Ventricular sympathetic innervation in patients with transposition of the great arteries after arterial switch operation and Rastelli procedure: impact of arterial dissection and coronary reimplantation

Clinical Course of TGA After Arterial Switch Operation in the Current Era

Background

The number of patients with an arterial switch operation (ASO) for transposition of the great arteries (TGA) is steadily growing; limited information is available regarding the clinical course in the current era.

Objectives

The purpose was to describe clinical outcome late after ASO in a national cohort, including survival, rates of (re-)interventions, and clinical events.

Methods

A total of 1,061 TGA-ASO patients (median age 10.7 years [IQR: 2.0-18.2 years]) from a nationwide prospective registry with a median follow-up of 8.0 years (IQR: 5.4-8.8 years) were included. Using an analysis with age as the primary time scale, cumulative incidence of survival, (re)interventions, and clinical events were determined.

Results

At the age of 35 years, late survival was 93% (95% CI: 88%-98%). The cumulative re-intervention rate at the right ventricular outflow tract and pulmonary branches was 36% (95% CI: 31%-41%). Other cumulative re-intervention rates at 35 years were on the left ventricular outflow tract (neo-aortic root and valve) 16% (95% CI: 10%-22%), aortic arch 9% (95% CI: 5%-13%), and coronary arteries 3% (95% CI: 1%-6%). Furthermore, 11% (95% CI: 6%-16%) of the patients required electrophysiological interventions. Clinical events, including heart failure, endocarditis, and myocardial infarction occurred in 8% (95% CI: 5%-11%). Independent risk factors for any (re-)intervention were TGA morphological subtype (Taussig-Bing double outlet right ventricle [HR: 4.9, 95% CI: 2.9-8.1]) and previous pulmonary artery banding (HR: 1.6, 95% CI: 1.0-2.2).

Conclusions

TGA-ASO patients have an excellent survival. However, their clinical course is characterized by an ongoing need for (re-)interventions, especially on the right ventricular outflow tract and the left ventricular outflow tract indicating a strict lifelong surveillance, also in adulthood.

Cardiac Fibrosis and Innervation State in Uncorrected and Corrected Transposition of the Great Arteries: A Postmortem Histological Analysis and Systematic Review

In the transposition of the great arteries (TGA), alterations in hemodynamics and oxygen saturation could result in fibrotic remodeling, but histological studies are scarce. We aimed to investigate fibrosis and innervation state in the full spectrum of TGA and correlate findings to clinical literature. Twenty-two human postmortem TGA hearts, including TGA without surgical correction (n = 8), after Mustard/Senning (n = 6), and arterial switch operation (ASO, n = 8), were studied. In newborn uncorrected TGA specimens (1 day-1.5 months), significantly more interstitial fibrosis (8.6% ± 3.0) was observed compared to control hearts (5.4% ± 0.8, p = 0.016). After the Mustard/Senning procedure, the amount of interstitial fibrosis was significantly higher (19.8% ± 5.1, p = 0.002), remarkably more in the subpulmonary left ventricle (LV) than in the systemic right ventricle (RV). In TGA-ASO, an increased amount of fibrosis was found in one adult specimen. The amount of innervation was diminished from 3 days after ASO (0.034% ± 0.017) compared to uncorrected TGA (0.082% ± 0.026, p = 0.036). In conclusion, in these selected postmortem TGA specimens, diffuse interstitial fibrosis was already present in newborn hearts, suggesting that altered oxygen saturations may already impact myocardial structure in the fetal phase. TGA-Mustard/Senning specimens showed diffuse myocardial fibrosis in the systemic RV and, remarkably, in the LV. Post-ASO, decreased uptake of nerve staining was observed, implicating (partial) myocardial denervation after ASO.

Nuclear Imaging in Pediatric Cardiology: Principles and Applications

Nuclear imaging plays a unique role within diagnostic imaging since it focuses on cellular and molecular processes. Using different radiotracers and detection techniques such as the single photon emission scintigraphy or the positron emission tomography, specific parameters can be assessed: myocardial perfusion and viability, pulmonary perfusion, ventricular function, flow and shunt quantification, and detection of inflammatory processes. In pediatric and congenital cardiology, nuclear imaging can add complementary information compared to other imaging modalities such as echocardiography or magnetic resonance imaging. In this state-of-the-art paper, we appraise the different techniques in pediatric nuclear imaging, evaluate their advantages and disadvantages, and discuss the current clinical applications.

Myocardial Perfusion in Hypoplastic Left Heart Syndrome

BACKGROUND

The status of the systemic right ventricular coronary microcirculation in hypoplastic left heart syndrome (HLHS) is largely unknown. It is presumed that the systemic right ventricle's coronary microcirculation exhibits unique pathophysiological characteristics of HLHS in Fontan circulation. The present study sought to quantify myocardial blood flow by cardiac magnetic resonance imaging and evaluate the determinants of microvascular coronary dysfunction and myocardial ischemia in HLHS.

METHODS

One hundred nineteen HLHS patients (median age, 4.80 years) and 34 healthy volunteers (median age, 5.50 years) underwent follow-up cardiac magnetic resonance imaging ≈1.8 years after total cavopulmonary connection. Right ventricle volumes and function, myocardial perfusion, diffuse fibrosis, and late gadolinium enhancement were assessed in 4 anatomic HLHS subtypes. Myocardial blood flow (MBF) was quantified at rest and during adenosine-induced hyperemia. Coronary conductance was estimated from MBF at rest and catheter-based measurements of mean aortic pressure (n=99).

RESULTS

Hyperemic MBF in the systemic ventricle was lower in HLHS compared with controls (1.89±0.57 versus 2.70±0.84 mL/g per min; P<0.001), while MBF at rest normalized by the rate-pressure product, was similar (1.25±0.36 versus 1.19±0.33; P=0.446). Independent risk factors for a reduced hyperemic MBF were an HLHS subtype with mitral stenosis and aortic atresia (P=0.017), late gadolinium enhancement (P=0.042), right ventricular diastolic dysfunction (P=0.005), and increasing age at total cavopulmonary connection (P=0.022). The coronary conductance correlated negatively with systemic blood oxygen saturation (r, -0.29; P=0.02). The frequency of late gadolinium enhancement increased with age at total cavopulmonary connection (P=0.014).

CONCLUSIONS

The coronary microcirculation of the systemic ventricle in young HLHS patients shows significant differences compared with controls. These hypothesis-generating findings on HLHS-specific risk factors for microvascular dysfunction suggest a potential benefit from early relief of frank cyanosis by total cavopulmonary connection.

The Coronary Arteries in Adults after the Arterial Switch Operation: A Systematic Review

Coronary artery status in adults long after the arterial switch operation (ASO) is unclear. We conducted a systematic review to provide an overview of coronary complications during adulthood and to evaluate the value of routine coronary imaging in adults after ASO, in light of current guidelines. Articles were screened for the inclusion of adult ASO patients and data on coronary complications and findings of coronary imaging were collected. A total of 993 adults were followed with a median available follow-up of only 2.0 years after reaching adulthood. Myocardial ischemia was suspected in 17/192 patients (8.9%). The number of coronary interventions was four (0.4%), and coronary death was reported in four (0.4%) patients. A lack of ischemia-related symptoms cannot be excluded because innervation studies indicated deficient cardiac innervation after ASO, although data is limited. Anatomical high-risk features found by routine coronary computed tomography (cCT) included stenosis (4%), acute angle (40%), kinking (24%) and inter-arterial course (11%). No coronary complications were reported during pregnancy (n = 45), although, remarkably, four (9%) patients developed heart failure. The 2020 European Society of Cardiology (ESC) guidelines state that routine screening for coronary pathologies is questionable. Based on current findings and in line with the 2018 American ACC/AHA guidelines a baseline assessment of the coronary arteries in all ASO adults seems justifiable. Thereafter, an individualized coronary follow-up strategy is advisable at least until significant duration of follow-up is available.

Long-term Outcomes of the Arterial Switch Operation for d-Transposition of the Great Arteries

Dextrotransposition of the great arteries (d-TGA) is a relatively rare form of complex childhood congenital heart disease, which occurs in approximately 0.2 in 1000 live births (Long et al, 2010). The most common palliative procedure for this anatomy has become the arterial switch operation (ASO). We will review in this paper the evidence that is currently available regarding the clinical management following the ASO. Individuals with d-TGA who undergo ASO at a young age thus far have excellent long-term outcomes. Long-term complications for the ASO should be monitored for and patients should have routine follow-up with specialists in adult congenital heart disease.

Left ventricular function and exercise capacity after arterial switch operation for transposition of the great arteries: a systematic review and meta-analysis

BACKGROUND

The arterial switch operation for transposition of the great arteries was initially believed to be an anatomical correction. Recent evidence shows reduced exercise capacity and left ventricular function in varying degrees in the long term after an arterial switch operation.

OBJECTIVE

To perform a meta-analysis on long-term exercise capacity and left ventricular ejection fraction after an arterial switch operation.

METHODS

A literature search was performed to cover all studies on patients who had undergone a minimum of 6 years of follow-up that reported either left ventricular ejection fraction, peak oxygen uptake, peak workload, and/or peak heart rate. A meta-analysis was performed if more than three studies reported the outcome of interest.

RESULTS

A total of 21 studies reported on the outcomes of interest. Oxygen uptake was consistently lower in patients who had undergone an arterial switch operation compared with healthy controls, with a pooled average peak oxygen uptake of 87.5±2.9% of predicted. The peak heart rate was also lower compared with that of controls, at 92±2% of predicted. Peak workload was significantly reduced in two studies. Pooled left ventricular ejection fraction was normal at 60.7±7.2%.

CONCLUSION

Exercise capacity is reduced and left ventricular ejection fraction is preserved in the long term after an arterial switch operation for transposition of the great arteries.

Update on the Management of Adults With Arterial Switch Procedure for Transposition of the Great Arteries

OPINION STATEMENT

The arterial switch operation (ASO) is now the most frequently performed surgical correction in individuals with dextro-transposition of the great arteries (D-TGA). Patients who undergo this procedure as neonates have overall good clinical outcomes yet continued clinical follow-up is important to evaluate for postoperative complications. In this group, the highest mortality is in the immediate postoperative period and is generally associated with reimplantation of the coronary arteries. As these patients live into adulthood, longitudinal follow-up for other ASO complications including neo-pulmonary stenosis, right ventricular outflow tract (RVOT) obstruction, or neo-aortic root dilation and resulting aortic insufficiency should be performed. In adults, extra care should be taken to identify and treat traditional cardiovascular risk factors as individuals with coronary obstruction may not present with typical anginal symptoms. Management of these patients should be performed in collaboration with an adult congenital heart center of excellence. This population offers a unique opportunity to provide timely feedback to adult congenital heart community of providers regarding late outcomes from surgical intervention and in the next decade will hopefully demonstrate a model for clinical feedback cycles in lifelong congenital care.

Chronological changes in stenosis of translocated coronary arteries on angiography after the arterial switch operation in children with transposition of the great arteries: comparison of myocardial scintigraphy and angiographic findings

BACKGROUND

The peri-operative mortality of the arterial switch operation in neonates with transposition of the great arteries is considerably low; however, long-term outcomes of translocated coronary arteries still remain one of the most crucial issues. Methods and results A total of 110 neonates with transposition of the great arteries after arterial switch operation were evaluated; three (2.7%) late deaths occurred. The remaining 107 patients except for one underwent follow-up angiography. Angiography showed coronary artery stenosis in nine (8.4%), with right coronary artery lesions in two and left main trunk lesions in seven. In two patients, right coronary artery stenosis regressed during follow-up. In left main trunk lesions, the severity of stenosis improved in four, did not change in one, and progressed to total occlusion in two patients. In children with coronary artery stenosis, myocardial scintigraphy showed perfusion defects in five out of six (83%) with left main trunk with ⩾75% stenosis and in four out of four with left main trunk stenosis ⩾90%. In contrast, patients whose coronary artery stenosis disappeared during follow-up had no perfusion defects on scintigraphy.

CONCLUSIONS

Regression of ostial stenosis of the transplanted coronary artery on angiogram was observed. The stenosis regressed over time in six patients; two coronary arteries with 99% stenosis and delayed angiographic enhancement of the distal coronary artery resulted in total occlusion within 1 year after the arterial switch operation. Combination of angiography and myocardial scintigraphy could be useful to differentiate deceptive stenosis from progressive stenosis.

Exercise Capacity Long-Term after Arterial Switch Operation for Transposition of the Great Arteries

Transposition of the great arteries (TGA) is a congenital heart defect successfully corrected through arterial switch operation (ASO). Although this technique had significant impact in improving survival, little is known about the functional capacity of the operated patients long-term after surgery.

OBJECTIVE

The aim of this study was to compare the functional capacity of children with TGA long-term after ASO with that of healthy children.

DESIGN

Retrospective study.

PATIENTS

All patients that performed cardiopulmonary exercise test (CPET) were included in the study. As a control group, healthy children in evaluation for physical activity that performed CPET during the same period were also enrolled.

RESULTS

Thirty-one TGA patients (19 male) were compared with 29 age-matched controls (21 male). Maximum oxygen consumption was higher in the control group (45.47 ± 8.05 vs. 40.52 ± 7.19, P = .017), although within normal limits in both groups (above 90% of predicted value). The heart rate behavior during exercise was different in both groups, with a mean chronotropic index significantly lower in the TGA group (63% ± 14 vs. 81% ± 12, P < .001).

CONCLUSIONS

Our results showed that exercise capacity long-term after ASO in TGA is well preserved although lower than in healthy children what might be explained by the presence of chronotropic incompetence in the TGA group.

Innervating sympathetic neurons regulate heart size and the timing of cardiomyocyte cell cycle withdrawal

Sympathetic drive to the heart is a key modulator of cardiac function and interactions between heart tissue and innervating sympathetic fibres are established early in development. Significant innervation takes place during postnatal heart development, a period when cardiomyocytes undergo a rapid transition from proliferative to hypertrophic growth. The question of whether these innervating sympathetic fibres play a role in regulating the modes of cardiomyocyte growth was investigated using 6-hydroxydopamine (6-OHDA) to abolish early sympathetic innervation of the heart. Postnatal chemical sympathectomy resulted in rats with smaller hearts, indicating that heart growth is regulated by innervating sympathetic fibres during the postnatal period. In vitro experiments showed that sympathetic interactions resulted in delays in markers of cardiomyocyte maturation, suggesting that changes in the timing of the transition from hyperplastic to hypertrophic growth of cardiomyocytes could underlie changes in heart size in the sympathectomized animals. There was also an increase in the expression of Meis1, which has been linked to cardiomyocyte cell cycle withdrawal, suggesting that sympathetic signalling suppresses cell cycle withdrawal. This signalling involves β-adrenergic activation, which was necessary for sympathetic regulation of cardiomyocyte proliferation and hypertrophy. The effect of β-adrenergic signalling on cardiomyocyte hypertrophy underwent a developmental transition. While young postnatal cardiomyocytes responded to isoproterenol (isoprenaline) with a decrease in cell size, mature cardiomyocytes showed an increase in cell size in response to the drug. Together, these results suggest that early sympathetic effects on proliferation modulate a key transition between proliferative and hypertrophic growth of the heart and contribute to the sympathetic regulation of adult heart size.