase in ejection fraction and an 11% reduction in end-systolic volumes) and, to a lesser extent, improved left ventricular filling (6%), suggesting that impaired diastolic function can be affected by exercise training in adolescents with type 1 diabetes. Insulin use decreased by ∼10%, but no change in glycemic status was observed. CONCLUSIONS These data demonstrate that in adolescents, the impairment in left ventricular function seen with type 1 diabetes can be improved, although not normalized, with regular intense physical activity. Importantly, diastolic dysfunction, a common mechanism causing heart failure in older subjects with diabetes, appears to be partially reversible in this age group.

Exercise capacity and cardiac function in adolescents born post-term

There is some evidence that children born post-term (≥42 weeks of gestation) have metabolic abnormalities that may be associated with an increased risk of adverse health outcomes in adulthood. However, there are no data as to whether adolescents born post-term display alterations in aerobic capacity or cardiovascular function. We studied 48 adolescents (56% males) in Auckland (New Zealand) with a mean age of 14.3 years (SD = 1.7): 25 born post-term and 23 born at term (37–41 weeks of gestation). Assessments included metabolic markers in blood, whole body DXA scans, 24-hour ambulatory blood pressure monitoring, maximal exercise capacity, as well as cardiac MRI scan at rest and during submaximal exercise. Exercise capacity was lower in the post-term than in control participants (44.5 vs 47.8 ml/kgffm/min; p = 0.04). There were no differences in left ventricular volumes at rest and during exercise between groups. The 24-hour ambulatory blood pressure monitoring also showed no differences between the two groups. Being born post-term was associated with reduced exercise capacity, but with no observed differences in central cardiac function. We speculate that the reduction in exercise capacity may be due to changes in the peripheral vascular system.