Imaging of congenital heart disease in adults

Abstract

Imaging is fundamental to the lifelong care of adult congenital heart disease (ACHD) patients. Echocardiography remains the first line imaging for inpatient, outpatient, or perioperative care. Cross-sectional imaging with cardiovascular magnetic resonance (CMR) or computed tomography (CT) provides complementary and invaluable information on cardiac and vascular anatomy and other intra-thoracic structures. Furthermore, CMR provides quantification of cardiac function and vascular flow. Cardiac catheterization is mostly reserved for assessment of pulmonary vascular resistance, ventricular end-diastolic pressure, and percutaneous interventions. There have been further advances in non-invasive imaging for ACHD including the application of advanced echocardiographic techniques, faster automated CMR imaging, and radiation dose reduction in CT. As a result ACHD, a heterogeneous population, benefit from appropriate application of multiple imaging modalities matched with tertiary ACHD expertise.

Introduction

The number of adults with congenital heart disease continues to increase due to significant advances in early diagnosis and management.¹ However, residual or post-operative right- and left-sided anatomic and haemodynamic abnormalities are common. Cardiovascular imaging is essential in the long-term care of adult congenital heart disease (ACHD). Periodic surveillance imaging is important for detecting haemodynamic change, as symptoms may be late.² With age, comorbidity including acquired heart disease also comes into play.³ The choice and frequency of imaging modality is determined by lesion-specific patient characteristics, strengths, and weaknesses of imaging modality and institutional resources and expertise. A multimodality imaging approach is often required to obtain all the necessary information.

Use of different imaging modalities in lifelong follow-up

Echocardiography

Echocardiography remains the workhorse and first line in imaging for assessment of anatomy and physiology. It is widely available, portable, has high temporal resolution and is free from ionizing radiation exposure. Small, mobile intracardiac structures such as valves and vegetations and small intracardiac shunts are well shown (Figure 1). Doppler echocardiography is usually the superior method for non-invasive haemodynamic assessment of right ventricular (RV) and pulmonary artery (PA) pressure gradients and valvular pathology and function in ACHD. To assess RV systolic function, percentage fractional area change (FAC) and tricuspid annular plane systolic excursion (TAPSE) from a four-chamber view are widely used. Tricuspid annular plane systolic excursion represents longitudinal contractile function of the RV, is reproducible, and easy to measure though it may be influenced by tricuspid regurgitation, abnormal ventricular geometry, and recent surgical procedures. Moreover, TAPSE has prognostic value, for example, in Eisenmenger syndrome⁴ (Figure 2). Tissue Doppler imaging of myocardial velocities and speckle tracking for myocardial deformation have both been applied in ACHD for regional and global ventricular myocardial deformation assessment (Figure 3), but their clinical application to the RV in ACHD remains to be elucidated. Transthoracic echocardiography (TTE) acoustic windows may become suboptimal as patients age or have chest wall deformity from prior surgery. Obtaining 3D echocardiography images that include all of the RV in ACHD is not always possible and RV volumes may be underestimated. Transoesophageal echocardiography (TOE) is useful in selected cases to guide interventional procedures (Figure 4) or further evaluate valvular anatomy.

Figure 1.

Acute presentation of endocarditis with vegetation (asterisk) related to previous VSD surgical repair patch leak shown in apical four-chamber 2D echocardiography view (A) and magnified from apical five-chamber view (B).

Figure 2.

Echocardiography indices tricuspid annular plane systolic excursion <15 mm, right atrial area ≥25 cm², right atrial to left atrial area ratio ≥1.5, and right ventricular systolic over diastolic ratio ≥1.5 are all predictive of survival in Eisenmenger syndrome. Images show right atrial enlargement (A), prolonged tricuspid regurgitation on Doppler compromising filling (D = diastole, S = systole in B), biventricular hypertrophy and a flattened interventricular septum (C), and impaired tricuspid annular plane systolic excursion of 11 mm (D), in this patient with longstanding Eisenmenger syndrome.

Figure 3.

Speckle tracking of the left ventricular (LV) from apical four-chamber (A), apical three-chamber (B), and apical two-chamber (C) views in adult patient with repaired anomalous coronary artery from the pulmonary artery syndrome. Despite normal LV ejection fraction, speckle tracking shows LV myocardial dysfunction. The bullseye plot (D) shows that the anterior and inferior segments are akinetic. Total global longitudinal strain is −14%.

Figure 4.

Large atrial septal defect (asterisk) at 3D transoesophageal echocardiography (A) with relative lack of a posterior rim (B). Fenestrated atrial septal defect from left atrial aspect (C) and from right atrial aspect (D); in these cases, 2D echocardiography could potentially underestimate the size of the overall defect/shunt if the plane sampled is perpendicular to the small defect only (dotted arrow).

Cardiovascular magnetic resonance and computed tomography

Cardiovascular magnetic resonance (CMR) allows unlimited access to imaging the heart and thoracic cavity unrestricted by rib spaces, does not involve ionizing radiation, and is therefore ideally suited and recommended for long-term ACHD follow-up.⁵ In addition to addressing many questions that TTE can answer, CMR is the reference standard for accurate and reproducible quantification of right and left ventricular (LV) volumes, mass, and function.⁵ Other strengths include assessment of degree of valvar dysfunction, especially pulmonary regurgitation, multi-level outflow tract obstruction, shunt quantification (from pulmonary and systemic flows), differential branch PA flow, and non-invasive tissue characterization. Advances in CMR allow for acquisition and reconstruction of comprehensive data sets in any plane for subsequent analysis of anatomy, function, and flow. In patients scheduled for reoperation, CMR [or computed tomography (CT)] provides information to assess the relationship between vascular structures, the heart, and the sternum. Limitations include availability, higher cost, artefacts from stainless steel implants, and relative contraindication in patients with pacemakers or implantable cardioverter-defibrillators (ICDs). Magnetic resonance-compatible devices are increasingly used and are desirable for ACHD patients; selected patients with in situ conventional devices may safely undergo CMR with appropriate local protocol.⁶ However, predicting the impact of artefact noise on image quality is difficult. Siting the device on the opposite side of the chest from the position of the heart may be preferable in ACHD patients.

Multi-detector ECG-gated cardiac CT has excellent 3D spatial resolution and allows for detailed evaluation of small blood vessels such as coronary arteries (Figure 5), pulmonary veins (Figure 6), collaterals, arteriovenous malformations, distal PA branches, and in situ pulmonary thrombosis. Acquisition time is rapid (<2 min) allowing patients who are unable to lie still or flat for long to be imaged. Computed tomography may also have added value in younger patients, for instance to assess aberrant coronary anatomy. Pulmonary parenchyma imaging is also provided which is highly relevant for patients with pulmonary hypertension. Furthermore, CT complements assessment of mechanical heart valve dysfunction and allows 3D visualization of abscess formation in endocarditis. Computed tomography is an alternative to selective coronary angiography in older patients referred for ACHD surgery. However, CT exposes the patient to ionizing radiation and iodinated contrast agents and does not provide information on haemodynamics, flow rate, or velocity. Computed tomography can be used to acquire ventricular volumes and function but with lower temporal resolution than CMR or echocardiography and at the expense of additional radiation exposure. It tends to overestimate ventricular volumes and is clearly unattractive for serial measurements because of radiation.⁷ Multi-detector CT enables dose reduction algorithms and is routinely practiced in our centre.

Figure 5.

Anomalous coronary artery from the pulmonary artery (Ai and Aii) studied with computed tomography preoperatively. Post-operative computed tomography (Bi and Bii) shows patent left internal mammary graft to mid left anterior descending artery (images courtesy of Dr Mike Rubens). Ao, aorta; LAD, left anterior descending; LCA, left coronary artery; PA, pulmonary artery; RCA, right coronary artery.

Figure 6.

Anomalous right pulmonary venous drainage to the inferior vena cava creating a curvilinear ‘scimitar’ silhouette (arrows) on chest X-ray (A) with corresponding images from computed tomography (B and C) (images courtesy of Dr Mike Rubens).

Chest X-ray, nuclear scintigraphy, and cardiac catheterization

Chest X-ray is simple, cheap, and reproducible and provides diagnostic information; furthermore, cardiothoracic ratio relates to functional class and predicts survival in ACHD⁸ (Figure 6). Nuclear scintigraphy has been reserved for selected patients only, for example for myocardial stress perfusion imaging or differential pulmonary blood flow quantification when CMR is not available. Diagnostic cardiac catheterization and angiography are less frequently performed in ACHD nowadays; they are reserved for specific clinical indications such as calculation of pulmonary vascular resistance or where the diagnosis remains uncertain after non-invasive imaging or for percutaneous interventions.

Imaging goals in specific congenital heart diseases

Selected lesions are discussed in subsections below and the goals of imaging are summarized in Table 1.

Table 1.

Cardiac imaging goals in selected adult congenital heart diseases with strengths and weaknesses of different imaging modalities

	Echocardiography	Cardiovascular Magnetic Resonance	Computed Tomography
Modality
Strengths	Widely available Portable Estimation of pressure gradients Valvular pathology (mechanisms and degrees of dysfunction) Assessing small fine structures (chordal attachments, vegetations) Intracardiac shunts (fenestrations, PFO, VSD)	Quantification of:- ventricular size and function- regurgitant lesions- branch pulmonary artery flow- pulmonary: systemic flow Myocardial viability	Quantification of:- ventricular size and function Aortic pathology Coronary artery imaging
Weaknesses	Limited acoustic windows	Artefacts from steel implants Relative contraindications in patients with intracardiac leads	Exposure to ionizing radiation and iodinated contrast
Lesion
Left ventricular outflow tract obstruction, including aortic coarctation	Aortic valve morphology, function, and pressure gradient Subaortic anatomy (membrane) and pressure gradient Aortic root and ascending aortic anatomy LV size, function, and wall thickness	Ascending, transverse and descending thoracic aortic pathology (dilation, multi-level stenosis and aneurysm) Aortic valve morphology LV size, function, and mass Aortic collaterals	Ascending, transverse, and descending thoracic aortic pathology (dilation, aneurysm) *Particularly useful in the case of prior stents Aortic collaterals
Secundum ASD	Atrial septal anatomy Pulmonary venous anatomy (possible) RV size and function Right ventricular pressure AV valve morphology	Identification of multiple/fenestrated ASD Identification of rims for device closure Pulmonary:systemic flow ratio Quantification of RV volumes Pulmonary venous anatomy	*Rarely used
Sinus venous ASD	Atrial septal anatomy Pulmonary venous anatomy (possible) RV size and function Right ventricular pressure	Anomalously draining pulmonary venous connections and drainage Atrial septal anatomy RV size and function Pulmonary:systemic flow ratio	*Rarely used
Atrioventricular septal defect	Ventricular size and function Residual intracardiac shunts AV valve morphology (residual cleft or stenosis), attachments, function Left ventricular outflow tract anatomy/obstruction	Ventricular size and function Residual intracardiac shunts Pulmonary:systemic flow ratio AV valve morphology (residual clefts), attachments, function Valvular regurgitant fractions Left ventricular outflow tract anatomy and obstruction	*Rarely used
Tetralogy of Fallot repair	RV size and function RVOT, branch Pas Residual intracardiac shunts Right ventricular pressure Tricuspid regurgitation Pulmonary regurgitation LV size and function Aortic root size	RV size and function Regional wall motion RVOT aneurysms Branch PA anatomy and flow Pulmonary:systemic flow ratio Pulmonary regurgitant fraction LV size and function Aortic root and ascending aortic size Aortic-to-pulmonary artery collaterals Origin and proximal course of coronary arteries	*In selected cases where CMR is contraindicated Ventricular size and function Branch PA anatomy Aortic root and ascending aortic size Aortic-to-pulmonary artery collaterals Origin and proximal course of coronary arteries RV to PA conduit calcification and proximity to coronary arteries
Transposition of the great arteries, atrial switch procedure	Systemic RV size and function Systemic and pulmonary venous pathways (baffle leaks or obstructions) Residual intracardiac shunts Tricuspid regurgitation LV size and function LVOT obstruction (pulmonary stenosis)	Systemic RV size and function Systemic and pulmonary venous pathways (baffle leaks or obstructions) Residual intracardiac shunts Tricuspid regurgitant fraction LV size and function LVOT obstruction (pulmonary stenosis) Origins and proximal courses of the coronary arteries	*In selected cases where CMR is contraindicated Ventricular size and function Systemic and pulmonary venous pathways (baffle leaks or obstructions) Residual intracardiac shunts LVOT obstruction (pulmonary stenosis) Origins and proximal courses of the coronary arteries
Transposition of the great arteries, arterial switch procedure	LV size and function Residual intracardiac shunts Main PA and proximal branch PA stenosis Neo-aortic root dilation and regurgitation	LV size and function Residual intracardiac shunts Main PA and proximal branch PA stenosis Neo-aortic root dilation and regurgitation Origin and proximal course of coronary arteries Myocardial stress perfusion	*In selected cases LV size and function Residual intracardiac shunts Main PA and proximal branch PA stenosis Neo-aortic root dilation and regurgitation Origin and proximal course of coronary arteries
Congenitally corrected transposition of the great arteries	Systemic RV size and function Residual intracardiac shunts Tricuspid valve morphology and regurgitation Aortic regurgitation LV (subpulmonary) size and function LVOT obstruction (pulmonary stenosis)	Systemic RV size and function Residual intracardiac shunts Tricuspid valve morphology and regurgitation Aortic regurgitation LV (subpulmonary) size and function LVOT obstruction (pulmonary stenosis)	*In selected cases Ventricular size and function Residual intracardiac shunts Tricuspid valve morphology and regurgitation Aortic regurgitation LVOT obstruction (pulmonary stenosis)
Single ventricle, Fontan procedure	Ventricular size and function Atrioventricular valve regurgitation Fontan pathway patency Branch PA calibre LVOT obstruction Aortic regurgitation	Ventricular size and function Atrioventricular valve regurgitant fraction Fontan pathway patency Branch PA calibre and flow LVOT obstruction Aortic regurgitation fraction Pulmonary venous compression Aortic-to-pulmonary collaterals Systemic-to-pulmonary venous collaterals	*In select cases Ventricular size and function Atrioventricular valve regurgitant fraction Fontan pathway patency Branch PA calibre LVOT obstruction Pulmonary venous compression

ASD, atrial septal defect; AV, atrioventricular; LV, left ventricle; LVOT, left ventricular outflow tract; PA, pulmonary artery; PFO, patent foramen ovale; PS, pulmonary stenosis; RV, right ventricle; RVOT, right ventricular outflow tract; VSD, ventricular septal defect.

Left ventricular outflow tract obstruction and aortic coarctation

Echocardiography is used to assess LV outflow tract (LVOT) obstruction for example due to subaortic ridge, aortic valvar, and supravalvar stenosis plus aortic coarctation or re-coarctation; Doppler-derived diastolic tail in the descending thoracic aorta and continuous abdominal aortic flow indicate significant coarctation.⁹ Additional information, such as aortic valve morphology, the presence of ventricular septal defect or LV hypertrophy is sought. Aortopathy involving the aortic root or proximal ascending aorta should be sought on 2D echocardiography.¹⁰ Repaired coarctation patients require screening for the complications of recoarctation or aneurysm formation (Figure 7). Echo Doppler may reveal non-specific high-flow velocities across the isthmus in patients after coarctation repair given the fact that elasticity of the aortic wall is lost in this trajectory, causing flow velocities to increase even in the absence of stenosis. Cardiovascular magnetic resonance is the gold standard for assessing LV mass and can be useful to assess multi-level LVOT obstruction, aortic valve morphology, calibre of the entire aorta, and collateral flow. All adults with aortic coarctation should undergo cross-sectional imaging (usually CMR) at least once.¹¹ Computed tomography is more suited for assessing stent lumen and fracture.

Figure 7.

Contrast-enhanced cardiovascular magnetic resonance angiography (CE-CMRA) in an adult presenting with systemic hypertension due to severe aortic coarctation (A). Computed tomography imaging following endovascular stenting (B). Aneurysm related to endovascular stenting of coarctation studied with cine CMR (C; dotted arrow), and aneurysm related to Dacron patch coarctation repair studied with CE-CMRA (D; arrow).

Atrial septal defects

The diagnosis of an atrial septal defect (ASD) and/or anomalous pulmonary veins should be considered in adults presenting with RV dilation. Transthoracic echocardiography is used to assess size and location of the defect (secundum and primum) (Figure 4), TOE is the gold standard for accurately assessing size, number, rims, and relationships to important neighbouring structures to determine suitability for percutaneous device closure. Computed tomography and CMR are especially useful for detecting associated anomalous pulmonary veins that insert into the superior vena cava above the level of the azygous vein. Transthoracic echocardiography may be suitable for sinus venosus ASD imaging, however TOE, CMR, or CT are often needed to delineate the frequent association of anomalous pulmonary venous return (Figure 8). Cardiovascular magnetic resonance and CT give information on the distance of the anomalous pulmonary vein from the cardiac mass, which in turn is important for planning the surgical approach to pulmonary venous redirection.

Figure 8.

Cardiovascular magnetic resonance (or computed tomography) may be useful in the diagnosis of sinus venosus defects, which can be at the orifice of the superior (or less commonly inferior caval veins) and to delineate anomalous pulmonary venous drainage. Cardiovascular magnetic resonance images showing sinus venosus atrial septal defect (asterisk) in (A) and the anomalous drainage of the right upper pulmonary vein to superior vena cava (B). IVC, inferior vena cava; LA, left atrium; RA, right atrium; RUPV, right upper pulmonary vein; PA, pulmonary artery; RCA, right coronary artery; SVC, superior vena cava.

Atrioventricular septal defect

Patients with atrioventricular septal (canal) defects have a common atrioventricular junction with a spectrum of lesions with potential for shunting at atrial level (ostium primum defects), ventricular level, or both atrial and ventricular level. The most common adult complication for repaired patients is left atrioventricular valvar regurgitation (of note this valve has abnormal tri-leaflet morphology). Imaging must also assess for other potential complications including pulmonary hypertension and LVOT obstruction. Transthoracic echocardiography is usually able to address the majority of concerns and TOE used to assess for suitability for repair vs. replacement of the left atrioventricular valve.

Repaired tetralogy of Fallot and right ventricular outflow tract obstruction

Patients with repaired tetralogy of Fallot (TOF) constitute one of the largest groups of ACHD patients surviving into adulthood. Residual haemodynamic and electrophysiological abnormalities contribute to increasing morbidity and mortality rates arising in adulthood.¹² The surgical strategy for TOF repair, particularly with regard to RV outflow tract (RVOT) reconstruction, has evolved with time.¹³ Conduits from the RV to PA are sometimes required for TOF repair, for example with associated pulmonary atresia or anomalous coronary arteries. These may be difficult to assess with TTE alone due to their anterior location. A multimodality imaging approach is often utilized.¹⁴ Pulmonary regurgitation is common and is an important factor for the long-term outcome of these patients. Aortic root dilation is also common in patients with repaired TOF in some patients associated with significant aortic regurgitation.¹⁵ Cardiovascular magnetic resonance is recommended for all patients and is especially helpful for multi-level RVOT (including branch PA) obstruction, pulmonary regurgitation, and RV volumes.¹⁶ Right ventricular outflow tract regional wall motion abnormalities and aneurysms are common and contribute to RV systolic dysfunction and adverse ventricular interactions.¹⁷ Right ventricular outflow tract akinetic area length predicts the onset of sustained ventricular arrhythmia. Pulmonary regurgitation can be assessed with echocardiography¹⁸ although the gold standard for its quantification is CMR. Free pulmonary regurgitation, that is whereby forward and reverse flow jets are comparable in size, and imaging shows little or no effective remaining valve tissue, typically occurs with regurgitation fraction 30–40%. Quantification of right atrial size is helpful as large right atrial area has been associated with sustained atrial tachyarrhythmias in these patients.¹⁹

Right ventricular volumes quantified by CMR are followed serially for progressive dilatation; it has been suggested that elective pulmonary valve replacement should be considered before RV end-diastolic volume indexed to body surface area reaches 150–160 mL/m².²⁰ Right ventricular volumes can also be assessed to define the degree of RV reverse remodelling following valve implantation (Figure 9). Echocardiography can identify the presence of a restrictive RV physiology with the presence of an antegrade ‘a’ wave (end-diastolic forward flow) in the RVOT on pulse wave Doppler throughout the respiratory cycle demonstrating a non-compliant RV which is unable to distend further with atrial systole.²⁴ This again may be relevant in interpreting pulmonary regurgitant fraction or volume²¹ and RV volumes from CMR for timing of pulmonary valve replacement. Left ventricular dysfunction is present in >20% of adults with TOF²² and is associated with increased mortality.^23–25

Figure 9.

Diastolic still image from cardiovascular magnetic resonance cine pre-pulmonary (A) and post-pulmonary (B) valve replacement for pulmonary regurgitation status post repaired tetralogy of Fallot. Reduction in RV volume and increased LV filling in (B). Late gadolinium enhancement cardiovascular magnetic resonance evidence of ventricular fibrosis/scarring is seen in (C); block arrows point to bright areas of scar in the right ventricular outflow tract and dotted arrows to the ventricular septal defect patch site. (D) Derived from 3D cardiovascular magnetic resonance acquisition after segmentation of chambers, outflows, and scar using Mimics, Materialise NV (courtesy of collaboration with Drs Veronica Spadotto and Jennifer Keegan). LV, left ventricle; RV, right ventricle.

Focal RV fibrosis on late gadolinium enhancement CMR imaging is associated with adverse clinical prognosticators in adults with repaired TOF; prospective studies are required.²⁶ The INDICATOR prospective study of 873 repaired TOF patients showed that CMR-derived RV and LV ejection fraction predict sustained ventricular tachycardia and mortality.²⁴

Cross-sectional imaging prior to catheter-based pulmonary valve reinterventions can be informative regarding the origins and proximal course of the coronary arteries in relation to the RVOT (Figure 10). Furthermore, cardiac CT provides information on the extent of conduit calcification for stent deployment. Prior to redo sternotomy, cross-sectional imaging shows the proximity or even adherence of the anterior RV wall and/or ascending aorta to the sternum, thus allowing for surgical planning and avoidance of injury.

Figure 10.

Cardiac computed tomography in a patient with RV–PA conduit (A), showing virtually single origin coronary arteries passing between the aorta and narrow segment of conduit (B–D) (images courtesy of Dr Mike Rubens). Ao, aorta; Cx, circumflex; LAD, left anterior descending; PA, pulmonary artery; RCA, right coronary artery; RV, right ventricle.

Systemic right ventricle after atrial redirection for transposition of the great arteries or in the setting of congenitally corrected transposition of the great arteries

Many surviving adults with transposition of the great arteries (TGA) would have had atrial switch surgery (Mustard or Senning operation). Systemic RV dysfunction is a determining factor for late morbidity and mortality. Echocardiographic parameters (RV FAC, TAPSE) can be used for detecting changes in RV function. Total isovolumic time and peak systolic strain measures have prognostic value. Systemic atrioventricular (tricuspid) valve regurgitation usually reflects progressive RV dilatation and dysfunction and is most sensitively assessed by echocardiography, as is the presence of pulmonary hypertension or baffle leaks (better delineated with the use of contrast). Associated lesions such as pulmonary stenosis and ventricular septal defect can also be assessed. Pulmonary hypertension can be difficult to diagnose when there is no mitral regurgitation but equal LV and RV size on apical four-chamber view is suggestive of pulmonary hypertension or significant baffle leak. Imaging of patients after a Mustard or Senning operation requires assessment of all three baffled atrial flow pathways (superior/inferior caval and pulmonary venous atrial) for the presence and degree of obstruction. Increased flow velocity >1.6 m/s or continuous baffle flow are suggestive of obstruction. Cardiovascular magnetic resonance in addition to echocardiography is often helpful for assessment of baffle patency.

Congenitally corrected TGA (ccTGA) comprises atrioventricular and ventriculoarterial discordance (L-loop TGA/double discordance). The spectrum of clinical presentation is wide and depends on associated lesions; presentation in adulthood is possible. The tricuspid valve in ccTGA is often intrinsically abnormal (Ebstein type and may be underdiagnosed) and results in tricuspid regurgitation; the latter may also be secondary to RV dysfunction and annular dilatation. Echocardiography can be used to assess RV dysfunction and tricuspid regurgitation. Diastolic dysfunction can be assessed by Doppler flow of RV filling pattern. Absent Doppler ‘A’ wave in the presence of sinus rhythm and clear p waves often indicate very high filling pressures. Cardiovascular magnetic resonance allows gold standard quantification of systemic RV ejection fraction. This may be used to enable clinical decision-making with regard to tricuspid valve surgical replacement. Computed tomography may be of value in the setting of systemic RV dysfunction with wide QRS when cardiac resynchronization is contemplated to assess the coronary sinus anatomy. Tissue characterization by CMR has shown areas of late gadolinium enhancement consistent with focal RV fibrosis^27,28 (Figure 11). We have recently shown that systemic RV late gadolinium enhancement correlates with histological fibrosis, is associated with clinical disease progression, and predicts outcomes,²⁹ justifying its periodic use. In our practice, we consider patients with RV ejection fraction of ≤35% and extensive RV fibrosis for primary prevention for sudden cardiac death; ICD is offered on an individualized basis following multidisciplinary discussion.

Figure 11.

Cardiovascular magnetic resonance images of simple transposition of the great arteries (TGA) (A and B) and congenitally corrected TGA (ccTGA) (C and D) showing parallel discordant outflows (A and C) and hypertrophic systemic RV (B and D). Late gadolinium enhancement in TGA with atrial redirection surgery (E) and in ccTGA (F); bright areas of enhancement within the RV (arrows) suggestive of fibrosis. Ao, aorta; LA, left atrium; LV, left ventricle; PA, pulmonary artery; PVAC, pulmonary venous atrial compartment; RV, right ventricle; RA, right atrium.

Transposition of the great arteries after arterial switch surgery

Arterial switch procedure, i.e. anatomic repair, involving switching the great vessels and reimplanting the coronary arteries has been the treatment of choice for infants with TGA over the past three decades. Supravalvar pulmonary stenosis, neo-aortic root dilatation, aortic valve regurgitation, LV dysfunction, and coronary occlusion are relatively common complications. Echocardiography with Doppler can assess aortic valve and LV function and RV pressures, whereas the main and branch pulmonary arteries are often difficult to image. Cardiovascular magnetic resonance (or CT) can provide detailed information on RVOT or branch PA stenoses. Computed tomography is particularly suited to image the proximal coronary arteries, reimplanted during repair. Cardiovascular magnetic resonance evaluation of coronary origins is also excellent, although CT is superior in excluding coronary stenoses. In the case of symptoms, LV dysfunction or LV scar at CMR assessment of viability with CMR stress perfusion and with exercise echocardiography should be performed.

Single ventricle, Fontan procedure

Many survivors to adulthood of ‘single ventricle’ physiology have undergone the Fontan operation to re-route systemic venous return to the pulmonary arteries. In the earlier era, this was done with an anastomosis from the right atrial appendage to the pulmonary arteries (atriopulmonary Fontan), whereas more recently, this involves total cavopulmonary connection (TCPC), either using an intra-atrial/lateral tunnel or extracardiac conduit. The superior vena cava is connected end to side to the top of the right PA, whereas the inferior vena cava is channelled by a patch, flap, or conduit up one side of the right atrium to the PA. Thrombus may form in the dilated right atrium in the atriopulmonary Fontan due to sluggish flow (Figure 12) or in the disconnected pulmonary trunk after TCPC. Failure of the Fontan type circulation ensues with obstruction of Fontan pathways, ventricular, and/or valvular dysfunction. Restrictive ventricular septal defect in the setting of ventricular arterial discordance is unfavourable, causing subaortic stenosis. Ventricular systolic and diastolic dysfunction determine outcome; echocardiography can assess both. Cardiovascular magnetic resonance can establish patency of pathways, exclude thrombus, quantify the volume of the dominant/primary ventricle and its ejection fraction, and has demonstrated areas of ventricular fibrosis more commonly in patients with documented non-sustained ventricular tachycardia.³⁰

Figure 12.

(A and B) Patent Fontan pathways status post-atriopulmonary Fontan. In patient (C), thrombus has formed (arrows) due to sluggish flow in the dilated right atrium. In (D), late gadolinium enhancement cardiovascular magnetic resonance evidence of rudimentary endocardial right ventricular fibrosis is seen (arrows). (E and F) Patent total cavopulmonary pathways (asterisks). Ao, aorta; IVC, inferior vena cava; LA, left atrium; LPA, left pulmonary artery; LV, left ventricle; RA, right atrium; RPA, right pulmonary artery; SVC, superior vena cava.

Summary

Imaging is fundamental to the lifelong care of ACHD patients. Echocardiography remains the first line imaging for inpatient, outpatient, or perioperative care. Cross-sectional imaging with CMR or CT provides complementary and invaluable information on cardiac and vascular anatomy and other intra-thoracic structures. Furthermore, CMR provides quantification of cardiac function and vascular flow. Cardiac catheterization is, mostly reserved for assessment of pulmonary vascular resistance, ventricular end-diastolic pressure, and percutaneous interventions. There have been further advances in non-invasive imaging for ACHD including the application of advanced echocardiographic techniques, faster automated CMR imaging, and radiation dose reduction in CT. As a result ACHD, a heterogeneous population, benefit from appropriate application of multiple imaging modalities matched with tertiary ACHD expertise.

Funding

S.V.B.-N. is supported by an Intermediate Clinical Research Fellowship from the British Heart Foundation (FS/11/38/28864). This project was supported by the National Institute for Health Research (NIHR) Cardiovascular Biomedical Research Unit of Royal Brompton and Harefield National Health Service (NHS) Foundation Trust and Imperial College London. This report is independent research by the NIHR Biomedical Research Unit Funding Scheme. The views expressed in this publication are those of the author(s) and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health.

Conflict of interest: none declared.