Simple and Complex Congenital Heart Disease: Adults

Anatomy and Natural History

Ebstein anomaly is a malformation of the tricuspid valve and right ventricle, which encompasses a large spectrum of disease severity. There is failure of delamination of the septal and posterior tricuspid valve leaflets from the myocardium, resulting in apical displacement of the tricuspid valve (≥0.8 cm/m ² relative to the anterior mitral leaflet insertion site). The portion of the right ventricle proximal to the functional tricuspid valve becomes “atrialized.” The anterior leaflet of the tricuspid valve is large and redundant, and often has fenestrations and tethering attachments to the right ventricular (RV) free wall. The posterior leaflet is often dysplastic and atrially displaced.

The etiology of Ebstein anomaly is not known; however, in rare cases, genetic factors such as mutations in the transcription factor NKX2.5,10p13–p14 deletion, or 1p34.3–p36.11 deletion have been described. The most severe cases of Ebstein anomaly result in fetal hydrops and fetal demise. Patients with Ebstein anomaly often develop progressive right heart failure and exercise intolerance. However, some individuals with mild forms of this disease can be asymptomatic into adulthood.

Surgical Repairs

When possible, the surgical intervention for Ebstein anomaly involves tricuspid valve repair. In the current era, the repair generally involves a right atrial (RA) reduction, plication of the atrialized right ventricle and a tricuspid valve repair involving the creation of a monocusp tricuspid valve using the redundant anterior tricuspid valve leaflet with a posterior annuloplasty (cone procedure). In patients who are unsuitable for tricuspid valve repair, a bioprosthetic tricuspid valve replacement is generally performed. Evaluation of the patient after Ebstein repair involves assessing the degree of residual tricuspid regurgitation or stenosis, assessing RA size and the RV size and function. The right coronary artery lies in close proximity to the repaired tricuspid valve annulus site and it is important to assess for evidence of late gadolinium enhancement (LGE) following surgery for Ebstein anomaly.

Cardiovascular Magnetic Resonance Evaluation of Ebstein Anomaly

Right Atrial and Right Ventricular Size and Function

Progressive tricuspid regurgitation and abnormal RV myocardium lead to right heart dilation. Measurements of RA and RV volumes are typically performed in axial or short-axis orientation with endocardial contours drawn in end systole and end diastole. When contouring the right ventricle, it can be useful to assess the functional RV size that excludes the atrialized right ventricle and only includes the RV volume distal to the functional tricuspid valve annulus and coaptation point. Many centers will report both the functional RV size and function and the anatomic RV size and function (using the anatomic tricuspid annulus as a landmark). The ability to accurately and reproducibly measure RV volume is important because RV size has been associated with clinical outcomes in patients with Ebstein anomaly. Additionally, mismeasurement of RV stroke volume can result in errors when calculating tricuspid regurgitation severity.

Progressive RV dilation or dysfunction in the setting of severe tricuspid regurgitation is imaging criteria for tricuspid valve surgical intervention. The index of right-sided to left-sided heart volumes derived from CMR has been shown to correlate well with other established markers of heart failure. Contouring the end-diastolic volume measurements of the right ventricle, RA, left ventricle, and left atrium (LA) can provide a total right/left-volume index ( Fig. 41.1 ):

$\begin{array}{c}\text{Total right}/\text{left-volume index}\\ =(\text{right atrium}+\text{atrialized right ventricle}\\ +\text{functional right ventricle})/(\text{LA}+\text{left ventricle})\end{array}$

Indexes such as these may eventually be used to help guide timing of tricuspid valve intervention.

Anatomy and Natural History

Coarctation of the aorta is typically a fibrous ridge in the aortic isthmus, just distal to the insertion of the left subclavian artery. Although often discrete, aortic coarctation can also be long segment or associated with a diffusely hypoplastic transverse aorta. Aortic coarctation is associated with a diffuse vascular abnormality and is associated with aortic aneurysm, cerebral aneurysms, or endothelial dysfunction. Awareness of these abnormalities is important because the entire aorta and cerebral vessels should be imaged in patients with aortic coarctation.

Aortic coarctation sometimes presents in adulthood as difficult-to-manage systemic hypertension and the diagnosis may be suspected from a murmur, diminished lower extremity pulses, or arm–arm or arm–leg blood pressure discrepancy. Those who had an aortic coarctation repair early in life have up to a 5% risk of re-coarctation in adulthood and present similarly.

Surgical Repairs

There are several types of surgical repairs for native aortic coarctation, and they are dictated by the anatomy. For patients with a discrete coarctation, an end-to-end anastomosis is performed. If there is associated transverse aortic arch hypoplasia, an extended end-to-end procedure may be required.

Some patients with complex aortic coarctation have undergone interposition graft repairs, and those with Dacron material are particularly susceptible to aneurysm formation. The subclavian flap procedure was performed in the early surgical experience, and involved transecting the left subclavian artery and placing it over the narrowed portion of the descending aorta. Patients who have undergone this procedure will no longer have the left subclavian artery attached to the transverse arch.

Cardiovascular Magnetic Resonance Evaluation of Aortic Coarctation

Aortic Arch

CMR imaging of native and re-coarctation will be discussed together. The anatomic features of aortic coarctation can be seen with bright-blood cine or double-inversion black-blood spin echo images in the oblique sagittal plane. Gadolinium-enhanced magnetic resonance angiography (MRA) also demonstrates the coarctation ( Fig. 41.2 ) and double oblique reformats can be used to measure the minimal luminal diameter and the reference vessel size. If collateral vessels are seen on contrast-enhanced (CE) MRA or PCMR demonstrates flow augmentation in the descending aorta, the obstruction is probably hemodynamically important. A prolonged deceleration time of the systolic flow in the distal descending thoracic aorta also indicates hemodynamically significant aortic coarctation.

Four-dimensional velocity mapping is not widely available but is an emerging technique to show turbulence at the coarctation site, and characterize altered aortic velocity profiles, providing insight into which patients may be at higher risk for aortic wall complications, such as dissection.

Patients with aortic coarctation are prone to aneurysms in the ascending aorta, cerebral vasculature, and at the site of surgical repair. Aneurysms at the site of previous Dacron patch repair are particularly prone to rupture and should be managed aggressively. Screening for cerebral aneurysms is recommended, although neither optimal management nor frequency of surveillance is well defined.

Anatomy and Natural History

Evaluation of patients with repaired tetralogy of Fallot (TOF) is one of the most common adult congenital heart disease diagnoses referred for CMR. TOF represents the most common form of cyanotic congenital heart disease affecting up to 0.5 per 1000 live births. Survival following TOF repair is excellent, but there is a 3-fold increase in mortality beginning in the third postoperative decade of life, and 14% of patients develop markedly impaired functional status late after surgical repair, highlighting the importance of regular surveillance of these patients. This congenital anomaly results from the anterior deviation of the conal septum, resulting in varying degrees of RVOT obstruction, VSD, an overriding aorta, and RV hypertrophy. Importantly, the degree of RVOT obstruction can range from only mild subpulmonary stenosis to the most severe form involving complete absence of the main pulmonary artery (TOF/pulmonary atresia), which occurs in approximately 15% of patients with TOF.

Surgical Repairs

In the current era, the majority of patients undergo surgical repair in infancy or childhood, although older adults may have first undergone a palliative shunt (Blalock-Taussig, Waterston, or Potts shunt) as a young child and then undergone a complete repair at an older age. Strategies to repair TOF have evolved over time. The early experience involved placing a transannular patch to eliminate the RVOT obstruction; however, current strategies have been modified to alleviate most of the RVOT obstruction while trying to preserve some of the integrity of the pulmonary valve. Patients with TOF/pulmonary atresia and those with anomalous left coronary artery from the right sinus may undergo an RV-to-pulmonary artery (RV-PA) conduit. Knowledge of the patient's surgical history before CMR is ideal because it will determine the specific CMR protocol to employ, focusing on the potential residual lesions.

Many patients with repaired TOF undergo a pulmonary valve replacement in adulthood. CMR is increasingly being used to aid in the decision making of timing of these interventions. Box 41.3 lists suggested imaging criteria for consideration of pulmonary valve replacement in asymptomatic patients with severe pulmonary regurgitation (PR).

Cardiovascular Magnetic Resonance Evaluation of Tetralogy of Fallot Repair